Fluid circulation and heat extraction from engineered geothermal reservoir

The hypocenters of microearthquakes in the Kakkonda geothermal _eld have been relocated along the Kakkonda River using a new velocity structure model[ Compared to the solution used by the previous velocity modelthe depth of the hypocenters is shallower in the relocation[ The mic! roearthquakes occurred in a highly fractured region\ as suggested by geological and petrological studies based on well data\ but did not occur along major tectonic folds and faults[ An alternative hydraulic condition might be necessary to trigger the earthquakes[ Seismicity in 0884 was lower than in 0877 in Kakkonda[ The decrease in the number of events is possibly due to the decrease in the amount of reinjection ~uid or the change in the characteristics of the geothermal reservoir[ The number of microearthquakes decreases rapidly at 0 1km below sea!level[ Probability density of seismic energy distribution is utilized to indicate the active seismic regions[ The model also shows that a contour map of the lower boundary of the high seismic energy region corresponds to the occurrence of cordieritewhich was produced by heat from the neo!granitic pluton body\ implying that the occurrence of microearthquakes in the Kakkonda geothermal _eld is con! trolled by the neo!granitic rocks at depth[ The top of the granite can be imagedusing the probability density of seismic energy distribution[ 0887 CNR[ Published by Elsevier Science Ltd[ All ri`hts reserved