Structural interpretation of gravity, topography and seismicity

2019 ◽  
Vol 487 (1) ◽  
pp. 315-343 ◽  
Author(s):  
Regan L. Patton ◽  
A. John Watkinson
Keyword(s):  
Moment Tensor ◽  
Shear Banding ◽  
Point Of View ◽  
Centroid Moment Tensor ◽  
Polar Wander ◽  
Long Wavelength ◽  
True Polar Wander ◽  
Shape Perturbation ◽  
Tectonic Features ◽  
Low Amplitude

AbstractGlobal geophysical observations constrain all theories of terrestrial dynamics. We jointly interpret EGM2008 gravity, RET2014 topography and the Global Centroid Moment Tensor database from a structural point of view. We hypothesize that lateral variations of gravity and topography reflect the scale-dependent competence of rocks. We compare the spectral and spatial characteristics of the observed fields with structural predictions from the mechanics of differential grade-2 (DG-2) materials. The results indicate that these viscoelastic materials are a powerful tool for exploring dynamic processes in the Earth. We demonstrate that the known spectral range of Earth's gravity and topography can be explained by the folding, shear banding, faulting and differentiation of the crust, lithosphere and mantle. We show that the low-amplitude long-wavelength bias apparent in the disturbance field can be explained by perturbations to Earth's overall ellipsoidal shape, induced by internal slab loading of the mantle. We find by examining the directional isotropy of the data that the zonal energy in Earth's gravity disturbance is maximized about an axis coincident with the shape-perturbation minimum. The symmetry of tectonic features about this axis, extending from eastern Borneo to Brazil, and its coincidence with the equator suggest the coupling of current plate motions to true polar wander.

Supercontinent cycles, true polar wander, and very long-wavelength mantle convection

2007 ◽  
Vol 261 (3-4) ◽  
pp. 551-564 ◽  
Author(s):  
Shijie Zhong ◽  
Nan Zhang ◽  
Zheng-Xiang Li ◽  
James H. Roberts
Keyword(s):  
Mantle Convection ◽  
Polar Wander ◽  
Long Wavelength ◽  
True Polar Wander

From Rodinia to Pangea: an extroversion process driven first by plume push followed by downwelling pull, absorption and merging

2020 ◽  
Author(s):  
Zheng-Xiang Li ◽  
William Collins ◽  
Lei Wu ◽  
Sergei Pisarevsky
Keyword(s):  
Mantle Convection ◽  
Planetary Science ◽  
Mantle Structure ◽  
Geophysical Research ◽  
Deep Time ◽  
Polar Wander ◽  
Long Wavelength ◽  
Earth’S Mantle ◽  
True Polar Wander ◽  
Gondwana Margin

