Global positioning system measurements of deformations associated with the 1987 Superstition Hills Earthquake: Evidence for conjugate faulting

Abstract

Large station displacements observed from Imperial Valley global positioning system (GPS) campaigns are attributed to the November 24, 1987, Superstition Hills earthquake sequence. Thirty sites from a 42‐station GPS network established in 1986 have been reoccupied during 1988 and/or 1990. Displacements at three sites within 3 km of the surface rupture approach 0.5 m. Eight additional stations within 20 km of the seismic zone are displaced at least 10 cm. This is the first occurrence of a large earthquake (MS 6.6) within a preexisting GPS network. Best‐fitting uniform slip models of rectangular dislocations in an elastic half‐space indicate 130 ± 8 cm right‐lateral displacement along the northwest‐trending Superstition Hills fault and 30 ± 10 cm left‐lateral displacement along the conjugate northeast‐trending Elmore Ranch fault. The geodetic moments are 9.4 × 1025 dyn cm and 2.3 × 1025 dyn cm for the Superstition Hills and Elmore Ranch faults, respectively, consistent with teleseismic source parameters. The data also suggest that postseismic slip along the Superstition Hills fault is concentrated at shallow depths. Distributed slip solutions using singular value decomposition indicate near uniform displacement along the Elmore Ranch fault and concentrated slip to the northwest and southeast along the Superstition Hills fault. A significant component of nonseismic secular displacement is observed across the Imperial Valley, which is attributed to interseismic plate‐boundary deformation.

GPS-derived Deformation of the Central Andes Including the 1995 Antofagasta M w = 8.0 Earthquake

“…The inversion yields the slip distribution from the surface deformation. The modeling performed in this study used the computer code GINV developed by S. Larsen (LARSEN et al, 1992). We divide the fault plane into a set of nonoverlapping rectangular elements; each with uniform slip.…”

Fault interaction and earthquake triggering in the Koyna‐Warna region, India

“…We present the analyses of available earthquake data to suggest that geometric pattern in the inferred faults, which leads to interaction amongst the fault zones, is a major cause for frequent and sustained seismicity of the region, in addition to the favourable reservoir effects on the seismogenic faults. Geometric disposition of fault segments leading to fault interaction plays an important role in the kinematics and dynamics of the earthquake occurrence processes [ Barka and Kadinsky‐cade , 1988; Hudnut et al , 1989; Larson et al , 1992; Segall and Pollard , 1980; King and Nábelek , 1985; Sibson , 1985; Talwani , 1988]. In this article, we first analyse the effect of fault interaction amongst the inferred fault zones in the Koyna‐Warna region and then discuss the effect of reservoirs in triggering earthquakes on the causative faults.…”

Coulomb stress accumulation along the San Andreas Fault system

“…We attribute this behavior to not only lack of data, but also the fact that the fault trace of this region was estimated by connecting the lower Anza segment with the upper Imperial fault trace. In this region, many small subparallel branches exist [Larsen et al, 1992] and we have most likely oversimplified the fault geometry. Seismicity is not particularly evident within 10 km of our estimated fault trace, and is found primarily to the southwest and constricted to the upper 10 km of the crust [Hill et al, 1991].…”