Research on b-Values Based on Fault Buffers
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The b-value is closely related to the crustal stress. By studying the b-value trends of regions before large earthquakes, we can obtain the evolution of crustal stress, which is generally considered useful earthquake precursor information. A quake is closely related to fault tectonic movement. In the past, the traditional b-value calculation method did not consider the spatial distribution of the fault. Here, we propose a new algorithm based on the fault’s buffer area, combining the spatial distribution and trend of the fault. This algorithm can accurately calculate the b-value changes for a specific fault using the fault as the basic independent unit. This method provides a useful reference for earthquake hazard judgment. Based on this algorithm, we use a total of 428,963 earthquakes from 1980 to 2013 after removal of the aftershock sequences and combine these quakes with the active fault distribution data to study the b-value changes before major earthquakes in western Sichuan. The results show that the b-values of the Fubianhe fault, Longmenshan main fault, and Shuangshi–Pengguan fault in western Sichuan decreased for at least 2 years before the earthquakes. The Longmenshan main fault area began to decrease slowly 5 years before the Wenchuan Ms8.0 earthquake and sharply decreased in the year before the quake, which reflects a significant change in crustal stress during this time. This conclusion and the method are available for long-term earthquake hazard assessment as a reference.
Keywordsb-value fault buffer earthquake hazard assessment
This research was supported by funding from the Science for Earthquake Resilience of the China Earthquake Administration (XH17022), the National Key Basic Research Program of China (2013CB733305), the Research Fund of the Institute of Seismology and Institute of Crustal Dynamics, China Earthquake Administration (Grant no. IS20146141) and the National Natural Science Foundation of China (Grant no. 41204014).
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