96-01979 Houston The PIs propose an interdisciplinary study of the nature of deep earthquakes. This research will test the validity of the proposed mechanism of transformation-induced faulting that accompanies the metastable phase change from olivine to spinel in subducting lithospheric slabs. Laboratory microstructural and rheological experiments and seismological studies will be continued and will be enhanced by geodynamic modeling studies at both laboratory (micromechanical modeling of the transformation-induced instability) and earth scales (large-scale thermal and mechanical modeling). Understanding the failure mechanism of deep earthquakes is important for determining the internal mineralogical structure of subducting slabs and identifying the driving forces for convection in the earth's mantle. ***
