Data-Driven Spatiotemporal Assessment of Seismicity in the Philippine Region

The present study provides a retrospective analysis of the geographical and chronological fluctuations of three basic statistical characteristics of seismicity using a big dataset of events that occurred between 1940 and 2022 in the Philippine region. For determining the spatial-time changes in a-value (seismic activity), b-value (recurrence graph slope), and z-value, the contemporary expanded software package ZMAP with numerous sophisticated seismological functions for earthquake catalog analysis is employed (parameter of the relative seismic quiescence). For the various statistical interpretations, catalog data from the United States Geological Survey (USGS) occurred in spatial windows 0° N – 20° N and 118°E – 130oN are used. The overall conclusion is that unusually low b-values and high z-values, which define zones of comparatively seismic quiescence, may be a signal of the approaching release of more severe stress in areas near zones of relatively high a-values. Thus, the suggested joint interpretation of the spatial-time fluctuations of these three statistical characteristics of seismicity may be seen as a form of the predictor of the more powerful recent seismic occurrences in the region. Furthermore, the occurrence probability of a seven magnitude event is near about one with a return period of 2 years.