Seismological investigations in geothermal regions

Technical Report · Mon May 01 04:00:00 EDT 1978

DOI:https://doi.org/10.2172/6700896· OSTI ID:6700896

Majer, E L

Seismological methods, including studies of microearthquakes, P- and S-wave velocities and P-wave attenuation were investigated as tools for the exploration and delineation of geothermal resources. Seismograms from explosions and microearthquakes were examined for changes in frequency content and relative arrival times across a known geothermal area, The Geysers, California, and a potential geothermal region, Grass Valley, Nevada. Microearthquakes within the two regions were examined for evidence of spatial variations in radiated P- and S-waves. Additional information concerning Basin and Range structure was provided by regional refraction studies. Detailed structural analysis in Grass Valley was obtained by commercial reflection and refraction work. Heat flow modeling, consistent with structure inferred by seismological techniques, was used to discriminate between conductive and convective heat flow anomalies in Grass Valley. Concentrated observations in Grass Valley around Leach Hot Springs revealed moderate microearthquake activity on a trend crossing the southern end of the valley, with occasional swarms in the area of high heat flow (4 to 6 hfu) at the north end of the 1915 Pleasant Valley earthquake (mag = 7.5) fault trace. Studies in The Geysers steam field reveal significant velocity and attenuation anomalies associated with the production zone. It is concluded that with proper sampling in space and time, P- and S-wave velocity and attenuation data can detect and delineate significant anomalies associated with the static properties of a geothermal resource. Microearthquake data are useful for monitoring the dynamic strain relief processes associated with fluid movement, temperature and pressure gradients in geothermal environments.

• Research Organization: California Univ., Berkeley (USA). Lawrence Berkeley Lab.
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6700896
• Report Number(s): LBL-7054
• Country of Publication: United States
• Language: English

Related Subjects

15 GEOTHERMAL ENERGY
150301* -- Geothermal Exploration & Exploration Technology-- Geophysical Techniques & Surveys
CONVECTION
EARTHQUAKES
ENERGY TRANSFER
EXPLORATION
FLOW MODELS
FLUID FLOW
GEOLOGIC FAULTS
GEOLOGIC STRUCTURES
GEOPHYSICAL SURVEYS
GEOTHERMAL EXPLORATION
GEOTHERMAL FIELDS
GEYSERS GEOTHERMAL FIELD
Geothermal Legacy
HEAT FLOW
HEAT TRANSFER
HOT SPRINGS
MATHEMATICAL MODELS
MICROEARTHQUAKES
NATURAL CONVECTION
NEVADA
NORTH AMERICA
PRESSURE GRADIENTS
SEISMIC DETECTION
SEISMIC EVENTS
SEISMIC P WAVES
SEISMIC S WAVES
SEISMIC SURVEYS
SEISMIC WAVES
TEMPERATURE GRADIENTS
THERMAL SPRINGS
USA
VELOCITY
WESTERN REGION