EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Temporal b-value variation before and after ML ≥ 6.0 Taiwan earthquakes from 2012 to 2019

Po-Yuan Chen1, Sean Kuanhsiang Chen1, and Yih-Min Wu1,2,3
Po-Yuan Chen et al.
  • 1Department of Geosciences, National Taiwan University, Taipei 10617, Taiwan
  • 2Research Center for Future Earth, National Taiwan University, Taipei 10617, Taiwan
  • 3Institute of Earth Sciences, Academia Sinica, Taipei 11529, Taiwan

Recent studies show that earthquake b values gradually decrease before large earthquakes at the epicenters and then immediately increase after the earthquakes. Temporal b-value variations may result from crustal stress changes associated with a large earthquake. However, the physical process is rarely observed and remains unclear. Taiwan island is a young orogeny leading to frequent earthquakes with magnitudes greater than ML 6.0, which provides an excellent laboratory to examine the physical process. We calculated b-value variation before and after ML ≥ 6.0 Taiwan earthquakes at the epicenters from 2012 to 2019. The time period is based on an enhancement of earthquake detection capability from the Central Weather Bureau Seismic Network in Taiwan, which allows the magnitude of completeness (Mc) down to 1.5 in the inland region. We used a relocated earthquake catalog to precisely estimate b value and Mc by the maximum likelihood method and maximum curvature method, respectively. We designed three steps in our research. First, we calculated the b value and Mc at the epicenters of the ML ≥ 6.0 earthquakes in overall 8 years to know the background seismic activity. Based on this, second, we calculated b values and Mc per half year to test the sensitivity between the radius from epicenters (r) and the number of earthquakes with magnitudes greater than Mc (n). Finally, we will apply moving window approach with specific criteria to continuously calculate temporal b-value variations. Our results showed that spatial b values in Taiwan in overall 8 years have an average of 1.0. The b values are systematically lower in the epicenters of ML ≥ 6.0 earthquakes from 2012 to 2019. We have determined suitable r and n values for each earthquake at the epicenters and some epicenters share similar r and n values. We preliminarily observed temporal b-value decreases before the 2018 Mw 6.4 Hualien earthquake. Considering temporal b-value variation by moving windows, we aim to realize whether temporal b-value variation by a large earthquake can be frequently observed in Taiwan.

How to cite: Chen, P.-Y., Chen, S. K., and Wu, Y.-M.: Temporal b-value variation before and after ML ≥ 6.0 Taiwan earthquakes from 2012 to 2019, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-9249,, 2021.

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