9506409 Olson The PI will investigate the dynamics of lithospheric deformation in active tectonic regions on timescales ranging from 1000 to 1,000,000 years, using numerical models that include both brittle faulting and ductile flow. These models will be applied to three important problems in active tectonic regions: rheological control of the transition from diffuse extensional deformation on continents to concentrated rifting and seafloor spreading; mechanics of transform fault initiation between overlapping spreading centers in oceanic lithosphere; and evolution of the system of major faults and seismicity in Southern California and the adjacent portion of the Basin and Range. ****