Carpinteria Salt Marsh Reserve

03 Feb, 11 PM - 05 Feb, 10 AM

In 1812, a 3.4 m tsunami hit the Gaviota coastline of the Santa Barbara Channel (National Geophysical Data Center, 2011). Since that earliest recorded tsunami, other smaller tsunamis have hit the Santa Barbara area in 1896 (2.5m) and 1964 (1.6m), and the March 11th, 2011 Tohoku Japan earthquake resulted in a tsunami approximately 1.0 m above predicted tidal levels (National Geophysical Data Center, 2011). Borrero et al. (2001) conducted a numerical modeling study in order to address the tsunami hazard for the Santa Barbara Channel (SBC). They suggested that purely tectonic sources could produce runups of only 2 m. However, they did find that earthquake-induced slumps could produce tsunamis with local runup as large as 15 m. In addition, they only considered earthquakes along the Channel Islands Thrust and did not consider tsunamis produced by distant sources or by recent claims of earthquakes producing nearly 8 m of uplift along the crest of the Ventura Avenue Syncline near Pitas Point (Rockwell, 2011; Fig. 1). Indeed, Rockwell (2011) contends that movement along the Ventura Avenue Syncline offshore may be capable of producing tsunamis as high as 8-10 m. The possibility of unmapped or underappreciated offshore earthquake activity causing tsunamis was highlighted by the March 11, 2011 Tohoku Japan tsunami. Despite the historic occurrence of tsunamis, the presence of offshore slides capable of producing large tsunamis (Greene et al., 2000), and work documenting the earthquake hazards of the area (Rockwell, 2011), little is known about the frequency or magnitude of tsunamis along the SBC. The purpose of this proposal is to test suggestions by Rockwell (2011) that large tsunamis may be a common threat to the coastlines of southern California. Our overall objective is to determine the frequency of earthquake-induced tsunamis for the southern California coastline. The central hypothesis of this proposal is that displacement along the Ventura Avenue Fault or other offshore sources produced tsunamis capable of flooding low-lying coastal areas and estuaries of the SBC. We will test our hypothesis by obtaining 30 shallow cores from three small coastal estuaries along the northern and eastern SBC. These three estuaries are Gaviota Slough, Devereux Slough, and Carpinteria Slough (Fig. 1). We will use the shallow cores to look for sand sheets or similar tsunami deposits during the past 3000-5000 years. We will use 14C and/or 210Pb dating to constrain the age of suspected tsunami deposits. In addition, the cores taken for this project will be used to place additional constraints on the sea-level and climate history for the region over the Holocene. Our research group is well prepared for this task. The PI has several years of experience studying the sedimentology and Holocene stratigraphy of estuaries, lagoons, and coastal ponds. In addition, our research group benefits from being located within the study area as well as having the equipment and expertise needed to carry out this project.

Visit #27257 @Carpinteria Salt Marsh Reserve

Approved

Under Project # 24790 | Research

Reconstructing the Holocene record of sea-level, climate, and tectonic changes from Carpinteria Slough

faculty - University of California, Santa Barbara

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Group of 3 Graduate Student Feb 3 - 5, 2012 (3 days)

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