Groundwater Temperature

Abstract

Changes of temperature in response to earthquakes have long been documented and, in the case where systematic patterns of change can be discerned, may reveal important hydrogeologic processes. Progress in our understanding of these processes, however, has been slow, largely because systematic measurements are relatively scarce. In this chapter we review some cases where earthquake-induced changes of groundwater temperature were documented and interpreted. More importantly, we show that most interpretations are under-constrained and accurate explanation of the measured changes is often difficult. In order to better constrain the interpretation, co-located measurement of groundwater flow from conductive fractures or formations intersecting the wells is needed to interpret temperature measurements. An often neglected mechanism is turbulent mixing of water in wells, which may occur frequently during earthquakes because the water column in a well at thermal equilibrium with the local geotherm is usually in a state of mechanical disequilibrium.