Science Center Objects

Objectives: Conduct surveys to reconstruct the timing of large earthquakes in northern Cascadia from earthquake-triggered landslide deposits in Lake Ozette, WA.

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

Two men work on a boat pulling up a long cable from the water.

USGS scientists Dan Powers (left) and Andy Ritchie retrieving a core sample from beneath Lake Ozette aboard research vessel Hadai. Credit: Danny Brothers, USGS

Participants

USGS scientists Danny Brothers (Principal Investigator), Andy Ritchie, Pete Dal Ferro, Dan Powers, and Jackson Currie

Partners

U.S. National Park Service, USGS Earthquake Science Center scientist Brian Sherrod,

Platforms Used

San Lorenzo, R/V Hadai

Data collected

Swath bathymetry, chirp sub- bottom, boomer seismic-reflection, and vibracores

Highlights

  • Combined with new subaerial LiDAR data, topo-bathymetry data of the entire Ozette lake basin is resolved to ~2 m resolution
  • Bathymetry highlight areas of blocky, rugged, lake floor that appear to be covered in mass transport deposits (MTDs)
  • Coring and sub-bottom imagery reveal a series of Holocene stacked discrete graded sandy beds that may record shaking during large earthquakes
An illustrated map shows seafloor features and is labeled with dots to show where samples were collected.

Bathymetric map of Lake Ozette, showing locations of core samples (red circles). Credit: Danny Brothers, USGS