Earth Monitor (EMON) 
Seismic Monitoring and Display Software for the PC

Version 7.0a
January, 1998


Ted Blank
954 Foxswallow Ct.
San Jose, CA 95120

ted_blank@pobox.com
Disclaimer
The software in this package is provided free of charge for non-commercial purposes only.  It may be 
copied and redistributed without restriction.  Please report all bugs to the author.  This documentation is 
distributed with version 7 of the software.  
Introduction
The personal computer has been used productively in laboratories as a data collection device for many 
years. Now, amateur scientists can also take advantage of the power of the personal computer. If you 
have a PC and an interest in the Earth sciences, you might want to consider setting up a seismic 
monitoring station at home or in a classroom. Excellent results can be obtained with a home-made 
seismometer, constructed from readily available materials. Several Scientific American articles over the 
past 15 years (see the bibliography) give instructions for building various types of seismometers. Mercury 
tilt-meters, pendulum-based designs, and capacitance-based designs are just some of the approaches 
that have been tried with excellent results. 
All of the early amateur seismograph designs used some sort of chart or drum recorder to make a 
permanent record of an amplified earthquake signal. With the EMON software package, your PC can do 
the job of the chart recorder- and much more! Saving earthquake records to disk allows the power of the 
PC to be applied to the data analysis - a task at which the computer excels. 
What is the EMON package
The EMON package is a suite of DOS-based programs which will let you turn your PC into an amateur 
seismic station.  You will be able to collect, display, analyze and print seismic data from any home-made 
or professional seismometer using any one of several commercial digitizing boards costing in the 
neighborhood of $100-200.  The EMON software package is distributed free of charge via the San Jose 
Public Seismic Network web site.  The URL for the site is http://psn.quake.net.
What are the differences between EMON and SDR?
SDR (Seismic Data Recorder) is another free program to record seismic data.  It saves data in the same 
format as EMON (plus some other formats) but requires Windows and only works with the the A/D board 
from Larry Cochrane.  If your data collection PC is not capable of running Windows you should use 
EMON.  If it is capable of running Windows, you have a choice of using SDR or EMON for your data 
collection.  
Where to find a seismometer
While you might salvage a seismometer from a local college or research laboratory, dont dismiss the 
homemade idea prematurely. Building one can be lots of fun and makes an excellent home or classroom 
project. It is decidedly low-tech in nature, and inspires rich possibilities for further exploration.   Plans for 
building your own seismometer and amplifier can be found in articles listed in the Appendix as well as on 
the Public Seismic Network web site.
The EMON Software Package
The collection of programs in this package will let you 
  view the signal from your seismometer in real time, 
  save earthquake recordings to disk, 
  display and analyze the earthquake records, and 
  zoom in on interesting parts of the earthquake records. 
  print part or all of an earthquake recording
It is the PC of course that makes the last three capabilities possible. 
What kind of PC should I use?
The same PC can be used for both data collection and analysis, or you can use two different PCs. The 
PC you use for data collection does not need to be particularly powerful. In fact, an old IBM PC/XT (the 
first PC to have a hard drive) or AT with an internal or external 3  floppy drive installed is just about 
the perfect data collection machine. The hard drive allows lots of data to be collected, and the floppy 
drive allows you to archive the important files or share them with friends.   
When it is time to display and analyze the data though, a faster machine (minimum of 286 class, but the 
faster the better) makes this part much more enjoyable. If you want to display your data on a different PC 
than the one on which it was collected, just make sure the two machines have at least one size of floppy 
disk in common, or some sort of serial or parallel port connection which allows file transfer. 
Also, remember to keep good written records. From the day you start monitoring for earthquakes, keep a 
log or journal. Anytime you make any change to your system, write down what youve done in your log. 
This way you and others will know what has changed. 
You might want to start a folder for each significant earthquake you record. Keep a printout of the record 
in the folder, along with a disk containing a copy of the quake file. You might also want to put a map on 
the wall of your station with a pin in the location of earthquake youve recorded. 
Installing EMON
To install the EMON software, follow the instructions below.  You will need access to PKUNZIP to unpack 
the files.
1. Create the directory in which the software will reside.  E.g. MKDIR C:\EMON
2. Place the floppy disk in the computer and copy the file EMON.ZIP to the directory you just created, 
e.g., COPY A:EMON.ZIP C:\EMON
3. Make the directory you just created the current directory, e.g. CD C:\EMON
4. Unzip the file with the command PKUNZIP EMON.ZIP.
5. Edit and customize the EMON.OPT and QUAKEVU.INI files as described below.
Package Contents
The EMON package consists of the following software.
File Name
Description
EMON.EXE
Monitors, displays and records the output of the 
seismometer
EMON.OPT
Options file for EMON;  edit with any text editor 
which does not add TABs to files
QUAKEVU.EXE
Displays data files on CGA graphics screen; 
computes P-S interarrival time and distance; 
allows user to enter comments
QUAKEVU.INI
Initialization file for QUAKEVU
EL.EXE  (EmonList)
Displays list of EMON quake data files in any 
directory;  allows you to invoke QUAKEVU from a 
full screen menu
MSPLICE.EXE
Program to splice multiple EMON quake data files 
into a single file
HOWFAR.EXE
Program to compute distance between any two 
locations on the earths surface given their latitude 
and longitude.
HOWFAR.LOC
File containing your stations latitude and longitude; 
saves typing this information in every time you use 
HOWFAR program.
EMON7.DOC
This file (MS Word 2.0 document) including screen 
captures of programs.
EMON7.WRI
This file saved as Windows WRI file
EMON7.TXT
This file (text format)
READ.ME
Instructions for printing, unzipping etc.
Your Seismic Station: The Basic Components
To assemble a basic seismic monitoring station you will need the following components.  Each is 
discussed in more detail later.
  PC
  Software
  Seismometer
  Amplifier/filter
  Analog-to-Digital converter card
  Cables
  Someplace protected from weather to put the seismometer and PC
Monitoring Seismic Activity with EMON
 
Figure 1.   Display of EMON main screen showing data trace and three saved files.
The Earth Monitor (EMON) program is designed to run continuously in the PC. It periodically checks the 
input from the seismometer and amplifier for earthquake-like activity. An earthquake data file is saved to 
disk only when an earthquake signal is detected. An options file called EMON.OPT is read at startup. 
You can change the parameters that control saving data by changing entries in the OPT file. You can 
collect data from up to three seismometers simultaneously. A separate quake file will be written for each 
device. Figure 1 shows a sample of how the EMON screen appears when it is monitoring for 
earthquakes. Notice that three quake files have already been saved to disk, and their names appear in 
the space at the bottom of the screen. If your PC has graphics capability (as this one did), the box at the 
upper right displays a real-time trace of the output of the seismometer. However, EMON can collect data 
on a PC which does not have graphics capability. You will just need to use a different PC to display the 
data later. 
Customizing EMON: the OPT file
Earthquake recording stations differ in more than just their location.  For instance, a quiet location in the 
country could record small, distant events without worrying about interference from local noise, whereas 
a location in a large city might need to more carefully discriminate earthquake activity from earth 
movements due to trains, subways or the like. 
You customize EMON for the characteristics of your location through an options file called EMON.OPT. 
You can edit this file with any  ascii text editor. Do not use word processors - they can insert tabs into the 
file making it unreadable.  The EMON.OPT file is read from disk when the program starts.  It should be in 
the same directory as the EMON program.
In the OPT file you give EMON information like the local noise level (used to discriminate true seismic 
activity from local noise). Other information you supply includes the three character ID of your station 
(which becomes the file extension on all saved files) and the disk (or directory) to which you want the 
quake files to be saved.  You can also change some of these same parameters on the screen after 
EMON has started. However, changing a parameter on the screen does not make the change 
permanent. You must edit the EMON file and make the same change if you wish it to be effective 
automatically every time the EMON program starts.  Figure X on page  explains each parameter in the 
options file.
Displaying earthquake recordings with QUAKEVU
 
