Latest Quaternary paleoseismology and evidence of distributed dextral shear along the Mohawk Valley fault zone, northern Walker Lane, California

Abstract

The dextral-slip Mohawk Valley fault zone (MVFZ) strikes northwestward along the eastern margin of the Sierra Nevada in the northern Walker Lane. Geodetic block modeling indicates that the MVFZ may accommodate~3 mm/yr of regional dextral strain, implying that it is the highest slip-rate strike-slip fault in the region; however, only limited geologic data are available to constrain the system's slip rate and earthquake history. We mapped the MVFZ using airborne lidar data and field observations and identified a site near Sulphur Creek for paleoseismic investigation. At this site, oblique dextral-normal faulting on the steep valley margin has created a closed depression that floods annually during spring snowmelt to form an ephemeral pond. We excavated three fault-perpendicular trenches at the site and exposed pond sediment that interfingers with multiple colluvial packages eroded from the scarp that bounds the eastern side of the pond. We documented evidence for four surface-rupturing earthquakes on this strand of the MVFZ. OxCal modeling of radiocarbon and luminescence ages indicates that these earthquakes occurred at 14.0 ka, 12.8 ka, 5.7 ka, and 1.9 ka. The mean~4 kyr recurrence interval is inconsistent with slip rates of~3 mm/yr; these rates imply surface ruptures of more than 10 m per event, which is geologically implausible for the subdued geomorphic expression and 60 km length of the MVFZ. We propose that unidentified structures not yet incorporated into geodetic models may accommodate significant dextral shear across the northern Walker Lane, highlighting the role of distributed deformation in this region.

The Tahoe-Sierra frontal fault zone, Emerald Bay area, Lake Tahoe, California: History, displacements, and rates

“…Within the Basin and Range Province and, in particular, the Walker Lane belt, discrepancies commonly exist between geodetically determined strain rates and slip rates determined from geologic measurements along component range-bounding faults (e.g., Bormann et al, 2016;Gold et al, 2014;Herbert et al, 2013;Lifton et al, 2013;Personius et al, 2017, Wesnousky et al, 2005. This study, like many previous reports, emphasizes the fact that geodetic strain rates do not necessarily reflect long-term slip rates on discrete faults.…”

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

“…In sum, it appears that dextral shear has been more or less equally distributed across the central Walker Lane throughout the late Quaternary and that the locus of slip temporally transfers within the system of strike-slip faults of this study. This pattern of equally distributed and temporally variable strain release may be common throughout the Walker Lane (e.g., Frankel et al, 2011;Gold et al, 2014). The Walker Lane has been interpreted as an incipient plate boundary (Faulds et al, 2005), and shown to be relatively structurally complex when compared to the San Andreas (Wesnousky, 2005b), the main plate boundary fault between North America and the Pacific plate (Fig.…”

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

“…The Northern Walker Lane encompasses the northwest‐striking dextral strike‐slip Pyramid Lake (Angster et al., 2016; Briggs, 2004), Warm Springs (Chupik, 2019; R. Gold et al., 2013), Honey Lake (R. D. Gold et al., 2017), Polaris (Hunter et al., 2011), and Mohawk Valley (R. D. Gold et al., 2014) faults (Figure 1). The Southern Walker Lane is composed of predominantly northwest‐striking dextral and normal faults, including the Owens Valley (Beanland & Clark, 1994; Haddon et al., 2016; Kirby et al., 2008; Lee et al., 2001), Fish Lake Valley‐Furnace Creek‐Death Valley (Frankel et al., 2007, 2011; Ganev et al., 2010), and White Mountains (Kirby et al., 2006; Stockli et al., 2003) faults.…”