Publications

A velocity model of the Awibengkok (aka Salak) geothermal field, West Java, was generated from thousands of micro-earthquake events. By using seismic tomography, delay travel times of P-waves and S-waves were studied in conjunction with geothermal production and injection. A non-linear approach was used to solve delay time tomography. This enabled extension of the study to generate attenuation and anisotropy 3-D models from waveform analysis of first arrival micro-seismic events. In attenuation tomography, t* is an operator comparable with travel time in velocity tomography, derived from fitting a theoretical spectral curve with observed spectral data. The attenuation 3-D model was generated constrained by a velocity model. The first step in generating the anisotropy cube was determination of S-wave splitting. The maximum S-wave split time was derived from polarization of micro-seismic records in horizontal components. The split travel times of shear waves can be used to estimate anisotropy of the transmitting medium (rock) through which it passed. Polarization angles of horizontal components are correlated with fracture orientations measured by conventional methods. Combinations of velocity, attenuation, and anisotropy tomography can characterize the structural geology, reservoir delineation, fluid content, and fracture area of a geothermal field. Keywords: geothermal, velocity, attenuation, anisothrophy, tomography, micro-seismic