Oral Presentation

Studies outside the most populated regions of California may aid in development of seismic hazard assessments across the State. The Walker Lane (WL) that extends northward from Eastern California Shear Zone (ECSZ) in the Mojave and northward along the east flank of the Sierran Nevada is now part of the discussion. A look at the literature shows studies of active faults within the Mojave are generally assigned to the Eastern California Shear Zone, similar studies up further north near Reno to be in the Walker Lane, and both the Walker Lane or Eastern California Shear Zone are used at latitudes in between, with the latter generally being a function of from where the individual investigator heralds. The entire zone is characterized by numerous active faults, abundant seismicity, a history of large surface rupture earthquakes, and the potential to host more. Modes of deformation are diverse and well-manifest in the physiography. Whereas the San Andreas Fault System is largely characterized by a relatively continuous set of interconnected and anastomosing faults, the ECSZ-WL is a broad disjointed set of northwest striking right-lateral and normal faults interrupted by east striking left-lateral faults, such that none are continuous along the entire length of the system. The contrast with the San Andreas system to the west is the result of the lower amount of accumulated strike-slip and transtensional nature of motions that here drives fault displacement, distinct from the generally transpressional nature of deformation that characterizes the San Andreas north of the Salton Sea. The pull-apart genesis of the Death Valley, Panamint Valley, and Saline Valley basins and rangefronts has long been attributed to bends along the strike-slip faults that host them. The Sierran Range front fault striking subparallel to the great 1872 Owens Valley earthquake is analog to the partitioning manifest along the San Andreas during the 1980 Coalinga earthquake in California. To the north, the creation of large basins resulting from rotation of crustal blocks is well displayed as is the creation of large en-echelon arranged basins in response to right-lateral displacement. Add to this the abundant seismicity and the WL-ECSZ is a natural laboratory for SCEC to consider issues of seismicity, fault mechanics, and the tectonic processes that drive them, all factors important to understanding the seismic hazard in California.