| dc.description.abstract | Taiwan is located on the boundary between the Eurasia Plate and the Philippines Sea Plate, where large earthquakes occur frequently and can induce lots of disasters and casualties. Thus, it is important to understand factors that would influence the temporal and spatial evaluations of seismicity in Taiwan, and this analysis will provide critical view for studies of earthquake hazard. Earthquake forecast has yet developed completely, but some preliminarily characters can be studied by the relationship between Coulomb stress changes and rates of earthquake occurrence. The positive correlation between increase of static Coulomb stress and high occurrence of aftershocks based on many researches has thus provided evidence that stress increase promotes seismicity. In this study, we chose three large earthquakes in Taiwan, including the 1998 Ruey-Li earthquake (Mw5.8), the 2003 Chen-Kung earthquake (Mw6.8) and the 2010 Jia-Shian earthquake (Mw6.0) to study the relationship between static Coulomb stress changes and seismicity rate changes.
We estimated Coulomb stress changes on a optimal-oriented faults implied by regional tectonic stress fields. Results show that most of aftershocks are located in the area where Coulomb stress increases. Accordingly, about 61%, 66% and 35% of aftershocks located in the area of positive Coulomb stress changes for the earthquake sequences of Ruey-Li, Chen-Kung and Jia-Shian earthquake, respectively. In addition, we observed that the seismicity rate is higher after the occurrence of three main shocks than before. For the Chen-Kung earthquake, increased seismicity rates in area of positive stress changes decayed to background level five years after the main shock, and the trend of decay follows the Omori’s law.
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