Descriptions, with supporting evidence, of segment boundaries as they are expressed in gravity, aeromagnetic, seismological, fault-geometric, topographic, and structural data.
This publication presents probabilistic earthquake forecasts developed by the Working Group on Utah Earthquake Probabilities which developed 30,50, and 100 year forecasts that include combined time dependent probabilities of large earthquakes for the five central segments of the Wasatch Fault Zone.
This report presents the results of the Utah Quaternary Fault Parameters Working Group (hereafter referred to as the Working Group) review and evaluation of Utah’s Quaternary fault paleoseismic-trenching data. The purpose of the review was to (1) critically evaluate the accuracy and completeness of the paleoseismictrenching data, particularly regarding earthquake timing and displacement, (2) where the data permit, assign consensus, preferred recurrence-interval (RI) and vertical slip-rate (VSR) estimates with appropriate confidence limits to the faults/fault sections under review, and (3) identify critical gaps in the paleoseismic data and recommend where and what kinds of additional paleoseismic studies should be performed to ensure that Utah’s earthquake hazard is adequately documented and understood. It is important to note that, with the exception of the Great Salt Lake fault zone, the Working Group’s review was limited to faults/fault sections having paleoseismic-trenching data. Most Quaternary faults/fault sections in Utah have not been trenched, but many have RI and VSR estimates based on tectonic geomorphology or other non-trench-derived studies. Black and others compiled the RI and VSR data for Utah’s Quaternary faults, both those with and without trenches.
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.
"Rough-Hewn Land tells the geologic story of the American West--the story of its rocks, rivers, mountains, earthquakes, and mineral wealth, including gold. It tells it by taking you on a 1000-mile-long field trip across the rough side of the continent from the California coast to the Rocky Mountains. This book puts you on the outcrop, geologic hammer in hand, to explore the evidence for how the spectacular, rough-hewn lands of the West came to be. When North America broke free from Eurasia and Africa some 200 million years ago, it triggered a cascade of violent geologic events that shaped the West we see today. As the west-moving continent crunched across the seabed of the ancient Pacific, islands and assorted pieces of ocean floor collected against its prow to build California--and plant gold there too. Meanwhile, mountains squeezed upward from California to Colorado, and vast quantities of molten rock seeded the crust with precious metals while spewing volcanic fire across the land. Later, the land stretched like an accordion to form the washboard-like Basin and Range province and Great Basin within it, while California began to crackle along the San Andreas fault. Throughout the West today, a near-constant drumroll of earthquakes testifies to a world still reshaping itself in response to the ceaseless movements of the Earth's tectonic plates. Rough-Hewn Land weaves these stories into the human history of the West. As we follow the adventures of John C. Frémont, Mark Twain, the Donner party, and other historic characters, we see how geologic forces have shaped human experience, just as they direct the fate of the West today"--