SCEC Award Number 16023 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Properties and dynamics of different types of seismicity clusters in southern California
Investigator(s)
Name Organization
Ilya Zaliapin University of Nevada, Reno Yehuda Ben-Zion University of Southern California
Other Participants one graduate student, TBN (USC)
one undergraduate student, TBN (UNR)
SCEC Priorities 2b, 2f, 4e SCEC Groups FARM, Seismology, EFP
Report Due Date 03/15/2017 Date Report Submitted 03/15/2017
Project Abstract
 The project aimed at improving the ability to use seismicity clusters to clarify physical processes associated with faulting in the crust. Specific science targets included identifying and analyzing earthquake clusters in the global seismicity and comparing cluster quantitative characteristics with the heat flow level and type of deformation defined by parameters of the strain rate tensor. The project also developed earthquake declustering techniques. The project builds on the PIs results from previous SCEC projects on quantitative characterization of earthquake clustering in space and time in relation to different event sizes and physical properties of the lithosphere.
The analysis suggests that the dominant type of seismicity clusters in a region depends strongly on the heat flow, while the deformation style and intensity play a secondary role. The results show that there are two dominant types of global clustering: burst-like clusters that represent brittle fracture in relatively cold lithosphere (e.g., shallow events in subduction zones) and swarm-like clusters that represent brittle-ductile deformation in relatively hot lithosphere (e.g., mid-oceanic ridges). The global results are consistent with theoretical expectations and previous analyses of earthquake clustering in southern California based on higher quality catalogs. The observed region-specific deviations from average universal description of seismicity provide important constraints on the physics governing earthquakes and can be used to improve local seismic hazard assessments.
The results can inform a range of studies focused on earthquake dynamics, as well as to improve seismic hazards assessment efforts.
Intellectual Merit The study combines novel approaches to earthquake cluster identification/classification, global earthquake catalogs, heat flow, and geodetic data toward improved understanding of seismicity in relation to physical properties of the lithosphere. 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 research can inform and impact significantly various related studies on earthquake physics. 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 2b: Global spatial distribution of the proportion of foreshocks among foreshocks and aftershocks. The proportion exhibits a clear global correlation with the heat flow production, being high in hot regions and low in cold regions.