Geology of the Tahoe City sub-basin, Lake Tahoe, California-Nevada

The Tahoe City sub-basin is located near the northwestern edge of Lake Tahoe and extends from Tahoe City on the west to Dollar Point fault on the east. Understanding the depositional and deformational history of the Tahoe City sub-basin is important because what happens here affects the entire Lake Tahoe basin and areas downstream of Lake Tahoe. Two lacustrine units have been identified in the Tahoe City sub-basin, the Pliocene lacustrine sediments (3--2 Ma) and Quaternary clay (2--0.63 Ma). A basaltic lapilli tuff and several basalt flows interfinger with the lacustrine units. Faulting began in the Tahoe City sub-basin around or shortly after 3 Ma and has continued up until the Holocene. The total amount of vertical separation observed on basin bounding faults is 220--240 m. The results of this study indicate that a significant seismic hazard exists for Tahoe City.