Revisiting the global detection capability of earthquakes during the period immediately after a large earthquake: considering the influence of intermediate-depth and deep earthquakes

Abstract

This study examines the global earthquake detection capability of the Global Centroid Moment Tensor (GCMT) catalogue during the periods immediately following large earthquakes, including intermediate-depth (70 ≤ depth < 300 km) and deep (300 km ≤ depth) events. We have already shown that the detection capability beyond an aftershock zone degrades remarkably and that this condition persists for several hours after the occurrence of large shallow (depth < 70 km) earthquakes. Because an intermediate-depth or deep earthquake occasionally generates seismic waves with significant amplitudes, it is necessary to investigate the change in the detection capability caused by such events. To this end, from the GCMT catalogue, we constructed the time sequences of the earthquakes that occurred immediately after the large earthquakes, and stacked these time sequences. To these stacked sequences, we then applied a statistical model representing the magnitude-frequency distribution of all observed earthquakes. This model has a parameter that characterizes the detection capability, and the temporal variation of the parameter is estimated by means of a Bayesian approach with a piecewise linear function. Consequently, we find that the global detection capability is lower after the occurrence of shallow earthquakes with magnitudes ≥ 5.45, intermediate-depth earthquakes with magnitudes ≥ 5.95, and deep earthquakes with magnitudes ≥ 6.95.