Global adjoint tomography—model GLAD-M25

Lei, Wenjie; Ruan, Youyi; Bozdag, E.; Peter, Daniel; Lefèbvre, Matthieu; Komatitsch, Dimitri; Tromp, Jeroen; Hill, Judith; Podhorszki, Norbert; Pugmire, David

doi:10.1093/gji/ggaa253

Cited by 174 publications

(176 citation statements)

References 69 publications

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“…In this section, we review results of previous seismological studies of the crust and upper mantle structure beneath Greenland and surrounding regions, focusing mainly on seismic tomography studies. The structure has been investigated using several tomographic methods with various spatial scales, including regionalscale surface wave tomography (Antonijevic & Lees, 2018;Darbyshire et al, 2004Darbyshire et al, , 2018Levshin et al, 2017;Mordret, 2018;Pourpoint et al, 2018), surface wave tomography of the North Atlantic region (Pilidou et al, 2004), body wave tomography of the whole Arctic region (Jakovlev et al, 2012), full waveform tomography of the North Atlantic region (Rickers et al, 2013), full waveform tomography of the whole Arctic region (Lebedev et al, 2017), and global tomography (e.g., Hosseini et al, 2020;Lei et al, 2020;Zhao, 2001Zhao, , 2004Zhao et al, 2013).…”

Section: Previous Studiesmentioning

confidence: 99%

P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

2020

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We study the 3-D P wave velocity (Vp) structure of the crust and upper mantle beneath Greenland and surrounding regions using the latest P wave arrival time data. The Greenland Ice Sheet Monitoring Network (GLISN), initiated in 2009, is an international project for seismic observation in these regions using 34 stations. We use a regional seismic tomography method to simultaneously invert P wave arrival times of local earthquakes and P wave relative traveltime residuals of teleseismic events. These data are extracted from the ISC-EHB catalog; however, for the teleseismic data, we picked new arrival times from seismograms using a cross-correlation method. Our tomographic results clearly reveal the Iceland plume, the Jan Mayen plume, and a newly discovered "Svalbard plume," which merge together in the mantle transition zone. A high-Vp body exists beneath the Greenland Sea, which might act as an obstacle against the rising Svalbard plume. Furthermore, our results reveal a remarkable low-Vp anomaly elongated in the NW-SE direction at depths ≤250 km beneath central Greenland, which is connected with the Iceland and Jan Mayen hotspots. Although previous studies have suggested a similar feature, our result is the first to show the low-Vp zone existing at all depths in the Greenland lithosphere, and its spatial distribution coincides with a high heat flux region. These characteristics indicate that the low-Vp zone reflects residual heat from the Iceland plume when the Greenland lithosphere passed over this plume at~80-20 Ma. Our results also indicate the possible existence of residual heat from the Jan Mayen plume. Plain Language Summary Greenland is a stable land mass that has preserved~4 Gyr of Earth's history. In its vicinity, there are the Mid-Atlantic Ridge, the Iceland and Jan Mayen hotspots, and a geothermal area in Svalbard, which indicate the complexity of this region. We apply seismic tomography to analyze the latest data recorded by a new seismograph network, and we obtain detailed 3-D images of the crust and upper mantle. Our results clearly image the conduit-like Iceland plume, the Jan Mayen plume, and a newly discovered "Svalbard plume," which merge together in the mantle transition zone. These new findings will improve our understanding of the tectonic and thermal evolution of this region. We also find a low seismic velocity zone running in the NW-SE direction beneath central Greenland, which is connected with the Iceland and Jan Mayen hotspots. This zone is located within the Greenlandic plate, and its spatial distribution agrees well with an area of high geothermal heat flux. These results suggest that the low-velocity zone reflects residual heat from the Iceland plume when the Greenlandic plate passed over the plume at~80-20 Ma. Our model further suggests a possible heat track left by the Jan Mayen plume.

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Section: Previous Studiesmentioning

confidence: 99%

P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

2020

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“…Considering these ambiguous results, Montelli et al (2006) suggested a possibility that the Iceland plume is not continuous but pulsating. More recent studies revealed further elusive features of this plume with a complicated shape not only in the vertical direction but also in the lateral direction (e.g., Zhao et al, 2013 and Hosseini et al, 2020 for global P wave tomography; Lei et al, 2020 for global S wave tomography; and Rickers et al, 2013 for regional S wave tomography). Zhao et al (2013) revealed a prominent localized low‐ V zone beneath Iceland down to ~500 km depth, whereas it becomes wider in the lower mantle (750–1,500 km depth) and less prominent in the lowermost mantle (2,300–2,800 km depth).…”

Section: Introductionmentioning

confidence: 98%

“…Attempts to reveal the shape and depth extent of the Iceland plume have been continued mainly by researchers of seismic tomography, which is a powerful tool used to obtain detailed 3-D images of underground structures. A consensus among these studies is the existence of an upper-mantle plume that extends down to at least 400 km depth, which is clearly revealed by both local/regional tomography (e.g., Allen et al, 2002;Foulger et al, 2000Foulger et al, , 2001Hung et al, 2004;Rickers et al, 2013;Wolfe et al, 1997) and global tomography (e.g., Hosseini et al, 2020;Lei et al, 2020;Zhao, 2001Zhao, , 2004Zhao et al, 2013). However, the existence of a lower-mantle plume beneath Iceland, as well as its depth extent, have long been hotly debated.…”

