Open AccessDeformation near the Coyote Creek fault, Imperial County, California: Tectonic or groundwater‐related?
Author(s) -
Mellors Robert J.,
Boisvert Alex
Publication year - 2003
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2001gc000254
Subject(s) - geology , interferometric synthetic aperture radar , fault (geology) , seismology , aquifer , groundwater , tectonics , slip (aerodynamics) , longitude , active fault , fault scarp , geomorphology , latitude , geodesy , synthetic aperture radar , geotechnical engineering , physics , remote sensing , thermodynamics
Interferometric synthetic aperture radar (InSAR) measurements show a consistent, 40‐km 2 wedge‐shaped area of deformation partially bounded by a branch of the Coyote Creek fault (a southern extension of the San Jacinto fault) in Imperial County, California, west of the Salton Sea. The deformation is centered at 33.1 N latitude, 116.0 W longitude. 18 ERS‐1 and ERS‐2 (descending) interferograms falling within 1992 to 2000 are analyzed. An average line‐of‐sight range change over the area of 6 ± 3 mm per year away from the satellite is observed with peak values up to 12 ± 3 mm per year. The southwestern edge of the deformation is partially bounded by a fault segment that ruptured in the 1968 M w 6.5 Borrego Mountain earthquake and which also showed triggered slip after the 1987 Superstition Hills earthquakes. The southeastern edge of the deformation also coincides with a mapped fault. The deformation is centered on a farming area that has pumped approximately 5.8 × 10 −6 m 3 per year of groundwater from 5 wells on the property and which shows declining water levels of 1.4 m per year. The area of highest change appears to be centered on location of the wells and away from the faults. The aquifer is at a depth of roughly 100 to 200 m and consists of sands with interbedded clays. It appears that the most likely explanation is subsidence due to groundwater withdrawal in a fault‐bounded aquifer rather than tectonic slip.