Seismicity of the Geysers-Clear Lake region, California

Bufe, Charles G.; Marks, S.M.; Lester, F.W.; Ludwin, R.S.; Stickney, Michael C.

doi:10.3133/ofr80988

Cited by 21 publications

(16 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Subsequent work by Hearn et al (1976Hearn et al ( , 1981 Tectonic activity has controlled not only basin development but also alignments of vents within the Clear Lake volcanic field (Hearn et al, 1988). Seismic evidence (Bufe et al, 1981;Oppenheimer, 1986) indicates that the Geysers-Clear Lake area is currently under extension. The extension is generated within the North American plate, between faults of the broad San Andreas transform fault system.…”

Section: Clear Lake Volcanicsmentioning

confidence: 94%

“…Corroborative evidence is provided by a major heat flow anomaly in which values over much of the volcanic field exceed 4 heat flow units (HFU) and exceed 12 HFU in parts of The Geysers geothermal field (Walters and Combs, 1992). A lack of deep earthquake foci under the volcanic field provides supporting evidence for the existence of a magma body at depth (Bufe et al, 1981). Because no magnetic high is associated with the gravity low, Isherwood (1976) proposed that the magma body is above its Curie point of approximately 550øC.…”

Section: Geophysical Datamentioning

confidence: 98%

See 1 more Smart Citation

The Geysers-Clear Lake area, California; thermal waters, mineralization, volcanism, and geothermal potential

Donnelly‐Nolan¹,

Burns²,

Goff³

et al. 1993

Economic Geology

View full text Add to dashboard Cite

Manifestations of a major thermal anomaly in the Geysers-Clear Lake area of northernCalifornia include the late Pliocene to Holocene Clear Lake Volcanics, The Geysers geothermal field, abundant thermal springs, and epithermal mercury and gold mineralization, The epithermal mineralization and thermal springs typically occur along high-angle faults within the broad San Andreas transform fault system that forms the western boundary of the North American plate in this area. The young volcanic rocks overlie Mesozoic marine rocks of the Great Valley sequence which have been thrust above the coeval Franciscan Complex and penecontemporaneously dropped back down along low-angle detachment faults.Many of the waters of the region are nonmeteoric as defined by their isotopic signature. One type of isotopically shifted water emerges from or near Great Valley sequence rocks and is the most chloride rich. It is interpreted to be evolved cormate in origin. A second type, evolved meteoric water, has moderate chloride contents, high boron contents, and high B/CI ratios and is found locally in Franciscan rocks, notably at the Sulphur Bank mercury mine, where it probably results from near-closed-system, repeated boiling of meteoric water in host rocks that also contribute organic components to the water. At the Sulphur Bank mine fracturing of otherwise impermeable Franciscan rocks by faulting has created a localized zone of permeability in which thermal water boils repeatedly with limited venting to the surface. Boron-rich fluids were apparently present at depth in The Geysers geothermal field when intrusion of silicic magma occurred, because the concealed intrusion of felsite is surrounded by a halo of tourmaline-bearing hornfels. The volume of this poorly dated early to middle Quaternary intrusive body probably exceeds the 100 km a of erupted Clear Lake Volcanics. Similar intrusions may have occurred in the eastern part of the area at Wilbur Springs and theMcLaughlin mine, where gold deposition and evidence of hydrothermal phenomena suggest more magmatic activity than is indicated by the small exposed bodies of early Quaternary basaltic lava. The Clear Lake Volcanics are the present locus of volcanism in the northern Coast Ranges and progressively older volcanic centers occur to the south. Geophysical data suggest that a large silicic magma body may be centered north of The Geysers steam field, providing the heat for the geothermal field.Geothermal power production has peaked at The Geysers and pressure declines indicate significant depletion of the fluid resource. The vapor-dominated field evolved from a preexisting hydrothermal system within fractured, otherwise impermeable Franciscan metamorphic rocks. A deep water table of saline fluid has been postulated to be present under the steam field, but no chloride-rich water has been found at drillable depth. We propose that recently discovered, isotopically shifted steam in the northwest Geysers area indicates the presence not of deep connate water but xather of boiled-down, boron-r...

show abstract

Section: Clear Lake Volcanicsmentioning

confidence: 94%

Section: Geophysical Datamentioning

confidence: 98%

The Geysers-Clear Lake area, California; thermal waters, mineralization, volcanism, and geothermal potential

