The Amateur Seismology Package User's Manual Rev 1.0.0 (March 31, 1991) Copyright (c) 1991 Robert K. Samuelson. All rights reserved. Dept. 256 4215 Winnetka Ave. N. New Hope, MN 55428 USA Table of Contents 1.0 Introduction . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Copyright Notices . . . . . . . . . . . . . . . . . 3 1.2 Disclaimer . . . . . . . . . . . . . . . . . . . . 4 1.3 Distribution . . . . . . . . . . . . . . . . . . . 4 2.0 User Support . . . . . . . . . . . . . . . . . . . . . . 4 3.0 Bibliography . . . . . . . . . . . . . . . . . . . . . . 5 4.0 SEISGRAPH . . . . . . . . . . . . . . . . . . . . . . . 8 4.1 Overview . . . . . . . . . . . . . . . . . . . . . 8 4.2 Installation . . . . . . . . . . . . . . . . . . . 8 4.3 Guided Tour . . . . . . . . . . . . . . . . . . . . 9 4.4 Features . . . . . . . . . . . . . . . . . . . . . 12 4.4.1 Invoking SEISGRAPH . . . . . . . . . . . 12 4.4.2 Reading Data Files . . . . . . . . . . . 12 4.4.3 Adjusting X Limits . . . . . . . . . . . 12 4.4.4 Adjusting Y Limits . . . . . . . . . . . 13 4.4.5 Autorange . . . . . . . . . . . . . . . . 13 4.4.6 Guide Window . . . . . . . . . . . . . . 14 4.4.7 Data Window . . . . . . . . . . . . . . . 14 4.4.8 Printing . . . . . . . . . . . . . . . . 14 4.4.9 Setup String . . . . . . . . . . . . . . 15 4.4.9.1 b (Binary File) . . . . . . . . . . 15 4.4.9.2 e (Eight Bit File) . . . . . . . . . 15 4.4.9.3 x (Skip Bytes) . . . . . . . . . . . 16 4.4.9.4 c (Color) . . . . . . . . . . . . . 16 4.4.9.5 a (Autorange) . . . . . . . . . . . 17 4.4.9.6 s (Samples Per Second) . . . . . . . 17 4.4.9.7 b (Bin Size) . . . . . . . . . . . . 17 4.4.9.8 p (Printer Port) . . . . . . . . . . 17 4.4.9.9 d (Printer Driver) and r (Resolution) . . . . . . . . . . . . 18 4.5 Data File Format . . . . . . . . . . . . . . . . . 19 4.6 Problems and Solutions . . . . . . . . . . . . . . 19 5.0 How Data Files Are Created . . . . . . . . . . . . . . . 21 6.0 The Future . . . . . . . . . . . . . . . . . . . . . . . 22 The Amateur Seismology Package User's Manual 2 1.0 Introduction The Amateur Seismology Package is a collection of programs, data files, and documentation which allows users of IBM (*1) compatible personal computers to load seismic data files and print seismograms. Seismograms are graphs of the motion of the Earth's surface at a given location due to the passing waves caused by a distant earthquakes and can be used to determine, among other things, the distance between the earthquake and the recording station's location. The Amateur Seismology Package is intended for use by 'amateur scientists' and students who are interested in the Earth sciences in general and seismology in particular. The package will allow users to study seismograms of recent earthquakes using data files distributed by the author. The data files are produced by the author's seismometer and recording system. Data files for notable events will be distributed as quickly as practical. Data files which are contaminated with noise or contain little of interest will probably not be distributed unless requested by a user who has also recorded the event. ALL DATES AND TIMES ASSOCIATED WITH SEISMIC DATA WILL BE IN COORDINATED UNIVERSAL TIME (UTC), ALSO KNOWN AS GREENWICH MEAN TIME (GMT) OR 'ZULU' (Z). Rather than explain the science of seismology and the practices of seismometry here, the reader is directed to the Bibliography. These sources will provide the information needed to gain a qualitative understanding of seismology and the techniques of seismometry. Some sources describe the construction of seismometers and recording systems which can be constructed by electronic hobbyists. *1 IBM is a trademark of International Business Machines Corporation. 1.1 Copyright Notices Elements of the Amateur Seismology Package (also referred to as 'the package') are identified by the phrase 'part of the Amateur Seismology Package.' Those elements which are copyrighted contain a copyright notice. This notice appears near the beginning of documents, on the opening screen of programs, and is encoded in ASCII near the beginning of data files. The phrase 'all rights reserved' means a person or organization other than the author may copy and distribute elements of the package only under those conditions defined in the 'Distribution' portion of this manual. In particular, no element of the package may be distributed unless accompanied by this user's manual. The Amateur Seismology Package User's Manual 3 1.2 Disclaimer The author hereby disclaims all warranties relating to the Amateur Seismology Package. All elements of the package are provided 'as is' and are not guaranteed to be suitable for any particular purpose. 1.3 Distribution The Amateur Seismology Package may be duplicated and distributed by persons or organizations other than the author subject to the following conditions: Elements may be duplicated for backup purposes as desired. Modified elements may not be distributed. Elements may be distributed as long as no fee is charged other than a nominal fee to cover the cost of the media used. If distributed via a bulletin board system (BBS), no additional charge beyond normal connect time or access fees may be made. Any element distributed must be accompanied by The Amateur Seismology Package User's Manual. 