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Federal Register / Vol. 86, No. 109 / Wednesday, June 9, 2021 / Notices
NSF/LDEO or the applicant submitted a request to the Services Marine Mammals Management Office MMM for authorization to take by Level B harassment a small number of northern sea otters Enhydra lutris kenyoni, hereafter sea otters or otters unless another species is specified from the Southeast Alaska stock. NSF/LDEO expects that take by unintentional harassment may occur during their planned high-energy marine seismic surveys at the Queen Charlotte Fault QCF in the Northeast Pacific Ocean within the U.S. Exclusive Economic Zone EEZ.

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Description of Specified Activities and Geographic Region The specified activity the project consists of Lamont-Doherty Earth Observatorys LDEO 2021 Marine Geophysical Surveys by the Research Vessel R/V Marcus G. Langseth Langseth of the QCF in the Northeast Pacific Ocean from July 1, 2021, to August 31, 2021. High-energy twodimensional 2D seismic surveys will be used to characterize crustal and uppermost mantle velocity structure, fault zone architecture and rheology, and seismicity of the QCF. The 2D
seismic surveys will be conducted along transect lines within the area of 5257
N and 131137 W Figure 1. Some deviation in actual transects, including order of survey operations, could be necessary due to poor data quality, inclement weather, or mechanical issues with the research vessel or equipment.
The surveys are proposed to occur within the EEZs of the United States and Canada, including U.S. Federal Waters, State of Alaska Waters, and
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Canadian Territorial Waters ranging from 50 to 2,800 meters m; 164 to 9,186
feet ft in depth. The Service cannot and is not authorizing the incidental take of marine mammals in waters not under the jurisdiction of the United States. Therefore, the Services calculation of estimated incidental take is limited to the specified activity occurring in United States jurisdictional waters within the stocks range. The proposed surveys are anticipated to last for 36 days, including approximately 27
days of seismic operations, approximately 2 days of transit to and from the survey area, 3 days for equipment deployment/recovery, and 4
days of contingency. The R/V Langseth will likely leave out of and return to the port of Ketchikan, AK, during summer 2021.
The R/V Langseth will tow 4 strings containing an array of 36 airguns at a depth of 12 m 39 ft, creating a discharge volume of approximately 0.11
cubic meter m3; 6,600 cubic inches in3. The peak sound pressure 1 m 3.2
ft from the center of the airgun array is 258.6 decibels Tolstoy et al. 2009.
Noise levels herein are given in decibels dB referenced to 1 mPa dB re: 1 mPa for underwater sound. All dB levels are dBRMS root-mean-squared dB level unless otherwise noted; dBRMS refers to the square root of the average of the squared sound pressure level typically measured over 1 second. Other important metrics include the sound exposure level SEL; represented as dB
re: 1 mPa2-s, which represents the total energy contained within a pulse and considers both intensity and duration of exposure, and the peak sound pressure also referred to as the zero-to-peak
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sound pressure or 0p. Peak sound pressure is the maximum instantaneous sound pressure measurable in the water at a specified distance from the source and is represented in the same units as the dBRMS sound pressure. See Richardson et al. 1995, Gotz et al.
2009, Hopp et al. 2012, Navy 2014, for descriptions of acoustical terms and measurement units in the context of ecological impact assessment.
The seismic array produces broadband energy that ranges from a few hertz Hz to kilohertz kHz. However, all but a small fraction of the energy is focused in the 10300 Hz range Tolstoy et al. 2009. The survey will also include the use of a single 655-cubiccentimeter cm3; 40-in3 airgun that will be used when the full array is powered down.
The receiving system will consist of a 15-kilometer km; 9.3-mile mi hydrophone streamer and approximately 60 short-period and 28
broadband Ocean Bottom Seismometer OBS devices, which will be primarily deployed from a second vessel, the Canadian Coast Guard R/V John P. Tully however, R/V Langseth may also deploy OBSs. The OBSs will be deployed at approximately 10-km 6.2mi intervals with 5-km 3.1 mi spacing over the central 40 km 25 mi of the fault zone. The OBSs have a height and diameter of 1 m 3.2 ft and an 80kilogram 176-pound anchor.
Additional project details may be reviewed in the application materials available as described under ADDRESSES
or may also be requested as described under FOR FURTHER INFORMATION
CONTACT.

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