SCEC Award Number 18054 View PDF
Proposal Category Collaborative Proposal (Integration and Theory)
Proposal Title Seismic coupling on faults and correlations between geodetic data, seismicity and climatic signals
Investigator(s)
Name Organization
Ilya Zaliapin University of Nevada, Reno Corné Kreemer University of Nevada, Reno Yehuda Ben-Zion University of Southern California
Other Participants One student TBD @ UNR;
One student TBD @ USC
SCEC Priorities 1c, 3d, 2a SCEC Groups EFP, Seismology, FARM
Report Due Date 03/15/2019 Date Report Submitted 03/13/2019
Project Abstract
 The goals of the project are to (i) Examine correlations between strain rate seasonal fluctuations and earthquake cluster characteristics, (ii) Examine correlations between climatic changes and earthquake dynamics. A unique opportunity to conduct this natural experiment is provided by the recent drought of 2011-2014 and the El Nino of 2015-2016, and (iii) Assess the effect of non-stationary dynamics (geodetic, seismic) on estimation of seismic coupling. The projects uses and further develops the earthquake cluster technique and geodetic modeling products developed by the PIs. The project resulted in a new approach to estimating the coupling, an improved earthquake cluster/declustering methodology, and a suit of findings related to detecting and quantifying seasonal changes in earthquake cluster and strain properties, as well as the existence of earthquake clusters of different types with distinct productivity characteristics.
Intellectual Merit The project develops a systematic analysis of the connections between strain rates and properties of aftershock series within a formalism associated with a physical model and combining statistical analysis of earthquake catalogs with geodetic information. Improved understanding of the effects of physical and ambient properties of the crust on fault loading process and partition of the accumulated seismic moment among seismic and aseismic processes is recognized among the fundamental problems of earthquake physics by SCEC5.
Broader Impacts The project obtains a suit of results that have an impact on research areas outside of the immediate project scope. The project develops a novel method for earthquake catalog declustering; documents non-stationary dynamics of strain rates and earthquake clustering; and quantifies different types of earthquake clusters with distinct productivity properties.
Exemplary Figure Figure 1: Left and right columns show results for polygons in northern and southern California, respectively. (a, b) Blue line shows seasonal variation in relative areal change (and the standard deviation therein). Red line indicates variation in Coulomb stress on a fault trending 35°W inferred from the strain tensor. Remaining panels (c–h) show in red the same Coulomb stress variations (with the results for southern California scaled up), blue lines show the examined statistic, temporally smoothed, and expressed relative to the median of all epochs (see section 3 and equation (1)) and thin dotted lines indicate the 5% and 95% empirical limits for each examined indicator, inferred by repeating the same analysis on multiple catalogs with reshuffled event times. (c, d) Number of mainshocks with m ≥ 2.5. (e, f) Proportion of mainshocks with magnitude above or equal to 4.5 among mainshocks with magnitude above or equal to 3.5. (g, h) Aftershock productivity per cluster; see equation (2), and the negative value (dashed line). The axis description between the left and right panels applies to both panels.

Kreemer, C. and I. Zaliapin (2018) Spatiotemporal Correlation Between Seasonal Variations in Seismicity and Horizontal Dilatational Strain in California. Geophysical Research Letters, 45(18), 9559-9568. https://doi.org/10.1029/2018GL079536