Lake Roberts Dam is located in Grant County in southwestern New Mexico. Tectonically the damsite is within the Southern Basin and Range Province and the Rio Grande rift as defined by Machette (1998). Although the historical seismicity in the region has been low, the site has undoubtedly been shaken by past large prehistoric earthquakes caused by active regional faults and in historical times, as recently as 1887 (Figures 2 to 4).

This report presents the results of probabilistic seismic hazard analyses for use in screening/scoping-level dam safety and/or risk assessments of Granite Reef Diversion and Theodore Roosevelt Dams in southern Arizona. The purpose of these evaluations is to estimate the levels of ground motions, which will be exceeded at specified annual frequencies (or return periods), at the damsites.

This report presents the results of sitespecific probabilistic seismic hazard analyses (PSHA) and deterministic seismic hazard analyses (DSHA) of four sites for the RMC tailings storage facilities options in southern Arizona.

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