AE Hypocenter Distribution Compared with Detailed Gravity Data and Resistivity in the Hatchobaru Geothermal Field

Abstract

In the Hatchobaru geothermalfield, located in the central part of Kyushu, Jqan, we have been carrying out AE (acoustic emission) observation using boreholes in a 6-station network since December 1996. Over a thousand AE and several AE swarms were observed over a ten-month period.

We tried to estimate the location and strike of faults by calculating the &pocenter and determining the .4E mechanism. Comparing the AE h t a with detailed gravity and resistivity data, we find that most of the hypocenters of AE swam are located in one of the low-gravity anomat) zones. The strikes of faults estimated by AE mechanical analysis agree with isogal and isoresistivig contours.

AE data is effective for estimating faults. Some high permeability wells were located near estimated faults in the AE swarm areas. Pariicularl'y in low resistivity zones, it is sometimes dificult to locate faultsfrom magnetotelluric abta, but can be rather effectivef rom AE data.