2.0 User Support This package depends upon user support for its continued existence. User support will enable improvements to the programs and to the availability and quality of the data files. Users can support this package by sending an annual support fee and/or distributing the package subject to the above limitations. The annual support fee for this package is $12 (US funds, please do not send cash). This amounts to a dollar a month and is much less than users will probably spend on telecommunication charges to download the data files. Users who send the annual support fee will be considered 'supporting users'. Supporting users will receive a confirmation letter and will be added to a mailing list (the mailing list will NOT be made available to anyone, so don't worry about receiving more junk mail). The mailing list will be used to inform supporting users of package improvements and other items of interest. (Minnesota residents please note: Since this support fee would probably be considered taxable and since the author is not currently set up to handle state sales tax, do not send the support fee. Instead, simply send a letter and you will be considered a supporting user. The number of Minnesota users will probably be too small to justify the trouble associated with processing sales tax, so the author will swallow the loss.) This package is new and will probably go through many changes in The Amateur Seismology Package User's Manual 4 the near future. Feel free to use it without sending in the support fee until you are satisfied with its performance. The author will gladly answer questions from all users, supporting or not, for the rest of 1991. The author is currently using PKZIP(*1) and PKUNZIP for file compression. These utilities are available on CompuServe (*2) via the PCVENC forum. On CompuServe, 'go pcvenc', enter the PKWARE library and download the self-extracting file PKZ110.EXE. Remember that the PKWARE packages also depend upon user support. The support address is contained in the copyright notice. Support can also be obtained by contacting the author via CompuServe electronic mail (address 70531,3012). At the present time, the primary location for this package and the activities associated with it will be the Geology section of the Science forum on CompuServe, with new uploads going into the 'new uploads' library of this forum. To reach the Science forum, log on to CompuServe and enter 'go science.' Note that there is presently no telephone support for this package. Please use electronic mail when possible. If users try to find the author's telephone number via directory assistance, they may reach someone who is irate and uncooperative. *1 PKZIP and PKUNZIP are trademarks of PKWARE, Inc. *2 CompuServe is a registered mark of CompuServe, Inc. 3.0 Bibliography These sources will help the reader gain an understanding of some aspects of the sciences of seismology and seismometry. The local library or an encyclopedia is the best place to start. Users finding a useful source of information are encouraged to contact the author so this bibliography can be expanded. Bolt, B. A. 1980. Earthquakes and Volcanoes. W. H. Freeman and Company, San Francisco. ISBN 0-7167-1164-8. This book is a collection of articles which appeared in Scientific American. Eiby, G. A. 1980. Earthquakes. Van Nostrand Reinhold Company, New York. ISBN 0-442-25191-2. This book provides an excellent introduction to the study of earthquakes and seismology. Jeffreys, H. and Bullen, K.E. 1967. Seismological Tables. This book contains the 'JB' tables used to determine the distance between a seismometer and an earthquake based upon the difference in arrival times of the different types of waves. It is probably out of print. If anyone does find a source for this book or the JB tables, please notify the author. Kalmbach Publishing Co. Earth Magazine. The Amateur Seismology Package User's Manual 5 This magazine is a new spinoff from Astronomy Magazine. It focuses on the Earth sciences. No articles on seismology as yet, but it appears to be a good source of information for the Earth science student. Kalmbach Publishing Co., 21027 Crossroads Circle, P.O. Box 1612, Waukesha, WI 53187. Subscription inquiries (800) 446-5489. Mimms, Forrest M. III. 1990. Engineer's Mini-Notebook Science Projects. Radio Shack (catalog number 276-5018). This book contains several electronic science projects, including an 'earth movement sensor' and analog data logger. Science Probe, Inc. Science PROBE! Magazine. This magazine has only been publishing for a few months and has not actually presented any articles on amateur seismology, but the subject has been mentioned and will probably be dealt with in future issues. Subscription address: Science PROBE!, Subscription Department, P.O. Box 54097, Boulder, CO 80322-4097. Stong, C. L. 1960. The Scientific American Book of Projects For the Amateur Scientist. Simon and Schuster, New York. Library of Congress Catalog Card Number 60-14286. This book is a classic collection of articles which appeared in the Amateur Scientist column in Scientific American during the 1950's. Three of these articles describe amateur seismology and the construction of seismometers and seismographs. The electronic information is dated, but the basic information is still useful. This book is long