Interpretation of shallow crustal structure of the Imperial Valley, California, from seismic reflection profiles

Technical Report · Fri May 01 04:00:00 EDT 1987

DOI:https://doi.org/10.2172/6060854· OSTI ID:6060854

Severson, L K

Eight seismic reflection profiles (285 km total length) from the Imperial Valley, California, were provided to CALCRUST for reprocessing and interpretation. Two profiles were located along the western margin of the valley, five profiles were situated along the eastern margin and one traversed the deepest portion of the basin. These data reveal that the central basin contains a wedge of highly faulted sediments that thins to the east. Most of the faulting is strike-slip but there is evidence for block rotations on the scale of 5 to 10 kilometers within the Brawley Seismic Zone. These lines provide insight into the nature of the east and west edges of the Imperial Valley. The basement at the northwestern margin of the valley, to the north of the Superstition Hills, has been normal-faulted and blocks of basement material have ''calved'' into the trough. A blanket of sediments has been deposited on this margin. To the south of the Superstition Hills and Superstition Mountain, the top of the basement is a detachment surface that dips gently into the basin. This margin is also covered by a thick sequence sediments. The basement of the eastern margin consists of metamorphic rocks of the upper plate of the Chocolate Mountain Thrust system underlain by the Orocopia Schist. These rocks dip to the southeast and extend westward to the Sand Hills Fault but do not appear to cross it. Thus, the Sand Hills Fault is interpreted to be the southern extension of the San Andreas Fault. North of the Sand Hills Fault the East Highline Canal seismicity lineament is associated with a strike-slip fault and is probably linked to the Sand Hills Fault. Six geothermal areas crossed by these lines, in agreement with previous studies of geothermal reservoirs, are associated with ''faded'' zones, Bouguer gravity and heat flow maxima, and with higher seismic velocities than surrounding terranes.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6060854
• Report Number(s): LBL-23888; ON: DE88000472
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150201* -- Geology & Hydrology of Geothermal Systems-- USA-- (-1989)
58 GEOSCIENCES
580201 -- Geophysics-- Seismology & Tectonics-- (1980-1989)
CALIFORNIA
EARTH CRUST
FEDERAL REGION IX
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
Geothermal Legacy
IMPERIAL VALLEY
NORTH AMERICA
SEISMIC SURVEYS
SURVEYS
TECTONICS
USA