Characterizing deformation patterns along the maximum slip zone of the 2019 M7.1 Ridgecrest earthquake surface rupture

Simone Yeager, Johanna M. Nevitt, Benjamin A. Brooks, Todd L. Ericksen, Kenneth W. Hudnut, & Craig L. Glennie

Published September 11, 2022, SCEC Contribution #12500, 2022 SCEC Annual Meeting Poster #168

The distribution of fractures and topographic relief associated with earthquake surface ruptures along strike-slip faults has been a topic of interest to scientists for many years, yet we still do not have a clear understanding of what factors (e.g., fault geometry) control the patterns of these deformation features. Understanding this type of deformation is important, because it can cause profound damage to infrastructure built on or near strike-slip faults. The 2019 M7.1 Ridgecrest earthquake rupture provides a unique opportunity for further research of these processes, because it occurred in an isolated desert region where fractures along the fault are easy to observe and were documented with ground-based and airborne lidar shortly following the event. The M7.1 Ridgecrest mainshock ruptured a right-lateral strike-slip fault on 5 July 2019 (local time) near the intersection of the Walker Lane and Eastern California Shear Zone. Early observations indicated a zone of maximum slip (~3-4 m) largely contained within China Lake Playa. We targeted a ~3-km section of the primary rupture in this region to image using truck-mounted mobile laser scanning (MLS) on 8 July 2019. From these data, we generated 118 digital elevation model (DEM) tiles, each 100 m x 100 m in area and with 5 cm resolution. Using QGIS, an open-source geographic information system platform, we map multiple sets of fractures and zones of uplift/subsidence along the rupture trace. Preliminary analysis indicates that the main set of fractures defining the rupture trace occurs primarily as left-stepping echelon arrays, in which individual fractures, ranging from ~0.3 m to ~ 21 m in length, are rotated slightly clockwise relative to the local rupture trend. Secondary fractures mapped are primarily oblique to the main set, rotated approximately 30° clockwise from the rupture trace. Within the left contractional steps, we observe ~200 instances of localized uplift on the order of ~0.5 m with areas between 0.2 m2 and 352 m2. We also observe ~10 instances of localized subsidence within right extensional steps, which are systematically larger in scale (41 m2 to 688 m2 area, ~1 m subsidence) though less numerous along strike. We explore how these features may relate to variations in fault zone dilatation, rupture trace orientation, and geomorphic units. We also evaluate the resolution limits of airborne lidar in terms of which features it cannot capture that MLS can.

Citation
Yeager, S., Nevitt, J. M., Brooks, B. A., Ericksen, T. L., Hudnut, K. W., & Glennie, C. L. (2022, 09). Characterizing deformation patterns along the maximum slip zone of the 2019 M7.1 Ridgecrest earthquake surface rupture. Poster Presentation at 2022 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)