Laserfiche WebLink
INTRODUCTION <br /> This report presents the results of a probabilistic seismic hazard analysis of a tailing dam <br /> located at the Climax mine in central Colorado. The purpose of this study is to evaluate the <br /> level of ground motions associated with the probability or likelihood of being exceeded in <br /> a specified time period at the damsite, which is owned and operated by the Cyprus Climax <br /> Metals Company. <br /> In this study, both published and unpublished geologic and seismologic data were used to <br /> evaluate potential seismic sources, the likelihood of earthquakes of various magnitudes <br /> occurring on those sources, and the likelihood of the earthquakes producing ground motions <br /> over a specified level. The probabilistic seismic hazard analysis methodology used in this <br /> study allows for the explicit inclusion of the range of possible interpretations in components <br /> of the model, including seismic source characterization and ground motion estimation. <br /> Uncertainties in models and parameters are incorporated into the hazard analysis through the <br /> use of logic trees. The following describes the seismotectonic setting of the damsite, our <br /> approach, the seismic source characterization, the attenuation relationships used in the <br /> probabilistic analysis of Climax mine tailing dam, and the results of the study. <br /> SEISMOTECTONIC SETTING <br /> Colorado is located in a transition between the seismically active Basin and Range Province <br /> to the west and the significantly less active, cratonic Midcontinent to the east. The majority <br /> of historical seismicity is located in the western half of the state (Wong et al., 1994), which <br /> is composed physiographically of the Colorado Plateau and Southern Rocky Mountains. <br /> Based on the brief 150-year historical record, the largest earthquake known in Colorado is <br /> the enigmatic 1882 Richter magnitude (ML) 61/2 earthquake, which may have occurred in the <br /> northern Front Range (Kirkam and Rogers, 1981), although its location has been the subject <br /> of considerable debate. The most significant event known to have occurred in western <br /> Colorado is the 1960 ML 51/2 earthquake near Ridgway which also occurred prior to adequate <br /> seismographic coverage (Wong et al., 1994). <br /> Significant advancements have been made in our understanding of earthquakes, their rupture <br /> processes, and associated tectonic stresses in western Colorado because of improved, albeit <br /> H:\C0NTRACT\TENM1LE\1 1 M0412951500 <br />