Gravity and fault structures, Long Valley caldera, California

Conference · Wed Jul 01 04:00:00 EDT 1987

OSTI ID:6051142

Carle, S F; Goldstein, N E

The main and catastrophic phase of eruption in Long Valley occurred 0.73 m.y. ago with the eruption of over 600 km/sup 3/ of rhyolitic magma. Subsequent collapse of the roof rocks produced a caldera which is now elliptical in shape, 32 km east-west by 17 km north-south. The caldera, like other large Quarternary silicic ash-flow volcanoes that have been studied by various workers, has a nearly coincident Bouguer gravity low. Earlier interpretations of the gravity anomaly have attributed the entire anomaly to lower density rocks filling the collapsed structure. However, on the basis of many additional gravity stations and supporting subsurface data from several new holes, a much more complex and accurate picture has emerged of caldera structure. From a three-dimensional inversion of the residual Bouguer gravity data we can resolve discontinuities that seem to correlate with extensions of pre-caldera faults into the caldera and faults associated with the ring fracture. Some of these faults are believed related to the present-day hydrothermal upflow zone and the zone of youngest volcanic activity within the caldera.

• Research Organization: Lawrence Berkeley Lab., CA (USA)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 6051142
• Report Number(s): LBL-23648; CONF-871024-15; ON: DE87014117
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
CALDERAS
CALIFORNIA
FEDERAL REGION IX
GEOLOGIC FAULTS
GEOLOGIC FRACTURES
GEOLOGIC MODELS
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
GRAVITY SURVEYS
Geothermal Legacy
LONG VALLEY
NORTH AMERICA
SURVEYS
USA