The general routine GET_SEISMIC_EVENT is used to find the nearest seismic event times recorded by the microseismic computer (data available via the MSEI banks). Its main usage is within the seismic cut hardwired filter (flt_seismic_cut).
The MSEI banks contains microseismic data recorded by the geophones. The time stamp of these events is the one from the microseismic computer (on which the microseismic software is running), with a precision up to the centisecond and which are given in Sudbury local time.
The routine will first convert the SNO GMT event time into Sudbury local time (by calling MSW_EE_CALC_DST to know wether we are in EDT or EST) in order to do the comparisons. The main incertainty in time is the one coming from the difference between the 10 MHz clock (accurate to 100 ns) and the microseismic PC clock, since the later is not synchronysed with the other computers (by the time of writing of this routine); so GET_SEISMIC_EVENT have been designed to return the nearest seismic event time both in the future and in the past relative to the current event time to properly take into account the possible time difference. The search is done after rounding the SNO event time to the centiseconds.
subroutine get_seismic_event (jday, iuts, iutns,
+ time_past, time_future , iretc)
* Parameters:-
* ==========
* JDAY in Julian day
* IUTS in Universal time seconds
* IUTNS in Universal time nanoseconds
* TIME_PAST out nearest seismic event time in seconds
* before current event.
* TIME_FUTURE out nearest seismic event time in seconds
* after current event.
*
* IRETC out = 0 no error
* -1 requesting seismic information for MC data.
* -2 no MSEI bank found which has validity ranges
* compatible with the current event time.