1. Informative Modes of Seismicity in Nearest‐Neighbor Earthquake Proximities.
- Author
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Hsu, Yu‐Fang, Zaliapin, Ilya, and Ben‐Zion, Yehuda
- Subjects
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EARTHQUAKES , *INDUCED seismicity , *FAULT zones , *K-nearest neighbor classification , *GEYSERS - Abstract
We analyze nearest‐neighbor proximities of earthquakes in California based on the joint distribution (T, R) of rescaled time T and rescaled distance R between pairs of earthquakes (Zaliapin & Ben‐Zion, 2013a, https://doi.org/10.1002/jgrb.50179), using seismic catalogs from several regions and several catalogs for the San Jacinto Fault Zone (SJFZ). The study aims to identify informative modes in nearest‐neighbor diagrams beyond the general background and clustered modes, and to assess seismic catalogs derived by different methods. The results show that earthquake clusters with large and small‐to‐medium mainshocks have approximately diagonal and horizontal (T, R) distributions of the clustered mode, respectively, reflecting different triggering distances of mainshocks. Earthquakes in the creeping section of San Andreas Fault have a distinct "repeaters mode" characterized by very large rescaled times T and very small rescaled distances R, due to nearly identical locations of repeating events. Induced seismicity in the Geysers and Coso geothermal fields follow mostly the background mode, but with larger rescaled times T and smaller rescaled distances R compared to tectonic background seismicity. We also document differences in (T, R) distributions of catalogs constructed by different techniques (analyst‐picks, template‐matching and deep‐learning) for the SJFZ, and detect a mode with very large R and small T in the template‐matching and deep‐learning based catalogs. This mode may reflect dynamic triggering by passing waves and/or catalog artifacts. Plain Language Summary: Earthquake patterns in space and time provide important information about the properties of active faults, the surrounding crust, and different loading mechanisms. Nearest‐neighbor diagrams of earthquake proximities in a combined space‐time‐magnitude domain can be used to detect different types of seismicity patterns. Using such diagrams to analyze several earthquake catalogs in California, we examine characteristics of different sections of the San Andreas and San Jacinto faults along with geothermal areas and the entire southern California. The results highlight features of seismicity beyond the well‐known background and clustered modes of earthquakes, including a mode of repeating events in the creeping section of the San Andreas fault and differences between events in regular tectonic areas and geothermal fields. Analyses of different catalogs for the region around the San Jacinto fault also reveal differences related to the different techniques used to construct the catalogs. The results show that nearest‐neighbor diagrams can provide a simple and efficient way to identify different types of seismicity and assess the quality of earthquake catalogs. Key Points: Nearest‐neighbor diagrams provide an efficient way to identify different types of earthquake patternsRepeating events, large versus small‐moderate mainshocks, and induced seismicity have characteristic signaturesNearest‐neighbor diagrams help to evaluate features in catalogs constructed by different methods [ABSTRACT FROM AUTHOR]
- Published
- 2024
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