Recent work in Fallen Leaf Lake has helped identify the WTDPF as potentially the most hazardous fault in the Lake Tahoe Basin, with the potential to produce M >7.0 earthquakes ( Brothers et al., 2009). These faults, the Stateline–North Tahoe fault, Incline Village fault, and the West Tahoe–Dollar Point fault (WTDPF), exhibit down to the east normal displacement ( Dingler et al., 2009) ( Fig. Onshore and offshore research in the Lake Tahoe Basin (northern Sierra Nevada, western United States) has defined the geometry and slip rates of the major faults accommodating active extension across the basin ( Brothers et al., 2009 Dingler et al., 2009 Gardner et al., 2000 Karlin et al., 2005 Kent et al., 2005 Schweickert et al., 2004 Seitz et al., 2006, 2005). This improved mapping of the WTDPF reveals the fault geometry and architecture south of Lake Tahoe and improves the geohazard assessment of the region. The Cascade Lake data combined with onshore Lidar allow us to map the WTDPF continuously between Fallen Leaf Lake and Cascade Lake. In addition, Chirp data beneath Cascade Lake image strands of the WTDPF offsetting the lake floor as much as ∼7.5 m. for large earthquakes on the Fallen Leaf Lake segment of the WTDPF, and the time since the most recent event (∼4.5 k.y. If this correlation is correct, we postulate a recurrence interval of ∼3–4 k.y. The temporal correlation of slides between multiple basins suggests triggering by earthquakes on the WTDPF system. Slide deposits imaged beneath Fallen Leaf Lake appear to be synchronous with slides in Lake Tahoe, Emerald Bay, and Cascade Lake.

Here we present results from high-resolution seismic Chirp (compressed high intensity radar pulse) surveys in Fallen Leaf Lake and Cascade Lake, multibeam bathymetry coverage of Fallen Leaf Lake, onshore Lidar (light detection and ranging) data for the southern Lake Tahoe Basin, and radiocarbon dates from piston cores in Fallen Leaf Lake and Emerald Bay. Fallen Leaf Lake, Cascade Lake, and Emerald Bay are three subbasins of the Lake Tahoe Basin, located south of Lake Tahoe, and provide an opportunity to image primary earthquake deformation along the WTDPF and associated landslide deposits. The West Tahoe–Dollar Point fault (WTDPF) extends along the western margin of the Lake Tahoe Basin (northern Sierra Nevada, western United States) and is characterized as its most hazardous fault.

Fallen leaf lake map