Post-processing of seismic parameter data based on valid seismic event determination

Claim 3

The method as defined in claim 1, and further including the step of automatically processing the values in the MASTER computer to calculate at least one of seismic event parameters including event location, accumulative event count, event distribution characteristic (b-value), stress drop, source dimensions, amount of fault slip, ratio of P- and S- velocities, and the components of the moment tensor.

Claim 4

The method as defined in claim 2, and further including the step of recording the processing results of the MASTER computer.

Claim 5

Apparatus for detecting a valid seismic event, which comprises (a) a plurality of WORKER processor means (4,6) each operable to monitor at a physically separated station a seismic signal (X) corresponding with the ambient seismic background level, said WORKER processor means including means digitalizing the seismic signal and for removing the mean therefrom to produce a first time series (X(t i )), means for computing from the first time series a new time series (X'(t i ) in accordance with the formula: ##EQU4## means for forming long-term (LTA) and short-term (STA) averages of the new time series (X'(t i )); and means producing a first abnormal-condition trigger signal when the ratio of short term average to long term average exceeds a first given value (C 1 ); (b) means for determining, in response to said trigger signal, the first time of onset (PT) of the first abnormal condition; (c) means for processing a primary segment (P) of said first time series (X(t i )) beginning at the onset time (PT) to determine amplitude (PA), quality (P), and polarity (PP) values, said primary segment being subsequently Fourier transformed to produce primary arrival spectral estimates of low-frequency level, corner-frequency value, and high-frequency slope; (d) means for producing a second abnormal-condition trigger signal when the ratio of short term average (STA) to the P-amplitude (PA) exceeds a second given value (C 3 ); (e) means for determining, in response to said second trigger signal, the second time of onset (ST) of the second abnormal condition; (f) means for processing a secondary segment (S) of said first time series (X(t i )) beginning at the second onset time (ST) values, said secondary segment being subsequently Fourier transformed to produce secondary arrival spectral estimates of low-frequency level, corner-frequency value, and high-frequency slope; (g) BOSS processor means (2) for monitoring the status of the dedicated WORKER processors to determine, upon the occurrence of a first abnormal-condition trigger signal in any one thereof, whether or not the first abnormal condition indicates a valid seismic event, including the step of determining whether a sufficient number of onset times (PT) are received during a given time window (TW); (h) means for aborting, when the WORKER abnormal conditions are not a valid seismic event, the processing sequences underway in the various WORKER processors; (i) means for collecting in the BOSS processor, when the WORKER abnormal conditions represent a valid seismic event, all the values computed by the WORKERS for the event, and returning the WORKER processors to their initial monitoring status; (j) and means for transmitting the values collected in the BOSS processor to a MASTER computer for processing the valid seismic event.

Claim 6

Apparatus for detecting a valid seismic event, which comprises (a) a plurality of WORKER processor means (4,6) each operable to monitor at a physically separated station a seismic signal (X) corresponding with the ambient seismic background level, said WORKER processor means including means digitalizing the seismic signal and for removing the mean therefrom to produce a first time series (X(t i )), means for computing from the first time series a new time series (X'(t i ) in accordance with the formula: ##EQU4## means for forming long-term (LTA) and short-term (STA) averages of the new time series (X'(t i )); and means producing a first abnormal-condition trigger signal when the ratio of short term average to long term average exceeds a first given value (C 1 ); (b) means for determining, in response to said trigger signal, the first time of onset (PT) of the first abnormal condition; (c) means for processing a primary segment (P) of said first time series (X(t i )) beginning at the onset time (PT) to determine amplitude (PA), quality (P), and polarity (PP) values, said primary segment being subsequently Fourier transformed to produce primary arrival spectral estimates of low-frequency level, corner-frequency value, and high-frequency slope; (d) means for producing a second abnormal-condition trigger signal when the ratio of short term average (STA) to the P-amplitude (PA) exceeds a second given value (C 3 ); (e) means for determining, in response to said second trigger signal, the second time of onset (ST) of the second abnormal condition; (f) means for processing a secondary segment (S) of said first time series (X(t i )) beginning at the second onset time (ST) values, said secondary segment being subsequently Fourier transformed to produce secondary arrival spectral estimates of low-frequency level, corner-frequency value, and high-frequency slope; (g) BOSS processor means (2) for monitoring the status of the dedicated WORKER processors to determine, upon the occurrence of a first abnormal-condition trigger signal in any one thereof, whether or not the first abnormal condition indicates a valid seismic event, including the step of determining whether a sufficient number of onset times (PT) are received during a given time window (TW); (h) means for aborting, when the WORKER abnormal conditions are not a valid seismic event, the processing sequences underway in the various WORKER processors; (i) means for collecting in the BOSS processor, when the WORKER abnormal conditions represent a valid seismic event, all the values computed by the WORKERS for the event, and returning the WORKER processors to their initial monitoring status; (j) and means for transmitting the values collected in the BOSS processor to a MASTER computer for processing the valid seismic event.