Donnelly‐Nolan¹,

Burns²,

Goff³

et al. 1993

Economic Geology

View full text Add to dashboard Cite

show abstract

“…Monitoring of microearthquakes related to production and injection has been conducted since the mid 1970's. MEQ has been applied as a general indicator of fluid paths and general response to injection at The Geysers for over 20 years (Majer, 1978, Majer and McEvilly 1979, Marks et al, 1978Ludwin and Bufe, 1980;Peppin and Bufe, 1980;Bufe et al, 1981;Allis, 1982;Denlinger and Bufe, 1982;Ludwin et al, 1982;Eberhart-Phillips and Oppenheimer, 1984;Oppenheimer, 1986;Stark, 1992, Stark and Majer, 1989, Beall et al, 1999, Smith et al, 2000. A dramatic increase in planned injection rates and spatial extent of injection due to the recent completion of the Santa Rosa wastewater pipeline has raised concerns regarding the societal and economic impact of injection related seismicity.…”

Section: Background and Past Workmentioning

confidence: 99%

Integrated High Resolution Microearthquake Analysis and Monitoring for Optimizing Steam Production at The Geysers Geothermal Field, California

Majer¹,

Peterson²,

Stark³

et al. 2004

View full text Add to dashboard Cite

“…haa demonstrated that understanding of the relationship between seismicity and steam production at The Geysers requires determining the source properties of microearthquakes there. Bufe et al, (1981) inferred that the wide variations of fault plane solutions found at The Geysers using P-wave first motion data were a function of time . .oppenheimer (1986) estimated the stress field orientation at The Geysers from 210 fault plane solutions.…”

Section: Introductionmentioning

confidence: 98%

“…The Geysers is also the world's largest generator oC electricity using geothermal energy. It has been suggested that seismicity in The Geysers is induced by some aspect of steam production but the specific mechanism has not been determined Eberhart-Phillips and Oppenheimer, 1984;Bufe et al, 1981). OC all the inducing mechanisms proposed to explain the seismicity, per~ turbation oC the regional stress field by volumetric contraction of the reservoir due to a net mass (water) withdrawal and conversion oC aseismic slip due to.…”

mentioning

confidence: 99%

Seismic velocity structure and microearthquake source properties at The Geysers, California, geothermal area

O’Connell¹

1986

View full text Add to dashboard Cite

The method oC progressive hypocenter-velocity inversion has been extended to incorporate S-wave arrival time data and to estimate S-wave velocities in addition to P-wave velocities.Synthetic tests demonstrate that the joint use oC P and S-wave arrival time data has the Collowing advantages over the-use-oC-P---w,av.e-data-alone;-{-l-}--P--wav-e-v·elacity-and-slowness~gradient-structure are more accurately estimated; (2) hypocenter mislocation errors are substantially reduced, especially hypocentral depth; (3) convergence oC progressive inversions to local minima is more detectable using RMS data, misfits oC P and S-wave data; (4) velocity model and hypocenter estimates are more accurately determined when station corrections are used; (5) errors in linearized resolution and error estimated are reduced; and (6) complete elastic properties are estimated providing greater constraints Cor geologic interpretation oC velocity structure. Adding S-wave data to progressive inversion does not completely eliminate hypocenter-velocity tradeoffs, but they are substantially reduced.Results oC a P and S-wave progressive hypocente~velocity inversion at The Geysers show that the top oC the steam reservoir is clearly defined by a large decrease oC Vp/V. at the condensation zone-production zone contact. The depth interval oC maximum steam production coincides with minimum observed VpfV., and Vp/V. increases below the shallow primary production zone suggesting that reservoir rock becomes more fluid saturated. 2The moment tensor inversion method wast applied to three· microearthquakes at The Geysers. Estimated principal stress orientations were comparable to those estimated using Pwave first motions as constraints. Well constrained principal stress orientations were obtained for one event for which the 17 P-first motions could not distinguish between normal-slip and strike-slip mechanisms. The moment tensor estimates of principal stress orientations were obtained using far fewer stations than required for first-motion focal mechanism solutions. The three ,focal mechanisms lobtain!!d' here support the hypothesis that' focal mechanisms are a Junction of,depth at. The Geysers.'Progressive inversion as developed here and the moment tensor inversion method provide a complete approach for determining earthquake locations, P and S-wave velocity structure, and earthquake source mechanisms.

show abstract

Seismicity of the Geysers-Clear Lake region, California

Cited by 21 publications

References 0 publications

The Geysers-Clear Lake area, California; thermal waters, mineralization, volcanism, and geothermal potential

The Geysers-Clear Lake area, California; thermal waters, mineralization, volcanism, and geothermal potential

Integrated High Resolution Microearthquake Analysis and Monitoring for Optimizing Steam Production at The Geysers Geothermal Field, California

Seismic velocity structure and microearthquake source properties at The Geysers, California, geothermal area

Contact Info

Product

Resources

About