EARTHQUAKE CUTOFF DEPTH AS A POSSIBLE GEOTHERMOMETER - APPLICATIONS TO CENTRAL JAPAN

Geothermal models of the Earth's crust are constructed for eight indiv idual structural units of Honshu island, Japan. For each unit, thermal models responding to Possible property variations are calculated. In addition to conductive heat transfer, the considered geothermal models account also for the thermal effects of fluid circulation within the crust and tectonic motions across the faults. On the basis of these ge othermal models rheological models of the crust are derived. Those the rmal models are considered as most reliable where there is reasonable correspondence between rheological stratification of the crust and the variations of crustal seismicity. It is demonstrated that earthquake cutoff depth, serving as a kind of ''geothermometer'', can be used as additional information to decrease the uncertainties involved in the g eothermal models.