SCEC Award Number 12080 View PDF
Proposal Category Collaborative Proposal (Data Gathering and Products)
Proposal Title Do the Wetlands of California Preserve a Record of Paleotsunami?
Name Organization
Brady Rhodes California State University, Fullerton Matthew Kirby California State University, Fullerton
Other Participants Two as yet unidentified undergraduate students will participate in this project, which will comprise their undergraduate theses. Robert Leeper, a CSUF undergraduate student will participate as part of his employment with the USGS Multihazard Demonstration Project. Khadija Nadimi is a CSUF international graduate student who is funded via a Fulbright Fellowship. Her MS thesis will focus on an as yet undetermined part of this project. Christine Hiner is an undergraduate student at CSUF and will participate in this project via her role as a laboratory technician in the CSUF Paleoclimatology and Paleotsunami Lab.
SCEC Priorities 4a, 4d, 4e SCEC Groups Geology, FARM, CEO
Report Due Date 03/15/2013 Date Report Submitted N/A
Project Abstract
The coastal wetlands of Southern California provide the most promising environment for locating a record of ancient tsunami deposits. Reconnaissance field work has included the description of over 50 push cores of between 1 and 5 meters depth from sites in 4 southern California Wetlands. Following the reconnaissance exploration, over 30 m of sediment cores were collected from Los Penasquitos Lagoon and the Seal Beach Wetlands. In Los Penasquitos lagoon, we discovered a distinctive fossil hash layer at a depth of 2-3 meters at several sites. Shell samples from this layer yielded C-14 dates of 1895, 1795, and 1835 YBP. Our preliminary hypotheses are that this shell layer represents either a flood deposit, tidal channel lag deposit, or paleotsunami deposit. Reconnaissance cores from Seal Beach show a up to 4 peat layers extending down to the base of our cores, with intervening muddy to fine sandy layers. Our working hypothesis is that the buried peat layers represent episodic subsidence of the wetlands, perhaps due to seismic events on one or more strands of the Newport-Inglewood Fault. Further reconnaissance coring, vibracoring, and laboratory analyses, including microfossil data, will test our hypothesis.
Intellectual Merit Finding and documenting a tsunami record in the wetlands of Southern California will address 2 important elements in the 2012 Science Collaboration Plan: 1) We will directly address one of the priorities for Earthquake Geology listed in the Collaboration Plan: “Search for possible tsunami deposits from offshore sources, including both faults and landslides.” 2) We will also address one of the priorities listed for Fault and Rupture Mechanics: “Explore similarities between earthquakes and offshore landslide sources with the goal of better understanding their mechanics and the tsunami hazard from sources in Southern California”. By documenting a tsunami record in the wetlands of California, we will be able to correlate our records laterally along the coast. Knowing the lateral extent of the tsunami deposits will constrain the source area. Furthermore, analysis of the thickness, grain size, and sedimentary structures in the tsunami deposits, will provide parameters that can be used to model the tsunami’s run-up height, and velocity. The variation of these parameters along the coast could be used to interpret whether the source was a landslide, local fault, or distant fault. Our data will valuable to modelers as they attempt to quantify the tsunami hazard in Southern California.
Broader Impacts Education: The educational impact on this project centers around the laboratory and field training of CSUF undergraduate and graduate students. To date, 5 CSUF undergraduate students, Robert Leeper, Jeremy Cordova, O’hara Creager, Bree Baumgartner, and Alex Woodward have participated in one or more days in the field. O’hara and Jeremy will derive UG theses from this project in 2013. We will be hiring another UG student, Dylan Garcia in early 2013. In addition to completing an BSc thesis on this project, Dylan will also act as a dedicated lab technician for this project. Additionally, one MSc student, Khadija Nadimi is completing her MSc thesis on this project. Khadija has spent several days in the field with both PI’s and has been fully trained in the laboratory techniques for core analysis. Khadija aims to complete her MSc thesis in Summer 2013.

Training and Development: We are working closely with our students so they are involved in all aspects of this project. All BSc and MSc students are required to write a proposal for their project. All students have, or will participate in field work, including both reconnaissance coring and piston coring. All students will be trained in the CSUF Paleoclimatology and Paleotsunami laboratory, including the use of the NSF-funded Malvern laser diffraction grain size analyzer. All of our students will be strongly encouraged to present the results of their research at the Fall SCEC and AGU meetings in 2013 and/or 2014.

Outreach Activities: In April 2012, B. Rhodes gave an overview of this project in a public presentation for the Fullerton Library “Town and Gown Series”. As results become available, we will be working with the visitor centers at San Elijo, Oneonta and Seal Beach to make displays for the public that summarize our work.
Exemplary Figure Figure 2. Core logs from a N-S transect in the Seal Beach wetlands. Inland is to the left. Location of sites is shown on Figure 1. Black lines show the interpreted correlations of the tops of peaty units. We hypothesis that these horizons mark times of abrupt subsidence of the marsh.