ANSS STRONG-MOTION DEPLOYMENT IN SOUTHERN NEVADA

Strong-motion instrumentation coverage in the Las Vegas Valley has improved significantly since the summer of 2001, primarily through the USGS Advanced National Seismic System (ANSS) initiative. This initiative has provided new instruments to the Nevada Seismological Laboratory and funded their installation and operation. Network goals include improving urban strong-motion data coverage and quality and providing better information for emergency planners and the public. Eleven ANSS stations and two pre-ANSS recorders are distributed uniformly over the valley. One provides a hard-rock reference site on Frenchman Mountain. Four more are planned for this year. Six strong-motion instruments are telemetered in real time to UNR. A range of telemetry solutions have been employed. Four stations are directly on the Internet. Two use a virtual local area network model accessed by IP tunneling and a 2 GHz spread-spectrum link from the IP access point. One tunneled site employs a multi-point radio to which other line-of-site stations can be linked, including one near old downtown. Internet is used to keep costs down. Antelope Real-Time software records data from all telemetry sources, detects and locates events, and builds databases. Since the summer of 2001 no ground motions have occurred in the Las Vegas Valley strong enough to trigger the installed recorders. However, having continuous data has allowed us to collect moderate and regional events, such as M5.3 earthquake in E. San Diego County, and a M4.3 event 70 km north of the valley. Over time we expect to develop reasonable site effects assessments even if no large earthquakes occur in the valley. Thus the new network should allow us to understand something about potential strong ground shaking in Las Vegas Valley without having to wait for rare, large local events.