Project Sipoholon-Seismo Geothermal Energy Development in Indonesia A joint German-Indonesian multi-disciplinary project is established to develop geothermal energy in Indonesia. In our sub-project we will use seismological methods for geothermal exploration in advance of production. We will measure the natural micro-seismicity in the area around Sipoholon (Sumatra fault, Lake Toba area) over a period of 6 month. The data will be used (1) to study the seismic and geological structure using tomography, (2) to determine the locations of micro-earthquakes and (3) focal mechanismus, and (4) to determine stress field and fault distributions as the crucial items for geothermal exploration and production. The project is closely linked with other research activities including structural geology, temperature and stress field modeling, MT exploration, geochemistry, and petrology.