Seismicity in the Vicinity of Yucca Mountain, Nevada, for the Period October 1, 2003 to September 30, 2004

von Seggern, David ; Smith, Ken

Nevada System of Higher Education

关键词: Nevada Seismological Laboratory (Nsl);    Management;    Amplitudes;    Focal Mechanisms;    Ground Motion;   

DOI  :  10.2172/917919
RP-ID  :  TR-05-001
RP-ID  :  FC28-04RW12232
RP-ID  :  917919

美国|英语

来源: UNT Digital Library

【 摘 要 】

This report describes the seismicity and earthquake monitoring activities within the Yucca Mountain region during fiscal year 2004 (FY2004 - October 1, 2003, through September 30, 2004) based on operation of the Southern Great Basin Digital Seismic Network (SGBDSN). Network practices and earthquake monitoring conducted at the Nevada Seismological Laboratory (NSL) under DOE directives for prior fiscal years are covered in similar yearly reports (see references). Real-time systems, including regional data telemetry and data management at NSL, provide for the automatic determination of earthquake locations and magnitudes and notification of important earthquakes in the region to UNR staff and DOE management. All waveform and meta-data, including automatic locations, phase arrival information, and analyst reviewed information, are managed through a relational database system allowing quick and reliable evaluation and analysis of ongoing earthquake activity near Yucca Mountain. This network, which contains weak-motion and strong-motion instrumentation, addresses the seismic hazard of the Yucca Mountain area by providing accurate earthquake magnitudes for earthquake recurrence estimates, spatial hypocentral control to very low magnitudes for identifying and assessing active faults and verifying tectonic models, true ground motions over the complete range of expected earthquake amplitudes for developing predictive models, and earthquake source information for characterizing active faulting. The Nevada Seismological Laboratory operated a 30-station monitoring network within a ring of approximately 50 km radius around Yucca Mountain during FY2004. This year showed the second-lowest seismic moment rate in the NTS and Yucca Mountain region for any fiscal year reporting period since prior to the 1992 M 5.6 Little Skull Mountain (LSM) earthquake. A total of 2180 earthquakes were located for FY2004. The largest event during FY2004 was M 2.99 and there were only 12 earthquakes greater than M 2.00. This is the second year since the LSM event that no M ≥ 3.00 earthquake was recorded within 65 km of Yucca Mountain. (FY2003 was the first.) For FY2004, focal mechanisms were developed for 24 earthquakes. These focal mechanisms show predominantly strike-slip motion with a tension axis oriented WNW-ESE. Four earthquakes in FY2004 were within 10 km of Yucca Mountain, all having M < 0. A total of 31 earthquakes have occurred in this immediate zone around Yucca Mountain since the digital network operations started in October 1995. Activity in the Death Valley area was monitored by several analog stations still maintained in conjunction with the Yucca Mountain monitoring. There is continuing aftershock activity in the zone of the 1993 M 6.1 Eureka Valley and 1999 M 5.6 Scotty’s Junction earthquakes. Overall, the seismicity level of the Death Valley area is significantly greater than that in the vicinity of Yucca Mountain.