Large mainshocks can alter stress field on subsurface asperities across broad spatial and temporal windows, which would promote or inhibit fault motion. Beyond rapid rupture during earthquakes, fault can also slip at a steady rate without seismic radiation. In between these two end members, slow slip events have been documented within the conditionally stable transition zone. Recent advancements in seismic instrumentations provide an unprecedented opportunity to capture weak seismic event, and the 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 them are still missing, especially during intensive earthquake sequences. These missing events could be detected by 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 seeks to illuminate how fault relieve stresses in both fast and slow manners. First, I would present studies on earthquake interactions in both intraplate (Tibet) and subduction zone (North Island of New Zealand and Nicoya Peninsula) environments by large mainshocks. We suggest that transient stress carried by passing seismic wave can trigger fault slip at long-range distances, and the aftershock sequence can be driven by continuing fault slip following the mainshock rupture. Second, by monitoring the seismic activities prior to the 2010 Mw 7.2 El Mayor-Cucapah as well as the 2008 Mw 7.9 Wenchuan earthquake, we aim to unravel diverse fault slip behaviors and their roles in mainshock nucleation.