out of print, but if you can find it, it is a good starting point. Please note that the torsional seismometer kit mentioned in "The Attractions of Amateur Seismology" is no longer available. Stong, C. L. 1975. The Amateur Scientist Column of Scientific American, September, 1975. "Electronic stratagems are the key to making a sensitive seismometer." Scientific American Inc., New York. This article describes an electronic seismograph suitable for construction by an electronic hobbyist. Stong, C. L. 1979. The Amateur Scientist Column of Scientific American, July, 1979. Scientific American Inc., New York. This article describes an electronic seismograph suitable for construction by an electronic hobbyist. U.S. Geological Survey. Bimonthly. Earthquakes & Volcanoes. This publication contains articles of interest to students of Earth science and the general public. It is available from the Superintendent of Documents, U.S. Government Printing Office, Washington, DC 20402. Order from GPO at (202) 783-3238 (VISA or MASTERCARD). Also try 'go gpo' on CompuServe. U.S. Geological Survey. Monthly. Preliminary Determination of Epicenters. This publication (commonly known as PDE) contains a listing of earthquakes for a given month along with the origin time, The Amateur Seismology Package User's Manual 6 location, depth, magnitude, etc. This publication is a few months behind, for example the issue containing earthquakes for July, 1990 was published in February, 1991. It is available from the Superintendent of Documents or try 'go gpo' on CompuServe (see above). There must be an online and more timely source of this information somewhere. If anyone knows of such a source, please contact the author. Other miscellaneous sources: For timely information on earthquakes, try the online news wire services offered on CompuServe and perform a keyword search on 'earthquake.' Beware: news services do not always use UTC. The Amateur Seismology Package User's Manual 7 4.0 SEISGRAPH - A Program for Viewing and Printing Seismograms SEISGRAPH is a computer program which allows the user to load seismic data files, select a portion of interest for viewing, and print the image displayed on a dot matrix printer. 4.1 Overview SEISGRAPH is designed to run on IBM PC compatibles with Hercules, CGA, EGA, or VGA graphics. SEISGRAPH is written in Borland Turbo C (*1) and makes use of the Quinn-Curtis Science/Engineering/ Graphics Tools (part #IPC-TC-006) (*2). This program is not especially fast or sophisticated. It is intended to be an inexpensive alternative to the many excellent (but expensive) data plotting software packages available. Since this program supports features for monitors and printers that the author does not have access to, it was not possible to fully test this program (for example, it has never been tried on a system with CGA graphics). It is hoped that by carefully using the Quinn-Curtis tools, which have been tested on many systems, most problems have been avoided. It is certain that this program contains undetected 'bugs'. This statement is based upon experience as a programmer and a software tester. The detection of bugs depends upon the users. Those who use the program in a predictable way on a limited variety of data files may never have a problem. Those who take fiendish delight in stressing software (sometimes called 'malicious users') will probably encounter problems. Malicious users are a quality conscious programmer's best allies. Oddly enough, it seems to be a curious fact that many malicious users are named Al or Allen. The author encourages the reporting of bugs and freely admits that the users are performing the quality control function. *1 Turbo C is a trademark of Borland International, Inc. *2 This product is a trademark of Quinn-Curtis. For information on this and other tools, contact: Quinn-Curtis, 21 Highland Circle, Needham, MA 02194 USA 4.2 Installation It is assumed that the user has some experience with installing PC software. The installation procedure is very simple. This package is usually distributed in the form of a ZIP files which contain this manual, the SEISGRAPH program, and a sample data file. Copy the SEISGRAPH program (sg.exe) and the sample data file (sample.dat) to a directory (for example c:\seis). In order to run the program while in another directory without having to type c:\seis\ before each command, it will be necessary to add c:\seis The Amateur Seismology Package User's Manual 8 to the PATH. If you are an inexperienced user and have problems, seek the help of a more experienced user. 4.3 Guided Tour The easiest way to explain this program is to walk the user through a sample session. The first step is to install the software as described above. Change the default directory to the directory in which the above files were installed or make sure the PATH has been properly set. To invoke SEISGRAPH, type the following at the prompt followed by return: sg sample.dat As SEISGRAPH executes, the following will appear on the screen: The copyright notice and support address. Reading data file: sample.dat Reading setup string: S10 Samples per second: 10 Time stamp: 910308114539.5 The copyright notice encoded in the data file and any additional text describing the contents of the data file. Samples read: 6000 First sample: 2065 Last