| Abstract: | Geodetic surveys since 1972-73 reveal significant crustal deformation in The Geysers-Clear Lake region. Resurveys of precise control networks are measuring both vertical and horizontal ground movement, with most of the change continuing in the area of geothermal fluid withdrawal. Preliminary evidence suggests right-lateral horizontal movement on northwest-trending fault systems and vertical and horizontal compression of the deep geothermal reservoir system. A direct correlation is suggested between ground-surface deformation and subsurface pressure changes in the reservoir system. Although surface changes appear too small to be of environmental concern in The Geysers-Clear Lake region, they indicate hydrodynamic changes in the reservoir of significant import.
Two types of vertical changes in The Geysers production area are indicated in the 1973-77 data--(a) a regional subsidence between the Collayomi and Mercuryville fault zones and (b) local subsidence directly related to the area of principal steam production. Maximum subsidence of 13 centimeters in 4? years occurred in the area of most concentrated steam withdrawals and where fluid-pressure declines were near maximum. Subsidence rates throughout the production area from 1973 to 1975 were about half the 1975-77 rates in apparent correlation with pressure changes measured in the reservoir system. Horizontal ground movement as great as 2.0 centimeters per year, generally inward toward the center of production, was measured around the perimeter of the steam production area. |
| Genre: | USGS Numbered Series |
| ProdID: | 10063 |
| Citation Author: | Lofgren, Ben Elder |
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| Citation Language: | ENGLISH |
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| Citation Phsyical Description: | iv, 26 p. :8 maps (fold. in envelope) ;27 cm. |
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| Citation Publisher: | U.S. Geological Survey, |
| Citation Series: | Open-File Report |
| Citation Series Code: | OFR |
| Citation Series Number: | 78-597 |
| Citation Search Results Text: | Monitoring crustal deformation in The Geysers-Clear Lake geothermal area, California; 1978; OFR; 78-597; Lofgren, Ben Elder |
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| Citation Year: | 1978 |
| Type: | citation/reference |
| Text: | Monitoring crustal deformation in The Geysers-Clear Lake geothermal area, California; 1978; OFR; 78-597; Lofgren, Ben Elder |
| URL (THUMBNAIL): | http://pubs.usgs.gov/of/1978/0597/report-thumb.jpg |
| URL (DOCUMENT): | http://pubs.usgs.gov/of/1978/0597/report.pdf |
| URL (PLATE): | http://pubs.usgs.gov/of/1978/0597/plate-1.pdf |
| URL (PLATE): | http://pubs.usgs.gov/of/1978/0597/plate-2.pdf |
| URL (PLATE): | http://pubs.usgs.gov/of/1978/0597/plate-3.pdf |
| URL (PLATE): | http://pubs.usgs.gov/of/1978/0597/plate-4.pdf |
| URL (PLATE): | http://pubs.usgs.gov/of/1978/0597/plate-5.pdf |
| URL (PLATE): | http://pubs.usgs.gov/of/1978/0597/plate-6.pdf |
| Date Other: | Sat, 1 Jan 1994 00:00 -0600 |
| Publisher: | U.S. Geological Survey, |
