locate event
command: LOCATE [<trc-list>] [<azim>] [<slow>] [<az-err>] [<slow-err>]
Locates event from arrival times of a seismic phase at a cluster of stations. If <trc-list> is specified, the delay of each trace is used as a relative travel time difference. Use the AL command to enter the delays. This can be applied only if all traces of the trace list start at the same absolute time! The program does NOT check this! In all cases applyable is to pick the arrival times by graphic cursor. This can be achieved omitting the <trc-list> parameter. As an output azimuth and slowness relative to the first station of the list is computed. Standard deviations of azimuth and slowness are computed as well.
Seismic Handler needs to know the station names where the traces in <trc-list> were recorded. If not all station names are given, an error occurs. Seismic Handler uses a location file to look for the location of a station. If a station name is not listed in this file, an error occurs. In this case the unknown station must be inserted to the location file using the FCT STATION command.
For each station latitude and longitude (in degrees) must be entered. Seismic Handler uses this information to compute the relative distances between the stations. Therefore the location information must be accurate enough. For station arrays there can be an array-relative location (in km) and an array ID number specified. If all stations of <trc-list> belong to the same array (same array ID number), Seismic Handler uses the array relative location to locate the event and not the latitude,longitude information. The the /NOARRAY qualifier forces Seismic Handler to use latitude,longitude information and to disregard array relative information (if any).
parameters
- <trc-list> parameter type: trace list
Input; List of traces to be used for location. If not specified the graphic cursor is used for picking traces and arrival times (see above).
- <azim> parameter type: symbol address
Output; Name of output variable to store resulting azimuth. The azimuth is given in degrees.
- <slowness> parameter type: symbol address
Output; Name of output variable to store resulting slowness. The slowness is given in sec/degree.
- <az-err> parameter type: symbol address
Output; Name of output variable to store resulting azimuth error.
- <slow-err> parameter type: symbol address
Output; Name of output variable to store resulting slowness error.
qualifiers
- /nomark
If passed, the picked arrival times are not marked (only valid if <trc-list> parameter is not specified).
- /noarray
The stations are assumed to be no array even if array coordinates are given for all stations in the location file. If no array coordinates are given the qualifier has no effect.
example
- locate
- locates event by selected times on different traces. Selections are made by graphic cursor
