2018 Regional geophysical surveys of southern Cascadia (offshore northern California and southern Oregon)

Science Center Objects

Objectives: Characterize offshore geohazards and source-to-sink sedimentary dynamics offshore southern Cascadia.

These surveys are part of the USGS project, “Cascadia Subduction Zone Marine Geohazards.”

Illustration of the seafloor off the coast with areas highlighted to show detail.

2018 USGS regional geophysical surveys of southern Cascadia (offshore northern California and southern Oregon)

Participants

USGS Scientists Janet Watt and Jenna Hill (PIs), Daniel Brothers, Jared Kluesner, Rachel Marcuson, Chuck Worley (Photo 3)

Partners

Humboldt State University (Photo 1)

Platform Used

Humboldt State University’s R/V Coral Sea (Photo 5)

Data collected

Sparker multi-channel seismic (MCS), Chirp sub-bottom, magnetometer (Photos 2 and 4)

Highlights

  • Active faulting and folding along numerous cross-shore structures on the shelf; including the Table Bluff anticline, Little Salmon, Mad River, and Bald Mountain-Big Lagoon faults
  • First high-resolution sparker imagery of faulting at the deformation front (~3,500 m water depth)

 

A  small group gathers around a woman who's extracting a sediment core from a marshy area while a man talks.

Photo 1: Humboldt State University Assistant Professor Melanie Michalak (kneeling) and California State Geological Survey scientist Jay Patton (standing, center) explaining core stratigraphy within Humboldt slough and evidence for past tsunami inundation. Integrating evidence of past earthquakes and tsunamis from offshore and onshore geologic evidence is key to understanding the hazards posed by the Cascadia subduction zone. Credit: Janet Watt, USGS

Geophysical equipment sits on the deck of a boat.

Photo 2: Marine magnetometer (in storage box on left) and chirp sub-bottom profiler on the back deck of R/V Coral Sea. Credit: Janet Watt, USGS

 

A group of 6 people wearing lifejackets stand on a ship smiling up at the camera person.

Photo 3: USGS scientists (left to right) Jenna Hill, Chuck Worley, Rachel Marcuson, Janet Watt, Danny Brothers, and Jared Kluesner on the back deck of Humboldt State University’s R/V Coral Sea. Credit: Janet Watt, USGS

Four people on the stern of a boat wear life jackets and prepare a long cable.

Photo 4: USGS science crew prepare to pull in the multi-channel streamer to troubleshoot the system. Credit: Janet Watt, USGS