Vp/Vs-ratios and anisotropy on the northern Jan Mayen Ridge, North Atlantic, determined from ocean bottom seismic data

Kandilarov, Aleksandre; Mjelde, Rolf; Flueh, Ernst R.; Pedersen, Rolf B.

doi:10.1016/j.polar.2015.06.001

Cited by 10 publications

(10 citation statements)

References 45 publications

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“…Rather than using a constant Vp/Vs ratio, a linear relationship between Vp and Vs (Vp = 1.36 Vs + 1.90) based on experimental results (Christensen, 2004; Ji et al, 2013; Salisbury & Christensen, 1978) was implemented to determine the S velocity for the crust and P velocity for the mantle. This equation approximates the change in Vp/Vs ratios due to composition and is roughly consistent with regional models for Vp/Vs ratios from P and S wave tomography (Barklage et al, 2015) and expected ratios for an oceanic plate (Hyndman, 1979; Kandilarov et al, 2015). The mantle shear velocities from the surface wave tomography model were corrected for radial anisotropy by applying a 1% increase to the observed Sv velocities to obtain the Voigt average S velocity, assuming 3% radial anisotropy as is typically found for the uppermost mantle (Montagner, 2007).…”

Section: Discussionmentioning

confidence: 99%

Seismicity of the Incoming Plate and Forearc Near the Mariana Trench Recorded by Ocean Bottom Seismographs

Eimer

Wiens

Cai

et al. 2020

Geochem Geophys Geosyst

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Earthquakes near oceanic trenches are important for studying incoming plate bending and updip thrust zone seismogenesis, yet are poorly constrained using seismographs on land. We use an ocean bottom seismograph (OBS) deployment spanning both the incoming Pacific Plate and the forearc to study seismicity near the Mariana Trench. The yearlong deployment in 2012-2013 consisted of 20 broadband OBSs and 5 suspended hydrophones, with an additional 59 short period OBSs and hydrophones recording for 1 month. We locate 1,692 earthquakes using a nonlinear method with a 3D velocity model constructed from active source profiles and surface wave tomography results. Events occurring seaward of the trench occur to depths of~35 km below the seafloor, and focal mechanisms of the larger events indicate normal faulting corresponding to plate bending. Significant seismicity emerges about 70 km seaward from the trench, and the seismicity rate increases continuously towards the trench, indicating that the largest bending deformation occurs near the trench axis. These plate-bending earthquakes occur along faults that facilitate the hydration of the subducting plate, and the lateral and depth distribution of earthquakes is consistent with low-velocity regions imaged in previous studies. The forearc is marked by a heterogeneous distribution of low magnitude (<5 M w ) thrust zone seismicity, possibly due to the rough incoming plate topography and/or serpentinization of the forearc. A sequence of thrust earthquakes occurs at depths~10 km below seafloor and within 20 km of the trench axis, demonstrating that the megathrust is seismically active nearly to the trench. Plain Language Summary Studying earthquakes near oceanic trenches is important forunderstanding subduction zones but can be difficult using only distant land-based instruments. This study uses seismographs designed to work on the seafloor to study earthquakes near the central Mariana Trench. As the subducting plate bends, faults form due to the increased extensional stress. These faults can become pathways for water to penetrate into this subducting plate. Understanding the amount of water stored in the plate is essential for constraining the global water cycle, and the earthquake distribution allows us to determine the distribution of active faults. We found that the earthquakes occur shallower than 35-km depth and within 70 km seaward of the trench. We also study earthquakes occurring along the megathrust, which is the interface between the subducting plate and the overriding plate that is prone to seismic activity. We found that the earthquakes show a patchy distribution, indicating that the megathrust interface is not uniform. This could be related to topographic features on the subducting plate interacting with the plate above. We also observed earthquakes at depths shallower than 10 km below the seafloor, indicating that the megathrust can rupture close to the trench.

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Section: Discussionmentioning

confidence: 99%

Seismicity of the Incoming Plate and Forearc Near the Mariana Trench Recorded by Ocean Bottom Seismographs

Eimer

Wiens

Cai

et al. 2020

Geochem Geophys Geosyst

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“…Previous studies, including (i) the interpretation of reflection seismic data (Blischke et al, 2016;Peron-Pinvidic et al, 2012a, 2012b, (ii) wide-angle refraction seismic data (Breivik, Mjelde, Faleide, Murai, 2012;Hermann & Jokat, 2016;Kandilarov et al, 2012Kandilarov et al, , 2015Klingelhöfer, Géli, & White, 2000;Klingelhöfer, Géli, Matias, et. al., 2000;Kodaira et al, 1997Kodaira et al, , 1998bTan et al, 2017;Voss & Jokat, 2007;Weigel et al, 1995), and (iii) studies of dredged samples (e.g., Elkins et al, 2011Elkins et al, , 2016Haase et al, 2003;Klingelhöfer, Géli, & White, 2000;Mertz et al, 2004;Schilling, 1999), show that the study area is characterized by large variations in terms of crustal structure as well as mantle composition, and mantle melting degree.…”