sample: 2179 Press ESC to quit or any other key to continue. Press the ESC key. The prompt should reappear and the computer should behave normally, allowing you to do a DIR or any other command. This verifies that SEISGRAPH was able to allocate memory, read the data file, and deallocate memory without clashing with any other software that may be running on your computer. If the computer is not operating normally at this point or a message appeared that was not listed above, you have found a bug (sorry Al). Proceed to the Problems and Solutions section. If things have gone well so far, invoke SEISGRAPH again and press the space bar (or any key other than ESC). The screen will go blank, the borders of several boxes will be drawn on the screen, and all but two of the bordered boxes will disappear as other information is placed on the screen. Across the top of the screen is an area called the 'stamp window.' At the left side of the window is the file time stamp. This contains the time of the first sample in the file in the format 'yr mo da ho:mi:se.t', where yr is the year, mo is the month, ho is the hour, mi is the minute, se is the second and t is tenths of a second. ALL DATES AND TIMES ASSOCIATED WITH The Amateur Seismology Package User's Manual 9 SEISMIC DATA WILL BE IN UTC. At the right side of the window is data describing the active range of y values in the format 'y_min y_span y_max' where y_min is the smallest value to be plotted, y_max is the largest value to be plotted, and y_span is the difference of y_max and y_min. Along the left side of the screen is a narrow vertical strip called the 'guide y window.' At the top of this window is a (partially obstructed) + sign and at the bottom is a (partially obstructed) diamond. These marks are used to graphically show the relative locations of y_min and y_max. Along the top of the screen, below the stamp window and to the right of the guide y window is the 'guide window.' This window will be used to display the entire data file at a reduced scale, making it possible to plot a small section of the file and still 'get the big picture.' Directly below the guide window is the 'guide x window.' This window is used like the guide y window to show the locations of 'x_min' (the first sample to be plotted) and 'x_max' (the last sample to be plotted) relative to the entire file. Directly below the guide x window is the 'x text window.' This window is used to show the times associated with x_min and x_max in the format min:sec and the sample number within the file between the []. The time difference between x_min and x_max (the span of time to be plotted) is centered in the x text window. Directly below the guide x window is the largest of the windows, the 'data window.' This is where the data bounded by y_min, y_max, x_min, and x_max will be plotted. To the left of the data window is the 'data y window' and directly below the data window is the 'data x window.' The functions of these windows parallel the functions of the guide y and guide x windows, respectively. Press the 'g' key. The entire data file will be plotted in the guide window. Depending on the speed of your computer, this may take from 3 to 30 seconds. After the data is plotted, an x axis will be drawn in the guide window with tick marks at one minute intervals (the tick marks may be too small to see). Note the diamond mark at the far left of the guide x window. Press the right arrow key once. The diamond will move to the right one tick along the x axis, and the x text window will be updated to show that x_min has increased by one minute. Press the space bar. The diamond on the left of the guide x window will change to a + and the + on the far right of the guide x window will change to a diamond. This signifies that x_max is now the active limit. Press the left arrow key twice. Notice that x_max decreases by two minutes. Press the right arrow key once. Notice that x_max increases by one minute. The Amateur Seismology Package User's Manual 10 In general, a diamond indicates that the corresponding limit is active and will be adjusted when an appropriate arrow key is pressed. The left and right arrow keys affect only x_min and x_max while the up and down arrow keys affect only y_min and y_max. Pressing the space bar changes between adjusting the min or max limits. Using the space bar and arrow keys, adjust the y_min and y_max values in the guide y window and the x_min and x_max values in the guide x window until an area of interest in the guide window is bounded by the four limits. Press the 'g' key. The guide window will be redrawn, with the y_min and y_max values selected, but the entire file will be plotted, not just the area between x_min and x_max. This is because the guide window is designed to show the entire file. In fact, it is desirable to redraw the guide window with different y limits only if the initial y limits do now allow enough detail to be shown. The autorange feature (see Features, below) makes it possible to draw the guide window once with limits set based upon the actual minimum and maximum values of the data in the data file. Press the 'd' key. The area of interest selected will now be plotted in the data window. An x axis will be drawn along the bottom of the data window with tick marks at 10 second intervals. The four