Seismic crustal imaging using fin whale songs

Science ◽  
2021 ◽  
Vol 371 (6530) ◽  
pp. 731-735
Author(s):  
Václav M. Kuna ◽  
John L. Nábělek
Keyword(s):  
Lower Crust ◽  
Seismic Velocity ◽  
Ocean Bottom ◽  
Fin Whale ◽  
Northeast Pacific ◽  
Air Gun ◽  
Ocean Bottom Seismometers ◽  
Animal Vocalizations ◽  
Oceanic Sediment ◽  
Northeast Pacific Ocean

Fin whale calls are among the strongest animal vocalizations that are detectable over great distances in the oceans. We analyze fin whale songs recorded at ocean-bottom seismometers in the northeast Pacific Ocean and show that in addition to the waterborne signal, the song recordings also contain signals reflected and refracted from crustal interfaces beneath the stations. With these data, we constrain the thickness and seismic velocity of the oceanic sediment and basaltic basement and the P-wave velocity of the gabbroic lower crust beneath and around the ocean bottom seismic stations. The abundant and globally available fin whale calls may be used to complement seismic studies in situations where conventional air-gun surveys are not available.

The structure of Archean–Ketilidian crust along the continental shelf of southwestern Greenland from a seismic refraction profile

1992 ◽  
Vol 29 (2) ◽  
pp. 301-313 ◽  
Author(s):  
Deping Chian ◽  
Keith Louden
Keyword(s):  
Lower Crust ◽  
Velocity Structure ◽  
Seismic Refraction ◽  
Mobile Belt ◽  
Ocean Bottom ◽  
Upper Crust ◽  
S Wave ◽  
Seismic Line ◽  
Wave Velocities ◽  
Air Gun

The velocity structure of the continental crust on the outer shelf of southwestern Greenland is determined from dense wide-angle reflection–refraction data obtained with large air-gun sources and ocean bottom seismometers along a 230 km seismic line. This line crosses the geological boundary between the Archean block and the Ketilidian mobile belt. Although the data have high noise levels, P- and S-wave arrivals from within the upper, intermediate, and lower crust, and at the Moho boundary, can be consistently identified and correlated with one-dimensional WKBJ synthetic seismograms. In the Archean, P- and S-wave velocities in the upper crust are 6.0 and 3.4 km/s, while in the intermediate crust they are 6.4 and 3.6 km/s. These velocities match for the upper crust a quartz–feldspar gneiss composition and for the intermediate crust an amphibolitized pyroxene granulite. In the Ketilidian mobile belt, P- and S-wave velocities are 5.6 and 3.3 km/s for the upper crust and 6.3 and 3.6 km/s for the intermediate crust. These velocities may represent quartz granite in the upper crust and granite and granitic gneiss in the intermediate crust. The upper crust is ~5 km thick in the Archean block and the Ketilidian mobile belt, and thickens to ~9 km in the southern part of the Archean. This velocity structure supports a Precambrian collisional mechanism between the Archean block and Ketilidian mobile belt. The lower crust has a small vertical velocity gradient from 6.6 km/s at 15 km depth to 6.9 km/s at 30 km depth (Moho) along the refraction line, with a nearly constant S-wave velocity around 3.8 km/s. These velocities likely represent a gabbroic and hornblende granulite composition for the lower crust. This typical (but somewhat thin) Precambrian crustal velocity structure in southwestern Greenland shows no evidence for a high-velocity, lower crustal, underplated layer caused by the Mesozoic opening of the Labrador Sea.

Source levels of fin whale 20 Hz pulses measured in the Northeast Pacific Ocean

2013 ◽  
Vol 133 (2) ◽  
pp. 741-749 ◽  
Author(s):  
Michelle J. Weirathmueller ◽  
William S. D. Wilcock ◽  
Dax C. Soule
Keyword(s):  
Pacific Ocean ◽  
Fin Whale ◽  
Northeast Pacific ◽  
Northeast Pacific Ocean

scholarly journals Source Levels of 20 Hz Fin Whale Notes Measured as Sound Pressure and Particle Velocity from Ocean-Bottom Seismometers in the North Atlantic