Figure 2.  QUAKEVU screen showing identification of  P- and S-wave arrivals.
The QUAKEVU program displays the data files created by EMON.  Figure 2 shows a sample of the 
QUAKEVU screen.  QUAKEVU allows you to identify the P and S wave  arrivals on the screen by 
moving small pointers via either the mouse or the keyboard arrow keys.  As you pick out the P and S 
wave arrival points, QUAKEVU then automatically calculates for you:
  the time the P wave arrived at the recording station
  the time the S wave arrived at the recording station
  the time the quake occurred (the Origin time)
  the distance from the recording station to the epicenter of the quake along a great-circle arc (in 
kilometers, miles and degrees)
This information is updated every time you move either the P or S pointers.  Notice that  QUAKEVU 
does not calculate the location of the earthquake, just the distance from the recording station.  You will 
need to obtain distance calculations from at least three stations in different parts of the globe, and use 
triangulation on a map or globe to figure out the actual location.  This makes it fun to trade quake files 
with other people or groups who also monitor earthquakes.  The easiest way to do this is to use the PSN 
web site.  Instructions are available at the site. 
QUAKEVU will also allow you to save a subset of the data to a smaller file for easier transmission across 
telephone lines.  During the process of saving the subset file you can also add a comment to the file 
being saved (up to 60 characters) as well as the true origin time, depth, location etc. if you know them. 
QUAKEVU will work only on a PC with a Color Graphics Adapter (CGA) and graphics display, or its 
equivalent.  QUAKEVU uses the CGA in hi-resolution (640x200) mode,which is equivalent to SCREEN 
2 in BASIC.  (In this mode only black and white areavailable.)  Most computers with any type of graphics 
capability support this graphics mode, since it has been around almost since the PC was invented.  You 
can display from one to three recordings of the same earthquake on the screen at the same time.
Note:  A Windows program called WinQuake is available from the PSN web site.  It does require 
Windows but it has much more function than QUAKEVU, including high quality printing to laser printers.  
Many users who collect data with EMON display it on a different PC using WinQuake.
Each earthquake data file contains reserved space for a 60 character comment describing the contents 
of the file.  QUAKEVU will allow you to to insert text into this reserved area when you save a file.  Once 
a comment area is filled in, QUAKEVU displays it on the screen  when the file is displayed.  This allows a 
limited form of self-documentation for the data files. For instance, you might want to add a comment like 
ML6.6 Solomon Islands 11.0S 163.5E.  This would remind when you displayed the quake file of the 
magnitude (on the Richter scale), the location, and the latitude and longitude of the quake being 
displayed. Note that the recording station name (up to 15 characters) is already saved in the file in a 
different place, so there is no need to add that to the comment.
You can get information on the true location of the earthquake from news reports, via a call to the U.S. 
National Earthquake Information Center (NEIC) computer bulletin board, or from the World Wide Web.  
Within a few hours of a major quake, the NEIC in Golden, Colorado, makes a preliminary determination 
of its location using data just like you will be collecting from stations all around the world that recorded 
the event.  An example of one of their messages is shown below.  It is sent out as soon as possible to 
assist disaster relief agencies around the world in responding quickly to major earthquakes.  Location of 
smaller quakes are usually calculated and available within 1-2 weeks after the event.
U.S. GEOLOGICAL SURVEY NATIONAL EARTHQUAKE INFORMATION CENTER
World Data Center A for Seismology

the following is from the united states geological survey, national earthquake information center:

preliminary hypocenter for earthquake of 1993 jan 19, SEA OF JAPAN:
latitude 38.7 degreesnorth
longitude 133.5 degrees east
origin time 14 39 27.4 utc
depth 460, magnitude 6.0 mb.

stations used: mat p 144044.0 smy p 144507.9 adk p 144552.9sdn p 144707.8 brw p 144719.7 tta p 144721.5 svw 
p 144724.9ima p 144727.3 ap 144845.3 bgl p 144736.2 crp p 144736.5ap 144907.5 cp2 p 144736.8 kdc p 
144738.8 ap 144850.9...tuc p 145126.6 alq p 145130.1 ap 145312.8 wmok p 145148.8tbr p 145208.0 nav p 
145214.4 bla p 145216.3 cvl p 145216.7ceh p 145223.6 prm p 145225.3 jsc p 145226.7 lhs p 145226.9
 
Customizing QUAKEVU startup: the INI file
Different users found they used QUAKEVU in different ways.  Some with slower PCs start in 
QuickDisplay mode, zoom in on a portion of the file, then display at full resolution.  Others like to start 
immediately identifying the P and S waves to get an estimate of distance.  Since there was no way to 
satisfy all these different requirements, QUAKEVU V6 now includes a file called QUAKEVU.INI which 
tells QUAKEVU how to start up. After starting the program you can continue to use the keyboard or 
mouse as before. You can edit the INI file with any ASCII text editor.  The contents of the file are self-
explanatory.
Utility programs
Several utility programs are included to assist in handling the files after they are collected.  These 
programs and their associated files are described below.
EL.EXE   (EMONList)
EL.EXE is the EMONList program.   EL ? gets you help. Just supply a filemask in standard form, like *.* 
or 97*.* and EL will find all matching files in the current directory (or the  directory you specify).  It lists 
the peak sample, date and time sampling started, and the first 40 characters or so of the comment.  Hit 
enter on any line to view that file with QUAKEVU.  You can also use the UpArrow, DownArrow, PgUp, 
PgDn, Home and End keys to move around the list. Pressing the Del key will erase the file from disk 
(after giving you a chance to confirm). Deleting a file will remove it from the on-screen list as well.
If you have several files for the same quake from different  locations, you can view all of  them on the 
same QUAKEVU screen.  To do this, mark up to three files with the spacebar. An X will appear in front 
of the name of the file. When all files have been marked, press enter - QUAKEVU will then load all three 
and display them on the same time scale.
HOWFAR.EXE
The HOWFAR program computes the great circle distance between any two points on the earth given 
the latitude and longitude of each. You will be prompted for both sets of coordinates. However, if you 
create a file called HOWFAR.LOC containing the latitude and longitude of your station, the HOWFAR 
program will use that information as one of the locations and you only need to enter the second one.  
The HOWFAR.LOC file must be in the same directory as HOWFAR.EXE. The format of the 
HOWFAR.LOC file is:
LINE 1 - Text describing the place that this set of coordinates refers to.  For instance, you might put 
something like:   XYZ School, Woonsocket, RI
LINE 2 - latitude in degrees, e.g. 43.52.  Use negative numbers  if you are SOUTH of the equator, 
positive if you are NORTH of the equator.
LINE 3 - longitude in degrees, e.g. 108.16. Use negative numbers  if you are in the half of the world 
WEST of Greenwich.  
Example for Tokyo, Japan station at 35.65 N latitude and 139.72 E longitude:
Tokyo, Japan
35.65 
139.72
MSPLICE.EXE
A past 7.8 quake in Bolivia released an enormous amount of energy. At one users station, 6 EMON files 
were saved from this one great quake. Rather than dealing with these files one at a time, the MSPLICE 
program allows you to splice together two or more data files which, back-to-back, span a long event.   All 
sets of data are are combined into a new file spanning the entire event, although at a lower resolution.  
The new file contains 25000 samples like all EMON data files.
Hardware
Up to now weve talked only about the software side of running a seismic monitoring station. However it 
is important to have some familiarity with the hardware required to interface a PC to the outside world.  
The three pieces of hardware we will discuss are the PC clock, the analog-to-digital converter (ADC) 
card, and the signal amplifier/filter.
PC Clock
An accurate PC clock is a must for seismic data collection.  Scientists have agreed that all monitoring 
stations will use Coordinated Universal Time (UTC, formerly known as Greenwich Mean Time).  You 
should therefore keep your PC set to UTC time rather than local time.  In the U.S.A.,  a call to 1-900-410-
TIME will cost you 50 cents and will allow you to set your PC clock to the U.S. Naval Observatory Master 
Clock.  If you have a short-wave radio, the British Broadcasting Company (BBC) accurately marks the 
time on the hour. Also, several packages are on the market to continuously synchronize your PC clock to 
the WWV time signal which can be received in most of the continental US.Beware of daylight savings 
time - it may affect the number of hours between your time and UTC.
If you find that your PC clock does not maintain the correct time,  there may be add-in clock boards 
available which keep excellent time.  The factory clocks in some olderPCs may drift as much as a 
minute a week. You should try to keep your PC within one second of true UTC.  Shareware programs like 
RighTime and AccuSet, available on Compuserve and other bulletin board systems, can also help your 
PC stay on time.Larry Cochranes A/D card included an option for accurate timekeeping.
Analog-to-Digital Converter (ADC) Card
The job of an ADC card is to convert an analog signal from the outside world, usually a voltage, into a 
digital signal - a range of numbers that a computer can manipulate.  (This process is also known as 
digitizing).  Low voltage = small number, high voltage = big number.  (Sometimes the range is from a 
negative number to the same positive number.)  Each card has a different smallest and biggest 
number.  Here, as in most places, you get what you pay for.  An inexpensive ADC card might convert a 
range of input voltages (say, 0 to 5 volts) into numbers from zero to 255. Zero would represent the lowest 
voltage and 255 would represent the highest voltage.
A more sensitive (and expensive) ADC card might be able to divide the same 5-volt range into many 
more than just 255 separate steps. For seismographic work you should choose only an ADC card which 
can convert a voltage range into a range of at least 4096 different numbers. A card with this capability is 
called a 12-bit card, since its output has 12 bits (binary digits) of data, which gives 4096 possible 
combinations of ones and zeros.  13-bit, 14-bit and 16-bit cards are also available, but will probably 
only be worth the extra money in very quiet locations.
The ADC card usually fits into an expansion slot on the PC main circuit board. Since there may be 
several cards installed, all cards are designed to have different addresses and to respond only to 
commands directed to that address.  The EMON program uses this scheme to send commands to the 
ADC card.  So how do you tell EMON the address of your ADC card?
Addressing
Each add-on card in a PC is designed to respond to commands to a specific address. However, different 
manufacturers dont always know which addresses other manufacturers are using.  Most companies now 
put switches on their cards so that the user (thats you!) can choose another address for the card if the 
address set at the factory is already in use by another card in your PC. You will need the manual 
supplied with the ADC card to change the switches from their factory setting.  However, most of the time 
you can use the address set at the factory. You will find this in the documentation that came with the 
card.
ADC card designers are very creative. There are many different types of ADC cards on the market with 
many different features.  EMON currently supports several different types of cards which are listed in the 
EMON.OPT file which came with your copy of EMON.  For our use we can group them into the following 
categories:
  Single-address, single-channel
  Multi-address, multi-channel
  Single-address, multi-channel
Each section below includes an example of how you might set up the EMON.OPT file for that type of 
card.  Each example assumes you want to monitor more than one seismometer. If you have only one, 
just set the second and third seismometer addresses to zero and EMON will ignore them.  In EMON 
version 6.1 and higher, use the FirstSeismometerActive (etc.) options in the EMON.OPT file to control 
how many channels EMON will sample from. Starting in version 6.1, only these parametersand not the 
zero address controls the devices which are monitored.  This is because some cards can use three zero 
addresses and only change the channel being sampled.
Single-address, single-channel
Only the very cheapest and simplest cards are of this type.  One card can monitor only one device.  
Each seismometer you wished to monitor would therefore require a separate card and thus an entire 
expansion slot.  Here is an example of part of the OPT file for a single-address, single-channel card.

