How Sensitive Are Fault-Slip Rates in the Los Angeles Basin to Tectonic Boundary Conditions?

Abstract

Geodetic studies have produced different interpretations of the relative vertical thickening versus escape tectonics occurring within the Los Angeles basin based on calculated horizontal strain rates ranging from 56 ‫ן‬ 10 ‫9מ‬ /yr contraction at N36ЊE to 85 ‫ן‬ 10 ‫9מ‬

Using Vertical Rock Uplift Patterns to Constrain the Three-Dimensional Fault Configuration in the Los Angeles Basin

“…We apply 72 nanostrain per year of contraction at N09°E and 0 nanostrain per year contraction at S81°E according to present-day geodetic velocities (Argus et al, 2005). Within three-dimensional models, these tectonic boundary conditions produce fault slip senses that match expected slip sense (Griffith and Cooke, 2005) and slip rates that match the available geologic slip rates (Cooke and Marshall, 2006). Present-day tectonic boundary conditions may not have persisted over the 2.9 Ma following the beginning of deposition of the Pico Member and younger strata.…”

“…the LA basin have the greatest uncertainty in terms of geometry, connectivity, slip rate, and earthquake potential (e.g., Davis and Namson, 1994;Yeats and Huftile, 1995;Shaw et al, 2002;Griffith and Cooke, 2005), three-dimensional characterization of fault shape must be inferred from fold shape. Whereas kinematic models provide a geometric means for inferring fault shape from folds (e.g., Suppe, 1983;Davis et al, 1989;Woodward et al, 1989;Suppe and Medwedeff, 1990;Shaw and Suppe, 1996), they exclude the mechanics of deformation.…”

Community Fault Model (CFM) for Southern California

“…However, for nonplanar faults, faults that do not dip vertically or that are concealed beneath the Earth's surface (i.e., blind faults), more precise three-dimensional representations are needed to accurately define subsurface fault geometry. Precise fault system geometries better define earthquake source parameters, such as the fault surface area, and have been shown to have an important influence on slip rate estimates derived from geodetic constraints (e.g., Griffith and Cooke, 2005;Meade and Hager, 2005a) and on rupture dynamics (e.g., Poliakov et al, 2002;Ogelsby, 2005). Thus, scientists of the Southern California Earthquake Center (SCEC) have contributed to the development of a community-based three-dimensional fault model (CFM) for southern California to study active faulting and earthquake phenomena and to improve regional earthquake hazards assessments (Fig.…”

“…1). The CFM is currently being used to more accurately model crustal deformation based on observed geodetic displacements, to improve representations of earthquake sources and basin structure in order to predict strong ground motions, and to assess probabilistic seismic hazard (e.g., Aochi and Olson, 2004;Graves and Wald, 2004;Field et al, 2005;Griffith and Cooke, 2005;Meade and Hager, 2005a). This paper describes the CFM and how it was constructed and then evaluates the completeness of the model based on comparisons with regional earthquake catalogs.…”

The geodynamics of faults and petroleum migration in the Los Angeles basin, California

“…It is within the active transform boundary zone, and deformation is ongoing due to the relative motion of the North American and Pacific plates (Wright, 1991;Griffith and Cooke, Biddle, 1991). The background elevation map was generated by Global Multi-Resolution Topography (GMRT) Synthesis (Ryan and others, 2009). 2005; Fisher and others, 2009).…”