The western United States and the Pacific-North American plate boundary are now the focus of the major NSF-sponsored initiative Earthscope that is largely aimed at (1) employing modern observational technologies such as Global Positioning Systems and seismic instrumentation to investigate the structure and evolution of the North American continent and (2) contributing to the mitigation of risks from geological hazards. Pacific-North American plate motion is not limited to California's San Andreas fault system. It also encompasses the Great Basin physiographic province which is characterized by Basin and Range style deformation and encompasses an area reaching 800 km in width between about Reno, NV to the west and Salt Lake City, UT to the east. The Great Basin is one of the world's type-examples of diffuse continental extension. This field study is aimed to quantify the late-Pleistocene occurrence of earthquake displacements (paleoseismology) on major range-bounding active faults across the interior of the Great Basin. The locations of the studies are along an anticipated Earthscope-deployment of Geographic Position System instruments that will form a dense array across the Great Basin. The motivation for the field study stems from the understanding that the kinematics and mechanics of the North-American plate boundary will require measurements of the rate, style, and evolution of deformation across the entirety of the boundary through geologic time. Thus while Earthscope-Plate Boundary Observatory Geographic Position System instruments are measuring strain accumulation, our study is measuring how that strain is released. The knowledge we are gaining is being used to understand the physics of the earthquake process, the development of the structure and physiography across the western United States, and the contemporary strain signal itself. Additionally, the research is supporting the education of a Ph.D. student, and study sites are being used in University field classes as introductions to research methods. It is also intended that this work to understand the physics of the earthquake process will be incorporated into efforts to define seismic hazards and forecast the locations and sizes of future earthquakes.
