PALEOSEISMIC STUDIES ALONG THE WESTERN MARGIN OF THE BASIN AND RANGE PROVINCE, THE MOST ACTIVE PART OF THE PROVINCE

Recent paleoseismic and geodetic studies indicate the highest levels of tectonic activity within the Basin and Range province occur along the province's western margin. Between about 38^o N. and 39.5^o N. latitude, deformation is distributed between the Sierra Nevada and central Nevada, but is concentrated along the eastern front of the Carson Range, where most of western Nevada's population is located. Paleoseismic studies indicate the morphologically prominent southern part of the Carson Range frontal fault system (Genoa fault) is the most active normal fault in the region, and it has produced multiple large-magnitude earthquakes during the late Holocene. To the north, the system is more distributed and evidence of recent activity is less impressive. Nonetheless, overall throw is similar along the entire system (2000-2500 m), and all parts of the system studied to date show permissably similar timing for the two most recent events. Frontal-fault displacements are smaller to the north, but additional displacement may occur on subparallel fault traces. This possibility, along with evaluation of the northward continuation of activity, are subjects of ongoing paleoseismic studies. Recent GPS results also suggest deformation may be concentrated east of the Carson Range. Campaign networks (e.g., Thatcher et al., 1999; Svarc et al., 2002) suggest that 25% to 40% of Basin and Range deformation occurs across basins immediately east of the Carson Range. Continuous GPS stations suggest deformation is more evenly distributed across the western Basin and Range (e.g., Wernicke et al., 2000), but a station within the Carson Range (SLID) indicates a vector compatible with the campaign measurements, and the apparent discrepancy may be explained by station distribution relative to the obliquely trending Walker Lane belt. Taken together, the recent paleoseismic and geodetic results indicate the Reno/Carson City urban corridor is subject to the highest seismic hazard in Nevada.