Temporal b-Value Variations through out a Seismic Faulting Process: The 2008 Taoyuan Earthquake in Taiwan


Temporal b-value variations have been completely obtained for the seismic faulting process of the 4 March 2008 Taoyuan earthquake (ML = 5.2), southern Taiwan. In addition to triggering several hundred after shocks, the mainshock was preceded by two groups of foreshocks (64 events) that clustered along the narrow major fault zone. A high b-value of ~1.25, estimated from the foreshock series, representing fault growth, was significantly larger than the b-values of 0.80 and 0.81, obtained respectively from after shocks and back ground seismicity. Also there were some pre-shocks (i.e., micro-earth quakes) that occurred one month before the earthquake sequence, with an extremely high b-value of ~2.1. This number might successfully indicate pre-nucleation seismic features in the vicinity of the fault zone. These seismic characteristics are fundamentally very similar to general features such as fracture nucleation and growth observed in rock samples under controlled stress in laboratory experiments, and thus ought to be considered to improve our understanding of crustal fault growth.

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