Tectonic setting of deep geothermal system in island arc

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We have conducted three transects of MT soundings across central Java, south Sumatra and the Flores island in the Sunda arc. The present tectonic situation of the Sunda arc is divided by three types based on the plate subduction style. The Sumatra area is characterized by the oblique subduction of the Indian Ocean plate. The Jawa - Sumbawa area is characterized by the normal subduciton at Jawa trench and the Flores - Timor area is characterized by the collision of the arc with the northward moving the Australian continental plate.These situation may have affected a crust structure regarded as a stage of volcanic and geothermal activity. Although the crust structure has reflected these present situations as well as the tectonic evolution in each area for a long time, present crust activities, such as volcanic, geothermal and seismic activity, are reflecting present tectonic situation. We attempted to delineate the framework of the crust structure which strongly reflected long time tectonic revolution and the feature of structure relating to present crust activity in this study.The 2D resistivity structure revealed that the resistivity of the crust in the fore-arc side is genenrally higher, but back-arc side is relatively low. This may reflect the geothermal situation in the crust and shows the temperature gradient is probably higher in the back-arc side. The batholith was appeared beneath the big volcanoes and the geothermal water circulation zone seemed develop around the batholith. The resistivity of the crust tend to generally low in the Sumatra. The pull-a-part basins were formed associating with the activity of the transcurrent fault dragging by the oblique subuduction and the volcanoes and geothermal field developed in these area. We obtained these knowledge concerning the back ground structure of deep-seated geothermal resource in the island arc.