FirstSeismometerActive = Yes          Active and being sampled (EMON v6.1+)
FirstSeismometerOrientation = N       Orientation (N = North/South)
FirstSeismometerAddress = 340         Decimal Address of 1st seismometer
FirstSeismometerChannel = 0           Channel for 1st seismometer

SecondSeismometerActive = Yes         Active and being sampled
SecondSeismometerOrientation = E      Orientation (E = East/West)
SecondSeismometerAddress = 341        Decimal Address (0 if not installed)
SecondSeismometerChannel = 0          Channel for 2nd seismometer

ThirdSeismometerActive = Yes          Active and being sampled
ThirdSeismometerOrientation = Z       Orientation (Z = Vertical)
ThirdSeismometerAddress = 342         Decimal Address (0 if not installed)
ThirdSeismometerChannel = 0           Channel for 3rd seismometer


Single-address, multi-channel 
This is the most common type of card. Several different input channels (signals) can be monitored by 
this type of card while taking up only one expansion slot.  The OPT file for this type of card might look 
like this: 
FirstSeismometerActive = Yes          Active and being sampled (EMON v6.1+)
FirstSeismometerOrientation = N       Orientation (N = North/South)
FirstSeismometerAddress = 340         Decimal Address of 1st seismometer
FirstSeismometerChannel = 0           Channel for 1st seismometer

SecondSeismometerActive = Yes         Active and being sampled
SecondSeismometerOrientation = E      Orientation (E = East/West)
SecondSeismometerAddress = 340        Decimal Address (0 if not installed)
SecondSeismometerChannel = 1          Channel for 2nd seismometer

ThirdSeismometerActive = Yes          Active and being sampled
ThirdSeismometerOrientation = Z       Orientation (Z = Vertical)
ThirdSeismometerAddress = 340         Decimal Address (0 if not installed)
ThirdSeismometerChannel = 2           Channel for 3rd seismometer
Multi-address, multi-channel 
In this type of ADC, the same card responds to commands directed to any of several different addresses. 
One card can monitor several different channels, with each address corresponding to a different channel. 
The base address of the card monitors the first channel, the base address plus 1 reads the second 
channel, etc. The OPT file entries would be identical to those for the single-address, single channel 
card described above. However, commands to any of the three addresses would actually be processed 
by the same card instead of being processed by three different cards. 
Table 1 on page 20 describes the types of A/D cards supported by EMON.  If your card is not listed 
please contact me and I will try to add support if possible.
Signal Amplifier and Filter
ADC cards usually are able to sense voltages as low as 1 millivolt (1/1000 volt). However, the voltage 
output from a seismometer responding to the passage of an earthquake wave from a distant event might 
be only 1 microvolt (1/1,000,000 V). In this case no signal would be recorded.   For this reason the 
voltage output of the seismometer is usually amplified by a factor of from several hundred to several 
thousand before it is sent to the ADC card. In addition, noise from electrical equipment is usually filtered 
out before the signal is amplified. 
Plans for building your own signal amplifier / filter are available at the PSN web site.  There you will also 
find an excellent amplifier and filter card sold by Larry Cochrane.
Amplification level (gain)
If you use a higher amplification level (also called gain) you will be able to record more distant large 
events, and smaller local events. However if your local environment is noisy, turning up the gain will 
amplify local noise as well. This noise will usually be of two types: 60 cycle noise from home electrical 
devices, and low-frequency noise from traffic, wind, home appliances and (of course) children. Electronic 
filters can remove most 60 cycle noise. However, lower frequency noise can be difficult to distinguish 
from the seismic signals themselves. A general rule then is to turn the amplification level on your 
amplifier up until you begin to see too much noise in the signal (too much vertical jitter) or begin 
recording too many false alarms, and then turn it back down a bit. Now experiment with the 
EMON.OPT parameters NoiseRangeToIgnore and SampleCountToSaveFile to minimize the number 
of false alarms.  Now lets take a more detailed look at the programs. 
Software description
The purpose of a trigger algorithm is to detect earthquake activity while screening out false alarms. The 
algorithm I chose uses the concept of a noise zone around the normal output value of the A/D 
converter. You specify the width of this noise zone (in percentage of full range of the ADC card) in the 
NoiseRangeToIgnore parameter in EMON.OPT.  Signals outside (above or below) this noise zone are 
the important ones. The number of samples that fall above or below the noise zone are counted as the 
program runs. Periodically EMON checks to see if at least a certain number of samples (a number you 
choose via the OPT parameter SampleCountToSaveFile) has been observed both above and below 
this zone. 
Data collection
The EMON program performs the monitoring and collection of the seismic data. The program saves data 
to disk only when it appears that a quake has been detected. For this purpose it includes a trigger 
algorithm - a kind of decision-making process which you can control. 
Trigger Algorithm
The EMON trigger algorithm allows you to apply several different filters to your signal to insure you only 
save data from real quakes.  You define a noise zone which you can think of as a range above and 
below the normal output of your seismometer.  EMON counts samples above and below this noise zone 
and also counts the number of peaks above and below the noise zone.  When both of these numbers are 
above values you specify for a certain time period, then EMON assumes a quake has occurred and 
begins the process of accumulating enough samples to save a complete file.
 
