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Environmental Impact Mitigations

The proposed research would be conducted in accordance with U.S. and international rules and regulations. All necessary federal and state permits, authorizations, and approvals are being (or have been) sought for the proposed research activities, including those pursuant to the U.S. Marine Mammal Protection Act, Endangered Species Act, Magnuson-Stevens Act (Essential Fish Habitat, Coastal Zone Management Act (CZMA), and National Environmental Policy Act (NEPA). Several of these regulatory processes have included opportunities for the public to provide comment on the proposed research activities, including:

• Draft Environmental Assessment
• Draft Incidental Harassment Authorization: pending

As earth and environmental researchers dedicated to preserving our natural environment, we follow strict procedures to minimize any disruption to protected species. During seismic operations on board the R/V Langseth, we have proposed that several protected-species observers would be on board listening and watching for marine life. If marine mammals or other protected species come within a designated radius of the ship, its sound sources would be shut down. The cruise has been proposed to minimize conflict with marine life, such as marine mammal migrations. Research activities would comply with all international, federal and state regulatory requirements.

Ocean Bottom Seismic Instrumentation

OBS and OBN’s are instruments equipped with sensitive hydrophones and seismometers and digital recording packages that, when placed on the seafloor, detect and record the very subtle vibrations of the seafloor and sounds propagating through the ocean produced by natural sources like distant earthquakes and local microseisms, storms, or cetaceans, as well as from man-made sources like ship traffic and airguns.

We call OBSs to instruments that are generally larger in size (~1m by 1m by 1m), have sensors capable of responding to lower frequency sources, and operate in shallow to very deep ocean depths (up to ~6,000 m). OBS are generally deployed from ships as free-fall instruments which sink due to the weight of an anchor (click here for a video of a typical deployment). For recovery, an acoustic signal triggers the release of the anchor and the OBS floats back to the surface due to its buoyancy.

We call OBNs to instruments that are smaller in size (~1 foot by 1 foot ~ 6 inches), are sensitive to higher frequency sources, and operate in shallow to intermediate ocean depths (up to ~3,000 m). Due to their reduced size, OBNs lack buoyancy and therefore have to be deployed on, and retrieved from, the seafloor using remotely operated vehicles (ROV).

Relevant links:
Short-period OBS (WHOI)
Short-period OBS (SIO)
Ocean Bottom Nodes

USGS Initiatives

Scientists at the USGS are actively working to improve our understanding of earthquake and tsunami hazards in the Pacific northwest through several initiatives, which include monitoring and mapping studies to improve earthquake hazard assessment and mitigation planning. The proposed long-streamer multi-channel seismic survey would provide imaging deep into the subduction zone reaching to the megathrust that is designed to complement the higher resolution seismic surveys the USGS is currently conducting of the sediments of the Cascadia accretionary wedge. The proposed OBS/OBN studies are planned as a direct partnership with the USGS.

Relevant links:
USGS John Wesley Powell Center for Analysis and Synthesis
USGS Coastal and Marine Hazards and Resources Program
USGS Subduction Zone Blueprint

NSF GeoPRISMS

The Cascadia Subduction Zone is one of the focus sites for targeted investigation through the National Science Foundation funded GeoPRISMS program. This site was chosen by the US scientific community as an ideal location to study fundamental research questions pertaining to Subduction Zone Cycles and Deformation. As part of this program and the complementary NSF-funded EarthScope program, a wide range of geological, geophysical, and geochemical studies have been conducted at Cascadia. These studies provide multi-disciplinary observations ranging in scale from plate-scale mantle structure to identification of numerous local seafloor seeps along the Cascadia margin. The proposed studies would provide the subsurface framework for interpreting the extensive suite of existing observations based on new high-fidelity seismic images of the offshore subsurface architecture of the Cascadia SZ.

Relevant links:
GeoPRISMS
Cascadia Initiative
Cascadia Initiative Team

PNW Seismic Network and Earthquake Early Warning Efforts

Plans are underway for a Cascadia early warning system that would involve deployment of instruments for offshore seismic and geodetic monitoring. Our proposed studies would provide characterization of the megathrust and accretionary wedge that would be useful for optimally locating the monitoring instrumentation envisioned for these monitoring efforts.

Relevant links:
Pacific Northwest Seismic Network
ShakeAlert
Cascadia Offshore

Societal Benefits

Because of the high seismic and tsunami hazard, the PNW is a region of great national interest and growing public awareness. Based on new high-fidelity seismic images of the offshore subsurface architecture of the Cascadia subduction zone, our proposed study would provide a framework for interpreting the extensive suite of existing observations made during the last decades by federal and state agencies, universities, and research centers. This framework is critically needed for improving earthquake and tsunami hazard assessments for Cascadia, which affects mitigation and response planning.