1. Where and when do you propose to do this survey?

If we are authorized following the pending environmental compliance process, we plan to survey the western North America margin extending from 10-20 km (~6-12 miles) to 100-200 km  (~62-124 miles) offshore from west of Haida Gwaii Island to southeast Alaska in late summer, 2020. Additional ocean bottom seismometers will be deployed for up to 12 months to record and characterize aftershocks from the 2012 and 2013 earthquakes and background seismicity.

See Experiment Map

2. Why do you want to study this region and what do you expect to learn?

Our goal is to characterize the properties of the Queen Charlotte Fault, a strike-slip plate boundary that separates the Pacific and North American tectonic plates. Compared to subduction zones, the time-space evolution of continental-oceanic strike-slip margins is understudied, despite their important role in the planet’s plate tectonic system. These settings are potentially one of the most favorable for subduction initiation due to the juxtaposition of plates with contrasting density and thermal structure. The QCF system provides an ideal location to investigate how this type of plate boundary responds to systematically increasing degrees of convergence at the lithospheric scale. The study area includes two potential fault segment boundaries that mark abrupt changes in observed crustal deformation, as suggested by changes in seafloor morphology and previous imaging. Current observations allow for a wide range of possible future earthquake and tsunami scenarios. Comprehensive characterization is needed to quantify earthquake and tsunami hazards within the region.

The 900 km-long fault zone lies almost entirely offshore. Thus marine surveys are needed to investigate its structure. The specific goals of our study are to use modern deep penetration multi-channel seismic (MCS) and ocean bottom seismometer data to image the internal structure and characterize the properties of this key offshore region. The data would be used to characterize variations in fault structure along the margin that may be linked to transitions in fault properties. The data would also enable researchers to investigate the physical properties of the continental slope sediments and crust, which are critical for predicting the rupture behaviors and intensity of earthquake-triggered shaking along the Pacific Northwest and assessing tsunami/landslide hazards under hypothetical scenarios of future earthquake rupture. The proposed study would be the first such regional-scale seismic imaging investigation ever conducted spanning nearly the entire length of the QCF margin.

Though separately managed, we plan to coordinate with two additional efforts. Researchers from the Pacific Geoscience Center and the University of British Columbia have proposed an onshore experiment to model the subsurface beneath Haida Gwaii Island through the deployment of onshore seismometers during the same timeframe as the proposed marine survey.  Scientists from the Japan Agency for Marine Earth Science and Technology (JAMSTEC) have proposed to place additional ocean bottom seismometers offshore Haida Gwaii. The additional recordings of the offshore sources would help image the potential underthrusting that cause the 2012 M7 Haida Gwaii earthquake.

 3. Have research seismic surveys occurred in the region before?  If so, why do you need to conduct more?

Aside from the localized surveys conducted in 1994 by R/V Ewing using an 8-km (5 mile) streamer, no modern deep penetration multi-channel seismic (MCS) data have been acquired in the QCF region.  (See #7 for more information about streamers)  Data acquired prior to these surveys were collected in the ‘80s and ‘90s with much shorter streamers (2.6–4 km or 1.6-2.5 mile) and in most cases, with poorer quality sound sources, and thus provide a weak-to-no image of the deep earthquake fault zone. Long streamer (>8 km) MCS data represent major advances over the previous generation of MCS studies in the region for two primary reasons.  First, the data acquired with long streamers enable application of advanced computational techniques providing clearer images of the fault zone to much greater geologic depths beneath the seafloor than previously obtained.  Second, long-streamer data enable us to determine the speed at which sound waves propagate through the sediments and crust at high-resolution, which both improves the imaging of structures and also provides information on physical properties of the fault zone. These properties are linked to whether and how different parts of the fault zone may slip in a large earthquake in the future. The proposed study would also provide the first homogeneous regional-scale characterization, enabling the first study of how properties of the fault zone vary along the margin in a systematic and self-consistent manner.

Modern long-offset marine seismic reflection imaging techniques provide the best tools available to scientists for illuminating the details of subduction zones to the depths of the earthquake source region and below. Over the past 2 decades, regional surveys using these tools have been conducted at many of the world’s continental margins including regions near population centers of South and Central America, Japan, New Zealand and eastern North America. The proposed study would provide similar data from the QCF margin as now exists for these other regions and would provide a modern basis of characterization useful for various studies of earthquake and tsunami hazard.