A small amount of data from before the event started is also included.  Otherwise, the counters are reset 
to zero and monitoring continues.  If you set the width of this noise zone too narrow, many files with 
nothing but noise will be saved to disk and you will have to spend a lot of time going through them to 
determine if they contain anything of interest.  On the other hand, if you set the noise zone too wide, 
only the very largest earthquakes will be recorded, and you may only see one or two files per year! The 
proper settings for the trigger algorithm parameters are different for every location, and can only be 
determined by trial and error. They may change with the seasons too. If you live near the ocean, for 
example, winter storm waves hitting the shore might generate enough local seismic noise to force you to 
temporarily raise the value of NoiseRangeToIgnore.
EMON Options File
The EMON options file (default name: EMON.OPT) allows you to customize the EMON program for your 
setup and local seismic environment. You can use any text editor to modify the file  The parameters in 
the OPT file are described in more detail below.  The name of the option is given in bold characters, and 
a description follows.
Savefile = Yes / No
YES is for normal operation.  NO is for special installations where you never want to actually save a file, 
like in a museum installation.
PeakCountFilter = n
Minimum number of peaks (above or below noise zone) required before saving file.  Default is 25.
DisplayTimeCompression = n
Compresses display horizontally.  Higher numbers display only every nth sample, allowing display to run 
slower than sampling rate, leaving data on screen for longer time.
FirstSeismometerActive = Yes / No
SecondSeismometerActive = Yes / No
ThirdSeismometerActive = Yes / No

YES - device will be sampled and data saved. 
NO - device will not be sampled. Note: devices must be activated in order, from 1st to 3rd. Do not skip a 
device. 
FileNameDisplay = Short / Long
SHORT - Display only name of file being saved (not extension). 
LONG - Display entire name plus extension of the file being saved. To make room for the additional 
characters, only the hour of the time the file was saved is displayed. In the previous version of EMON, 
only the name of the quake data file was displayed on the screen but not its extension. This was because 
the extension was a constant, the location ID. In EMON V6 you can now put variable data (like a 
sequence number) in the file extension. If you choose to put variable data in the file extension, you 
should choose the LONG option to display the entire file name. If you choose the LONG option, only the 
hour of the time at which the file was saved is displayed. If you choose the SHORT option, both the hour 
and the minute of the time the file was saved are displayed. 
PromptOnQuit  = Yes / No
YES - Prompt before leaving EMON 
NO - Leave immediately without prompting Note: If a quake is in progress, you will always be given the 
opportunity to save the current data before exiting. 
BeepOnFileSave = Yes / No / Alarm / Immediate
NO - No beep 
YES - Beep once when a quake file is saved 
ALARM - Beep every 15 minutes until a key is pressed, once a file is saved 
IMMEDIATE - Same as ALARM but begin beeping immediately when a quake is detected, without 
waiting for a file to be saved. 
AlarmLevel = n
A number between 0 and 100. Each time a file is saved to disk, a relative strength value is calculated. 
This is a percentage of the range of the A/D card that the input signal reached during that event. 100 
means the A/D card reached its limit. If you only want EMON to beep or sound an alarm for larger 
quakes, set this value to a higher number. If you want EMON to beep or sound the alarm for all quakes 
saved to disk, set this value to zero. Note: AlarmLevel is activated only if BeepOnFileSave is set to YES 
or ALARM. If BeepOnFileSave is set to IMMEDIATE, *all* files will trigger the audible alarm and 
AlarmLevel will be ignored. 
FileFormat = Old / New
NEW - Generate data files in new format   Recommended.
OLD - Generate data files in old format. EMON V6.00 and higher has the capability to write quake data 
files in an improved format. With the new format files, more information about your ADC card can be 
kept in the file, which will allow better display and analysis of the data files. Also, the new quake file 
format has room for you to insert more information about the quake (like depth and USGS magnitude) in 
new reserved locations in the file for improved estimates of distance. To display the new-format data 
files, you will need QUAKEVU v6.00 or higher. If your version of QUAKEVU is older than this, you can 
tell EMON to go back to creating old-format data files by setting FileFormat to OLD. However it is 
recommended that you allow EMON to create the new format files and use QUAKEVU v6.00 or higher, 
or WinQuake v1.6 or higher. Either of these new display programs will still work fine on all your old 
format data files. If you dont specifically set the FileFormat parameter, it will default to NEW. However, 
an annoying Note screen will pop up every time you start EMON. To eliminate this screen, add a line 
setting FileFormat to NEW (or OLD) to your options file. 
ActivityLog = Yes / No
YES - Write a record to a trace file for significant events 
NO - No tracing The EMON activity log can help you determine what went wrong if there is a problem 
saving data files or figuring out which files correspond to which event. A one line entry with date and time 
is appended to the log file each time EMON is started or stopped, or a data file is saved to disk. 
ActivityLogFile = filename
If you specified YES to ActivityLog, enter the name of the file to use for the EMON activity log. The 
default value is EMON.LOG, and the default path is the current drive and directory. 
FirstSeismometerMagCorr = n
SecondSeismometerMagCorr = n
ThirdSeismometerMagCorr = n
The WinQuake program by Larry Cochrane displays EMON data files in a Windows environment. It has 
significant advantages over QUAKEVU in usability, and includes some additional function (like Fourier 
transforms) as well. WinQuake allows you to define a correlation factor for your seismometer which 
relates the peak value in a data file with the magnitude of the quake. Once you empirically determine 
this value you can enter it here and it will be stored in all data files saved for that device. (However, this 
is only done if you specify FileFormat = NEW). 
FileNamePattern = string
*=============================================================================*
*             File Name Pattern building blocks to choose from:               *
*                                                                             *
*   YY   = year                            Example:                           *
*   MM   = month                           Quake at 3:03 am on 2 May 94       *
*   DD   = day                             Vertical sensor, 1st quake of day  *
*   JJJ  = Julian date (001-366)                                              *
*   HH   = hour (00-23)                    Pattern below gives: File name     *
*   H    = hour (A-X)                      -------------------  ----------    *
*   TT   = minute (00-59)                  MM-DD-YY-O-S.III     050294Z1.TBJ  *
*   T    = two minute interval (A-Z,0-3)   (QK)+YY+MM+DD.II+S   QK940502.GCS  *
*   O    = Orientation (N, E or Z)         YY/MM/DD/O/S.III     940502Z1.RAC  *
*   S    = seq no. (A-Z,0-9)               YY-MM-DD-II.O-SS     940502RC.N01  *
*   SS   = seq no. (01-99)                YY-JJJ-H-M-O.III     9412232Z.MSS  *
*   SSS  = seq no. (001-999)                                                 *
*   II   = station ID (1st two chars)   * Filename is maximum 8 characters    *
*   III  = station ID (three chars)     * Extension is maximum 3 characters   *
*   (cc) = any character string in ()   * You must use O somewhere in the   *
*   .    = . (separates name from ext)     pattern if you have >1 seismometer *
*                                                                             *
*=============================================================================*
The FileNamePattern parameter allows you to choose how your data files are named. You assemble the 
pattern you like best from building blocks that represent items like the year, month, day, sequence 
number, time, location ID, etc. Separate the building blocks with either slash /, plus + or dash - 
characters. You can also place a character string in the file name by enclosing it in parentheses. Use the 
dot . to identify the start of the extension. Note: do not put separator characters around the dot.  For 
example, specifying a pattern of MM-DD-YY-O-S.III would result in the file name being built of 2 
characters each of month, day and year, one character for the orientation of the sensor (N, E or Z), one 
character of sequence (A-Z and 0-9), and a file extension of the station ID (three characters).
OperatingMode = Normal / Random / File
EMON can operate (obtain its data) in one of three ways, identified as Normal, Random and File. 
  Normal
This is the normal mode of operation in which data is read from the Analog to Digital Converter 
(ADC). The card must be installed and operational or unpredictable results may occur.
  Random
If random is specified, no ADC card is necessary to run the program. A random signal will be 
generated internally by the program and displayed on the screen as if it were real data. In 
random mode the trigger algorithm is overridden. Every set of 25000 samples generated is 
saved on disk as if an earthquake had occurred. You can use this mode to test the program and 
adjust other parameters. 
  File
If file is specified, data is read from a previously-recorded quake file. You will be prompted 
during EMON initialization for the name of an existing data file. This file will be loaded during 
initialization, and EMON will get its input, sample by sample, from that set of data. This 
capability allows you to test new trigger settings on old recordings. When trying a radically new 
trigger setting, you might want to be sure that an event which was seen and saved at the old 
settings would not be missed at the new settings. 
AnalogToDigitalConverterType = n
EMON supports A/D cards from several manufacturers and some home-made ones as well.  Table 1 on 
page 20 describes the supported A/D cards.
Table 1.  Supported A/D Cards
EMON 
ADC 
Type
Mfg and Model
Bits
Channels
Base 
Address 
(default)
Min 
voltag
e 
value
Null 
voltag
e 
value
Max 
voltag
e 
value
Comment
0
Homemade
12
1




