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Physics-based Earthquake Source Characterization and Modeling with Geostatistics

Seok Goo Song, & Paul G. Somerville

Published 2010, SCEC Contribution #1300

Physics-based ground motion simulation requires the development of physically self-consistent source
modeling tools to emulate the essential physics of earthquake rupture. Because of the high computational
demand of full dynamic rupture modeling, the kinematic description of earthquake source processes
provides the most practical way of covering a wide range of rupture and wave propagation scenarios. We
apply 2D spatial data analysis tools, commonly used in geostatistics, to characterizing earthquake rupture
process and developing an effective source modeling tool for strong motion prediction. The earthquake
source process is described by key kinematic source parameters, such as static slip, rupture velocity, and
slip duration. The heterogeneity of each source parameter is characterized with auto-coherence while the
linear dependency (coupling) between parameters is characterized with cross-coherence. Both zero and
non-zero offset spatial coherence can be considered in the form of cross-coherence. We analyzed both
synthetic and real dynamic rupture models to demonstrate the efficiency of these new techniques and
found that many important features of earthquake rupture can be captured in this way, which may be
difficult to analyze, or even detect by zero offset coherence only. For instance, the correlation maximum
between slip and rupture velocity can be shifted from the zero offset, i.e., large slip may generate faster
rupture velocity ahead of the current rupture front, which may be important for rupture directivity. We
demonstrate that we can generate a number of realizations of earthquake source models to reproduce the
target coherence using stochastic modeling techniques (e.g., sequential Gaussian simulation) once
coherence structures in earthquake rupture are well understood. This type of coherence analysis may
provide the potential for improved understanding of earthquake source characteristics, and how they
control the characteristics of near-fault strong ground motions.

Song, S., & Somerville, P. G. (2010). Physics-based Earthquake Source Characterization and Modeling with Geostatistics. Bulletin of the Seismological Society of America, 100, 482-496. doi: 10.1785/0120090134.