CSEDI: A Test of Dehydration Weakening Hypothesis for the Occurence of Intermediate/Deep-Focus Earthquakes

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96-28861 Fei Abstract The PIs propose to constrain experimental laboratory studies of stable hydrous silicate phases with seismological data to test whether dehydration weakening in subducting slabs causes moderate- and deep-focus earthquakes. The program is aimed at understanding the role of hydrous phases in intermediate and deep-focus earthquakes through high pressure and temperature simulation experiments in the laboratory. They will experimentally determine the existence of hydrous phases for P-T conditions expected within the descending slab, the maximum dehydration pressures of hydrous phases in both simple MgO-SiO2-H2O and complex hydrous peridotite systems, and the dehydration/melting temperatures of hydrous peridotite as a function of pressure (depth). The PIs also propose to compare the characteristics of oceanic lithosphere seismicity to evaluate the hypothesis that intermediate- and deep-focus events occur on faults that were initally formed in oceanic lithosphere before subduction. ***