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Preliminary Mapping of Surface Fault Rupture and Ground-Deformation Features of the 2019 M6.4 and M7.1 Ridgecrest Earthquake Sequence From Post-Earthquake Lidar Datasets

Session: Fault Displacement Hazard: New Data and Modeling Advances II

Type: Oral

Date: 4/23/2021

Presentation Time: 10:45 AM Pacific

Description: 

We present preliminary mapping of surface ruptures and ground-deformation features associated with the 2019 Ridgecrest Earthquake Sequence. The mapping utilizes high-resolution (up to 80 pulses per square meter) airborne lidar flown post-earthquake by the National Center for Airborne Laser Mapping (Hudnut et al., 2020). The M_w 6.4 and M_w 7.1 earthquakes produced rupture and ground deformation zones approximately 18 km and 50 km in length, respectively, with widespread deformation occurring off the main fault strands. Our goal is to produce a comprehensive, spatially accurate dataset depicting surface ruptures associated with the Salt Wells Valley and Paxton Ranch Fault Zones. We used seamless lidar-derived hillshades, illuminated at 45- and 315-degrees and supplemented with a multi-directional hillshade as the base imagery. Mapping was done at a consistent (1:500 – 1:1000) scale, the largest scale at which imagery resolution is not degraded. Use of this large scale increases our confidence that we have only mapped features that are related to ground deformation from the earthquake. The surface rupture was mapped to highlight the width of deformation zones and to characterize the rupture’s expression through varying terrain, such as along pre-existing fault scarps, hillslopes, fan surfaces, and relatively flat playa surfaces. Our mapping shows that the lidar can reliably resolve ruptures with tens of centimeters and more of relative vertical displacement. Areas with known surface rupture, mapped either in the field or on aerial imagery, but with little relative vertical displacement, are less likely to be well-resolved on the lidar. Thus, characterizing zones of deformation, important for the assessment of fault displacement hazard, will likely require a paired approach using both lidar and high-resolution aerial imagery. We plan to produce a comprehensive comparison of what ground deformation features can be resolved using post-earthquake orthoimagery vs. lidar.

Presenting Author: Carla M. Rosa

Student Presenter: No

Authors