Late Quaternary slip rates for faults of the central Walker Lane (Nevada, USA): Spatiotemporal strain release in a strike-slip fault system

Abstract

The Walker Lane is a broad shear zone that accommodates a significant portion of North American-Pacific plate relative transform motion through a complex of fault systems and block rotations. Analysis of digital elevation models, constructed from both lidar data and structure-from-motion modeling of unmanned aerial vehicle photography, in conjunction with 10 Be and 36 Cl cosmogenic and optically stimulated luminescence dating define new Late Pleistocene to Holocene minimum strike-slip rates for the Benton Springs (1.5 ± 0.2 mm/yr), Petrified Springs (0.7 ± 0.1 mm/yr), Gumdrop Hills (0.9 +0.3 / −0.2 mm/yr), and Indian Head (0.8 ± 0.1 mm/yr) faults of the central Walker Lane (Nevada, USA). Regional mapping of the fault traces within Quaternary deposits further show that the Indian Head and southern Benton Springs faults have had multiple Holocene ruptures, with inferred coseismic displacements of ~3 m, while absence of displaced Holocene deposits along the Agai Pah, Gumdrop Hills, northern Benton Springs, and Petrified Springs faults suggest they have not. Combining these observations and comparing them with geodetic estimates of deformation across the central Walker Lane, indicates that at least one-third of the ~8 mm/yr geodetic deformation budget has been focused across strike-slip faults, accommodated by only two of the five faults discussed here, during the Holocene, and possibly half from all the strike-slip faults during the Late Pleistocene. These results indicate secular variations of slip distribution and irregular recurrence intervals amongst the system of strike-slip faults. This makes the geodetic assessment of fault slip rates and return times of earthquakes on closely spaced strike-slip fault systems challenging. Moreover, it highlights the importance of understanding temporal variations of slip distribution within fault systems when comparing geologic and geodetic rates. Finally, the study provides examples of the importance and value in using observations of soil development in assessing the veracity of surface exposure ages determined with terrestrial cosmogenic nuclide analysis.

Accommodation of Plate Motion in an Incipient Strike‐Slip System: The Central Walker Lane

“…The geomorphology of this fault zone, including its length, discontinuous expression, scarcity of well-preserved lateral offsets, and subdued linear morphology, is similar to other dextral faults in the region with rates of this magnitude (e.g. Angster et al, 2019).…”

“…The resulting 10 Be concentrations as a function of depth were modeled using the Hidy et al (2010) MATLAB code, which uses a Monte Carlo simulation to find the best fit of the data and resulting surface age. As soil descriptions are critical to correctly interpreting results of cosmogenic ages (e.g., Angster et al, 2019), the soil exposed in the profile was described following Birkeland (1984) and soil textural grain size was analyzed by A&L Great Lakes Laboratories, Inc.…”

“…This domain has accommodated >50° of clockwise vertical axis rotation since the Miocene (Carlson, 2017; P. H. Cashman & Fontaine, 2000). The eastern domain, modified here after the Walker Lake block of Stewart (1988), includes the northwest‐striking dextral strike‐slip Benton Springs, Indian Head, Gumdrop, and Petrified Springs faults (Angster et al., 2019; Wesnousky, 2005). Together, these closely spaced faults accommodate ∼4 mm/yr of dextral shear (Angster et al., 2019).…”

“…The eastern domain, modified here after the Walker Lake block of Stewart (1988), includes the northwest‐striking dextral strike‐slip Benton Springs, Indian Head, Gumdrop, and Petrified Springs faults (Angster et al., 2019; Wesnousky, 2005). Together, these closely spaced faults accommodate ∼4 mm/yr of dextral shear (Angster et al., 2019). The southerly Mina Deflection (e.g., Wesnousky, 2005) is composed of east‐west‐striking sinistral faults and forms a large right step between the dextral faults of the Southern Walker Lane and the eastern domain of the Central Walker Lane.…”

Active Tectonics and Earthquake Geology Along the Pallatanga Fault, Central Andes of Ecuador

“…Therefore, the whole fault system would show changes at local (2-3 to 4-6 mm/yr) to regional (2-10 mm/yr) scales. Spatial changes are described both along long-living and segmented faults, like the 400 km-long Doruneh Fault in Iran (Farbod et al, 2016) or along young and evolving fault systems, like the Eastern California Shear Zone (Kirby et al, 2008;Frankel et al, 2011;Angster et al, 2018). In this latter case, variability is distributed over comparable along-strike distances.…”