[S25-1] Development and application of geothermal databases

[S25-1-01] Reference framework for crustal geotherms, with constraints based on seismic data for the lower crust

^○Valiya Hamza¹, Carlos Alexandrino² (1.National Observatory, Rio de Janeiro, Brazil, 2.Univeristy of VJM, Teofilo Otoni, Brazil)

invited

In the present work, we consider the possibility of setting up a reference framework for crustal geotherms, as a useful tool in comparative studies of heat flow in different tectonic settings. The essence of the procedures for crustal geotherms has already been discussed in many of the earlier geothermal studies, but its implications for setting up a global framework has not so far been explored. Geotherms considered in the present work are based on analytical solution to the standard heat conduction problem in stratified media, coupled with empirical relations between seismic velocities and temperatures at the crust-mantle interphase. Iterative trial and error methods has been employed in establishing successful coupling. A major advantage of this approach is that estimates of deep crustal temperatures may be obtained that are relatively free from the perturbing effects of petrological complexities in the upper crust. It also minimizes uncertainties in downward extrapolation of main model parameters. Results of initial tests, carried out for selected sites in stable continental settings, are found to be in broad agreement with indirect estimates of temperatures obtained in deep crustal studies. Another major aspect of this new approach is that it allows estimation of crustal temperatures and mantle heat flow that has connecting links with seismic data, which is useful in comparative evaluation of geotherms across different tectonic settings. The reference frame works for geotherms could serve as a useful supplement to existing IHFC database.