SCEC Award Number 13036 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Spatio-temporal evolution of seismic clustering in southern California
Investigator(s)
Name Organization
Ilya Zaliapin University of Nevada, Reno Yehuda Ben-Zion University of Southern California
Other Participants 1 graduate, 1 undergraduate student
SCEC Priorities 2, 4 SCEC Groups EFP, FARM, WGCEP
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 This project is focused at revealing stable evolutionary patterns of seismic clusters and their relations to the occurrence the largest earthquakes. The project is based on the PI’s results on detection and classification of seismic clusters, and the new waveform-relocated catalog of southern California (both obtained within recent SCEC projects). The project directly addresses two of the SCEC4 fundamental problems of earthquake physics. The novelty of this project is in systematic uniform analysis of thousands of robustly detected seismic clusters of small-to-medium magnitude events, as opposed to the handful of largest clusters analyzed in most cluster studies. The previous SCEC projects by the PIs have established the existence of three types of earthquake clusters (burst-like, swarm-like, and singles) of small-to-medium magnitude in southern California, and demonstrated that the cluster type is tightly related to the heat flow and other properties governing the effective viscosity of a region. This project focused on spatio-temporal evolution of earthquake clustering and its relation to large earthquakes. We analyzed data from southern California, Turkey, and Midwestern US. The project results demonstrate increase of seismic clustering in the spatio-temporal vicinity of large events (M≥ 6.5) in southern California during 1981-2011 and the Duzce, M7.1, 1999 earthquake in Turkey. Furthermore, we show that cluster properties of seismicity in Arkansas, US, have significantly changed prior and during the swarm of 2010-2011. The results contribute to studies of earthquake predictability and to better understanding of the detailed structure of seismic catalogs in relation to physical properties of the crust.
Intellectual Merit The study combines novel approaches to earthquake cluster identification/classification and high quality earthquake catalogs from different environments toward improved understanding of seismicity in relation to large events and human-induced earthquakes. An ability to track the evolving response of the crust to different loadings may be used to monitor the build up of stress in a region. The developed tools and results can have transformative impact on analysis of seismic hazard in active tectonic environments, oil and other production areas, and regions containing both, such as California.
Broader Impacts The addressed problems on natural/induced seismicity and seismic anomalies preceding large events have critical societal and economic importance. The developed cluster framework can be applicable to other processes that develop in space-time-energy domains (e.g., river/subsurface flows, aerosol dynamics, chemical reactions, and fires).
Exemplary Figure Figure 1
Premonitory increase of earthquake clustering in Southern California. Proportion of singles among the earthquake clusters with m>3 within a circle with radius of about one rupture length (100 km) around Landers (top) and El Mayor-Cucapah (bottom) epicenters. The proportion drops significantly in the vicinity of large events. This suggests increased homogeneity of the stress field (since heterogeneity can enhance the formation of singles) and increased tendency of earthquakes to cluster (form multi-event families).