Temporal Variations of Earthquake Magnitude-Frequency Relation in the Source Area of M ≥ 6.0 Earthquakes: A Systematic Survey in Taiwan

Sean Kuanhsiang Chen, Po Yuan Chen, Yih Min Wu, Chien Chih Chen, Chung Han Chan

研究成果: 雜誌貢獻期刊論文同行評審

摘要

Recent studies in the earthquake magnitude-frequency relation (b-value) found that the b-value can decrease with time before large earthquakes in the source area. Such a decrease even coincided with a burst of foreshocks immediately before the earthquakes implying a preslip migrating toward the nucleation zone. We systematically survey the b-value variations in space and time in the source area of 17 earthquakes with magnitudes greater than ML 6.0 in Taiwan. We relocated the earthquakes released by the Central Weather Administration of Taiwan since 2012 as timing can provide a sufficiently low completeness magnitude (MC) of 1.5. We carefully determine the spatiotemporal search criteria on seismicity in the source area of all targeted earthquakes. We surveyed the temporal b-value systematically using moving time windows with a given number of earthquake events with the magnitudes greater than MC. We found the b-value decreased clearly for 2 days before the 2018 ML 6.3 Hualien earthquake, coinciding with a burst of ML 5.8 earthquake and its aftershocks nearby as foreshocks. The foreshocks migrated updip toward the hypocenter of the 2018 ML 6.3 Hualien earthquake and revealed a second decrease in the b-value 10 hours before it occurred. The b-value precursor primarily comes from a rapid reduction of small earthquakes in the foreshocks and agrees with recent key findings of preslip. However, there is no strong correlation between the b-value precursor and coseismic slip. Apart from this, the b-values did not change significantly in most cases of earthquakes in Taiwan before and after they occurred.

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文章編號e2023EA002927
期刊Earth and Space Science
10
發行號12
DOIs
出版狀態已出版 - 12月 2023

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