Dept. of Geosciences Colloquium: Earthquake interaction and earthquake triggering in Central Taiwan

Abstract:

Central Taiwan is a seismic active region dominated by active mountain building processes. The main goal of our study is calculating stress changes induced by earthquakes and erosional unloading and evaluate their contribution to earthquake triggering (nucleation) and rupture propagation in central Taiwan. In order to probe stress triggering and fault propagation effects from earthquakes, we use an elastic dislocation model and calculate Coulomb Failure Stress changes (ΔCFS) at the hypocenters of 14 M >= 6.0 mainshocks and on 7 active fault systems in the study area. The mainshocks were selected by applying a declustering algorithm to all moderate-to-large magnitude earthquakes occurred between 1900 and 2016. Each mainshock was selected as a receiver fault and its preceding earthquakes as source faults in our ΔCFS calculations. We found that 6 mainshocks were promoted, in which the Coulomb stress changes
were larger than 0.1 bar. The remaining 7 mainshocks were inhibited to failure, in which the ΔCFS were smaller than -0.1 bar. Our ΔCFS analysis of nearby fault systems revealed that 4 of the 7 systems have been promoted to failure during the past 100 years and can generate moderate to large magnitude earthquakes. We also explore earthquake triggering by surface unloading due to rapid erosion induced by wet typhoons. In particular, we are interested to evaluate triggering relations between the very wet 2009 Morokat Typhoon, which pour ~3 meter of rain within 5 days, and two M>6 earthquakes occurred in the vicinity of the hit area within 1 year following the typhoon. Preliminary result of the stress changes at the hypocenters of potentially triggered earthquakes due to the increased erosion after 2009 typhoon indicate ΔCFS in the range 0.006-0.04 bar, which is smaller than earthquake triggering threshold estimates.

Event Organizers: Dr. Roy Barkan and Dr. Asaf Inbal