SCEC Award Number 14082 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Seismicity cluster anomalies in relation to different loadings and large earthquakes
Name Organization
Ilya Zaliapin University of Nevada, Reno Yehuda Ben-Zion University of Southern California
Other Participants an undergraduate student at UNR - TBN; a graduate student at USC - TBN
SCEC Priorities 2b, 2f, 4e SCEC Groups EFP, CSEP, Seismology
Report Due Date 03/15/2015 Date Report Submitted N/A
Project Abstract
The project aimed on clarifying the dynamics of seismicity in relation to large earthquakes and different types (e.g., tectonic vs. human induced) loadings. A key focus of the work was to indentify and separate seismicity clustering effects associated with steady tectonic loading, premonitory effects that may indicate likely approaching times of large damaging earthquakes, and anomalies associated with human induced loadings related to oil and gas exploration activities. The study utilized recent results of the PIs on robust non-parametric methodology for identification and classification of different types of seismicity clusters and correlations between clustering and properties of the crust. The previous SCEC projects by the PIs have established the existence of several different basic types of seismic clusters (burst-like, swarm-like, and singles) of small-to-medium magnitude earthquakes in southern California, and demonstrated that the cluster type is related to the properties governing the effective viscosity (indicated primarily by heat flow) of a region. The results of this project suggest that (i) the cluster properties systematically evolve in time, according to several robust cluster measures, in the spatio-temporal vicinity of the largest earthquakes in southern California, and (ii) seismic clustering differs, and probably can be used to discriminate between the regions dominated by tectonic vs. human-induced seismicity.
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 4: Temporal decay of the offspring intensity in the six seismogenic regions. The figure shows the normalized daily density of events as a function of time. Different symbols correspond to different regions (see legend). The density decay is closely approximated by a power law in the form (density) ∝ (time)^-p with index p decreasing from about 2 for induced earthquakes (Geysers and TauTona) to 1.5 for mixed seismicity (Coso and Salton Sea geothermal fields) to 1 for tectonic earthquakes (Coso non-geothermal and San Jacinto).