While modern deep penetration MCS studies are very limited along the QCF margin, there have been other kinds of research seismic expeditions conducted in the recent past in the region. In 2016, the USGS began a series of high-resolution seismic and bathymetric mapping studies using small energy sources designed to image the structure of the sediment section along the margin. Our proposed study complements these earlier studies and would provide information on regional structure useful for advanced interpretation and analysis of these other data sets.

 4. Who is funding this research?

The projects would be funded by the National Science Foundation (NSF) with additional resources from US Geologic Survey (USGS), Natural Sciences and Engineering Research Council of Canada (NSERC) and Pacific Geoscience Center. The projects were reviewed through a peer-reviewed process with awards to researchers at the University of New Mexico and the University of Washington.  If we are authorized following the environmental compliance review now in progress, we would use the R/V Langseth, the premier U.S. academic seismic research vessel, which is owned by the NSF and operated by the Lamont-Doherty Earth Observatory of Columbia University (read more here), and the CCGS John P. Tully, which is operated by the Canadian Coast Guard (read more here).

 5. Where, when and to whom would the results be made available?

If, following the environmental compliance process, our projects are approved, our data would be under a two-year moratorium, after which computer-processed and quality controlled data will be made openly available. The data will be placed in NSF-supported, public archives at the Lamont-Doherty Earth Observatory of Columbia University (read more here) and the consortium of Incorporated Research Institutions for Seismology (IRIS) (read more here).

 6. How do you propose to collect the data?

Like a medical sonogram that uses sound to make an acoustic image of tissue beneath the skin, our proposed plan is to make acoustic images and derive estimates of the physical properties of features within sediment and crustal layers below the seafloor using an array of seismic airguns as our sound source.  Towed hydrophone streamers and ocean bottom seismometers (OBSs) would detect and record the returning sound source signals. A long term deployment (~12 months) of OBS would detect and record natural seismic sources, i.e., earthquakes.

 7. What are airguns, hydrophones, and ocean bottom seismometers (OBSs) ?

An airgun is a device towed roughly 100 feet behind a ship that at regular intervals releases a bubble of compressed air below the sea surface. Like the pop of a balloon that creates a sound wave, an airgun creates a sound wave that travels down and into the seafloor. Hydrophone “streamers” (which act like a microphone) towed behind the ship listen for airgun signals, or “echoes”, to return from sediment and crustal layers below the seafloor. Shipboard computers arrange these echoes to make acoustic images of this layering.

OBSs 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.

OBSs are generally mid-size (~1x1x1 meter or 1x1x1 yard), have sensors capable of responding to lower frequency sound, 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. For recovery, an acoustic signal triggers the release of the anchor and the OBS floats back to the surface due to its buoyancy.

 8. What is the size of the sound source you plan to use for your study and why is it needed?

We propose to use 36 airguns (and 4 spares) towed 12 meters (~13 yards) below the sea surface which together would release a total of 6600 cubic inches of compressed air. The sound wave generated by this bubble of compressed air would enable us to image to depths of 20 km (12.5 miles) or more beneath the seafloor where the Queen Charlotte fault zone is located near the coast. Further offshore, this sound wave would enable us to image structures even deeper than the fault zone, thus linking deep geological structures within the Earth’s upper mantle to the properties of the earthquake fault zone.  The sonogram-like images we would obtain to these great depths would provide new information pertaining to the properties and processes contributing to large earthquakes along this margin. Smaller energy sources have recently been used for studies along the margin to image the sediment layers and the shallow he fault zone, but the fault zone at depth cannot be detected using these smaller sources.

 9. Where can I find more information about effects of sound in the ocean?

An excellent resource for more information on sound within the oceans is the “Discovery of Sound in the Sea” (DOSITS) website. This website is a resource developed by ocean acousticians to introduce students, public officials and the general public to the wide range of sound sources in the sea (animals, volcanoes, hurricanes, ships, etc.) as well as to how sound is used to study the seafloor and oceanographic processes.  DOSITS content is based on peer-reviewed literature and high-quality sources of scientific data. Of particular relevance to those interested in our project are the following pages: seismic-airguns and sound-in-air-water.