limits can be adjusted again. The guide x and guide y marks will show which area of the entire file will be plotted in the data window the next time the 'd' key is pressed and the data x and data y marks will show the same area but in greater precision since the data marks relate to the data window which is at a different scale than the guide window. The steps by which the limits move in response to the arrow keys is adjusted by the function keys. The effect of each key is described in the Features section, below. Press the ESC key to exit. The sample data file used during this tour shows the p and s wave arrivals (at 30 seconds and 8 minutes 23 seconds into the file, respectively) recorded in Minnesota from an earthquake which struck near the northern end of the Kamchatka peninsula at about 1136 UTC. This is an excellent file, not all events are recorded this well. This completes the guided tour. Read the Features section and experiment to gain an intuitive understanding of the operations of the various features. The Amateur Seismology Package User's Manual 11 4.4 Features The features of this program are presented in detail below roughly in the order they were used in the guided tour. 4.4.1 Invoking SEISGRAPH SEISGRAPH is started by typing the name of the program, an optional 'setup string', and the name of the data file to be examined. In the example above, no setup string was used. The setup string can be used to change some of the ways SEISGRAPH executes. See the Setup String section, below, for details. 4.4.2 Reading Data Files After displaying the copyright message, SEISGRAPH reads the data file specified on the command line. The first portion of the data file contains a setup string which contains information about the format of the data file. In most cases, the only information contained in this setup string will be the rate at which data was sampled. The setup string is read and displayed. Any actions taken as a result of the information contained in the string will be displayed. In the example above, the setup string S10 was found and was interpreted as meaning that the data in the file was sampled at 10 samples per second. The second portion of the data file contains the file time stamp which will be displayed in the stamp window. This is the time of the first sample in the file. The next portion of the data file contains text such as copyright information or a description of the file contents. Finally, the data portion of the file is read. SEISGRAPH can read a maximum of 32767 samples and will stop reading the data file when this many samples have been read. Also, only an integral number of seconds worth of data will be read and any extra data will be discarded. When finished reading the data, SEISGRAPH will display the number of samples read and the value of the first and last sample. 4.4.3 Adjusting X Limits The x_min and x_max limits are adjusted using the left and right arrow keys. The limit denoted by the diamond shape is the active limit which will be changed in response to the arrow keys. The active limit is chosen by pressing and releasing the space bar until the desired limit changes from a + to a diamond. The function keys F1 through F4 determine the step size for x limit adjustments as follows: F1 1 second steps F2 10 second steps The Amateur Seismology Package User's Manual 12 F3 1 minute steps (default at program start) F4 10 minute steps The TAB key moves the range of x values to the 'next' interval and the SHIFT-TAB key moves the range of x values to the 'previous' interval. The END key moves the active x limit to the end of the current data window if the active x limit is currently within the current data window. Otherwise it moves the active x limit to the beginning or end of the file. The x limits will not come closer together than the current x step size and TAB/SHIFT-TAB will not move the x range if there is not enough room left between the current range and the beginning or end of the file. 4.4.4 Adjusting Y Limits The y_min and y_max limits are adjusted using the up and down arrow keys. The limit denoted by the diamond shape is the active limit which will be changed in response to the arrow keys. The active limit is chosen by pressing and releasing the space bar until the desired limit changes from a + to a diamond. The function keys F5 through F9 determine the step size for y limit adjustments as follows: F5 1 count steps F6 10 count steps F7 100 count steps F8 1000 count steps (default at program start) F9 10000 count steps The HOME key performs different functions depending upon whether the 'autorange' feature is enabled. When autorange is not enabled, the HOME key moves y_min to 0 and moves y_max to a reasonable value (65535, 16383, 4095, 1023, or 255) depending upon the largest data value in the file. When autorange is enabled, the HOME key moves y_min to the smallest value and y_max to the largest value present in the file. See the autorange feature, below, for instructions on enabling autorange. The y limits will not come closer together than the current y step size. 4.4.5 Autorange The autorange feature is enabled and disabled by the F10 function key. When enabled, 'Autorange' will be displayed in the stamp window. Autorange is not enabled when the program starts, but this can be changed through the use of the setup string. The Amateur Seismology Package User's Manual 13 4.4.6 Guide Window The guide window is used to display a plot of the entire file. The guide window is drawn when the 'g' key is pressed. 