USGS offshore, low-energy seismic-reflection data

Samuel Y. Johnson, USGS Pacific Coastal and Marine Science Center, Diablo Canyon SSHAC Workshop 1, 11/29 to 12/1/11, San Luis Obispo, CA

USGS offshore, low-energy seismic-reflection data

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• Data Acquired – Data Limits – 3 Data Gaps • Why? Geologic mapping, habitat mapping Earthquake hazard assessment Tsunami hazard assessment Coastal and marine spatial planning • How? Integrated interpretation of:

Seismic-reflection profiles, high-resolution bathymetry, marine magnetics, camera and sampling data

• Supported by: USGS Coastal and Marine Geology Program California Seafloor Mapping Program USGS/PG&E CRADA

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Seismic-reflection surveys

USGS Seismic-reflection (~1500 km) and magnetic surveys (X2)

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Source: SIG 500 joule mini-sparker, fired at ½ second interval Receiver: 15-m hydrophone streamer (single channel) Processing: AGC, bandpass filter, learning SIOSEIS Details and data presented in Sliter and others (2009), USGS OFR 2009-1100 http://pubs.usgs.gov/of/2009/1100/index.html

USGS RV Parke Snavely

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Shallow structure and stratigraphy through a gentle 4° bend along 1600 m of the Hosgri fault

Issue 1: Seafloor reverberation

Estero Bay

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Issue 2: Heave

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Issues 1 and 2: Shallow hard bottom – reverberation and heave

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Geologic maps (Watt, Johnson, & Graymer) - Coming soon Integration of Seismic-reflection, High-res bathy, Marine magnetics

Pismo Beach to Morro Bay Morro Bay to San Simeon

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Big data gap #1 – multibeam mapping in Estero Bay

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Goleta submarine landslide complex

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creep?

crack

Slide?

buried scarp?

pockmarks

Shelfbreak west of Hueneme Canyon, Offshore Oxnard, CA

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Offshore Point Buchon

Offshore Cambria

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Big data gap #2 – multibeam mapping of shelfbreak/upper slope, Follow-up high-res seismic-reflection mapping, as needed

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Location, Length, Dip, Slip Rate, Earthquake History and Recurrence

Data need (Data Gap 3): earthquake history/recurrence Is there a Hosgri fault earthquake event stratigraphy preserved in intra-fault zone basins? In basins along scarps? In adjacent submarine canyons or submarine fans? Can we sample (core) it?

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USGS – CSMP central CA groundtruthing cruise – summer of 2012

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Data Acquired – Data Limits – 3 Data Gaps

USGS offshore, low-energy seismic-reflection data

SYJ – 11/11