Seismic Reflection Imaging of the Low‐Angle Panamint Normal Fault System, Eastern California

Abstract

Shallowly dipping (<30°) low-angle normal faults (LANFs) have been documented globally; however, examples of active LANFs in continental settings are limited. The western margin of the Panamint Range in eastern California is defined by a LANF that dips west beneath Panamint Valley and has evidence of Quaternary motion. In addition, high-angle dextral-oblique normal faults displace middle to late Quaternary alluvial fans near the range front. To image shallow (<1 km depth), crosscutting relationships between the low-and high-angle faults along the range front, we acquired two high-resolution P wave seismic reflection profiles. The northern, 4.6-km-long profile crosses the 2-km-wide Wildrose graben and the southern, 0.8-km-long profile extends onto the Panamint Valley playa,~7.5 km S of Ballarat, CA. The profile across the Wildrose graben reveals a robust, low-angle reflector interpreted to represent the LANF separating Plio-Pleistocene alluvial fanglomerate and Proterozoic metasedimentary deposits. High-angle faults interpreted in the seismic profile correspond to fault scarps on Quaternary alluvial fan surfaces. Interpretation of the reflection data suggests that the high-angle faults vertically displace the LANF up to 80 m within the Wildrose graben. Similarly, the profile south of Ballarat reveals a low-angle reflector, which appears both rotated and displaced up to 260 m by high-angle faults. These results suggest that near the Panamint range front, the high-angle faults are the dominant active structures. We conclude that at least at shallow (<1 km) depths, the LANF we imaged is not active today.

Late Holocene rupture history of the Ash Hill fault, Eastern California Shear Zone, and the potential for seismogenic strain transfer between nearby faults

“…This scenario could allow for slip to initiate at depth along the Panamint Valley fault and directly transfer to the Ash Hill fault. Alternately, if both the Ash Hill and Panamint Valley faults are high‐angle structures, as suggested by Gold et al (2020), this suggests that slip can be transferred across a ‘soft’ connection in the absence of physically linked faults. The presence of a distributed network of short strike length, en échelon , and stepping fault scarps located between the southern Ash Hill and central Panamint Valley faults near Ballarat (Figure 1) suggest that there may be a network of poorly connected faults in an accommodation zone between the two faults.…”

“…Low‐angle fault outcrops that displace young alluvium, the kinematics of fault networks, and palinspastic reconstructions of the valley suggest the Panamint Valley fault may have a moderate west dip of ~15–25° (Burchfiel et al, 1987; Hoffman, 2009; Kirby & McDonald, 2016). However, recent seismic imaging of the Panamint Valley fault at Wildrose (Figure 1b) indicates this low‐angle fault may be offset by a more recently active high‐angle (>60°) fault (Gold et al, 2020). As such, it is uncertain if and how the Ash Hill and Panamint Valley faults interact and transfer strain at depth.…”

High‐Resolution Seismic Imaging of Fault‐Controlled Basins: A Case Study From the 2009 Mw 6.1 Central Italy Earthquake

“…Seismic reflection profiling is the premiere technique used to obtain detailed images of the subsurface, which are ideal for stratigraphic and structural interpretations. In recent years, great technological advancements in the acquisition and processing of high-resolution onshore data have led to a significant increase in the number of successful explorations of continental basins, providing to geoscientists an imaging resolution comparable to that of marine surveying (e.g., Bruno et al, 2017Bruno et al, , 2019Gold et al, 2020;Haberland et al, 2017). In this article, we present the first seismic reflection images of the Bazzano and Paganica basins and bounding faults obtained by applying advanced and target-oriented processing flows to the profiles acquired by Improta et al (2012).…”