10. Are the proposed activities related to oil and gas exploration or funded by the oil and gas industry?

No.  These projects would be sponsored by the National Science Foundation in support of basic research to increase our understanding of fundamental earth processes related to earthquake and tsunami hazard along the western Canada/southeast Alaska margin.

Although not funded through NSF, collaborators from the USGS, Pacific Geoscience Center, Canadian academic institutions (Dalhousie University and University of British Columbia) and JAMSTEC would work with us to achieve the research goals, providing logistical support, additional data acquisition and exchange.  Canadian colleagues are also interested in obtaining an improved understanding of the margin given the shared threats of a future large earthquake all along the west coast of North America.

11. Would your study have any adverse effects on marine life, or on industrial or recreational fishing?

Our proposed study would be conducted following protection protocols determined by international and U.S. federal and state environmental compliance processes, detailed explanation of which can be found in the National Science Foundation's Draft Amended Environmental Assessment (EA) and in the applications for Incidental Harassment Authorizations (IHA) submitted to the National Marine Fisheries Service (NMFS) and U.S. Fish and Wildlife Service (USFWS). If our survey is authorized, a robust monitoring and mitigation plan would be followed, similar to that conducted during a similar study in the Cascadia region in 2012 and proposed for earlier in the summer 2020. The monitoring and mitigation plan would include the use of Protected Species Observers, passive acoustic monitoring, shutdowns of the airguns for marine mammals observed within specified distances from the source.

In terms of fishing, no significant impacts on marine invertebrates, marine fish, and their fisheries, including commercial, recreational, and subsistence fisheries are anticipated. No adverse effects on Essential Fish Habitat (EFH) or Habitats of Particular Concern (HAPC) are expected given the short-term nature of the sound source study (approximately 35 days) and minimal bottom disturbance. In addition, we have initiated outreach efforts with the local commercial fishing community to minimize potential overlap between seafloor instrumentation deployments and fishing activities and help support coordination during our survey period.

12. What are the measures that will be used to protect endangered marine species?

The mitigation and monitoring measures that would be employed during the survey to reduce potential impacts to marine species, would include vessel speed reduction or minor course alteration, and the use of passive acoustic monitoring of marine mammals.  In addition,  Protected Species Observers (independently contracted and NMFS approved) would maintain visual watches for marine species around the vessel.  They would have absolute authority to enforce any terms and conditions in authorizations, such as an IHA, including shutting down the acoustic source if protected marine species are observed entering a specified radius around the vessel.  With the proposed mitigation and monitoring measures, impacts to marine species would, at most, be expected to be limited to short-term, localized changes in behavior and distribution close to the vessel.  No significant impacts to marine species populations or critical habitat would be anticipated from the proposed activities.

13. What is the environmental compliance process for the proposed activities?

The purpose of the environmental compliance process is to evaluate the potential effects that the proposed research would have on the environment.  These effects are determined by many science professionals with expertise in this area, supported by an extensive foundation of published literature. The environmental compliance process for these projects would include compliance with the National Environmental Policy Act (NEPA), Executive Order 12114, the Marine Mammal Protection Act (MMPA), the Endangered Species Act (ESA), and Essential Fish Habitat (EFH) per the Magnuson Stevens Act, and the Canadian Species at Risk Act.  At all levels, highly experienced individuals and agencies responsible for maintaining a balance between protecting the marine environment and advancing knowledge of our planet are evaluating the potential impacts of the proposed activities with the utmost care. Any required monitoring and mitigation measures identified through these regulatory processes would be adhered to during operations.

14. Can individuals or groups participate in the environmental compliance process?

Yes, there are public comment periods associated with some of the regulatory processes noted above.  For example, in compliance with the MMPA, the NMFS and USFWS gather information and advice from the many agencies described above and announce public comment periods in the Federal Register in association with the Incidental Harassment Authorization process. Public comment periods are also part of NSF’s compliance with NEPA.  Individuals and groups are invited to submit comments during the public comment periods, and are encouraged to include any supporting data or citations to help inform agency decisions.