Seismic Activity in the Kakkonda Geothermal System Characterized by the Quaternary Kakkonda Granite, Japan

Abstract

The seismic activity in the water-dominated Kakkonda geothermal system has been examined in relation to permeability. The microearthquakes occur only in the hydrothermal convection zone. The zone of hypocenters coincides with the permeable zone higher than 8?10-12m3 in permeability-thickness product (kh) value. The seismic activity in the Kakkonda geothermal system became active in association with the magma and/or magmatic water intrusion below Iwate Volcano, 13 km east of the field, and around the Mitsuishi-yama Volcano in February 1998. The microearthquakes in the Kakkonda geothermal system occurred along fractures in NE-SW and NW-SE direction, and occurred above the extended body of the Kakkonda Granite, the heat source of the geothermal system. The Kakkonda Granite underlies not only the exploited field but also the Mitsuishi-yama Volcano with acidic hydrothermal alteration and gas emission zones.