Teds first A/D 
card base on 
RTD PD-100 
prototype board 
and B/B 
ADC674A
1
IBM Data 
Acquisition and 
Control Adapter
12
8
0
-2048
0
2047
Requires 
DACAT03.COM 
driver in 
CONFIG.SYS
2
Metrabyte DAS-4
8






3
Jan Frooms 
modified parallel 
port adapter
12
3




Uses COLLECT 
interface 
(special code 
linked with 
EMON)
4
Alpha Products 
A-Bus AN/146
12






5
PC-LAB 714 
Super Card
12

544



Input signal is 
echoed to D/A 
channel 1
6
Metrabyte DASH-
16
12






7
PC-LAB 711s
12






8
ACQUTEK PA-
CP12
12






9
Real Time 
Devices Inc. 
DR112
13






10
BSOFT ANA-201
12






11
Computer Boards 
Inc. CIO-
DAS08/Jr-AO
12






12
Larry Cochrane
12
8
544
-2048
0
2047
12 bit version of 
SDR card
12
Larry Cochrane
16 
8
544
-32767 
0
32768
16 bit version of 
SDR card
13
Computer Boards 
CIO-DAS08Jr/16-
AO
16
8
768
-32767 
0
32768



0
Homemade
1
IBM Data Acquisition and Control Adapter
2
Metrabyte DAS-4
3
Jan Frooms modified parallel port adapter
4
Alpha Products A-Bus AN/146
5
PC-LAB 714 Super Card
6
Metrabyte DASH-16
7
PC-LAB 711s
8
ACQUTEK PA-CP12
9
Real Time Devices Inc. DR112
10
BSOFT ANA-201
11
Computer Boards Inc. CIO-DAS08/Jr-AO
12
Larry Cochrane
12
Larry Cochrane
13
Computer Boards CIO-DAS08Jr/16-AO
Table 2
FirstSeismometerOrientation = N / E / Z
N	for a device whose axis is aligned in a North-South direction, 
E	for a device whose axis is aligned in an East-West direction, and 
Z	for a device which is sensitive to vertical motion. 
FirstSeismometerAddress = n
This is the decimal I/O address of the card in the PC containing the analog-to-digital converter chip. 
Usually the card manufacturer provides switches on the card with which the user can choose one of 
several different addresses. 
FirstSeismometerChannel = n
Some ADC cards have input connectors for several inputs. These separate inputs are called channels.  
Refer to your cards documentation for information about choosing the correct channel.
SecondSeismometerOrientation 
SecondSeismometerAddress
SecondSeismometerChannel
Same as for the first seismometer.
ThirdSeismometerOrientation
ThirdSeismometerAddress
ThirdSeismometerChannel
Same as for the first seismometer.
SeismometerToMonitor = N / E / Z
Acceptable values are N, E or Z.  Choose which device you wish to use for the on-screen real time 
display. You can change this from the keyboard while the program is running.
AdcValueAtMaxVolts = n
AdcValueAtZeroVolts = n
AdcValueAtMinVolts = n
These three parameters tell EMON the range of numbers your ADC card generates at (1) its highest 
acceptable input voltage, (2) at zero volts input, and (3) at its lowest acceptable input voltage. Some 
cards convert voltages to values from 0 to 4096, with 2048 corresponding to 0V. Other cards generate 
values from -2048 to 2047 with 0 corresponding to 0V. Still other cards give you a choice by having 
switches on the card that you can set. It really doesnt matter which kind of card you have. Just make 
sure you tell EMON the proper values for your card. 
NoiseRangeToIgnore = n
This parameter is a percentage of the total ADC card range above and below the value of 
AdcValueAtZeroVolts. Signals within this zone will not be counted toward the decision to save a quake 
file. For example if your ADC returned values from 0 to 4095 with a zero value of 2048, specifying 
NoiseRangeToIgnore = 10 would result in EMON ignoring any points within a range of 10% (10 * 4096 / 
100 = 409.6, rounded to 410) above or below 2048. So any data points within a range of (2048-410) to 
(2048+410) would be ignored, while data points outside this zone would contribute toward the decision to 
save a quake file. A typical value in a noisy environment might be 10-15. In a quiet area, 1-3 is possible. 
SampleCountToSaveFile = n
This is the number of samples outside the noise zone that must be observed before a quake file will be 
saved. This prevents lots of junk files being saved when only one or two points above and below the 
noise zone are observed. Typical value might be 50 or 100. 
SamplesPerDataPoint = n
Multiple ADC samples can be averaged to obtain one data point. This provides limited smoothing if you 
are in a noisy environment, but its biggest benefit is to give you a way to control how many samples are 
taken per second. EMON does not delay between obtaining samples, so the only way to slow down the 
sampling rate is to tell it to make each data point an average of several samples. The fastest sampling 
rate is achieved by setting this value to 1. If this is not fast enough you either need a faster PC, a faster 
ADC card or both. However, sampling at the maximum rate may have some of the following drawbacks 
(especially on a faster PC): 
  Each file may then contain only 5-10 minutes worth of data, so you will have many more files to deal 
with. 
  You may find that distant events span multiple files, which means you will have to use MSPLICE to 
combine the files later. Try to achieve a sampling rate of about 10-20 per second. On an XT-class 
machine you may have to tell EMON to average 5-8 samples for each data point to achieve this. If 
you are running EMON on a 286 or faster machine (AT-class) you may need to average as many as 
40-50 samples for each data point to achieve a final sampling rate of 10-20 per second. The actual 
sampling rate is displayed on the EMON screen. 
StationName = string
Specify up to 15 characters for your station name. Only single blanks are allowed in the name. This 
information is placed into each quake file as it is saved. 
StationID = string
Specify a three character ID identifying your station. This will be used as the file name extension (.xxx) 
on all files saved. 
RecordingLatitude = n.n
Enter the latitude of your station, with up to three decimal digits of accuracy (fewer is OK too). Use 
positive values if you are north of the Equator, negative values if you are south. If your map provides 
latitude only in degrees, minutes and seconds you will have to convert to degrees. For example, 16 
degrees 30 minutes North latitude would be entered as 16.5, since 30 minutes is one half of a degree. 
RecordingLongititude = n.n
Enter the longitude of your station, with up to three decimal digits of accuracy (fewer is OK too).  Use 
positive values if you are east of Greenwich, negative values if you are west. 
DisplayLines = n
Enter the number of lines of data to display on the screen if you wish a real-time display of data.  
Entering 0 disables the real-time display. Only odd numbers are acceptable. If you enter an even 
number, EMON rounds it up to the next higher odd number. 
DisplayCompression = n
Enter a number to use as a vertical compression factor for the EMON real-time display. The higher this 
number, the more compressed each line of the display will be. Generally a value of 10-25 works well. 
The number you will need to get a good display will depend on the gain of your amplifier and the range of 
voltages generated by your seismometer. 
SavePath = path
This is the DOS path that EMON will use to locate the disk and directory in which to save quake files. It 
can consist of just a drive letter (for example, C:) in which case the current directory for that disk is 
assumed, just a directory (in which case the named directory is assumed to be a sub-directory in the 
current directory on the current drive, or a fully qualified combination of drive and directory. The directory 
must exist. If it does not already exist at startup, EMON will issue a warning message and terminate. The 
following examples are all acceptable: 
SavePath	 	Meaning
C:			Use current directory on C drive
C:\			Use root directory on C drive
QUAKES		Use QUAKES (sub-)directory on current drive and directory
C:\QUAKES		Use QUAKES directory on C drive regardless of current dir
C:\QUAKES\		Same as C:\QUAKES
A:			Use current directory on A drive
B:\			Use root directory on B drive
The following examples are not acceptable since they are not valid DOS paths: 
A
C::
C\
TemporaryBufferSize = n
If you look into the Appendix in which the program logic is described, youll see how the Temporary 
Buffers A and B are used. Unless you care how often EMON examines the counters related to quake 
signals, leave this at 4000. Acceptable values are 1000-8000. 
UserCommand1 = string
UserCommand2 = string
Here you specify two commands which can be executed against the currently marked file on the screen. 
Data collection is suspended during the execution of a UserCommand. Place the / character wherever 
you would like the name of the file to be substituted. For example, if the on-screen file marker were 
pointing at a file named 93066ACN.TBJ, the following substitutions would be made: 
UserCommand		Actual command executed
QUAKEVU /		QUAKEVU 93066ACN.TBJ
QUAKEVU / /Q		QUAKEVU 93066ACN.TBJ /Q
COPY / A:		COPY 93066ACN.TBJ A:
MYBAT /		MYBAT 93066ACN.TBJ
In the first example above, the QUAKEVU program will be invoked to view the file. Your PC must have 
enough conventional memory (i.e. memory below 640K) to allow several large programs to be active at 
one time, or you may get an out of memory message. Memory maker utilities which move portions of 
DOS above the 640K line may help you, but I have not tested them. Examples might be QEMM and 
MemMaker. In the second example above, QUAKEVU is invoked with the /Q or QuickDisplay option. 
This tells QUAKEVU to display only every 10th point in the file. On slower PCs this can give you a quick 
idea of whether the file contains anything interesting. In the third example above, the file is to be copied 
to the A: drive. In the last example above, the user has written a BAT file containing multiple DOS 
commands, and passes it the name of the marked file as its first parameter. 
ADCOffset = n
This is a constant value to be added to each sample taken. Negative numbers are acceptable also. This 
can be handy if your amplifier does not have a zero or level adjustment and you want to center the 
signal on the screen. 
ADCProgrammableGain = n
Certain ADC cards contain onboard amplifiers whose gain is controllable by the software. The Real Time 
Devices DR110 is one example. This card supports gain of 1, 10 and 100. This value is ignored if the 
ADC card you are using does not support programmable gain. 
EMON Main Screen
The EMON main screen is shown in the example below (repeated from Figure 1 on page 7).

