Microearthquake survey in the hot spring area in Parbati Valley (Himachal Pradesh, India)

Abstract A number of hot springs occur in the Parbati Valley in Himachal Pradesh in India. Temperatures range from 21 to 96°C, the boiling point of water at that altitude. Geological conditions, temperature variations and chemical composition of spring water in the Parbati Valley hydrogeological unit indicate that the deep thermal fluids are of meteoric origin. The maximum temperature acquired by water during its circulation is estimated to come close to 200°C. In order to assess the possibility of extracting geothermal energy, a seismic survey was arranged to locate the hypocentres of microearthquakes associated with the thermal source. A total of eight microearthquake units was set up at an interstation spacing of about 10 km and two months recording were obtained. During this period an average of 2–3 events per day was recorded with S—P interval less than 5 seconds. The data have been analysed with the help of Hypo 71, a Fortran IV computer program designed to determine the hypocentral parameters of earthquakes from seismic data. The results indicate faulting but there is no apparent spatial relationship to surface manifestations of geothermal energy.