This dissertation research assesses the behavior of young faults in central Nevada through analyses of landforms associated with these faults. Four large earthquakes have occurred since 1915 in a striking N-S belt in central Nevada; no comparable earthquakes have occurred elsewhere in the Great Basin. The frequency of large-earthquake occurrence, and temporal and spatial patterns and rates of faulting in central Nevada during the Holocene were assessed through geomorphic and geologic studies of young fault scarps. Ages of paleoseismic events were estimated primarily through analyses of fault scarp morphologies and characterization and quantification of soil development associated with alluvial surfaces. Rates of fault scarp degradation were explored through diffusion-based modeling of latest Pleistocene pluvial shoreline scarps. Morphologic scarp age depends strongly on scarp size; modest variations in local climate, particle size, and aspect are less important. Incorporating a factor that depends on scarp size almost always decreases the scatter in scarp age estimates, and is critical if only small scarps exist along a fault zone. An average of ±30% uncertainty about the mean scarp age estimate remains after these analyses. Soil development indices were calibrated using 14 Holocene to latest Pleistocene soil profiles in central Nevada whose maximum ages are constrained. Soil development indices were used to estimate ages of faulted and unfaulted alluvial surfaces along fault scarps. Soils and morphologic fault scarp age estimates for paleoseismic events are generally consistent. Temporal and spatial patterns and rates of faulting during the Holocene were evaluated using age estimates for paleoseismic events. The long-term rate of faulting is about 10 times lower than the historical rate. There were no other N-S belts of faulting during the Holocene, although scarp ages suggest that there may have been other temporal clusters of faulting. There have been spatial clusters of faulting during portions of the Holocene. The extensional deformation rate across central Nevada during the Holocene is about 0.5-0.75 mm/yr. Integrating this rate with fault-slip data from other portions of the northern Great Basin, the Holocene extensional deformation rate is 3.5-6.5 mm/yr, substantially lower than the historical deformation rate.

Late Pleistocene displacement along the Lone Mountain fault suggests the Silver Peak-Lone Mountain (SPLM) extensional complex is an important structure in accommodating and transferring strain within the eastern California shear zone (ECSZ) and Walker Lane. Using geologic and geomorphic mapping, differential global positioning system surveys, and terrestrial cosmogenic nuclide (TCN) geochronology, we determined rates of extension across the Lone Mountain fault in western Nevada. The Lone Mountain fault is the northeastern component of the SPLM extensional complex, and is characterized by a series of down-to-the-northwest normal faults that offset the northwestern Lone Mountain and Weepah Hills piedmonts. We mapped eight distinct alluvial fan deposits and dated three of the surfaces using ¹⁰BE TCN geochronology, yielding ages of 16.5 +/- 1.2 ka, 92.3 +/- 8.6 ka, and 142.2 +/- 19.5 ka for the Q3b, Q2c, and Q2b deposits, respectively. The ages were combined with scarp profile measurements across the displaced fans to obtain minimum rates of extension; the Q2b and Q2c surfaces yield an extension rate between 0.1 +/- 0.1 and 0.2 +/- 01 mm/yr and the Q3b surface yields a rate of 0.2 +/-.1 to 0.4 +/- 0.1 mm/yr, depending on the dip of the fault. Active extension on the Lone Mountain fault suggests that it helps partition strain off of the major strike-slip faults in the northern ECSZ and transfers deformation around the Mina Deflection northward into the Walker Lane. Combining our results with estimates from other faults accommodating dextral shear in the northern ECSZ reveals an apparent discrepancy between short- and long-term rates of strain accumulation and release. If strain rates have remained constant since the late Pleistocene, this could reflect transient strain accumulation, similar to the Mojave segment of the ECSZ. However, our data also suggest an increase in strain rates between ~92 ka and ~17 ka, and possibly to present day, which may also help explain the mismatch between long- and short-term rates of deformation in the region.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Science, 1982. / Microfiche copy available in Archives and Science. / Two maps and one illustration on 3 folded leaves in pocket. / Includes bibliographies. / by Brian Philip Wernicke. / Ph.D.

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth and Planetary Sciences, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND LINDGREN. / 3 maps and 2 ill. inserted in pocket inside back cover. / Bibliography: leaves 182-189. / by Peter Lorentz Guth. / Ph.D.