Documentation of Surface Fault Rupture and Ground-Deformation Features Produced by the 4 and 5 July 2019 Mw 6.4 and Mw 7.1 Ridgecrest Earthquake Sequence

Abstract

The Mw 6.4 and Mw 7.1 Ridgecrest earthquake sequence occurred on 4 and 5 July 2019 within the eastern California shear zone of southern California. Both events produced extensive surface faulting and ground deformation within Indian Wells Valley and Searles Valley. In the weeks following the earthquakes, more than six dozen scientists from government, academia, and the private sector carefully documented the surface faulting and ground-deformation features. As of December 2019, we have compiled a total of more than 6000 ground observations; approximately 1500 of these simply note the presence or absence of fault rupture or ground failure, but the remainder include detailed descriptions and other documentation, including tens of thousands of photographs. More than 1100 of these observations also include quantitative field measurements of displacement sense and magnitude. These field observations were supplemented by mapping of fault rupture and ground-deformation features directly in the field as well as by interpreting the location and extent of surface faulting and ground deformation from optical imagery and geodetic image products. We identified greater than 68 km of fault rupture produced by both earthquakes as well as numerous sites of ground deformation resulting from liquefaction or slope failure. These observations comprise a dataset that is fundamental to understanding the processes that controlled this earthquake sequence and for improving earthquake hazard estimates in the region. This article documents the types of data collected during postearthquake field investigations, the compilation effort, and the digital data products resulting from these efforts.

Multifault Models of the 2019 Ridgecrest Sequence Highlight Complementary Slip and Fault Junction Instability

“…sequence, the surface trace observations show the multiscale complexity of the fault system (DuRoss et al, 2020;Ponti et al, 2020), which appears inconsistent with the deeper aftershock seismicity (X. Wang & Zhan, 2020a).…”

Bookshelf Kinematics and the Effect of Dilatation on Fault Zone Inelastic Deformation: Examples From Optical Image Correlation Measurements of the 2019 Ridgecrest Earthquake Sequence

“…From our observations of the kinematics of surface strain, we also seek to understand the widespread occurrence of orthogonal cross-faulting along the surface rupture. Cross-faulting occurred at almost all scales as shown by 100-m long distributed fractures (Ponti et al, 2019;Xu et al, 2020), to the coseismic rupture strands involved directly in the foreshock-mainshock sequence and the distribution of aftershocks, which suggests cross-faulting is pervasive through the seismogenic crust and is not just a surficial feature (Ross et al, 2019). Similar cross-faulting rupture behavior has been observed during other large earthquakes (e.g., the 1987 Superstition Hills) and seems to be a common mode of strain release along the North American-Pacific plate boundary (Hudnut et al, 1989;Smith et al, 2020).…”

Detailed 3D Fault Representations for the 2019 Ridgecrest, California, Earthquake Sequence

“…The 5 July M 7.1 earthquake occurred about 34 hr later and 7 km to the west of the M 6.4 earthquake. The M 7.1 event ruptured a northwest-southeast-striking fault and exhibited right-lateral strike-slip faulting (Liu et al, 2019;Ross, Idini, et al, 2019;Stewart et al, 2019;Chen et al, 2020;Hudnut et al, 2020;Ponti et al, 2020). The earthquakes produced extensive ground rupture along planes consistent with their preferred nodal planes and aftershock alignments (Kendrick et al, 2019).…”

“…Moreover, there is substantial uncertainty in the geometric representations of many fault zones given a lack of subsurface data. The 2019 Ridgecrest, California, earthquake sequence (Liu et al, 2019;Ross, Idini, et al, 2019;Chen et al, 2020;Hudnut et al, 2020;Ponti et al, 2020) is a clear example of the need to expand and refine these models. The M 6.4 and 7.1 Ridgecrest earthquakes and their associated foreshocks and aftershocks occurred on faults broadly within the regional Little Lake fault zone associated with a series of highly segmented fault traces (Wills, 1988) with evidence of previous activity (Kozaci et al, 2019;Thompson Jobe et al, 2020).…”