SCEC Award Number 13121 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Collaborative Research: Assessing the earthquake potential of the Ventura-Pitas Point fault system: Determination of fault slip rates and paleo-earthquake ages and displacements
Investigator(s)
Name Organization
James Dolan University of Southern California John Shaw Harvard University Thomas Pratt United States Geological Survey
Other Participants Lee McAuliffe, Graduate Student
SCEC Priorities 4, 4c, 4e SCEC Groups Geology, WGCEP, USR
Report Due Date 03/15/2014 Date Report Submitted N/A
Project Abstract
 New data from a transect of continuously cored borehole and cone-penetrometer tests dated with luminescence and radiocarbon techniques constrain the timing and uplifts of Holocene earthquakes along the Ventura-Pitas Point fault at a study site in the City of Ventura. The ages of the most recent event (≤800 years ago) and an earlier folding and uplift event at ~ 5 ka correlate with ages from a study site 20 km to the west, suggesting that these record system-wide earthquakes. the large displacements observed at both sites indicate that these were very large-magnitude (Mw≥7.5) events that likely ruptured the entire Ventura-Pitas Point system, as well as nearby faults such as the San Cayetano and related faults. Ongoing stratigraphic analysis and dating of samples collected in 2013 will allow us to refine our age constraints on these two earthquakes, as well as two other possible events.
Intellectual Merit New data from a transect of continuously cored borehole and cone-penetrometer tests dated with luminescence and radiocarbon techniques constrain the timing and uplifts of Holocene earthquakes along the Ventura-Pitas Point fault at a study site in the City of Ventura. The ages of the most recent event (≤800 years ago) and an earlier folding and uplift event at ~ 5 ka correlate with ages from a study site 20 km to the west, suggesting that these record system-wide earthquakes. the large displacements observed at both sites indicate that these were very large-magnitude (Mw≥7.5) events that likely ruptured the entire Ventura-Pitas Point system, as well as nearby faults such as the San Cayetano and related faults. Ongoing stratigraphic analysis and dating of samples collected in 2013 will allow us to refine our age constraints on these two earthquakes, as well as two other possible events.
Broader Impacts Measurements of uplift during Holocene Ventura-Pitas Point fault earthquakes, combined with collaborative analyses of the overall fault architecture of the region, indicate that the earthquakes revealed by this study and related SCEC-funded efforts were very large magnitude events in the range of Mw 7.5-8. These data are thus of obvious importance for our understanding of seismic hazards in the densely populated southern California region, since such large-magnitude Transverse Ranges reverse-fault earthquakes have not occurred during historic time. These data are being incorporated into current seismic hazard analyses (e.g., WGCEP; UCERF3), as well as into state-of-the-art structural models of southern California (e.g., the SCEC Community Fault Model). In addition to the seismic hazard implications of this research, this project constitutes a significant portion of USC graduate student Lee McAuliffe's Ph. D. dissertation. As part of this project, McAuliffe has received broad training in a wide variety of disciplines, including seismic reflection acquisition and interpretation, subsurface stratigraphic analysis, structural modeling, and geochronology. Numerous graduate students from USC, Harvard, and UCLA have participated in data acquisition efforts, providing valuable field experience. The project has also fostered collaborative research between several US universities (USC, Harvard, UCLA), as well as with the U. S. Geological Survey and the Earth Observatory at Nanyang Technical University in Singapore. Moreover, these results are being incorporated into university courses taught by Dolan, Shaw, Rhodes, and Hubbard at their respective universities at both the undergraduate and graduate levels.
Exemplary Figure Figure 3 (borehole-CPT cross section from our day Road transect). From McAuliffe et al. (in prep.)