SCEC Award Number 19044 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Constraining convergence and uplift of the Ventura Avenue Anticline with new GPS observations
Investigator(s)
Name Organization
Eileen Evans California State University, Northridge Gareth Funning University of California, Riverside
Other Participants
SCEC Priorities 1a, 2a, 3e SCEC Groups Geodesy, CXM, Geology
Report Due Date 03/15/2021 Date Report Submitted 03/15/2021
Project Abstract
INTERIM REPORT: The purpose of this project is to provide constraints from Global Positioning System (GPS) data to constrain convergence and uplift across the Ventura Avenue anticline and Ventura fault in the western Transverse Ranges near Ventura, CA. Geologic observations and geophysical imaging suggest that the Ventura Avenue Anticline is uplifting at a rate of up to 5 mm/yr, however GPS observations in the immediate region are sparse, limiting geodetic estimates of active convergence and strain accumulation around the fault. The proposed work will densify the Southern California Earthquake Center (SCEC) Community Geodetic Model (CGM) in this region of sparse spatial coverage. We will evaluate existing benchmarks across the Ventura region and establish new monuments where necessary, and establish initial positions for determining secular velocities. This project has been delayed by 1) PI Evans’ maternity leave in the second half of 2019 and 2) the COVID-19 pandemic in 2020-2021. Due to easing of fieldwork restrictions, we expect the survey, archiving, and final model development to be completed by September, 2021.
Intellectual Merit The primary goal of this work is to densify GPS observations in a region with sparse spatial coverage and known seismic hazard so that these observations may be incorporated into future generations of the CGM. The CGM is also an essential constraint on other community models, Community Stress and Rheology Models.

The Ventura Avenue anticline in the western Transverse Ranges near Ventura, CA, is one of the most rapidly uplifting structures in southern California, as revealed by reflection seismology and uplifted marine terraces. Understanding contraction across the Ventura fault and anticline in the context of the surrounding fault system and geometry is essential for understanding the earthquake hazard associated with these structures. Geodetic observations indicate ~7 mm/yr of contraction across the region and up to 2mm/yr of interseismic vertical uplift. However, GPS observations are sparse across and to the north of the Ventura fault, especially at longitudes spanning the Ventura Anticline (-119.5° to -119.2°). These GPS observations are essential for constraining relative motions across the Ventura Region, informing seismic hazard in the region, and understanding the fundamental nature of tectonic uplift on geodetic and geologic timescales.
Broader Impacts In addition to updating the SCEC CGM, updated GPS velocities can be incorporated into seismic hazard estimation efforts such as the Uniform California Earthquake Rupture Forecast (UCERF) and the USGS National Seismic Hazard Model. All data that we acquire will be archived at the publicly available UNAVCO campaign GPS archive and made available to the broader community.

This project enabled Dr. Evans to advise undergraduate student Julia Carras in performing preliminary modeling. As part of this preliminary modeling, PI Evans created a Matlab GUI tool to quickly and easily generate 2D models of dip-slip faults. The tool will facilitate undergraduate research projects at CSUN. CSUN is a designated Minority Serving Institution and the current percentage of underrepresented minority students in the major is 33%, and the PIs are committed to providing inclusive and equitable access to field experiences. Dr. Evans will hire 1-2 undergraduate research assistants (using startup funds) to assist in summer field campaigns.
Exemplary Figure Figure 1