The northern Death Valley fault zone (NDVFZ) has long been recognized as a major right‐lateral strike‐slip fault in the eastern California shear zone (ECSZ). However, its geologic slip rate has been difficult to determine. Using high‐resolution digital topographic imagery and terrestrial cosmogenic nuclide dating, we present the first geochronologically determined slip rate for the NDVFZ. Our study focuses on the Red Wall Canyon alluvial fan, which exposes clean dextral offsets of seven channels. Analysis of airborne laser swath mapping data indicates ∼297 ± 9 m of right‐lateral displacement on the fault system since the late Pleistocene. In situ terrestrial cosmogenic 10Be and 36Cl geochronology was used to date the Red Wall Canyon fan and a second, correlative fan also cut by the fault. Beryllium 10 dates from large cobbles and boulders provide a maximum age of 70 +22/−20 ka for the offset landforms. The minimum age of the alluvial fan deposits based on 36Cl depth profiles is 63 ± 8 ka. Combining the offset measurement with the cosmogenic 10Be date yields a geologic fault slip rate of 4.2 +1.9/−1.1 mm yr−1, whereas the 36Cl data indicate 4.7 +0.9/−0.6 mm yr−1 of slip. Summing these slip rates with known rates on the Owens Valley, Hunter Mountain, and Stateline faults at similar latitudes suggests a total geologic slip rate across the northern ECSZ of ∼8.5 to 10 mm yr−1. This rate is commensurate with the overall geodetic rate and implies that the apparent discrepancy between geologic and geodetic data observed in the Mojave section of the ECSZ does not extend north of the Garlock fault. Although the overall geodetic rates are similar, the best estimates based on geology predict higher strain rates in the eastern part of the ECSZ than to the west, whereas the observed geodetic strain is relatively constant.

[1] Range-front alluvial fan deposition in arid environments is episodic and results in multiple fan surfaces and ages. These distinct landforms are often defined by descriptions of their surface morphology, desert varnish accumulation, clast rubification, desert pavement formation, soil development, and stratigraphy. Although quantifying surface roughness differences between alluvial fan units has proven to be difficult in the past, high-resolution airborne laser swath mapping (ALSM) digital topographic data are now providing researchers with an opportunity to study topography in unprecedented detail. Here we use ALSM data to calculate surface roughness on two alluvial fans in northern Death Valley, California. We define surface roughness as the standard deviation of slope in a 5-m by 5-m moving window. Comparison of surface roughness values between mapped fan surfaces shows that each unit is statistically unique at the 99% confidence level. Furthermore, there is an obvious smoothing trend from the presently active channel to a deposit with cosmogenic 10 Be and 36 Cl surface exposure ages of $70 ka. Beyond 70 ka, alluvial landforms become progressively rougher with age. These data suggest that alluvial fans in arid regions smooth out with time until a threshold is crossed where roughness increases at greater wavelength with age as a result of surface runoff and headward tributary incision into the oldest surfaces.Citation: Frankel, K. L., and J. F. Dolan (2007), Characterizing arid region alluvial fan surface roughness with airborne laser swath mapping digital topographic data,

The Death Valley‐Fish Lake Valley fault zone (DV‐FLVFZ) is a prominent dextral fault system in the eastern California shear zone (ECSZ). Combining offset measurements determined with LiDAR topographic data for two alluvial fans with terrestrial cosmogenic nuclide 10Be ages from the fan surfaces yields a late Pleistocene slip rate of ∼2.5 to 3 mm/yr for the northern part of the DV‐FLVFZ in Fish Lake Valley. These rates are slower than the late Pleistocene rate determined for the system in northern Death Valley, indicating that slip rates decrease northward along this major fault zone. When summed with the slip rate from the White Mountains fault, the other major fault in this part of the ECSZ, our results suggest that either significant deformation is accommodated on structures east of Fish Lake Valley, or that rates of seismic strain accumulation and release have not remained constant over late Pleistocene to Holocene time.

[1] Quantitative slip rate estimates are essential to understanding crustal deformation processes and assessing seismic hazard. Computing slip rates requires two fundamental ingredients: estimates of the age of an offset landform or deposit and displacement along the fault of interest. Because both of these measures contain uncertainty, slip rates are inherently uncertain. Methods to compute and report slip rates have not been standardized, and therefore slip rate data are presented inconsistently and are frequently ambiguous; in particular, slip rate uncertainty is often insufficiently characterized. We present a rigorous probabilistic approach to computing and reporting intermediate-to long-term fault slip rates; additionally, we have developed freely available software that provides standard age and displacement uncertainty models. We demonstrate the method using recent observations from the Neodani and Death Valley-Fish Lake Valley fault zones, and we compare slip rates determined using this approach with previously published results.

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