32-18 Active Faulting Between the Sierra Nevada and the Colorado Plateau as Exhibited by Deformation and Seismicity

Session: Latest Research Advances in Structural Geology and Tectonics (Posters)

Presenting Author:

Authors:

Abstract:

Northwest movement characterizes the deformation east of the Sierra Nevada and west of the Colorado Plateau and is documented by GPS data and seismicity. Zeng (2022) shows the northwestward movement of the area relative to stable North America. The movement increases from the edge of the Colorado Plateau to the Pacific coast. The rate relative to stable North America is about 15 mm/y along the eastern Sierra Nevada. Major mapped NW striking faults include the Owens Valley fault, the Ash Hill fault, the Panamint Valley fault, the southern and northern Death Valley fault zones, the Furnace Creek fault, the Stateline fault and the Las Vegas Valley shear zone. These faults are dominantly dextral. The ENE striking Garlock fault, the ENE striking Lake Mead fault zone and the E striking Mina deflection are the major sinistral faults in the region. Normal faults such as the Sierra Nevada frontal fault are also active. An intense period of low-angle normal faulting associated with large magnitude extension occurred in the Miocene while it no longer appears to be dominant. Most focal mechanisms show NNW dextral and ENE sinistral fault planes. Some solutions show N to NNE normal faulting. The October 25, 2024, M_W 4.7 earthquake in Death Valley has an ENE striking thrust mechanism (Global CMT Catalog).

Slip rates based on trenching studies are available only for a few faults. Zhang et al. (1990) show that the Panamint Valley fault has a Holocene dextral slip of 2.36 ± 0.79 mm/y. McGill and Sieh (1993) measured a sinistral slip rate for the central Garlock fault of 11 mm/y. This slip rate was later refined (McGill et al., 2009) to the range of 5.3 – 10.7 mm/y.

The overall deformation pattern is consistent with NW to NNW dextral shear and ENE sinistral shear. NS to NNE compression and EW tension account for the focal mechanisms showing strike slip, normal and thrust faulting. Fault slip data previously reported by us are consistent with NS compression and EW tension in the W near the Sierra Nevada. The stress directions rotate to NNE compression and ESE tension in the E near the Colorado Plateau.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9611

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