4.4.7 Data Window The data window is used to display a plot of the portion of the file bounded by x_min, x_max, y_min, and y_max. The data window is drawn when the 'd' key is pressed. The data window can be drawn with grids along the x axis by pressing the 'x' key or with grids along both the x and y axes by pressing the 'b' key. The timestamp can be displayed in the data window by pressing the 't' key and the x and y limits can be displayed in the data window by pressing the 'i' key. These features are useful when printing the data window. 4.4.8 Printing The plot displayed in the data window can be printed by pressing the 'p' key. The portion of the plot on the right of the data window will be the first portion printed. When printing the contents of an entire file, select a range of x values which divides evenly into the file length (so each print operation will use the same scale), press TAB until the end of the range coincides with the end of the file, and press 'p'. When finished printing this segment, press SHIFT-TAB to move the range toward the beginning of the file, press 'd' to draw the new range of data, and press 'p'. Repeat this process until the beginning of the range coincides with the beginning of the file. Unfortunately, the printer driver inserts a blank space between print operations. It is necessary to 'back up' the paper between operations or cut and paste the resulting plots (if using an Epson FX-85, turn the paper advance knob back 18 notches). Note that no tick mark is drawn at the left or right end of the x axis. Although time and range data normally do not appear in the data window, they may be displayed by pressing the 't' and 'i' keys, permitting them to be printed along with the data plot. The Quinn-Curtis tools support a number of printers and resolutions. For details on selecting the proper configuration for your printer, see the Setup String section. The Amateur Seismology Package User's Manual 14 4.4.9 Setup String The setup string is a series of letters and numbers which can be placed in a data file and/or on the command line to affect the way SEISGRAPH performs certain operations. When a setup string is encountered, SEISGRAPH displays the string and also displays the information extracted from the string. For example, invoking SEISGRAPH with a setup string (s50ea): sg s50ea sample.dat will cause SEISGRAPH to assume the data was sampled at 50 samples per second, that the data is eight bit data, and will enable the autorange feature. Any information contained in the command line setup string will override any similar information in the data file setup string. For instance, if the data file contains the setup string s10 (interpreted as 10 samples per second) and the command line contains the setup string s5 (interpreted as 5 samples per second), the 5 samples per second value will be used. The following sections describe the options available through use of the setup string. The default values described are the values SEISGRAPH will use unless overridden by the setup string. 4.4.9.1 b (Binary File) When a 'b' appears in a setup string, the data file will be assumed to be a binary file (which contains only data) and not a mixed file (which contains a setup string, timestamp, and possibly text information). Note that it makes no sense to place a 'b' in a setup string in a data file since a binary file by definition contains no setup string. Placing a 'b' in the command line setup string enables the user to read any file as a data file. This option is intended to at least make it possible to read files other than those which are a part of the Amateur Seismology Package. If a binary file has been read, note that no file timestamp will be available. By default, SEISGRAPH expects data files to be of the mixed type. 4.4.9.2 e (Eight Bit File) When an 'e' appears in a setup string, the size of the samples in the data file will be assumed to be one byte instead of the default size of two bytes. This option makes it possible to read data files which contain eight bit information but do not fill the extra byte with zeros. The Amateur Seismology Package User's Manual 15 4.4.9.3 x (Skip Bytes) An 'x' followed by a number in a setup string will cause SEISGRAPH to skip that number of bytes before beginning to read and store data. The number of bytes to skip must be <= 32767. Note that this is the number of BYTES to skip which will not be the number of samples to skip if the sample size is two bytes. This option makes it possible to read mixed files which have all their text information grouped together by placing a 'b' and an 'x' followed by the appropriate number of bytes in the setup string. The default value of Skip Bytes is 0. 