The PoroTomo Team includes: Kurt L. FEIGL(1), Elena C. REINISCH(1), Jeremy R. PATTERSON (1), Samir JREIJ(7), Lesley PARKER(1), Avinash NAYAK(1), Xiangfang ZENG(1,9), Michael A. CARDIFF(1), Neal E. LORD (1), Dante FRATTA(1), Clifford H. THURBER(1), Herbert F. WANG(1), Michelle ROBERTSON(2), Thomas COLEMAN(3), Douglas E. MILLER(3), Paul SPIELMAN(4), John AKERLEY(4), Corné KREEMER(5), Christina MORENCY(6), Eric MATZEL(6), Whitney TRAINOR-GUITTON(7), and Nicholas C. DAVATZES(8). (1) University of Wisconsin-Madison, Department of Geoscience, Madison, WI, United States; (2) Lawrence Berkeley National Laboratory, Berkeley, CA, United States; (3) Silixa, Houston, TX, United States; (4) Ormat Technologies Inc., Reno, NV, United States; (5) University of Nevada Reno, NV, United States; (6) Lawrence Livermore National Laboratory, Livermore, CA, United States; (7) Colorado School of Mines, Golden, CO, United States; (8) Temple University, Philadelphia, PA, United States; (9) State Key Laboratory of Geodesy and Earth's Dynamics,Institute of Geodesy and Geophysics, Chinese Academy of Sciences In the geothermal field at Brady Hot Springs, Nevada, subsidence occurs over an elliptical area that is ~4 km by ~1.5 km. Highly permeable conduits along faults appear to channel fluids from shallow aquifers to the deep geothermal reservoir tapped by the production wells. Results from inverse modeling suggest that the deformation is a result of volumetric contraction in units with depth less than 600 m [Ali et al., 2016]. Characterizing such structures in terms of their rock-mechanical properties is essential to successful operations of Enhanced Geothermal Systems (EGS). The goal of the PoroTomo project is to assess an integrated technology for characterizing and monitoring changes in the rock-mechanical properties of an EGS reservoir in three dimensions with a spatial resolution better than 50 meters. In March 2016, we deployed the integrated technology in a 1500-by-500-by-400-meter volume at Brady Hot Springs. The data set includes: active seismic sources, fiber-optic cables for Distributed Acoustic Sensing (DAS) and Distributed Temperature Sensing (DTS) arranged vertically in a borehole to ~400 m depth and horizontally in a trench 8700 m in length and 0.5 m in depth, 244 seismometers on the surface, three pressure sensors in observation wells, continuous geodetic measurements at three GPS stations, and seven InSAR acquisitions. The deployment consisted of four distinct time intervals ("stages"). Between each measurement interval, the hydrological conditions were intentionally manipulated by modifying the rates of pumping in the injection and production wells. To account for the mechanical behavior of both the rock and the fluids, we are developing numerical models for the 3-dimensional distribution of the material properties. In this paper, we provide a snapshot of work in progress, including the highlights listed in the Conclusions below. The work presented herein has been funded in part by the Office of Energy Efficiency and Renewable Energy (EERE), U.S. Department of Energy, under Award Number DE-EE0006760.

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