DOI: 10.5176/2251-3353_GEOS16.9

Authors: Mia Uswatun Hasanah, Billy S. Prabowo, Andri Dian Nugraha

Abstract: Micro-earthquake (MEQ) method is one of geophysical method that used in exploration and monitoring in geothermal field. In this study MEQ data has been applied in the evaluation of geothermal resource sustainability potential (saturations, state of saturations, pore pressure, porosity, permeability and also temperature). In this study, we determined subsurface seismic attenuation structures using micro-earthquake (MEQ) waveform from fluid injection activities for time period of May 19 up to July 19, 2005. In this study, there were 175 micro-earthquake events which are recorded by 17 stations. The variable to determine attenuation tomography inversion was operator attenuation (t*) which was calculated by spectral fitting method. We use source model for velocity amplitude spectrum to invert the t* value. For the attenuation tomographic inversion, we used the initial 3-D velocity model from the previous study in this region. We have been successfully calculated t* of P-and S-wave of 1,157 and 1,111, respectively. Overall, we observed prominent low Qp and low Qs values around reservoir zone coincide with low Vp/Vs ratio value. Our interpretation, these anomalies may be associated with steam saturated zone. In this study, attenuation tomographic inversion results will give new insight into to infer steam saturated related to reservoir zone. We can see that the high attenuation value (low Q value) and low velocity anomaly structures may corresponded to fluid filled rock and also fault segment. We also aim to determine thermal structure from Q value to see the variation of temperature in geothermal field
Keywords: Attenuation, Q-tomographic, micro-earthquakes, geothermal

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