<p>Numerous works also suggested that mantle plumes or mantle upwellings associated with LLSVPs in a degree-2 mantle state play a major role in driving the break-up of a supercontinent. However, subduction and mantle downwelling may play an increasing role in the leadup to the assembly of the next supercontinent. Anderson (1994) noticed that continents tend to gather at mantle downwelling zones, which was later developed into the hypothesis of orthoversion assembly of supercontinents by Mitchell (2012). Zhong et al. (2007) conceptualised the assembly of supercontinents through the merger or absorption of mantle downwellings, leading to the assembly of supercontinents over a superdownwelling in a degree-1 mantle. Here we present a revised global paleogeographic reconstruction featuring an extroversion assembly of Pangea (i.e. through the closure of the Mirovoi superocean) over a pre-existing yet dynamic mantle downwelling zone (Li et al., 2019). In particular, we show that the Paleozoic world was dominated by two major subduction (dowelling) cells, one associated with the newly assembled Gondwana, and the other associated with the assembly of Laurasia. The two cells gradually merged together by the Carboniferous time, forming the supercontinent Pangea over a mantle superdownwelling (Zhang et al., 2010). It was during the merger of the two dowelling cells that continental and arc terranes was successively transported from Gondwana margin to future Laurasia.</p><p><strong>References:</strong></p><p>Anderson, D.L., 1994. Superplume or supercontinents? Geology 22, 39-42.</p><p>Huang, C., Zhang, N., Li, Z.-X., Ding, M., Dang, Z., Pourteau, A., Zhong, S., 2019. Modeling the Inception of Supercontinent Breakup: Stress State and the Importance of Orogens. Geochemistry, Geophysics, Geosystems 20, 4830-4848.</p><p>Li, Z.X., Mitchell, R.N., Spencer, C.J., Ernst, R., Pisarevsky, S., Kirscher, U., Murphy, J.B., 2019. Decoding Earth’s rhythms: Modulation of supercontinent cycles by longer superocean episodes. Precambrian Research 323, 1-5.</p><p>Mitchell, R.N., Kilian, T.M., Evans, D.A.D., 2012. Supercontinent cycles and the calculation of absolute palaeolongitude in deep time. Nature 482, 208-211.</p><p>Zhang, N., Zhong, S., Leng, W., Li, Z.-X., 2010. A model for the evolution of the Earth's mantle structure since the Early Paleozoic. Journal of Geophysical Research: Solid Earth 115, B06401.</p><p>Zhong, S., Zhang, N., Li, Z.-X., Roberts, J.H., 2007. Supercontinent cycles, true polar wander, and very long-wavelength mantle convection. Earth and Planetary Science Letters 261, 551-564.</p>

scholarly journals Contact of the Samoan Plume with the Tonga Subduction from Intermediate and Deep-Focus Earthquakes

2021 ◽  
Author(s):  
Pavla Hrubcová ◽  
Václav Vavryčuk
Keyword(s):  
Moment Tensor ◽  
Plate Boundary ◽  
S Wave ◽  
Low Velocity ◽  
Centroid Moment Tensor ◽  
S Waves ◽  
Velocity Anomalies ◽  
Deep Focus ◽  
Tectonic Features ◽  
Back Arc

AbstractThe Tonga subduction zone in the south-west Pacific is the fastest convergent plate boundary in the world with the most active mantle seismicity. This zone shows unique tectonic features including Samoan volcanic lineament of plume-driven origin near the northern rim of the Tonga subducting slab. The proximity of the Samoa hotspot to the slab is enigmatic and invokes debates on interactions between the Samoa plume and the Tonga subduction. Based on long-term observations of intermediate and deep-focus Tonga earthquakes reported in the Global Centroid Moment Tensor (CMT) catalog, we provide novel detailed imaging of this region. Accurate traveltime residua of the P- and S-waves recorded at two nearby seismic stations of the Global Seismographic Network are inverted for the P- and S-wave velocities and their ratio and reveal their pronounced lateral variations. In particular, they differ for the southern and northern parts of the Tonga subduction region. While no distinct anomalies are detected in the southern Tonga segment, striking low-velocity anomalies associated with a high Vp/Vs ratio are observed in the northern Tonga segment close to the Samoa plume. These anomalies spread through the whole upper mantle down to depths of ~ 600 km. Together with the fast extension of the northern back-arc Lau Basin, slab deformation and geochemical enrichment in the northern Tonga region, they trace deep-seated magmatic processes and evidence an interaction of the Tonga subduction with the Samoa plume.

scholarly journals Style of density stratification in the mantle and true polar wander induced by ice loading

2002 ◽  
Vol 107 (B10) ◽  
pp. ETG 16-1-ETG 16-17 ◽  
Author(s):  
R. Sabadini ◽  
A. M. Marotta ◽  
R. De Franco ◽  
L. L. A. Vermeersen
Keyword(s):  
Density Stratification ◽  
Polar Wander ◽  
True Polar Wander

Late Cretaceous True Polar Wander: Not So Fast

Science ◽  
2000 ◽  
Vol 288 (5475) ◽  
pp. 2283a-2283 ◽  
Author(s):  
R. D. Cottrell
Keyword(s):  
Late Cretaceous ◽  
Polar Wander ◽  
True Polar Wander
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