| Summary: | 碩士 === 國立中央大學 === 地球科學學系 === 105 === The Ilan geothermal field is the largest known productive geothermal area in Taiwan, and the distribution of geothermal reservoirs are related to the pattern of shallow structure. Using gravity analyses are well suited to investigate the reliable subsurface density structure. First, we combine with land and marine gravity data to obtain gravity anomaly. We use the filter based on the relationship between gravity anomalies and the depth of source to analysis gravity data. Second, we obtained two-dimensional density structure referred to north-south seismic profile.
In our study, residual gravity anomalies show that most of the faults in the north part of the Ilan Plain are reverse fault. The Choshui Fault is the boundary fault between the Hsuehshan Range and the Central Range. The pattern of SanShin fault is not clear, but the negative gravity anomaly was found in south part of the Ilan Plain might relate to the activity structure. Furthermore, there is a positive gravity anomaly beneath the Lanyang River, comparing with the magnetic result, we propose intrusive igneous rocks exist beneath the Ilan Plain.
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