Supplemental Station Files
As discussed in the main section on seismograph station data mloc can reference (with command sstn) supplemental station files to acquire information on the coordinates of stations that are not found in the master station file, i.e., stations that are not registered with the International Registry of Seismograph Stations (IR). Some clusters, e.g., those using only data from the ISC Bulletin, do not require any supplemental station files.
Supplemental station files are generally assembled for a specific cluster, and it is not uncommon to use several supplemental station files, possibly with different formats, for a cluster. mloc supports the use of up to 8 supplemental station files in addition to the master station file. With the current master station file (21,614 entries) and the default limit (24,000) on number of stations that may be defined, up to 2,386 stations can be defined in supplemental station files.
mloc supports several different formats for supplemental station files for convenience. When mloc opens a supplemental station file, the format is determined by an integer (isstn) in the first column of the first line. The rest of the first line (up to 96 characters total for the line) is considered an optional comment, which can be used to describe the dataset. The supported formats and corresponding values of isstn are:
- Master station file format
- ISC FFB format (geographic coordinates in deg-min-sec*10, elevation in m)
- SEISAN format, with station code starting in column 3. Degree-minute-decimal seconds. Extended for operational epoch.
- Generic format, decimal degrees, geographic coordinates. A basic format for quickly entering station data, supports 5-character station codes with agency and deployment codes.
- China Seismic Bureau format
- NEIC format
- MSU format
Master Station File Format (isstn = 0)
The format of the master station file can be used for a supplemental station file. The format is described here.
ISC Station File Fixed Format (isstn = 1)
This format is based on the record type 91 used in the ISC’s old Fixed Format (“96 Byte”) data format, extended to support 6-character station codes. It uses geographic coordinates in deg-min-sec*10, elevation in m. mloc no longer supports 6 characters for a station code so only the first 5 will be used.
|15:20||Station code (a6)|
|62:63||Latitude degrees (i2)|
|64:65||Latitude minutes (i2)|
|66:68||Latitude seconds*10 (i3)|
|69:69||“N” or “S” (a1)|
|70:72||Longitude degrees (i3)|
|73:74||Longitude minutes (i2)|
|75:77||Longitude seconds*10 (i3)|
|78:78||“E” or “W” (a1)|
|79:82||Elevation, m (i4)|
SEISAN Station File Format (isstn = 2)
The standard form of station data produced by the SEISAN software. Limited to 4-characters for station code. Geographic coordinates in degrees-decimal minutes. Elevation in m. The fields date_on and date_off are an extension of the format and they are optional.
|3:6||Station code (a4)|
|7:8||Latitude degrees (i2)|
|9:13||Latitude minutes (f5.2)|
|14:14||“N” or “S” (a1)|
|15:17||Longitude degrees (i3)|
|18:22||Longitude minutes (f5.2)|
|23:23||“E” or “W” (a1)|
|24:27||Elevation, m (i4)|
|34:40||Date_on (i7, optional)|
|42:48||Date_off (i7, optional)|
Generic Station File Format (isstn = 3)
This is a basic format designed to carry all the information that mloc might use. mloc converts all supplemental station information, regardless of its original file format, into this format and writes it to the “.stn” output file so it can be easily extracted to create a cluster-specific supplemental station file. Geographic coordinates in decimal degrees. It supports agency and deployment codes, operational epoch and both station elevation and depth of burial (positive number), but the only required fields are station code, latitude, longitude and elevation. A comment can be added after column 68, but it is not read by mloc.
|1:5||Station code (a5)|
|7:11||Agency (a5, optional)|
|13:20||Deployment (a8, optional)|
|41:45||Elevation, m (i5)|
|47:51||Depth of burial, m (i5, optional)|
|53:59||Date_on (i7, optional)|
|61:67||Date_off (i7, optional)|
China Seismic Bureau Station File Format (isstn = 4)
A format used by the China Seismic Bureau for their station lists. Uses a 3-character, lower-case station code. Only defined for positive latitude and longitude, but could be easily extended.
|1:3||Station code (a3)|
|5:8||Elevation, m (i4)|
|10:11||Latitude degrees (i2)|
|14:15||Latitude minutes (i2)|
|18:21||Latitude seconds (f4.1)|
|25:27||Longitude degrees (i3)|
|30:31||Longitude minutes (i2)|
|34:37||Longitude seconds (f4.1)|
NEIC Station File Format (isstn = 5)
This format is used with station coordinate data returned from the NEIC metadata server. If you use arrival time data from the NEIC ComCat server, especially for events within the U.S., you will probably need a supplemental station file to handle the many stations in U.S. regional networks that have not been registered with the International Registry at the ISC and also to solve the many station code conflicts that exist with registered stations.
A recent listing of the entire NEIC Metadata Server is provided as part of the mloc distribution, and the command nsmd is provided to help extract entries from it (in this format) that may be needed for a supplemental station file. Another method of building type 5 supplemental station files is to use the mdget utility program written and distributed by Dave Ketchum at NEIC ([email protected]). This ensures that the station data returned will be the most up-to-date.
|4:8||Station code (a5)|
|58:62||Elevation, m (i5)|
MSU Station File Format (isstn = 6)
A format used by Kevin Mackey at Michigan State University, especially for data from the former Soviet Union.
|1:5||Station code (a5)|
|6:7||Latitude degrees (i2)|
|9:10||Latitude minutes (i2)|
|12:15||Latitude seconds (f4.1)|
|16:16||“N” or “S” (a1)|
|17:19||Longitude degrees (i3)|
|21:22||Longitude minutes (i2)|
|24:27||Longitude seconds (f4.1)|
|28:28||“E” or “W” (a1)|
|30:33||Elevation, m (i4)|