4.4.9.4 c (Color) Placing a 'c' followed by a number in the setup string permits the user to choose which color SEISGRAPH will use. The following list is based upon the table for the Turbo C setallpalette function. The CGA values have not been tested. The default value of Color is 63. CGA EGA/VGA 0 black black 1 blue blue 2 green green 3 cyan cyan 4 red red 5 magenta magenta 6 brown 7 light gray light gray 8 dark gray 9 light blue 10 light green 11 light cyan 12 light red 13 light magenta 14 yellow 15 white 20 brown 56 dark gray 57 light blue 58 light green 59 light cyan 60 light red 61 light magenta 62 yellow 63 white The Amateur Seismology Package User's Manual 16 4.4.9.5 a (Autorange) Placing an 'a' in the setup string enables the autorange feature. This makes it possible to have autorange enabled when the program starts instead of having to press F10 HOME SPACE HOME before drawing the guide window. By default, autorange is not enabled. 4.4.9.6 s (Samples Per Second) An 's' followed by a number in the setup string determines the sample rate SEISGRAPH will use. Samples per second must be <= 32767. Samples per second is normally set in the data file, but may be changed on the command line. This feature is useful when reading binary data files. The default value of Samples Per Second is 10. 4.4.9.7 b (Bin Size) A 'b' followed by a number in the setup string determines the bin size used when drawing in the guide window. The number must be >= 2 and <= 32767. Instead of plotting every point in the guide window (which can be very time consuming), data is grouped into bins and the maximum value and the minimum value for each bin is plotted. Making the bin size small increases the fidelity of the plot in the guide window but slows down the plotting process due to the increased number of bins which must be plotted. Making the bin size large decreases the fidelity of the plot but speeds up the plotting process. The default value of Bin Size is 10. 4.4.9.8 p (Printer Port) A 'p' followed by an number in the setup string determines which printer port SEISGRAPH will use. The number must be 0 (for LPT1:) or 1 (for LPT2:). The default printer port is LPT1:. The Amateur Seismology Package User's Manual 17 4.4.9.9 d (Printer Driver) and r (Resolution) Placing a 'p' or 'r' followed by a number in the setup string selects which printer driver and resolution will be used when printing the image contained in the data window. The user needs to determine which driver and resolution are appropriate for the printer being used. The following table is taken from the documentation for the Quinn-Curtis ScreenDump function. The author has only tested this package using driver 5. The default value for Printer Driver is 5 and the default value for Resolution is 0. Important note: The author made some modifications to the Quinn- Curtis source code (function GetVertByte in screen.c) to speed up screen dumps at the expense being unable to scale the screen dumps in the x and y directions. GetVertByte is used by drivers 0, 2, and 5. These modifications were tested with driver 5 and should work with drivers 0 and 2. If troubles are encountered while using drivers 0, 2, or 5, please notify the author and do not blame the Quinn-Curtis tools. Driver: 0 Epson MX driver 1 Epson LQ driver 2 Toshiba P driver 3 HP Laser Jet driver 4 HP Ink Jet driver 5 Epson FX driver Resolution: Epson MX, FX drivers 0 single density normal speed 1 double density half speed 2 double density normal speed 3 quadruple density Epson LQ driver 0 single density normal speed 8 pin mode 1 double density half speed 8 pin mode 2 double density normal speed 8 pin mode 3 quadruple density 8 pin mode 4 standard density 24 pin mode 5 double density 24 pin mode 6 CRT III 24 pin mode 7 triple density 24 pin mode 8 hex density 24 pin mode Toshiba P driver 0 180x180 dot image transfer 1 180x360 dot image transfer HP Laser Jet driver 0 75 dots/inch 1 100 dots/inch 2 150 dots/inch The Amateur Seismology Package User's Manual 18 3 300 dots/inch 4.5 Data File Format SEISGRAPH can be used to read almost any kind of data file (except ASCII formats, commonly used by spreadsheet programs). This flexibility is provided by the 'b', 'e', 'x', and 's' options in the setup string. The data files distributed with SEISGRAPH and the data files periodically distributed following earthquakes will be in a 'mixed' format. The mixed format is described below. Users with data acquisition capability are encouraged to use this format to facilitate the exchange of files. The first portion of a mixed file is a setup string. This string may contain all of the types of information that a setup string on the command line may contain, but it should be limited to contain just the samples per second information. The second portion is the file time stamp. This string should be in the format described in the guided tour section. Note that the time stamp in the sample files includes tenths of a second but uses spaces for place holders for hundredths and thousandths of a second. This is to provide the ability to use more precise file time stamps in the future. The third portion is plain text. Note that all strings must be 80 characters or fewer in length and must be terminated with a newline character ($0A). When SEISGRAPH encounters two newline characters in a row, the rest of the data file will be assumed to be binary data. Data files can be examined using a 'dump' utility or an editor which has the capability to edit binary files. Trying to use a text editor on a data file may cause undesired results, possibly corrupting the data file. 4.6 Problems and Solutions The following is a list of possible error messages, the probable cause, and the