REMOTELY TRIGGERED SEISMICITY INFERRED FROM TAIWAN REGIONAL CATALOG

The June 1992 Landers (California) earthquake triggered an increase in earthquake activity at distances up to 1250 km. It posed the question whether the remote triggering was really widespread in nature, To check this, we use the regional catalog of seismicity in Taiwan where twelve large 6.0 less than or equal to M(D) less than or equal to 6.5 seismic events took place over the last twenty years. We calculate the number of M(D) greater than or equal to 2.0 earthquakes, as well as the number of M(D) greater than or equal to 4.5 earthquakes, starting 15 days prior to and ending 15 days after each M(D) greater than or equal to 6.0 event. The small-magnitude activity does not respond to the occurrence of a very large event. However, in 9 out of 12 cases, more M(D) greater than or equal to 4.5 earthquakes occurred after a large event than in the same time interval before. The number of additional events is proportional to the size of the triggering earthquake. Thus, these extra events are possibly remotely triggered.