Correlation between precision gravity and subsidence measurements at Cerro Prieto
Precision gravity measurements were made in the region of the Cerro Prieto geothermal field at yearly intervals from 1977 to 1981 to assess the feasibility of using gravity to determine subsurface reservoir changes with time. The extent of mass recharge in response to the continued production of fluids from this field was studied. Changes in gravity and ground elevation were observed throughout the region for the period of observation. Results indicate that the largest changes observed were the result of the Magnitude 6.1 (Caltech) Victoria earthquake of 8 June 1980. The epicenter of this earthquake was located 25 km southeast of the field on the Cerro Prieto Fault, which bounds the field on the southwest. Subsidence of up to 55 cm was measured east of the power plant, in the region between the northern end of the Cerro Prieto Fault and the southern end of the Imperial Fault. This area has been postulated to be the site of an active spreading center or pull-apart basin, and has been characterized by a high level of seismic activity during the last 10 years. Minor subsidence and small related gravity changes for the period preceeding the Victoria earthquake suggest that in spite of large fluid production rates, the reservoir is being almost completely recharged and that a measurable increase in subsurface density may be taking place. The results of measurements of horizontal ground motions made in this area are discussed in relation to the gravity and subsidence observations.
- Research Organization:
- Lawrence Berkeley Lab., CA (USA); California State Univ., Long Beach (USA)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 6505556
- Report Number(s):
- LBL-14894; CONF-8208109-2; ON: DE83005870
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
150301 -- Geothermal Exploration & Exploration Technology-- Geophysical Techniques & Surveys
150600* -- Geothermal Energy-- Environmental Aspects
CERRO PRIETO GEOTHERMAL FIELD
EARTHQUAKES
GEOLOGIC FAULTS
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
GEOTHERMAL FIELDS
GRAVITY SURVEYS
GROUND SUBSIDENCE
Geothermal Legacy
SEISMIC EVENTS
SEISMICITY
SURVEYS