Geologic exposures in the Salt Lake City region record a long history of sedimentation and tectonic activity extending back to the Precambrian Era. Today, the city lies above a deep, sediment-filled basin flanked by two uplifted range blocks, the Wasatch Range and the Oquirrh Mountains. The Wasatch Range is the easternmost expression of major Basin and Range extension in north-central Utah and is bounded on the west by the Wasatch fault zone (WFZ), a major zone of active normal faulting. During the late Pleistocene Epoch, the Salt Lake City region was dominated by a succession of inter-basin lakes. Lake Bonneville was the last and probably the largest of these lakes. By 11,000 yr BP, Lake Bonneville had receded to approximately the size of the present Great Salt Lake.

This CD contains a 41-page report and a 1:150,000-scale map defining seismic site conditions for the Wasatch Front urban corridor. This mapping, partially funded through the U.S. Geological Survey’s National Hazards Reduction Program, provides a basis for predicting how certain soils and bedrock types may respond to ground-motion amplification in a large-magnitude earthquake on the Wasatch fault. Average shear-wave velocities were used for the upper 30 meters and surficial geologic mapping to delineate and characterize earthquake-site-conditions units that relate to International Building Code site classes. Better understanding of soil properties and earthquake-site effects for the densely populated Wasatch Front allows for improved earthquake engineering and emergency planning and response. 41 pages + 1 plate

The purpose of these guidelines for investigating geologic hazards and preparing engineering-geology reports, is to provide recommendations for appropriate, minimum investigative techniques, standards, and report content to ensure adequate geologic site characterization and geologic-hazard investigations to protect public safety and facilitate risk reduction. Such investigations provide important information on site geologic conditions that may affect or be affected by development, as well as the type and severity of geologic hazards at a site, and recommend solutions to mitigate the effects and the cost of the hazards, both at the time of construction and over the life of the development. The accompanying suggested approach to geologic-hazard ordinances and school-site investigation guidelines are intended as an aid for land-use planning and regulation by local Utah jurisdictions and school districts, respectively. Geologic hazards that are not accounted for in project planning and design often result in additional unforeseen construction and/or future maintenance costs, and possible injury or death.