7.2 The Hypoinverse program, HYPINV

The latest version of Hypoinverse-2000 program (version 1.40, 2014) has been implemented in SEISAN to be use within EEV and as standalone. The original program has not been changed except to increase number of stations (25k). The original manual is found in INF. The main program has been given the name HYPINV (original version was HYP in conflict with HYP for HYPOCENTER) and can be run according to the original manual (Klein, 2014) and will not be described here. With a new driver program HYPINV_SEISAN, Hypoinverse can be run using Nordic files as input and output. Only the archive format for input and output is used directly with Hypoinverse.

The program does not work well at large distances ( $> 1000km$) so use it only for local earthquakes.

If original data, station and control files are available, it is just typing HYPINV and the program will run according to the manual. If none of these files are available, they can be made with the conversion programs, see below.

HYPINV can be operated in 3 ways:

Alternative 1: Manually do all steps:

1: Convert a CAT file a Hypoinverse input file with the program NORHIN, e.g. norhin collect.out. The input file in Nordic format is converted to a file norhin.out in Hypoinverse format. The following limitations and additions apply:

• Only local events with at least 3 stations will be converted.
• Since HYPOINVERSE only use first arrivals, all P and S phases will be converted to P or S, like PG to P. There is then the possibility that there will be e.g. two P's if the original data has e.g. Pg and Pn.
• The S-P time cannot be used by HYPOINVERSE. The weigh 9 will result in zero weight on the P but the corresponding S-time will be used so it should manually be weighed out.
• Lg and Rg phases are not used.
• Polarity and coda length are transferred.
• The hypocenter location is transferred to the norhin.out file but not the magnitudes.
• A fixed depth in input file is transferred to norhin.out. HYPOINVERSE cannot fix depth at zero, must be at least 0.01 km. If put to 0.000, depth is not fixed. If event qualifier is P or E, the depth is fixed in output file to 0.01 km.
• In order to recover the original component names, the two letter component code is put in at available places in the archive format (columns 87 and 109). This information is written out again by Hypoinverse.
• The event id (minus year) is saved on the hypoinverse header line in the field for id. It is later used for conversion back to Nordic format.

2. Make the control files with the program MAKEHIN. This creates the instruction file hypinst, station file hypinv.sta and model file hypinv.mod. These files are standard HYPOINVERSE files. The information is taken from the STATION0.HYP file in either the working directory or DAT. MAKEHIN cannot work with an alternative STATIONx.HYP file. If the hypinv.sta or hypinst files are present, they will not be generated. This allows for changes in the Hypocenter parameters to be used in subsequent runs. On the other hand, if the STATION0.HYP file is changed, the hypinst and hypinv.sta files must be deleted before the changes in STATION0.HYP will be used. The following parameters are partly generated from STATION0.HYP:

• Vp/Vs
• Start depth
• Minimum number of stations, however less than 3 is not allowed.
• Distance weighting starts at iteration 4, starts at HYPOCENTER parameter xnear and is zero at approximately xfar. However that assumes that xnear is further away than the second closest station. Hypoinverse parameter DISCUT is set to xnear, DISW1 is set to 1, and DISW2 = xfar/xnear. See Hypoinverse manual for details.

3. Type HYPINV and the program runs. There is a one-line output per event on the screen and the full output is in a file called print.out.

The output file from HYPINV is now hypinv.out and it can be converted back to Nordic format with program HINNOR, however, some of the original information is lost (like e.g. amplitudes). To avoid this, see alternative 2. HINNOR transfers the following information:

• Hypocenter with rms.
• Error line with gap and erz (vertical error) and erh (horizontal error). The Nordic values erlat and erlon are both replaced by erh.
• Magnitudes L and C in Hyoinverse file. If program HYPIN_SEISAN is used, the magnitudes are overwritten with the original values.
• Residuals.
• Distances, Hypinverse will give 999 if more than 1000 km.
• Angle of incidence.
• Azimuth.
• Weights used.
• Polarity.
• Coda length.

Alternative 2: Run the whole process using the driver program HYPINV_SEISAN. The program does the following:

• Run NORHIN
• Run MAKEHIN
• Run HINNOR
• Generate an output file in Nordic format hypinv_seisan.out that contains the new HYPINV location with corresponding residuals etc as well as all the original information in the Nordic input file like amplitudes, spectral information etc. The only thing lost is the original P and S phase names. All the R and D events skipped by NORHIN are put back in. To keep track of the events, the ID is used. The ID line will get the action flag HIN. The original magnitudes, agencies and number of stations are kept.

Using alternative 2 makes it very easy since Nordic file is both input and output.

Alternative 3: Running HYPINV from EEV using the command H. The steps are:

• EEV runs HYPINV_SEISAN using current s-file.
• The print.out file is printed on the screen.
• The user is asked if the data base should be updated with the combined file hypinv_seisan.out.

It is thus possible to use HYPINV to update the data base of local events with the limitations mentioned under alternative 1.

Note: Hypoinverse use residual weighing by default so rms and errors might be smaller than locating with Hypocenter.

Magnitudes

No magnitudes are transferred from Nordic files to Hypoinverse files. Coda magnitude is calculated with Hypoinverse using the Hypoinverse default relations. If the magnitudes have to be updated due to significantly changed location, it must be done with SEISAN EEV command 'u' and with the hypocenter fixed so the original HYPINV location is preserved.

How to run Hypoinverse with other parameters

Hypoinverse has many options of which the multiple models might be the most interesting. Generate the standard input files as in alternative 1 and then modify them according to the Hypoinverse manual. Then run HYPINV directly or, as the hypinst file is not changed if it exists, using alternative 2 or 3.

sectionHYP_ISC (Unix and Linux only)

Program written by Richard Luckett

ISC has for many years used a standard procedure to locate earthquakes and the ISC locations have often been used as a reference. The earth model used is the Bullen tables. ISC has recently rewritten the old location program and it was therefore possible to also port it to SEISAN. The purpose is that it should be possible to compare standard ISC locations with location using other programs and models. The implementation in SEISAN was done using the standard hyp program where only the location routines have been changed. The program then behaves almost identical to HYP and uses the same format input and output files.

Parameter files: STASTION0.HYP is used for station coordinates, magnitude scales and agency code. The crustal model information is not used and only the RESET TEST parameters related to magnitude are used. In addition, there is a new parameter file (in DAT) iscloc.def with parameters specific for the ISC location routines, see file for explanation of parameters.

Input data files: Just like for HYP

Output files: Hyp.out is like before, print.out is different.

Not all crustal phases used with HYP may be available. The weights used in SEISAN do not apply since the program uses residual weighing only, see parameter file.

Magnitudes are calculated exactly like in SEISAN.

In eev, the command to locate with HYP_ISC is `il'.

For more information about the ISC location program, see http://www.isc.ac.uk/Documents/Location/