부산대학교 도서관

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.