SCEC Award Number 21041 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Localization of seismicity prior to large earthquakes in California
Investigator(s)
Name Organization
Ilya Zaliapin University of Nevada, Reno Yehuda Ben-Zion University of Southern California
Other Participants two graduate students
SCEC Priorities 2e, 3d, 1d SCEC Groups EFP, Seismology, FARM
Report Due Date 03/15/2022 Date Report Submitted 03/09/2022
Project Abstract
 The project continues the PI efforts in tracking generation of earthquake-induced rock damage and evolving localization and coalescence of background seismicity (projects #19063 and #20065). The proposed studies apply refined techniques for analyzing localization of seismicity to expanded region that includes southern California, northern California and Alaska, and formulates general expectations of earthquake localization process in different seismicity settings. The project also examines localization in AE data from rock fracture experiments. The research on localization of background seismicity combines current efforts in quantifying earthquake-induced rock damage, time-dependent spatial localization of earthquakes, and earthquake declustering. The research uses the current updated version of the Hauksson et al. [2012] and Waldhauser and Schaff [2008] relocated catalogs, and other catalogs for California and Alaska. The project trains graduate students and facilitate the cross-disciplinary collaboration between UNR and USC.
Intellectual Merit The project developed a methodology for robust quantification of space-time localization of earthquakes – one of the principal mechanisms of generation of large earthquakes. The methodology has been applied to tracking time-dependent localization associated with preparation processes of large earthquakes in California and Alaska and system-size failures in rock fracture experiments. The project developed a methodology for space-time analysis if seismicity that allows eliminating effects of marginal space and time inhomogeneities related to the geometry of the fault network and region-wide changes in earthquake rates and quantifying coupled space–time rate variations that include aftershocks, swarms, and other forms of earthquake clustering. The methodology was applied to the seismicity of Southern California. The project contributed to the general theory of random self-similar trees that are used to represent earthquake flow and are the essential element of nearest-neighbor cluster analyses (including earthquake declustering).
Broader Impacts The project results have an impact on research areas outside of the immediate project scope. The project develops a novel method for localization of earthquake damage and quantifying space-time fluctuation of seismicity, and contributed to the general theory of random self-similar trees that has applicability beyond seismology.
Exemplary Figure Figure 1: Localization of background seismicity in Alaska. (Top) Relative localization with respect to a previous time interval. Its positive values indicate that the current spatial background distribution is a localized version of the earlier one – it has the same support and co-located yet more prominent peaks. (Bottom) Absolute localization. Its higher values indicate stronger deviation from the uniform spatial measure, or spikiness. The five large earthquakes with M > 7.8 are marked by red vertical lines. Every target event occurred within 3 years after the localization peak.