Section: Modeling the Structure And Density Of The Sediments And Cystmentioning

confidence: 99%

“…There are some published 2-D gravity models in the area based on seismic crustal constraints, and a few also have additional velocity measurements of the uppermost mantle (Hermann & Jokat, 2016;Kandilarov et al, 2012Kandilarov et al, , 2015Peron-Pinvidic et al, 2012a, 2012bVoss & Jokat, 2007;Weigel et al, 1995). However, none of these studies constrain the deeper velocity and hence the density of the mantle lithosphere and thus cannot be directly compared to our modeling results.…”

Section: Gravity Constrained Mantle Density Between Moho and 50 Km Depthmentioning

confidence: 99%

“…The continental crust of the JMMC is divided into an upper layer of lower V p (4.5–6.5 km/s) and modeled density (2,700 kg/m 3 ) and a lower layer of higher V p (6.5–6.85 km/s) and density (2,950 kg/m 3 ). A relatively dense upper (2,900 kg/m 3 ) and lower crust (3,050 kg/m 3 ) is restricted around the northern boundary of the JMMC where the Moho depth is greatest (Kandilarov et al, , ).…”

Section: Three‐dimensional Gravity Modelingmentioning

confidence: 99%

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Lithospheric Control on Asthenospheric Flow From the Iceland Plume: 3‐D Density Modeling of the Jan Mayen‐East Greenland Region, NE Atlantic

et al. 2018

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The density structure of the oceanic lithosphere north of Iceland is key for understanding the effects of the Iceland plume on the greater Jan Mayen‐East Greenland Region. We obtain the 3‐D density structure of the sediments and the crust from regional reflection and refraction seismic lines. The temperature and related density structures of the mantle between 50 and 250 km are derived from a shear wave velocity (Vs) tomography model. To assess the density between the Moho and 50‐km depth, we combine forward and inverse 3‐D gravity modeling. Beneath the Middle Kolbeinsey Ridge (MKR) region, a deep, broad negative mantle density anomaly occurs under the Kolbeinsey Ridge. It is overlain by a narrower uppermost mantle NE‐SW elongated negative density anomaly, which is increasingly displaced eastward of the spreading axis northward. It crosses the West Jan Mayen Fracture Zone and becomes weaker approaching the Mohn's spreading ridge. The effect of this anomaly is consistent with significantly shallower basement on the eastern side of the MKR. We interpret this as the result of thermal erosion of the lithosphere by hot asthenospheric flow out from the Iceland plume, possibly the main driver for several eastward jumps of the MKR during the last 5.5 Ma. The cause for the deviation of the flow may be that the West Jan Mayen Fracture Zone is easier to cross in a region where the difference in lithospheric thickness is small. That implies that the bottom lithospheric topography exerts a regional but not local influence on upper asthenospheric flow.

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“…After that, most excess volcanism occurred along the Faeroe‐Iceland‐Greenland ridge [e.g., Eldholm and Grue , ]. Today, the Norwegian island of Jan Mayen has an active volcano, and recent research [ Kandilarov et al , , ] has increasingly highlighted the surrounding areas affected by postbreakup magmatic processes (Figure ). The Eggvin Bank is located between Jan Mayen and the east coast of Greenland, straddling the axial zone of the Northern Kolbeinsey Ridge (NKR).…”

Section: Introductionmentioning

confidence: 99%

Crustal structure and origin of the Eggvin Bank west of Jan Mayen, NE Atlantic

et al. 2017

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The Eggvin Bank, located between the Jan Mayen Island and Greenland, is an unusually shallow area containing several submarine volcanic peaks, confined by two transforms on the Northern Kolbeinsey Ridge (NKR). We represent P and S wave velocity models for the Eggvin Bank based on an Ocean Bottom Seismometer profile collected in 2011, showing igneous crustal thickness variations from 8 km to 13 km. A 2–5 km increase is associated with two separate 20–30 km wide segments under the main seamounts. The oceanic crust has three layers: upper crust (L2A: 2.8–4.8 km/s), middle crust (L2B: 5.5–6.5 km/s), and lower crust (L3: 6.7–7.35 km/s). Both the thick layer 2(A/B) and the high ratio of layer 2(A/B) thickness to total crustal thickness indicate that secondary, intraplate magmatism built the seamounts of the Eggvin Bank. The seamount in the north where the crust is thickest has a flat top indicating subaerial exposure but is deeper than those with rounded tops in the south and is therefore probably older. Comparing lower crustal seismic velocity with crustal thickness also indicates that the degree of mantle melting may be higher in the north than in the south. An enriched mantle source presently feeds the NKR magmatism and probably influenced the Eggvin Bank development also at earlier times. To what extent the Eggvin Bank has been influenced by the Iceland plume is uncertain, both an enriched mantle component and elevated mantle temperature may have played a role at different times and locations.

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Vp/Vs-ratios and anisotropy on the northern Jan Mayen Ridge, North Atlantic, determined from ocean bottom seismic data

Cited by 10 publications

References 45 publications

Seismicity of the Incoming Plate and Forearc Near the Mariana Trench Recorded by Ocean Bottom Seismographs

Seismicity of the Incoming Plate and Forearc Near the Mariana Trench Recorded by Ocean Bottom Seismographs

Lithospheric Control on Asthenospheric Flow From the Iceland Plume: 3‐D Density Modeling of the Jan Mayen‐East Greenland Region, NE Atlantic

Crustal structure and origin of the Eggvin Bank west of Jan Mayen, NE Atlantic

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