Matsumoto S, Iio Y, Sakai S, Kato A. Strength dependency of frequency-magnitude distribution in earthquakes and implications for stress state criticality.
Nat Commun 2024;
15:4957. [PMID:
38862498 PMCID:
PMC11166660 DOI:
10.1038/s41467-024-49422-7]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Accepted: 06/05/2024] [Indexed: 06/13/2024] Open
Abstract
Earthquake size distribution is characterized by the "b-value" of the power law decay, which exhibits spatiotemporal variations. These variations are sometimes evident before a large earthquake. Understanding spatiotemporal variations is key to developing a model for large-earthquake generation. Previous studies have shown that changes in the b-value are caused by the tectonic stress regime. Furthermore, lab experiments have demonstrated the b-value dependency of acoustic emissions on the criticality of the failure condition. However, the factors controlling the b-values during natural seismic activity are unclear. In this study, changes in the b-value in small earthquake sequences are investigated, focusing on failure criticality. Based on our high-precision focal mechanism dataset, we conclude that the b-value decreases as it nears a critical failure condition, providing a physical explanation for the reduction in b-value before a major earthquake. Our findings elucidate fault failure models, facilitating improvement in earthquake alerts and disaster mitigation.
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