PERMFILE138596 - Laserfiche WebLink

Home Browse Search

Geotechnlcal Evaluation of Mlne-Induced Seismicity on Monument Dam Dorsey 8 Whitney, LLP conditions (1,000 to 1,400 feet) at an average horizontal distance of about 9,000 feet from the dam is 0.06 g. Pga at the dam site for the expected maximum M 2.0 event for areas of the E Seam that have overburden depths ranging from 300 to 1,000 feet at an average horizontal distance of about 3,500 feet from the dam is 0.077g. Calculated accelerations for selected mine-related earthquakes are summarized in Table 4.2. TABLE 4.2 CALCULATED ACCELERATIONS FOR SELECTED MINE-RELATED EARTHQUAKES M Year Magnitude Distance (km) Depth (km) Median pga (g) 1994 3.10 5 1 0.065 1994 2.80 3 1 0.075 1995 3.00 2 1 0.10 1995 2.90 1 1 0.12 2001 3.40 8 1 0.05 2003 3.40 3 1 0.11 Expected E Seam 2.30 2.73 0.30 0.06 Events 2.0 1.06 0.20 0.077 Noles: Earthquake events are from NEIC Catalog except where notetl as maximum expected E Seam event. 4.5 Attenuation Relationship for Natural Seismicity A search of the NEIC USGS Earthquake database found 91 earthquakes identified by the USGS as naturally-occurring based on event location and seismic waveform characteristics and recorded in a 100 km radius of the site. As for the mine-related seismicity, the attenuation relationship developed by Sadigh (1995) was used to calculate peak ground accelerations assuming a reverse fault type and hard rock site. Calculated pga at the site for selected larger and closer events identified by the search results are summarized in Table 4.3. TABLE 4.3 CALCULATED ACCELERATIONS FOR SELECTED NATURAL EARTHQUAKES Year Magnitude Distance (km) Depth (km) Median pga (g) 1977 4.0 49 5 0.004 1994 4.6 92 10 0.007 2001 3.1 11 1 0.03 2002 2.0 3 1 0.04 2004 2.2 5 1 0.03 2004 3.5 10 1 0.04 Notes: Earthquake events are from NEIC Catalog. GEI 15 060350 0603-10 Monummt barn Gmteclwul Eval March 2006