Abstract. Models of the evolution of fault scarp morphology provide time elapsed since slip initiated on a faulted surface and may therefore provide more accurate estimates of slip rate than the rate calculated by dividing scarp offset by the age of the ruptured surface. To accomplish this task, linear and nonlinear models of sediment transport are calibrated from the morphology of Lake Bonneville shoreline scarps and fault scarps formed by multiple, surface-rupturing earthquakes along the Wasatch Fault Zone (WFZ). Profile modeling of scarps formed by several events distributed through time is done using a constant slip rate (

[1] Seismic tomography can be used to image colluvial material in the subsurface by inverting first arrival travel times for velocity. Colluvial material deposited at the base of a fault-scarp free face often appears as a low-velocity zone (LVZ) on a tomogram because it is generally less compacted and cemented than the surrounding alluvium. A tomogram generated from a forward model of a synthetic velocity structure successfully images two LVZs stacked in the hanging wall of a normal fault. The Mercur fan, Oquirrh Mountains, Utah, provides an opportunity to look for stacked LVZs in a distributed fault zone. Three tomographic images across fault scarps on an intermediate age alluvial fan can be used to identify two stacked low-velocity zones. Interpretation of a fourth tomogram is less conclusive. These two low-velocity zones are interpreted as colluvial packages separated by higher-velocity alluvial material and suggest that tectonic activity is interspersed with pulses of fan building.

We have developed two case studies demonstrating the use of high-resolution seismic tomography and reflection imaging in the field of paleoseismology. The first study, of the Washington fault in southern Utah, USA, evaluated the subsurface deposits in the hanging wall of the normal fault. The second study, of the Mercur fault in the eastern Great Basin of Utah, USA, helped to establish borehole locations for sampling subsurface colluvial deposits buried deeper than those previously trenched along the fault zone. We evaluated the seismic data interpretations by comparison with data obtained by trenching and logging deposits across the Washington fault, and by drill-core sampling and video logging of boreholes penetrating imaged deposits along the Mercur fault. The seismic tomograms provided critical information on colluvial wedges and faults but lacked sufficient detail to resolve individual paleoearthquakes. IntroductionTime-space patterns of earthquake recurrence and magnitude reflect the pulse of the earthquake engine and are the primary parameters required for seismic hazard analysis of faulting (McCalpin, 2009). The pulse period indicates the recurrence interval of large earthquakes, and the pulse strength is the earthquake's magnitude. Knowing these two parameters is important for establishing earthquake risk in an inhabited region.Geologic mapping and regional geophysical surveys provide information on the locations and lengths of faults, but establishing the earthquake history requires excavating and logging unconsolidated deposits that are several hundred thousand years or fewer in age. High-resolution seismic surveys are useful in site characterization, especially prior to excavation. However, the results are commonly limited by resolution and complex stratigraphy adjacent to the faults, where vertically stacked colluvial wedges contain crucial information concerning the number and magnitudes of earthquake events represented in the subsurface deposits (e.g., Stephenson et al., 1993;Morey and Schuster, 1999;McCalpin, 2009).We present two case studies of normal faulting, in which seismic methods image faulted deposits prior to excavation. In both cases, the subsurface deposits were subsequently logged, and the results compared with the seismic interpretations. This "postmortem" cri-

The objective of this project is to develop a comprehensive, interdisciplinary, and quantitative characterization of a fluvial-deltaic reservoir which will allow realistic inter-well and reservoir-scale modeling to be constructed for improved oilfield development in similar reservoirs worldwide. The geological and petrophysical properties of the Cretaceous Ferron Sandstone in east-central Utah will be quantitatively determined. Both new and existing data will be integrated into a three-dimensional representation of spatial variations in porosity, storativity, and tensorial rock permeability at a scale appropriate for inter-well to regional-scale reservoir simulation. Results could improve reservoir management through proper infill and extension drilling strategies, reduction of economic risks, increased recovery from existing oil fields, and more reliable reserve calculations. Transfer of the project results to the petroleum industry is an integral component of the project.

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