Abstract

Evidence for active faulting in the Truckee Basin, north of Lake Tahoe, is observed in a meadow containing a scarp and small closed depression. Shallow, hand‐dug trenches show offset marsh stratigraphy of Holocene age. Lithostratigraphy descriptions and radiocarbon dates indicate the meadow was a marsh during the late Quaternary that was abruptly infilled with the deposition of the ∼7000  yr B.P. Tsoyawata tephra (Mt. Mazama). The tephra is offset up to 80 cm across a narrow, sub‐vertical, north–south‐striking fault zone. Additional offset of 30 cm occurred across the same structure during the late Pleistocene. Our study provides direct stratigraphic evidence for at least one surface‐faulting event during the Holocene, and another in the late Pleistocene, within the Truckee fault zone and provides new constraints on seismic sources capable of significant ground rupture and/or shaking in the greater Reno–Tahoe–Truckee area.

You do not currently have access to this article.