Abstract Title: A 50ka Record of Extension Across the Western Boundary of the 
Basin and Range Province: Constraints from Submerged Paleo-Shorelines and 
Normal Faults Beneath Lake Tahoe 

Abstract Author(s): Kent, Graham-Babcock, Jeff-Driscoll, Neal-Harding, 
Alistair-Dingler, Jeff (SIO)-Seitz, Gordon (SDSU)-Gardner, Jim (USGS)-Gayes, 
Paul (Coastal Carolina Univ.)-Goldman, Charles-Heyvaert, Alan-Richards, Bob 
(UCD)-Karlin, Bob (UNR)-Mayer, Larry (UNH)-Morgan, Craig (AVALEX)-Owen, Lewis 
(UCR)  

Abstract: Deformation across three major fault strands within the Lake Tahoe 
basin has been mapped using a novel combination of high resolution seismic 
CHIRP, airborne laser and acoustic bathymetric imagery, deep-water 14C-dated 
sediment piston-cores, and shallow-water 14C- and optically stimulated 
luminescence (OSL)-dated vibra-cores. Submerged erosional terraces of late 
Pleistocene age (17 +/- 2.5 ka) show vertical deformation that ranges between 
10 to 15 m, with 10 m observed across the central portion of the West Tahoe 
fault. Debris from the catastrophic McKinney Bay slide (~55 ka) is offset 
across the Stateline fault by at least 23 m. The submerged paleo-shorelines and 
debris avalanche provide a baseline from which to understand extension during 
the past 50 ka and to evaluate future seismic hazard of the region. Deformation 
across these two important tectonic markers, combined with chronological 
control from 14C and OSL measurements, yield an estimate of extension across 
the Lake Tahoe basin that is on the order of 0.4 to 0.6 mm/yr (assuming 60¡ 
dipping faults), with the potential for a large, seiche wave generating M7 
earthquake about every 3,500 years. These new underwater, geomorphic 
constraints beneath Lake Tahoe, in combination with trenching across the nearby 
Genoa fault [Ramelli et al., 1999] and basin-wide geodetic measurements [e.g., 
Thatcher et al., 1999], provide a complementary view to recent work done on the 
conjugate Wasatch fault system.