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Scholarly Works (2 results)

  • Thesis
  • Peer Reviewed
UC San Diego Electronic Theses and Dissertations (2020)

The Newport-Inglewood-Rose Canyon (NIRC) fault system is a major structural boundary that extends along coastal southern California from Los Angeles to San Diego. The material presented in this thesis provides new data that resolve uncertainties in fault behavior for the southern segment, the Rose Canyon fault (RCF).

Stratigraphic evidence from newly opened paleoseismic trenches are used to interpret six surface-rupturing earthquakes on the RCF in the past 3,300 years. Paleoearthquake ages constrained by radiocarbon dating suggest a late-Holocene recurrence interval of ~700 years, with the most recent large-magnitude event occurring in the mid-1700s. When combined with previous paleoseismic studies, the new paleoearthquake ages show an apparent temporal correlation of earthquake occurrence between the southern and northern segments of the NIRC fault system, suggesting a possible northward-cascading sequence of earthquakes.

The RCF includes a significant onshore segment, which provides an opportunity to use traditional geodetic techniques to resolve slip rate. Surface velocities from a combined campaign and continuous GPS network that spans the RCF are used to constrain elastic half-space models. The best-fitting model suggests a rate that is toward the higher end of geologic estimates, as well as a potential rheological contrast across the fault trace. The GPS surface velocities further suggest a more easterly trace for the RCF, and a possible connection with the San Miguel-Vallecitos fault system.

South of downtown San Diego, the RCF splays out into a complex network of faults that accommodate the subsidence beneath San Diego Bay. Using legacy multi-channel seismic data and recently collected high-resolution chirp profiles, the fault structure and stratigraphic character beneath San Diego Bay is examined. Gridded surface horizons and fault maps show widespread down-to-the-east displacement. Fault orientations in the western portion of the San Diego Bay pull-apart basin are well described by a Rose Canyon–Descanso pull-apart basin, but faults in the eastern portion of the basin lie outside of this model and exhibit the wrong sense of displacement. A separate but related Rose Canyon–San Miguel-Vallecitos pull-apart basin may explain the faulting seen in the eastern portion of the basin.

    Cover page: Neotectonics in San Diego, California: Paleoseismology, Slip Rate, and Offshore Structure of the Rose Canyon Fault
    • Article
    • Peer Reviewed
    UC Davis Previously Published Works (2020)
    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 bymapping 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 aswell 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.
      Cover page: 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
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