Understanding earthquake triggering and fault slip behavior based on improved earthquake catalogs
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Large earthquakes can alter the subsurface stress field on active faults across broad spatial and temporal windows, which would promote or inhibit slip on these faults. Besides dynamic ruptures during regular earthquakes, faults can also slip at a steady rate without any seismic radiation. In between these two extremes, slow slip events have been documented within the conditionally stable transition zone. Recent advancements in seismic instrumentation and computer programs provide an unprecedented opportunity to capture weak seismic events, and the resulting complete catalogs can be used to understand physical mechanisms of earthquake interactions from nearby to long-range distances, as well as diverse faulting processes inside the Earth. Earthquakes are routinely picked and located by analysts at seismic network centers. However, a significant fraction of events are missed, especially during intensive aftershock or swarm sequences. These missing events can be detected by a semi-automatic template matching method, which uses waveforms of existing events as templates to scan through continuous data for new events with high similarities. This dissertation focuses on improved understanding of fault slip behaviors and earthquake interactions based on improved catalogs from the template matching method. I first present studies on earthquake interactions in both continental-continental (Tibet) and oceanic-continental (North Island of New Zealand and Nicoya Peninsula) convergent environments following large mainshocks at nearby and far-field distances. The obtained results suggest that transient stress carried by passing seismic waves can trigger fault slip at long-range distances, and the aftershock sequence can be driven by continuing fault slip following the mainshock rupture. The second group of studies focuses on seismic activities prior to the 2008 Mw 7.9 Wenchuan earthquake, as well as the 2010 Mw 7.2 El Mayor-Cucapah earthquake. The primary target is to decipher diverse fault slip behaviors and understand their roles in mainshock nucleation.
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