IN SEARCH OF THE SURFACE TRACE OF THE DOG VALLEY FAULT NEAR TRUCKEE, CALIFORNIA
Several small-displacement faults are exposed in the roadcut on County Highway 261 (Dog Valley Road) and on the drought-exposed upper shoreface at the NE abutment of Stampede Dam, and have strikes that average 28°±10° with dip angles of between 36-56°NW and 74-87°SE. No shear striae were recognized along these faults, probably due to the coarse granular character of the sheared materials.
Using recent refinements in the Seismo-Lineament Analysis Method (Cronin et al., 2008; bearspace.baylor.edu/Vince_Cronin/www/SLAM/), we defined seismo-lineaments for all relevant earthquakes for which published focal mechanisms are available, including a M4 earthquake from 3 July 1983 and a M3.2 earthquake from 30 August 1992. The 1983 and 1992 events have epicenters just SW of the 1966 M6 event, and all three have left-lateral NE-striking fault-plane solutions. We interpret all three earthquakes to have occurred on the DVF, as did Reed (2014). The average orientation of their mean fault-plane solutions strikes 31°±5° dipping 78°±20°. Greensfelder (1968; Kachadoorian et al., 1967) wrote that ground effects of the 1966 M6 event were in a "narrow zone about 10 miles long trending N30°E." The more subtle lineament that we studied, and that largely coincides with the zone of ground effects and aftershocks of the 1966 event, parallels the mean fault-plane solution for the 1966, 1983 and 1992 events and is within the seismo-lineaments of all three earthquakes.