Section: Introductionmentioning

confidence: 99%

P Wave Tomography Beneath Greenland and Surrounding Regions: 2. Lower Mantle

2020

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We study the 3-D P wave velocity (Vp) structure of the whole mantle beneath Greenland and surrounding regions using the latest P wave arrival time data. We use a new method of global seismic tomography by setting 3-D grid nodes densely in the study volume to enhance the resolution. We invert~5.6 million arrival times of P, pP, and PP waves from 16,257 earthquakes extracted from the ISC-EHB catalog, which were recorded at 12,549 seismic stations in the world. Our results reveal a hot plume rising from the core-mantle boundary beneath central Greenland, which is called the Greenland plume. This plume has the main conduit and two branches in the lower mantle, and the main conduit rises to the mantle transition zone (MTZ) beneath eastern Greenland, so it is distinguishable from the Iceland plume that appears to rise from a midmantle depth (~1,500 km) beneath Iceland. The Iceland plume itself is a powerful plume, but it may also be fed by hot mantle materials from three joints with other plumes: a branch of the Greenland plume at~1,500 km depth, a plume beneath Western Europe at~1,000 km depth, and the main conduit of the Greenland plume at the MTZ, leading to many active volcanoes in Iceland. We deem that the main conduit of the Greenland plume mixes with the Iceland plume incompletely and splits mainly into the Jan Mayen and Svalbard plumes in the upper mantle, which supply magma to the Jan Mayen hotspot and a geothermal area in western Svalbard, respectively. Plain Language Summary Greenland and its surrounding regions have many clues for understanding global-scale tectonics of the Earth. Seismic tomography is a well-established method for obtaining 3-D images of the underground structure by inverting a large number of seismic wave arrival times. We obtain detailed tomographic images of the whole mantle beneath Greenland and adjacent regions using the latest dataset. Our high-resolution results show that the so-called Iceland plume could be composed of two plumes. One is located directly beneath Iceland but rising from~1,500 km depth, which we call the Iceland plume. The other is rising from the core-mantle boundary beneath central Greenland, which we call the Greenland plume. The Greenland plume has the main conduit and two branches in the lower mantle, and the main conduit rises to the mantle transition zone beneath eastern Greenland. Although the Iceland plume itself is a powerful plume, it may also have three joints with other plumes: the main conduit and a branch of the Greenland plume, and a plume beneath Western Europe, resulting in many active volcanoes in Iceland. The main conduit of the Greenland plume may also supply magmas to the Jan Mayen hotspot and a geothermal area in western Svalbard.

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“…In principle this approach, which uses every wiggle on the seismograms, should be more powerful. But in practice it has important limitations (see Lei et al 2020). To produce global models with useful resolution requires the use of the most powerful computers that exist, and even then can only use a relatively small number of seismograms.…”

Section: Introductionmentioning

confidence: 99%

“…To produce global models with useful resolution requires the use of the most powerful computers that exist, and even then can only use a relatively small number of seismograms. Lei et al (2020) used 1480 earthquakes, or three orders of magnitude fewer than Priestley et al (2019) and Schaeffer and Lebedev (2013) used. Though the rapid improvement in computer power shows no sign of coming to an end, it is likely to continue to be overwhelmed by the continuing rapid increase in the number of digital seismometers generating seismograms.…”

Section: Introductionmentioning

confidence: 99%

The structure of the lithosphere and upper mantle beneath the Eastern Mediterranean and Middle East

McKenzie

2020

Med. Geosc. Rev.

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Surface velocity measurements show that the Middle East is one of the most actively deforming regions of the continents. The structure of the underlying lithosphere and convecting upper mantle can be explored by combining three types of measurement. The gravity field from satellite and surface measurements is supported by the elastic properties of the lithosphere and by the underlying mantle convection. Three dimensional shear wave velocities can be determined by tomographic inversion of surface wave velocities. The shear wave velocities of the mantle are principally controlled by temperature, rather than by composition. The mantle composition can be obtained from that of young magmas. Application of these three types of observation to the Eastern Mediterranean and Middle East shows that the lithosphere thickness in most parts is no more than 50-70 km, and that the elastic thickness is less than 5 km. Because the lithosphere is so thin and weak the pattern of the underlying convection is clearly visible in the topography and gravity, as well as controlling the volcanism. The convection pattern takes the form of spokes: lines of hot upwelling mantle, joining hubs where the upwelling is three dimensional. It is the same as that seen in high Rayleigh number laboratory and numerical experiments. The lithospheric thicknesses beneath the seafloor to the SW of the Hellenic Arc and beneath the NE part of the Arabian Shield are more than 150 km and the elastic thicknesses are 30–40 km.

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Global adjoint tomography—model GLAD-M25

Cited by 174 publications

References 69 publications

P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

P Wave Tomography Beneath Greenland and Surrounding Regions: 1. Crust and Upper Mantle

P Wave Tomography Beneath Greenland and Surrounding Regions: 2. Lower Mantle

The structure of the lithosphere and upper mantle beneath the Eastern Mediterranean and Middle East

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