 
Header area
The first line shows the current date (in standard and Julian form) and time, the version of EMON you 
are running, and the address, channel and orientation of the seismometer currently being monitored. 
The second line shows your location and station id, latitude and longitude of your station, and which of 
the three internal buffers (A, B or Q) is being filled. The program alternates between filling the A 
and B buffers until a quake has been detected. At this time it switches to filling the Q buffer. 
The third line displays the sampling rate in samples per second. This line (along with the time of day) is 
updated only every few seconds to avoid slowing down the sampling rate. 
Seismometer output display area
This area contains a trace of the output of the seismometer. You can specify how many lines of trace it is 
to show in the OPT file along with the vertical scale. The large tick mark on the left edge of the display 
box shows where the line sould be when there is no quake activity. The small tick marks above and 
below this represent the upper and lower boundaries of the noise zone. If you change the size of the 
noise zone with the F4 key (or editing the OPT file), these markers will be adjusted to the new size. 
Filename display area
This area shows the files that have been saved since program was started. For each file the file name, 
date and time are shown. There is also a number between 1 and 100 which describes the relative 
intensity of the quake record contained in the file. (A value of 100 simply means that the ADC card 
recorded a signal which reached its maximum range. Lower numbers signify correspondingly lower peak 
signals.) This is to give you a rough idea of the size of the event in the file. 
A small marker is always in front of one of the file names. You can move this marker with the up and 
down arrow keys. The UserCommand keys always operate on the file with the marker in front of it. 
All of the actions you can take from the keyboard are described below. 
EMON Keyboard Actions
Up Arrow / Down Arrow
Use the up and down arrow keys to select the file you wish to operate on with the UserCommand keys. 
See the description of the EMON.OPT UserCommand1 and UserCommand2 parameters for further 
information. 
PgUp / PgDn
Use the PgUp and PgDn keys to change the vertical display compression for this invocation of EMON.  
This does not change the value permanently - you must edit the OPT file to do this.
F1 - Erase Current File
Erases the file currently being pointed to on the screen. You would generally use this key only after first 
examining the file with QUAKEVU, and copying all or part of it to another disk. Copy the file first if you 
want to keep it!
F2 - Turn On/Off Data Trace
The data trace shows the digitized value of each sample taken. It is useful for debugging the A/D 
converter, or understanding noise levels. If trace is off, pressing this key turns it on, and vice versa. 
F3 - A/D Conversions Per Sample
This value is the number of separate analog-to-digital samples to average to get one data point. In noisy 
environments, some control over noise can be obtained by averaging several samples, but at the cost of 
slowing down the sampling rate. On the other hand, if you wish to slow down the sampling rate, just 
specify a number larger than 1 for this parameter. Initial value specified in EMON.OPT. 
F4 - Noise Zone Width
Percentage above and below the zero volts value of the A/D converter that defines the noise zone. 
Only samples outside this noise zone will count toward the decision to save data to disk. 
F5 - DOS command
Single DOS commands can be entered, or you can just press ENTER to be placed at the DOS prompt. 
Typing EXIT returns you to EMON. 
F6 - Save path: 
Drive and path to be used when saving data files. A hard drive or 1.2Mb floppy disk are recommended. It 
is possible to save files to a 5  floppy, but only 7 files fit on a standard 360K disk. If the disk fills up, 
you will be prompted to insert a disk with more available space. Sampling will not resume until the data 
file just obtained has been successfully saved to disk. 
F7 - Display Next Device
When more than one seismometer is being monitored, pressing this key will rotate the display among the 
devices. 
F8 - <UserCommand1> <File>
F9 - <UserCommand2> <File>
This key executes a command against the listed file. The command is specified in the UserCommand 
parameters in EMON.OPT. The string <File> is replaced by the name of the file currently marked with 
the > character on the screen. 
F10 - Safe Quit
Return to DOS. If a quake is in progress, you will be asked if it is acceptable to discard the data currently 
being collected. If you reply n, the current data will be saved in a short data file before exiting. 
Displaying quake files with QUAKEVU
The QUAKEVU program displays the quake files captured by EMON. It uses the Color Graphics Adapter 
(CGA) in high resolution (640x200) mode. This is equivalent to SCREEN 2 in IBM BASIC. 
Note: If you are running QUAKEVU under DOS version 3.1 or higher, you must issue the DOS command 
GRAPHICS or GRAFTABL once each time you power-on or re-boot the machine. If you do not 
execute this command before running QUAKEVU, the screen will look very strange with lots of fuzzy 
square characters in the menus. DOS began to require this in version 3 as part of their support for 
languages other than English. If you find you have this problem, the simplest solution would be to add a 
line with the proper command to your PCs AUTOEXEC.BAT file. QUAKEVU will remind you when it 
starts if you need to run the GRAFTABL command but have not done so. 
QUAKEVU features
Functions supported by QUAKEVU are: 
  Multiple files from the same event (from the same or different recording stations) can be displayed 
simultaneously 
  Mouse support with pull-down menus 
  Online help 
  Variable scale, on both X (Time) and Y (Amplitude) axes 
  Interactive P- and S-wave identification via graphic pointers 
  Automatic epicenter distance and travel time calculations as the P and S pointers are moved 
  Expanded view (zoom) on a subset of the data in a file 
  Ability to create a new data file containing only a subset of data in the original file (and a comment if 
you wish) 
  Connect data points with lines, or plot as points only 
Mouse Interface to QUAKEVU
If your PC has a mouse, you can use it to do all of the above functions via pop-down menus. Several 
pop-down menu items list a keyboard function key (like F1 or F2) that does the same thing as the menu 
bar. You can use either one. 
Arrow keys while Zoomed
If you are zoomed in on a small section of a file, you can use the left and right keyboard arrow keys to 
move left and right through the file. Each keypress moves one screen left or right. 
Further help is available in the program. Enter QUAKEVU ? for details or select HELP while running the 
program. 
Printing the screen from QUAKEVU
Use the Shift-PRTSC key to print the screen if you want to save a hard copy. However, the DOS Print 
Screen function prints only in character mode and QUAKEVU runs in graphics mode. Luckily, DOS 
supplies a command called GRAPHICS which takes care of this problem. Execute the GRAPHICS 
command once each time you power-on your PC. Once you run this command, the Print Screen key will 
print your QUAKEVU screens properly. As with the GRAFTABL command the easiest solution may be to 
add the GRAPHICS command to the AUTOEXEC.BAT file of the PC where you usually run QUAKEVU. 
QUAKEVU example
We will use QUAKEVU to examine a recording of a recent earthquake recorded in San Jose, California.  
We issue QUAKEVU with the filename 971204AE.FOX, and we see the following screen:
 
We can now see for the first time the actual earthquake record.  You can see at the left the baseline 
signal, then the arrival of the P waves and later the arrival of the S waves.  (The L waves are off the 
recording and were recorded in the next file).  
Now lets tell QUAKEVU where we think the P and S wave arrivals are.  We click on Distance (or press 
F2) which brings up the next screen.  
 

