ORIGIN AND EVOLUTION OF THE SEATTLE FAULT AND SEATTLE BASIN, WASHINGTON

Analysis of seismic reflection data reveals that the Seattle basin (Wa shington) is markedly asymmetric and consists of approximately 9-10 km of Eocene and younger deposits. The basin began as a discrete geologi c element in the late Eocene (approximately 40 Ma), the result of a re organization in regional fault geometry and kinematics. In this reorga nization, dextral offset on the Puget fault southeast of Seattle stepp ed eastward, and the Seattle fault began as a restraining transfer zon e. North-vergent reverse or thrust faulting on the Seattle fault force d flexural subsidence in the Seattle basin to the north. Offset on the Seattle fault and subsidence of the Seattle basin have continued to t he present.