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Geotechnlcal Evaluation of Mine-Induced Selsmlcity on Monument Dam <br />Dorsey 8 Whitney, LLP <br /> <br />A random earthquake is defined as an event that can occur without an apparent association <br />with a known or identified tectonic feature and is included as a seismic source for the Rocky <br />Mountain region. A Maximum Considered Earthquake (MCE) for the random earthquake in <br />the Colorado Rocky Mountain Region is a M 6 to 6.5 at probabilistic epicentral distances of <br />18 km and 30 km, respectively, as developed for evaluation of Rattlesnake and Flatiron <br />Dams (William Lettis Associates, 1996). The MCE is a very long return period event and is <br />typically applied to high hazard dams that are located in a zone of seismic potential. The <br />peak ground acceleration for a M 6 at 18 km calculated using the Joyner and Boore (1988) <br />attenuation relation would be about O.15g (67`" percentile) or 0.09g (mean). <br />4.6 SEO Seismic Stability Analysis Requirements for Modification <br />to Dam <br />If modifications are made to an existing Class II Intermediate Dam, then the pseudo-static <br />stability analysis requirements include use of a minimum horizontal coefficient of O.OSg and <br />a resulting minimum factor of safety of 1.0 (SEO, 1988). <br /> <br /> <br />GEI` 16 06036006A1-16 MonummtDarn Gmtcdmicil Evil <br />March 2006 <br />