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HYPOELLIPSE EARTHQUAKE LOCATION PROGRAM

Contents:
Full Manual for HYPOELLIPSE
Quick-Start Manual for HYPOELLIPSE (quikstrt.pdf and quikstrt.doc)
UNIX
   The Sun/UNIX files below are also in a UNIX tar file: unix_version.tar.
   The Debian/linux modifications are not included in the tar files, but are located herehypoel\unix_version\source\linux\
    Source and Executables  
   
Sun/UNIX executable:  hypoel
   
Sample Run 1 with link to Quick-Start Manual
    Sample Run 2
PC/DOS (All of the PC files below in a UNIX tar file: pc_version.tar)
    Source and Executables
   
Executable, hypoel.exe
    Sample Run 1 with link to Quick_Start Manual 
    Sample Run 2
TTGEN, a program for creating optional, local travel-time tables
HYPOTABLE, Arthur Snoke's program for generating spherical-Earth travel time tables
    (The HYPOTABLE files are also locate here.)
HYPOELLIPSE Overview
Y2K Issues
Most recent Changes to HYPOELLIPSE

Note:  The IASPEI International Handbook of Earthquake and Engineering Seismology includes a CD with all of the following files and information, with the exception that no executable files are provided on the CD.

Hypoellipse Overview
The Southern Alaska Seismic Network earthquakes were located with the computer program HYPOELLIPSE.  This ftp area includes the program manual in PDF and MS Word 97 formats.  Also included are the source and executable files for UNIX computers, and the source and executable files for PC/DOS computers.  All of these files may be easily downloaded via the compressed tar file:  ftp://ghtftp.cr.usgs.gov/pub/LAHR/iaspei_pgms.tgz .

Two programs for creating travel-time tables for use with HYPOELLIPSE are included:  TTGEN, written by Fred Klein, generates local flat-earth tables; HYPOTABLE, written by Arthur Snoke, creates spherical-earth travel-time tables, allowing for the program to be used with stations beyond the distance at which significant travel-time errors are introduced by a flat-layer model.

HYPOELLIPSE was developed to meet the needs of the USGS in locating both the crustal and sub-crustal earthquakes of southern Alaska using a sparse regional network. This is a more difficult problem that locating shallow earthquakes within a dense network, which is the problem generally faced within California, so HYPOELLIPSE includes more user adjustable parameters than HYPO71, the program from which it evolved. 

A relatively new feature is the ability to work in areas with large topographic variations. Previous version assumed that all of the  stations were located at the same elevation and that slight elevation  corrections could be accounted for by station elevation corrections. The basic assumptions of this approach break down when there are significant topographic variations, especially for very shallow earthquakes. We faced  this problem working with a dense seismic network on Redoubt volcano in Alaska. HYPOELLIPSE currently allows stations to be "embedded" within the velocity model, and will correctly compute travel time and take-off angles even for stations that are at a lower elevation than the earthquake.

Although the processing of Alaskan data was done on a SUN computer, the PC version is provided for those who do not have a SUN platform available.
The SUN version may work on other UNIX platforms, but other platforms have not been tested at the USGS.

Y2K Issues

I've made  Y2K changes to HYPOELLIPSE following the plan that Fred Klein is using with HYPOINVERSE.  Refer to the manual for specific information about running HYPOELLIPSE.  The notes below, which describe the Y2K changes, are also reflected in the manual.

The summary records are the same, except everything is pushed to the right by 2 columns to allow for the century.  If an event is run that starts with a summary record:
1)  if the summary record is in the new format, with / in column 83, then the century is set to the first two columns 
2)  if the summary record is in the old format, with / in column 81, then the century is set to TEST(55). TEST(55) is a new variable which sets the default century.

If the event does not start with a summary record, which will be the case on the first run, then the century is determined by TEST(55).  In every case, the output summary and archive files will include the century in columns 1-2 and a / in column 83.

The phase (arrival time) records are unchanged. The century is set by the summary record or by TEST(55).

The format of the time-dependent station records has been changed.  In the columns where the expiration date was set by yrmody hrmn, which were read by (i6, i4) the new format has cnyrmody hr, which is read by (i8, i2).  No other columns on these records are modified.

Events spanning the end of a month or the end of a year.   The phase records for a given event must all have the same year and month.  If the arrivals do include times on the last day of the month (and/or year) and the first day of the next month, this situation is accommodated by increasing the number of seconds beyond 59.99.   A phase-record for an event near the end of 1999, for an arrival on January 1, 2000, at 0 hours, 0 minutes, and 13.11 seconds would look like this:
        RED IPU0 991231235973.11

A set of events can also span the 1999 - 2000 time boundary, but not if events in both 1999 and 2000 have no summary records, as TEST(55) will have to be either 19 or 20. 

For the transition from 1999 to 2000 one could:

Run all of the events up until the end of 1999 with TEST(55) set to 19.  Once all of the 1900's data has been run once,  the summary record that precedes the phase records will be in the new format and have 19 in the first two columns.

When first-time processing of data for 2000 begins, change TEST(55) to 20.

The "begin station list" record used to have yrmody for the date of the first event in the run. This has been changed to cnyrmody (century-year-month-day). 

The file y2ksta.f is the source for a simple filter program to converts old station list into the new format.  The UNIX executable is y2ksta.  This program is a filter that reads standard input and writes to standard output.   To run the program on stations.old to produce stations.new:

y2ksta   <stations.old    >stations.new

On a PC, use y2ksta.for and y2ksta.exe are the source and executable code for fixing a stations list that you are currently using.
This is only necessary if the stations list has time-dependent stations parameters.  

The best way to test that the new version is working the same as the old version is to compare the archive files generated by each version.   The only problem with this comparison is that the summary records written by the new version include the century.  The program del_cent.f (UNIX executable is del_cent) will remove the century from summary records generated by the new version to make the comparison easier.  To run it on new_version.arc to generate modified_new.arc:

del_cent   <new_version.arc    >modified_new.arc

Then comparison can be made with:

diff old_version.arc modified_new.arc

Recent Changes

Subroutines npunch, phasin, and opfls were modified on February 23, 1999, to correct an error related to time-dependent station parameters.

Subroutines xfmags.f and uamag.f were modified on February 24, 1999, to allow for dates between 1970 and 2069 in the University of Alaska station calibration system.

Subroutines hycrt, hyset, and hytab were modified on February 9, 2000, to correct a potential dimensioning problem due to the value of NLYR.