Earthquake locations in southern California obtained using source‐specific station terms

Abstract

Abstract. We relocate 297,400 events recorded by the Southern California Seismic Network (SCSN) between 1975 and 1998 using spatially varying station terms to improve relative location accuracy. Our method uses existing SCSN P and $ picks, a smooth one-dimensional velocity model, and an iterative grid search approach based on the L1 norm. We apply empirical corrections for three-dimensional structure by computing station timing corrections that continuously vary as a function of source position. Station terms for each event are obtained by smoothing the residuals from nearby events using a natural neighbor (Delaunay) tessellation of the seismicity and then iterating until a stable set of locations and station terms is achieved. Our approach achieves relative location accuracy comparable locally to master event methods but can be applied uniformly over large regions. Median estimated standard errors for our final locations are 328 m in horizontal position and 741 m in depth. Our locations exhibit much less scatter, particularly in depth, than those of the SCSN catalog and a greater tendency to align into linear and planar features suggestive of fault structures. Our results appear comparable to, and in some cases better than, previous SCSN relocation studies using joint-hypocentervelocity inversion techniques. Plots of daytime versus nighttime events permit discrimination between clusters of natural and artificial seismicity. We observe no simple relationship between the maximum depth of seismicity and surface geology.

Rupture Process and Aftershocks Relocation of the 8 June 2008 Mw 6.4 Earthquake in Northwest Peloponnese, Western Greece

“…In order to obtain more precise locations of this earthquake sequence, we used the COMPLOC package (Lin and Shearer, 2006) that applies a shrinking grid-search relocation algorithm using the source specific station term method (Richards-Dinger and Shearer, 2000;Lin and Shearer, 2005). The method accepts as input the initial location of events and their corresponding travel times, calculates iteratively station corrections for each source-receiver pair, and inverts for a new set of locations.…”

Late Quaternary slip rate gradient defined using high‐resolution topography and 10Be dating of offset landforms on the southern San Jacinto Fault zone, California

“…[3] The San Jacinto fault zone (SJFZ) has historically been more seismically active than the southern San Andreas fault zone [Thatcher et al, 1975;Richards-Dinger and Shearer, 2000], but its longer-term slip history is controversial. Although many previous studies across the fault zone have documented well-preserved offsets of Quaternary landforms [e.g., Sharp, 1967Sharp, , 1981Rockwell et al, 1990], fault slip rates are often more poorly defined due to the inherent difficulties of dating Quaternary deposits.…”

Interseismic strain accumulation and the earthquake potential on the southern San Andreas fault system

“…To explore this possibility, I hypothesise that the Coyote Creek fault is not the main branch of the southern San Jacinto fault system, and that most of strain accumulation occurs on an unmapped strike-slip fault connecting the southern termination of the San Jacinto fault and the Superstition Hills fault (see dashed red line in Figure 1). In case of the SAF, one might argue that the fault is dipping to the east 26,27 , based on a fact that seismicity occurs several kilometers off the fault trace 28 . The hypothesised alternative locations of shear zones driving the interseismic deformation at the brittle-ductile transition are denoted by dashed green lines in Figure 2.…”