STRUCTURAL CHARACTERIZATION OF THE LAS VEGAS BASIN USING SEISMIC REFLECTION DATA

The Las Vegas Valley is located in the southern Basin and Range, which has undergone a significant amount of extension that continues today. This extension has resulted in a series of normal faults as well as strike-slip faults that cut across the region. In the Las Vegas Valley, these faults have contributed greatly to the original geometry of the basin. The cities of Las Vegas, North Las Vegas, and Henderson sit atop this fault-bounded basin, which has been shown to have varying amplification factors (e.g., Su et al., 1998). Recent paleoseismic studies have illuminated that several normal faults in the Las Vegas region have Quaternary offsets and have the potential to produce an earthquake of M6.5 to 7.0 (Slemmons et al., 2001). A gravity inversion, which combined gravity, seismic reflection, and aeromagnetic data indicate that there are a series of sub-basins exist beneath the unconsolidated basin fill, with the deepest sub-basin occurring 5 km west of the fault block bounding the eastern edge of the basin and the basin depth ranging from 2 km in the west-northwest to 5 km in the east-northeast (Langenheim et al., 2001). As a result, new studies have taken place to characterize the Las Vegas Valley for seismic hazards. The primary questions we have set out to answer are: 1).What is the geometry and velocity structure of the Las Vegas basin? 2). Can we identify existing faults and address their significance for seismic risk? 3). Can we identify of any sub-basins within the larger basin, thereby testing the model produced from the gravity inversion? To answer some of these questions proprietary industry reflection sections have been acquired that cut across the Las Vegas Valley. These data will be used to tie into the velocity models being derived by the working group. In addition, these will be used to define the major structural trends in the sub-surface. These data will provide insight to potential focusing features within the Las Vegas basin.