We move the P pointer to the arrival of the first P wave (using the left and right arrow keys or the 
mouse).  Notice that the time of arrival of the P wave is updated as we move the pointer.  
 
QUAKEVU cannot compute the distance to the quake until we provide it with an estimate of when the S 
wave arrives so lets do that.  Select Distance (or press F2) again and the S pointer appears.  Move it to 
the arrival of the S wave.

Now that the P and S wave arrival times are both identified, QUAKEVU can compute the estimated 
distance from the recording station to the quake location.  Notice that as you move the P or S pointers, 
the estimate of distance changes.
You can fine tune the placements of the P and S waves by selecting Distance again (or pressing F2).

Saving a subset of the original file
You can use  File/Save (F8) to save a smaller size file containing only the portion of the original file 
currently being displayed.  Select File/Save (or press F8) and you will be prompted to specify up to 7 
characters of a file name. (The 8th character and the file extension are copied from the original file 
name).You can enter names like the following:
a:* 		Saves file on a: drive with same name as large file 
b:myquake 	Saves file as b:myquake.lll (where lll is station ID) 
\quakes\* 	Saves file in QUAKES directory with same name  
myquake 	Saves file in current drive/directory as myquake.lll 
* 		Replaces input file (large) with subset file (small)
Printing the screen contents
You might want to print what is on the screen to have a hard copy for your files. To print the screen 
contents, you must have issued the DOS command GRAPHICS in the DOS session before entering 
QUAKEVU. This command tells DOS that all future PrintScreen key presses should assume the screen 
is in graphics mode (like QUAKEVU uses), rather than just as text. If you did not issue the GRAPHICS 
command before invoking QUAKEVU, you can do so now via the DOS Command key. Then just press 
the Shift-PrtSc key and DOS will print your screen image on the printer. Note - some laser printers will 
not properly print this type of screen. You may have to use an old-fashioned dot-matrix printer or some 
other type of screen-capture program. 
Data files
Quake data files contain exactly 25,000 data points when first saved to disk by EMON. As mentioned in 
the QUAKEVU example, you can create a smaller file containing just the interesting portions of a 
recording. First, load the file into QUAKEVU. Next, use the Zoom function, and perhaps the right and left 
arrow keys (or CTRL-arrow keys), to show just the interesting part of the file on the screen. Finally, use 
the SAVE function to save just the part of the file showing on the screen. It is a good idea to do this if you 
are uploading the file to a BBS - it can save telephone charges if you upload smaller files, and saves 
other people money when they download your files to their PCs. During the save process you will be 
asked if you want to add descriptive information which you may have determined through other sources 
to reserved spaces in the file. These might be things like the true origin time, or a comment. For files 
saved by EMON V6 or later you will be asked if you want to add additional information like depth, latitude 
and longitude. 
Bibliography
General Background
Bolt, B. A.. Earthquakes. W. H. Freeman, 1988. 
Gere, J. M. and H. C. Shah. Terra Non Firma, Understanding and Preparing for Earthquakes. W. H. 
Freeman, 1984. 
Earthquakes & Volcanoes, published bimonthly by the U. S. Geological Survey. Available from: Supt. 
of Documents, U. S. Govt Printing Office, Washington, DC 20402. 
Seismic Monitoring Station Practices
World Data Center A for Solid Earth Geophysics, September, 1979. Manual of Seismological 
Observatory Practice, Report SE-20. Available from: United States Dept. of Commerce, National 
Oceanographic and Atmospheric Administration, National Geophysical Data Center, 325 Broadway, 
Boulder, Co. 80303 
Home Seismometer Construction and Design
Various older Scientific American Amateur Scientist columns: June, 1953, July, 1957, May, 1961, and 
August, 1970. 
The Amateur Scientist: A sensitive mercury tiltmeter that serves as a seismometer, Scientific 
American, November, 1973, pp. 124-129 
The Amateur Scientist: Electronic stratagems are the key to making a sensitive seismometer, Scientific 
American, September, 1975, pp. 182-187 
The Amateur Scientist: How to build a simple seismograph to record earthquake waves at home. 
Amateur Scientist column, Scientific American, July, 1979, pp. 152-161 (Plus a correction to the 
amplifier schematic in the Amateur Scientist column, August, 1979) 
Earthquake Interpretation
Simon, Ruth L. Earthquake Interpretations, A Manual For Reading Seismograms. Los Altos, Ca., William 
Kaufman, Inc., 1981. 
Jeffreys, H. and K. E. Bullen. Seismological Tables. Smith & Ritchie Ltd., Edinburgh, 1967. 
Personal Computer Data Acquisition
Webster, E., 1986. How To Use Your BBC Computer As a Cheap Storage Oscilloscope. Phys. Educ. 21, 
pp. 119-122 
Ciarcia, S. A., Computers on the Brain: Clever signal amplifiers, noise rejection and A/D conversion are 
all part of the HAL EEG, Byte, June, 1988. 
Seismic Software Design
Allen, R., 1982. Automated Phase Pickers: Their Present Use and Future Prospects. Bull. Seis. Soc. Am. 
72(6), pp.S225-S242 
Goforth, T. and E. Herrin, 1981. An Automatic Seismic Signal Detection Algorithm Based On The Walsh 
Transform. Bull. Seis. Soc. Am. 71(4), pp.1351-1360 
Seismometers in the Classroom
Barker, G. A Working Seismograph For The Classroom. Michigan Earth Scientist, Michigan Earth 
Science Teachers Association, September, 1983. 
Barker, G. Calculating the Size and Properties of the Earths Core. Michigan Earth Scientist, Michigan 
Earth Science Teachers Association, June, 1984. 
Appendix 1 - EMON Program Logic
When analyzing seismic recordings it is helpful to know what the local noise level looked like before the 
earthquake arrived. To insure that some pre-event data is available, two temporary data buffers, called A 
and B, are defined. Each holds 4000 samples (depending on the setting of the value 
TemporaryBufferSize), which is usually about 5-10 minutes worth of data, but this changes with the 
sampling rate. EMON fills each of them in turn. When each is full, a check is made to see if the trigger 
algorithm that monitors each buffer as it fills has detected enough earthquake-like signals in the data. 
The detection thresholds are defined by the user. If an event has been detected, the program then 
switches to filling a larger buffer (called the Q buffer) which holds about 20-30 minutes worth of 
additional data. When the large buffer is filled, the two temporary buffers are moved into the beginning of 
the Q buffer in the proper order. (Room was left for them when the Q buffer samping began). In this 
way the trace will always include a few minutes of data prior to the quake, plus as much of the actual 
quake data as will fit into the large data buffer. When the large buffer is full and the small buffers have 
been moved into their proper positions, the entire data array is saved to disk. Then monitoring resumes 
into the A and B buffers again. 

