<> "The repository administrator has not yet configured an RDF license."^^ . <> . . . "Degradation of the mechanical properties imaged by seismic tomography during an EGS creation at The Geysers (California) and geomechanical modeling"^^ . "Using coupled thermal-hydro-mechanical (THM) modeling, we evaluated new seismic tomography\r\nresults associated with stimulation injection at an EGS demonstration project at the Northwest Geysers\r\ngeothermal steam field, California. We studied high resolution seismic tomography images built from\r\ndata recorded during three time periods: a period of two months prior to injection and during two consecutive\r\none month periods after injection started in October 2011. Our analysis shows that seismic\r\nvelocity decreases in areas of most intense induced microseismicity and this is also correlated with\r\nthe spatial distribution of calculated steam pressure changes. A detailed analysis showed that shear wave\r\nvelocity decreases with pressure in areas where pressure is sufficiently high to cause shear reactivation of\r\npre-existing fractures. The analysis also indicates that cooling in a liquid zone around the injection well\r\ncontributes to reduced shear wave velocity. A trend of reducing compressional wave velocity with fluid\r\npressure was also found, but at pressures much above the pressure required for shear reactivation. We\r\nattribute the reduction in shear wave velocity to softening in the rock mass shear modulus associated\r\nwith shear dislocations and associated changes in fracture surface properties. Also, as the rock mass\r\nbecome more fractured and more deformable this favors reservoir expansion caused by the pressure\r\nincrease, and so the fracture porosity increases leading to a decrease in bulk density, a decrease in Young\r\nmodulus and finally a decrease in Vp."^^ . "2015" . . "240" . . "Elsevier"^^ . . . "Physics of the Earth and Planetary Interiors"^^ . . . "00319201" . . . . . . . . . . . . . . . . . . . . . . . . . . "Patrick F."^^ . "Dobson"^^ . "Patrick F. Dobson"^^ . . "Ankit"^^ . "Singh"^^ . "Ankit Singh"^^ . . "Jonny"^^ . "Rutqvist"^^ . "Jonny Rutqvist"^^ . . "Julio"^^ . "Garcia"^^ . "Julio Garcia"^^ . . "Craig"^^ . "Hartline"^^ . "Craig Hartline"^^ . . "Pierre"^^ . "Jeanne"^^ . "Pierre Jeanne"^^ . . "Lawrence"^^ . "Hutchings"^^ . "Lawrence Hutchings"^^ . . "Mark"^^ . "Walters"^^ . "Mark Walters"^^ . . "Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA, USA"^^ . . . "Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA, USA"^^ . . . "Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA, USA"^^ . . . "Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA, USA"^^ . . . "Lawrence Berkeley National Laboratory, Earth Sciences Division, Berkeley, CA, USA"^^ . . . "Calpine Corporation, 10350 Socrates Mine Road, Middletown, CA, USA"^^ . . . "Calpine Corporation, 10350 Socrates Mine Road, Middletown, CA, USA"^^ . . . "Calpine Corporation, 10350 Socrates Mine Road, Middletown, CA, USA"^^ . . . . . . "HTML Summary of #1684 \n\nDegradation of the mechanical properties imaged by seismic tomography during an EGS creation at The Geysers (California) and geomechanical modeling\n\n" . "text/html" . . . "Collective properties of seismicity" . . . "Geysers" . . . "Geothermal energy production" . .