This report presents the results of a paleoseismic investigation designed to date a long series of consecutive earthquakes on the Wasatch fault zone and to measure the variability of recurrence times between the events. Geologists have long recognized that the comparatively short average recurrence interval (compared to most other basin-and-range normal faults) between large surface-faulting earthquakes on the Salt Lake City segment of the Wasatch fault zone during mid- to late-Holocene time is potentially anomalous, and possibly affected by the rise and fall of Lake Bonneville. This study extends the paleoearthquake record back to Bonneville time, nearly doubling the previous record, and provides new information on the timing and periodicity of surface faulting on the Salt Lake City segment from the latest Pleistocene through the Holocene. The trench and accompanying auger hole for this study exposed 26 meters of vertical section, roughly four times that of a typical paleoseismic trench on the Wasatch fault zone, hence the name “Megatrench.”
This report presents the results of a preliminary evaluation of the East Bear Lake (EBF) and West Bear Lake (WBF) fault zones, which bound the east and west sides, respectively, of the Bear Lake Valley. The Bear Lake Valley straddles the Utah/Idaho border northeast of Logan, Utah. The results of this study show that both the EBF and the WBF have experienced surface-faulting earthquakes in the recent geologic past and therefore represent an ongoing seismic hazard to northeastern Utah and southeastern Idaho.
This Utah Geological Survey Miscellaneous Publication, Post-Provo Paleoearthquake Chronology of the Brigham City Segment, Wasatch Fault Zone, Utah, is the eleventh report in the Paleoseismology of Utah series. This series makes the results of paleoseismic investigations in Utah available to geoscientists, engineers, planners, public officials, and the general public. These studies provide critical information on paleoearthquake parameters such as timing, recurrence, displacement, slip rate, and fault geometry which can be used to characterize potential seismic sources and evaluate the long-term seismic hazard presented by Utah’s Quaternary faults. This report presents the results of the most extensive single paleoseismic-trenching project yet conducted on the Wasatch fault zone. The purpose of the study was to lengthen the paleoseismic chronology for the Brigham City segment of the Wasatch fault zone beyond the 6,000-year record previously available, and to resolve questions regarding the irregular pattern of paleoearthquakes reported by earlier workers for the Brigham City segment. This study makes extensive use of radiocarbon, thermoluminescence, and infrared stimulated luminescence dating techniques to develop a real-time chronology of past surface-faulting earthquakes.
Magnetic Stratigraphy is the most comprehensive book written in the English language on the subject of magnetic polarity stratigraphy and time scales. This volume presents the entirety of the known geomagneticrecord, which now extends back about 300 million years. The book includes the results of current research on sea floor spreading, magnetic stratigraphy of the Pliocene and Pleistocene, and postulations on the Paleozoic. Also included are both historicalbackground and applications of magnetostratigraphy. Individual chapters on correlation are presented, using changes in magnetic properties and secular variation. Key Features* Discusses pioneering work in the use of marine sediments to investigate the Earths magnetic field* Serves as a guide for students wishing to begin studies in magnetostratigraphy* Provides a comprehensive guide to magnetic polarity stratigraphy including up-to-date geomagnetic polarity time scales* Correlates magnetic stratigraphics from marine and non-marine Cenozoic sequences* Details reversal history of the magnetic field for the last 350 million years* Discusses correlation using magnetic dipole intensity changes* Up-to-date correlation of biostratigraphy with magnetic stratigraphy through the late Jurassic
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