Task 4 annual report

Most previous microearthquake studies have been carried out with temporary portable seismographs. However, because of the importance of the site, we felt microearthquakes should be monitored as close to continuously as possible. Therefore we decided to transmit data continuously back to the Seismological Laboratory at the University of Nevada, Reno. This was accomplished via radio links to a nearby microwave relay station. Four sites were selected, two on Yucca Mountain near the Solitario Canyon fault (YNB and YYM), one about 5 km to the west in Crater Flat (YCF), and one still further west on Black Cone (YBC) near the center of Crater Flat. The instrumentation and telemetry setup are discussed in Brune et al. The actual useful sensitivity of the system depends on the background seismic noise level. During windy periods we often reduced the sensitivity. Several stations of a permanent recording network (Southern Great Basin Seismic Network, or SGBSN) are also located in this same area. Data from this network is also telemetered to Reno, and it is processed through a realtime detection system called CUSP. Sensors of this network do not pass as high frequencies as those of the four microearthquake stations