                                             Integer array of size 25100

          +-------+ +--------+                    +----------+
          |       | |        |                    | Control  |  Header
          V       | |        V                    | info.    |  100 integers
    +----------+  | |   +----------+              +----------+
    | Small    |  | |   |  Small   |              | Reserved |
    | buffer   |  \ /   |  buffer  |              | space    |
    |   A      |   X    |    B     |              | for      |  4000 integers
    |          |  / \   |          |              | small b. |  (or other
    |          |  | |   |          |              |   #1     |   value
    +----+-----+  | |   +-----+----+              +----------+   spec. by
         |  no    | |     no  |                   | Reserved |   user)
         | quake->| | <-quake |                   | space    |
         ?--------+ +---------?                   | for      |  4000 integers
         |                    |                   | small b. |  (or same
    quake|                    |quake              |   #2     |   value as
         |                    | continue sampling +----------+   buff #1)
         +--------------------+-----------------> |          |
                                                  |          |
                                                  | Large    |
                                                  | buffer   |  17000 integers
                                                  | ( "Q"    |   (if small
                                                  |  buffer) |    buffer size
                                                  |          |    is 4000)
                                                  +----------+

                             Total file size: 25100 integers (50200 bytes)


Appendix 2 - EMON Seismic Data File Internal Format
The EMON seismic data files are saved in BASIC BSAVE format.  The BASIC BSAVE statement creates 
an unencoded, binary file, which is an exact image of memory contents. Seven bytes of control 
information are written at the beginning of the file, and these bytes are followed by the data bytes copied 
from memory.  The file length shown in the DOS directory entry will be the BSAVE-specified length plus 
7, rounded up to a multiple of the BASIC buffer size. EMON files 50,200 bytes in size as written by 
EMON. This is based on each file being a copy of an array of size 25,100 where each element of the 
array requires two bytes of storage.
The EMON seismic data files are saved in BASIC BSAVE format.  The BASIC BSAVE statement creates 
an unencoded, binary file, which is an exact image of memory contents.  Seven bytes of control 
information are
written at the beginning of the file, and these bytes are followed by the data bytes copied from memory.  
The file length shown in the DOS directory entry will be the BSAVE-specified length plus 7, rounded up 
to a multiple of the BASIC buffer size.  EMON files 50,200 bytes in size as written by EMON.  This is 
based on each file being a copy of an array of size 25,100 where each element of the array requires two 
bytes of storage.
Offset	 Length	 Contents
  0    	  1 	 x'FD' (Constant BSAVE file format identifier)
  1   	  2  	BASIC DS segment value at BSAVE execution time
  3   	  2    	Offset in the DS segment specified in the BSAVE statement
  5   	  2   	 Data length specifed in the BSAVE statement
  7   	  *   	 Memory image data
The segment value, offset, length and data values are all stored in Intel(tm) low-high-order format.
The BASIC BLOAD statement is used to load the file containing the array into memory. To load the array 
into memory, the following BASIC statements could be used:

DIM ARRAY%(25100)    'Define space for array.  Must be of type INTEGER
REM   LOAD DATA INTO STORAGE STARTING AT FIRST ELEMENT OF ARRAY%
DEF SEG = VARSEG(ARRAY%(0))     'This stmt required for MS QuickBASIC only
BLOAD "d:\path\filename.ext",VARPTR(ARRAY%(0))
DEF SEG                         'This stmt required for MS QuickBASIC only
PRINT "EMON data file - first 16 elements in header"
FOR I = 0 TO 15
   PRINT "Header entry number ";i;" is ";array%(i)
   NEXT I
PRINT "EMON data file - first 5 data points"
FOR I = 100 TO 104
   PRINT "Data point number ";i;" is ";array%(i)
   NEXT I

If a BLOAD statement is executed with an offset term, then that offset value and the BASIC DS segment 
value in effect at BLOAD execution time will be used to place the loaded data; if a BLOAD statement is 
executed without an offset term, then the stored segment and offset values will be used.  In both cases, 
the stored length value  determines the amount of data loaded.  The memory image data portion of the 
file is described  below.  These 2-byte integer fields are also stored in Intel low-high-order format.  
Offsets as listed should be used as shown to index into the array after it has been BLOAD'ed into 
memory, i.e. ARRAY%(1) contains the year of the start of data collection. This assumes you have not 
changed the BASIC default array origin of zero.
The file format is shown below:
 
REM *************************************************************************
REM *        OFFSET       NAME     CONTENTS                                 *
REM *                                                                       *
REM *           0         Format   Flag describing format of data           *
REM *                              A flag value of 2 means that the         *
REM *                              following file format is being used      *
REM *                              A flag value of 3 means COMMENT field    *
REM *                              starts 30 positions past where it used   *
REM *                              to (packed two per offset).  Initial     *
REM *                              30 positions now have more info about    *
REM *                              data collection equipment, and room to   *
REM *                              add info later (via QUAKEVU, WinQuake,   *
REM *                              etc.) about actual magnitude, location,  *
REM *                              depth etc.)
REM *                              per position in first 30 of original 60. *
REM *           1         SYEAR    Year of start of data collection         *
REM *           2         SMON     Start month of data collection           *
REM *           3         SDAY     Day of start of data collection          *
REM *           4         SHOUR    Hour of start of data collection         *
REM *           5         SMIN     Minute of start of data collection       *
REM *           6         SSEC     Second of start of data collection       *
REM *           7         STENTH   Tenths of second at start                *
REM *           8         FHOUR    Hour of finish of data collection        *
REM *           9         FMIN     Minute of finish of data collection      *
REM *          10         FSEC     Second of finish of data collection      *
REM *          11         FTENTH   Tenths of seconds at finish              *
REM *          12         COUNT    Count of valid elements in file          *
REM *                              including the 100-byte header            *
REM *          13         BASE     ADC output value for zero V input        *
REM *          14         MIN      Min. sampled value in this file          *
REM *          15         MAX      Max. sampled value in this file          *
REM *          16         ORIENTATION  N=N/S   E=E/W   Z=Vertical           *
REM *
REM * The next 4 values are dependent on the location of the station, and
REM * are supplied in the EMON.OPT file.
REM *
REM *          17         LATINT   Station latitude N of equator (neg for S)*
REM *                              Integer portion only
REM *          18         LATDEC   Decimal portion of latitude multiplied by
REM *                              1000 and rounded to nearest integer
REM *                              Also negative if South Latitude
REM *          19         LONGINT  Longitude E of Greenwich (neg. for W)    *
REM *                              Integer portion only
REM *          20         LONGDEC  Decimal portion of longitude multiplied by
REM *                              1000 and rounded to nearest integer
REM *                              Also negative if West Longitude
REM *          21         N/A      Nat. Earthquake Info. Center calculated
REM *                              origin time of quake.  This value is
REM *                              set to -1 by this program, modified by the
REM *                              user via the COMMENT program later after
REM *                              checking with the NEIC
REM *          22         N/A      NEIC minute of quake origin
REM *          23         N/A      NEIC second of quake origin
REM *          24         N/A      NEIC tenths of second of origin
REM *          25-39      LOCATION Name of recording location (15 chars)
REM *                              from EMON.OPT.
REM *
REM *2 If FORMAT = 2 THEN the following is valid
REM *2         40-99      COMMENT  Description of quake.  Added to quake file
REM *2                             with the COMMENT program at a later time.
REM *2 END FORMAT = 2 description.
REM *
REM *3 If FORMAT = 3 THEN the following is valid.
REM *3
REM *3     EMON will fill in the next section based on EMON.OPT input values
REM *3     or values in effect at the time of saving data file.
REM *3
REM *3         40         ADCTYPE  Type of A/D converter.  See EMON.OPT file.
REM *3         41         ADCNULL  Value returned by A/D at zero volts input.
REM *3         42         ADCMIN   Value returned by A/D at min  volts input.
REM *3         43         ADCMAX   Value returned by A/D at max  volts input.
REM *3         44         NUMCONV  Number of A/D conversions averaged per 
samp.
REM *3                             (from value in effect at end of interval)
REM *3         45                  Integer portion of MagCorr
REM *3         46                  Decimal portion of MagCorr * 10000
REM *3         47-49               Reserved for additional EMON data
REM *3
REM *3     QUAKEVU, COMMENT or WinQuake will fill in the next section:
REM *3
REM *3         50-51               Rsvd for 4 packed characters describing
REM *3                             method USGS used to calc magnitude (ML, 
etc.)
REM *3         52                  Rsvd for USGS Magnitude value * 10 (6.6 = 
66)
REM *3         53                  Rsvd for USGS Depth (in kilometers * 10)
REM *3         54                  Rsvd for integer portion of quake latitude
REM *3         55                  Rsvd for 1000 * decimal portion of quake 
lat
REM *3         56                  Rsvd for integer portion of quake longitude
REM *3         57                  Rsvd for 1000 * decimal portion of quake 
long
REM *3         58-69               Reserved for additional information
REM *3
REM *3         70-99      COMMENT  Description of quake.  Added to quake file
REM *3                             with another program at a later time.
REM *3                             Characters are packed two per two-byte-
REM *3                             integer value, padded with blanks.
REM *3 End FORMAT = 3 section.
REM *
REM *          100-25099           Two-byte-integer digitized seismometer   *
REM *                              output values.                           *
REM *************************************************************************
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