Br. Julian et al., 3-DIMENSIONAL SEISMIC IMAGE OF A GEOTHERMAL RESERVOIR - THE GEYSERS, CALIFORNIA, Geophysical research letters, 23(6), 1996, pp. 685-688
Three-dimensional seismic travel-time tomography of The Geysers geothe
rmal area, in the coast ranges of northern California, shows a strong
(-9%) anomaly in V-p/V-s, the ratio of the compressional and shear wav
e V-p alone and corresponds speeds, that is not evident in V-p closely
to the most intensively exploited part of the This anomaly probably i
ndicates low pore pressure and relatively dry conditions, caused partl
y by boiling of pore water as steam is extracted. Steam pressure decre
ases over the last decade have probably caused seismologically measura
ble changes in wave speeds. Tomographic measurement of V-p/V-s is a pr
omising technique both for identifying geothermal resources and for mo
nitoring them during exploitation.