2019 Seafloor Geodesy cruise

Science Center Objects

Objectives: Constrain the rate and spatial distribution of locking (stress accumulation) along the megathrust offshore Cascadia with seafloor geodetic instrument arrays that operate using indirect-path acoustic ranging methods with Global Navigation Satellite System positioning (GNSS-A) (Figure 1)

This survey is part of the USGS project, “Cascadia Subduction Zone Marine Geohazards.”

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

2019 USGS seafloor geodesy cruise off southern Cascadia


Scripps Institution of Oceanography, scientists David Chadwell (PI), David Price and students; USGS scientist Rob Wyland

Principal Investigators

USGS scientists Ben Brooks, Janet Watt, Tom Parsons, and Todd Erickson; Scripps scientist David Chadwell; UW scientist David Schmidt; and UH scientist James Foster


Scripps Institution of Oceanography (Scripps), University of Washington (UW), University of Hawaii (UH)

Platform Used

Humboldt State University’s R/V Coral Sea (Figure 2)

Data collected

Performed maintenance and retrieved data from existing seafloor geodetic stations as part of multi-year effort to construct and install 2 new GNSS-A geodetic stations on the seafloor offshore southern Cascadia


  • 6 seafloor transponders were recovered for maintenance and battery replacement (Figure 3)
  • Autonomous waveglider (Figure 4) recovered after recording positioning for existing seafloor geodetic stations
  • Deployment of 2 new GNSS-A sites (6 transponders and benchmarks) planned for 2021 field season


Schematic of the seafloor showing a cutaway and how monitoring sites are set up.

Figure 1: Schematic diagram showing how seafloor geodetic stations are used to investigate subduction zone coupling. Figure from Bürgmann and Chadwell, 2014.

Photo of a research boat anchored on the water.


Figure 2: Humboldt State University’s research vessel R/V Coral Sea


A device that's sort of round and brightly colored sitting on the deck of a ship near a person's feet.

Figure 3: A seafloor transponder recovered from the Cascadia subduction zone. Credit: Rob Wyland, USGS

An apparatus with various fins and equipment sits on the deck of a ship in a harbor.

Figure 4: Waveglider used to communicate with a geodesy station's seafloor transponders. Credit: Rob Wyland, USGS