2021 ◽  
Vol 9 (6) ◽  
pp. 646
Author(s):  
Andreia Pereira ◽  
Miriam Romagosa ◽  
Carlos Corela ◽  
Mónica A. Silva ◽  
Luis Matias
Keyword(s):  
Sample Size ◽  
Particle Velocity ◽  
North Atlantic ◽  
Ocean Bottom ◽  
Geographical Differences ◽  
Fin Whale ◽  
The North ◽  
Ocean Bottom Seismometers ◽  
Source Level ◽  
The North Atlantic

Source level is one factor that determines the effectiveness of animal signal transmissions and their acoustic communication active space. Ocean-bottom seismometers (OBS) are platforms of opportunity to monitor marine species because they record data as pressure fluctuations in the water using a hydrophone and/or as particle velocity of the seabed using a seismometer. This study estimates source levels of 20 Hz fin whale notes recorded simultaneously in these two OBS channels and in two areas of the North Atlantic (Azores and southwest Portugal). It also discusses factors contributing to the variability of the estimates, namely geographical (deployment areas), instrumental (recording channels and sample size), and temporal factors (month of detected notes, inter-note interval, and diving duration). The average source level was 196.9 dB re 1 µPa m for the seismometer (derived from particle velocity measurements) and 186.7 dB re 1 µPa m for the hydrophone. Variability was associated with sample size, instrumental characteristics, acoustic propagation, and month of recordings. Source level estimates were very consistent throughout sequences, and there was no indication of geographical differences. Understanding what causes variation in animal sound source levels provides insights into the function of sounds and helps to assess the potential effects of increasing anthropogenic noise.

Heterogeneity of Seismic Wave Velocity in Earth's Mantle

2020 ◽  
Vol 48 (1) ◽  
pp. 377-401 ◽  
Author(s):  
Jeroen Ritsema ◽  
Vedran Lekić
Keyword(s):  
Seismic Velocity ◽  
Principal Component ◽  
Oceanic Lithosphere ◽  
Boundary Region ◽  
Ocean Bottom ◽  
Seismic Wave Velocity ◽  
Tomographic Images ◽  
Seismic Waveforms ◽  
Ocean Bottom Seismometers ◽  
History Of

Seismology provides important constraints on the structure and dynamics of the deep mantle. Computational and methodological advances in the past two decades improved tomographic imaging of the mantle and revealed the fine-scale structure of plumes ascending from the core-mantle boundary region and slabs of oceanic lithosphere sinking into the lower mantle. We discuss the modeling aspects of global tomography including theoretical approximations, data selection, and model fidelity and resolution. Using spectral, principal component, and cluster analyses, we highlight the robust patterns of seismic heterogeneity, which inform us of flow in the mantle, the history of plate motions, and potential compositionally distinct reservoirs. In closing, we emphasize that data mining of vast collections of seismic waveforms and new data from distributed acoustic sensing, autonomous hydrophones, ocean-bottom seismometers, and correlation-based techniques will boost the development of the next generation of global models of density, seismic velocity, and attenuation. ▪  Seismic tomography reveals the 100-km to 1,000-km scale variation of seismic velocity heterogeneity in the mantle. ▪  Tomographic images are the most important geophysical constraints on mantle circulation and evolution.

Crustal structure of the Nova Scotian margin in the Laurentian Channel region

1987 ◽  
Vol 24 (9) ◽  
pp. 1859-1868 ◽  
Author(s):  
I. Reid
Keyword(s):  
Crustal Structure ◽  
Seismic Velocity ◽  
Structural Information ◽  
Seismic Refraction ◽  
Ocean Bottom ◽  
Eastern Canada ◽  
Crustal Layer ◽  
Air Gun ◽  
Lower Crustal

A seismic-refraction study on the outer Scotian Shelf of eastern Canada, carried out using large air-gun sources and ocean bottom seismograph receivers, has provided structural information on the entire crustal column. A thick (about 13 km) sedimentary sequence is characterized by significant lateral variation in this area, and a marked increase in seismic velocity around 8 km depth may delineate the synrift–postrift transition. Beneath the sediments is highly attenuated continental crust, about 11 km thick, with some evidence for a lower crustal layer of velocity around 7 km/s, which may be partly due to under-plating during rifting. Determination of the complete crustal structure, including the tentative delineation of the rift–drift transition, in a region of large crustal extension provides a useful test for models of continental rifting, and a simple uniform extension–subsidence model is found to produce an adequate fit to the interpreted structure.

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