appropriate actions. Bad command or file name PC users are used to this one. The user either mistyped sg, the file sg.exe is not in the current directory, or sg.exe is not in the current directory and the path has not been properly set. Get help from a more experienced PC user. No or data file name on command line. Usage: SG data file name. The user typed sg but did not specify a setup string or data file name. OUT OF MEMORY. The Amateur Seismology Package User's Manual 19 Unable to create guide data array. Program terminated. SEISGRAPH was unable to find enough memory to hold a maximum and minimum value for each bin. This is due to a small bin size which results in the need for a large number of bins. Increase Bin Size using the 'b' option in the setup string. OUT OF MEMORY. Unable to create data array. Program terminated. SEISGRAPH was unable to find enough memory to hold 32767 two byte samples. Either the system does not have enough memory or other programs are using the rest or the memory. Try running SEISGRAPH without any other programs (TSR utilities, etc.) present. Error opening file: SEISGRAPH was unable to find the specified data file. If the filename displayed looks like the setup string, it is because the command line contained a setup string and no data file or the data file was entered on the command line before the setup string. No data read. Program terminated. SEISGRAPH read the data file but did not find any data. This may be because there were not two newline characters in a row after the end of plain text in a mixed file or because Skip Bytes was set to a number larger than the total number of samples in the file. Less than one second of data or > 32767 samples per second. Program terminated. SEISGRAPH read the data file but did not find at least one second's worth of data or Samples Per Second was set > 32767. Reduce Samples Per Second using the 's' option in the setup string. Problem with registerbgidriver call. Program terminated. One of the registerbgidriver calls returned an error response. This should never happen unless sg.exe has somehow become corrupted. CANNOT FIND DRIVER FILE. Program terminated. SEISGRAPH was unable to correctly identify the graphics adapter installed in the computer. SEISGRAPH will not work with this graphics adapter. The Amateur Seismology Package User's Manual 20 5.0 How Data Files Are Created The seismometer used to produce the data files is a horizontal pendulum with a period of about 20 seconds. The transducer is a moving coil - fixed magnet type producing a velocity response. The seismometer output is filtered, amplified, and sampled at a 50 Hz rate by an analog to digital converter (A to D) card installed in a PC. The file time stamp is read from a Heath GC-1000 at the beginning of each data file. This clock is synchronized to WWV and is usually accurate to 0.01 second, but the computer interface only reports time to the nearest 0.1 second (the delay introduced by the data transfer between the clock and computer is not presently known exactly, but it is less than 0.1 second). The Heath clock is very accurate but the clock on the A to D card which actually controls the sample rate tends to drift. This is confirmed by the fact that the file time stamps do not differ by exactly ten minutes. A rough rule of thumb to follow until the system timing is examined and a better clock is used to control the sample rate is that times are accurate to within about one second. The seismometer is located at approximately 45 degrees north latitude and 93 degrees 20 minutes west longitude. The pendulum is aligned along a roughly north-south axis and is therefore most sensitive to motion in the east-west direction. The calibration of the system is rather rough at the present time. Pendulum movement toward the east with respect to the base of the seismometer (the equivalent of ground movement to the west) results in samples with higher values. The filter and amplifier are simple and uncalibrated. If enough user support materializes, a better amplifier and filter will be built and calibrated. Please note that although the sample rate is 50 Hz, the files are reduced to a sample rate of 10 Hz and compressed with PKZIP before distribution. If this were not done, the files would be large and would require a much longer time (and more money) to download. The effective sample rate of 10 Hz is sufficient for amateur uses. However, some of the noise picked up by the seismometer (traffic, trains, etc.) may contain frequencies higher than 5 Hz. Those familiar with the Nyquist theorem know that this causes 'aliasing'. If enough supporting users want data without this aliasing, an anti-aliasing filter will be installed or the digital data will be filtered before being converted to a 10 Hz sample rate. The Amateur Seismology Package User's Manual 21 6.0 The Future Plans for additions and enhancements to this package include: A program for converting data files to/from the ASCII formats used by other plotting/spreadsheet programs. Moving the seismometer to a quieter location. Adjusting the amplifier gain or sampling at two or more different gains so large amplitude waves do not saturate the A to D card. Calibrating the amplifier gain and filter response so the data is more useful. The Amateur Seismology Package User's Manual 22