Comparative Study of Local Interactions between Earthquakes and Tremor in California and Japan

Abstract:

The discovery of tectonic tremor in Japan more than a decade ago and subsequently around the world offers new insights into how fault releases tectonic stresses during an earthquake cycle. It is the proximity of tremor to the earthquake nucleation zone that has raised important questions about the relationship to earthquake occurrence. For example, it is well established that earthquakes can induce tremor activity, but it is not known if tremor (or related slow slip) activity can influence the earthquake cycle. In this study, we investigate the interaction of local earthquakes and tremor in two regions – the Nankai Trough of Southwest Japan and the Parkfield-Cholame segment of the San Andreas Fault. We utilize several catalogs – including low-frequency earthquake, tremor, and regular earthquake catalogs local to each region – to determine if relationships between event types occur within a 10-year study period. We search the catalogs for event clustering and increased activity rates to explore if there is any characteristic time lag, separation distance, or magnitude that can explain the interaction between earthquakes and tremor. These characterizations provide information about not only the mechanisms that initiate fault slip but also knowledge of the necessary conditions for triggering to occur. While there is evidence of local earthquakes triggering tremor in the short-term, tremor as a precursor to earthquake activity is less clear. In the future, we plan to investigate the behavior of the delayed triggering activity – such as whether tremor triggered by earthquakes follows a predictable decay similar to a regular aftershock sequence. Our ultimate goal is to understand overall fault behavior by studying the interaction of earthquakes and tremor at the local scale.