Abstract
Earthquakes can be dynamically triggered by the passing waves of events
from disconnected faults. The frequent occurrence of dynamic triggering
offers tangible hope in revealing earthquake nucleation processes.
However, the physical mechanisms behind earthquake dynamic triggering
have remained unclear, and contributions of competing hypotheses are
challenging to isolate with individual case studies. Therefore,
developing a systematic understanding of the spatiotemporal patterns of
dynamic triggering can provide insights into the physical mechanisms,
which may aid mitigation of earthquake hazards. Here we investigate
earthquake dynamic triggering in Southern California from 2008 to 2017
using the Quake Template Matching catalog and an approach free from
assuming an earthquake occurrence distribution. We develop a new set of
statistics to examine the significance of seismicity-rate changes as
well as moment-release changes. We show that up to 70% of global M≥6
events may have triggered earthquakes in southern California and that
the triggered seismicity often occurred several hours after the passing
seismic waves. On average, earthquakes are triggered about every 4 days
in the region, albeit at different locations. Although adjacent fault
segments can be triggered by the same earthquakes, the majority of
triggered earthquakes seem to be uncorrelated, suggesting that the
process is primarily governed by local conditions. Further, the
occurrence of dynamic triggering does not seem to correlate with ground
motion (e.g., peak ground velocity) at the triggered sites. These
observations indicate that nonlinear processes may have primarily
regulated the dynamic triggering cases.