C.C. Grant A. Ross B.R. Julian G.R. Foulger 1997 <div class=""><div class="article-section__content en main"><p>Industrial exploitation is causing clearly-measurable changes in Earth structure at The Geysers geothermal area, California. Production at The Geysers peaked in the late 1980s at ∼3.5 × 10³ kg s⁻¹<span>&nbsp;</span>of steam and 1800 MW of electricity. It subsequently decreased by about 10% per year [<i>Barker et al.</i>, 1992] because of declining reservoir pressure. The steam reservoir coincides with a strong negative anomaly (∼0.16, ∼9%) in the compressional-to-shear seismic wave speed ratio<span>&nbsp;</span><i>V_P</i>/<span>&nbsp;</span><i>V_S</i>, consistent with the expected effects of low-pressure vapor-phase pore fluid [<i>Julian et al.</i>, 1996]. Between 1991 and 1994 this anomaly increased in amplitude by up to about 0.07 (∼4%). This is consistent with the expected effects of continued pressure reduction and conversion of pore water to steam as a result of exploitation. These unique results show that<span>&nbsp;</span><i>V_P</i>/<i>V_S</i><span>&nbsp;</span>tomography can easily detect saturation changes caused by exploitation of reservoirs, and is a potentially valuable technique for monitoring environmental change. They also provide geophysical observational evidence that geothermal energy is not a renewable energy source.</p></div></div> application/pdf 10.1029/96GL03152 en American Geophysical Union Industrially induced changes in Earth structure at the geysers geothermal area, California article