7.3 Plugin for the iLoc location algorithm, ILOC_SEISAN (Linux only)

A plugin for version 2.04 of the iLoc program, written by István Bondár [Bondár and Storchak, 2011], has been implemented in SEISAN to be used within EEV or as stand-alone. The purpose of the plugin is to have the possibility of event location with a regional 3-dimentional velocity model. Since iLoc use the Regional Seismic Travel Time (RSTT) [Myers et al., 2010] velocity model as part of its event location it serves this purpose.

iLoc must be installed on the system used and the program iloc must be in the path. iloc is not included in SEISAN.

One only need to compile iLoc with the ISF I/O option to be used with SEISAN. RSTT is part of iLoc and is required. See the iLoc installation instructions: http://www.seismology.hu/index.php/en/home/iloc

Note, only stations registrated to the ISC are included in iLoc. Otherwise one must add used stations to the file isc_stalist in the iLoc aux_data folder. If your stations have been registreated at the ISC recently, download a new station file at: ftp://ftp.isc.ac.uk/pub/iscloc/isc_stalist
If iLoc does not have the station information it will type: textttReadISF: missing station STATIONCODE

There are three ways of using iLoc in SEISAN:

1 From EEV; in EEV type:
iloc
The process here is similar to the the stand-alone gien below, but the user will have the option to save the output in the database.

2 Stand-alone, type:
iloc_seisan <sfilename> <operator_id>
The program ILOC_SEISAN will read the sfile, convert the sfile to isf format, using the ISFNOR program (output filename: norisf.out). Next the iLoc program is executed, it reads the isf file. If data are not ok for hypocenter inversion iLoc will end. If data are ok for hypocenter inversion result is printed on the terminal and written as isf format in the file iloc-out.isf.

3 In a loop over many events:
Make a index.out file with SELECT program, run the program ILOC_LOOP. ILOC_LOOP will read all sfiles in index.out and add the iLoc solutiuon to the sfiles if a solution was found.

Below is the first header lines of an sfile that includes the iLoc hypocenter solution. The two last type L lines are from iLoc:

 2016 0229 2320 01.8 LE 67.177  20.623  0.1F UPP  9 0.2 1.5LUPP                1
 LOCALITY: 612636992 Sweden                                                    3
 2016 0229 2320 02.67   67.1608    20.6182    0.0   f 0.45  INTAR ILOC         L
 GAP 79 E 0.98 j  4.2 i  3.9 A 82 s  16 d  26m  0.04M  3.87 INTAR ILOC         L

The agency code is from the enviromental variable AGENCY or if that is not used from the station file, e.g. STATION0.HYP.

The format of the first type L line is the same as the type H line described in Appendix X. The format of the following comment line is:

1:4 ' GAP'
5:7 Gap in azimuthal coverage (degrees), i3
8:9 ' E'
10:14 Origin time error (seconds) f5.2
15:16 ' j'
17:21 Semi-major axis of 90% ellipse or its estimate (km), f5.1
22:23 ' i'
24:28 Semi-minor axis of 90% ellipse or its estimate (km), f5.1
29:30 ' A'
31:33 Strike of error ellipse clock-wise form North (degrees), i3
34:35 ' s'
36:39 Number of defining stations, i4
40:41 ' d'
42:45 Number of defining phases, i4
46 m
47:52 Distance to closest station (degrees), f6.2
53 M
54:59 Distance to furthest station (degrees), f6.2
60 Free
61:65 Agency, a5
66 Free
67:73 'ILOC   ' Method used, a7
74:79 Free
80 '3'

Peter Voss : Fri Nov 12 10:33:10 UTC 2021