Receiver function mapping of the mantle transition zone beneath the Western Alps: New constraints on slab subduction and mantle upwelling

The Alpine orogenic belt is the result of the continental collision and convergence&#160;between the Adriatic microplate and European plate&#160;during the Mesozoic.&#160;The Alps orogenic belt has a complex tectonic history and the deformation in and around the Alps are significantly affected by several microplates (e.g., Adriatic and Iberia)&#160;and&#160;blocks,&#160;in particular the Apennines, Betics, Dinarides. The mantle transition zone is delineated by seismic velocity discontinuities around the depths of 410 and 660 km&#160;which are generally interpreted as polymorphic phase changes in the olivine system and garnet-pyroxene system.The subduction depth of the European plate and the origin of the mantle flow behind the plate plays crucial roles for our understanding of regional geodynamic (Zhao et al., 2016; Hua et al.,&#160;2017).&#160;Therefore, we use&#160;receiver function&#160;method to study the seismic features of discontinuities beneath&#160;the Western Alps&#160;to constrain the structure of subducted plate and study the geodynamic origin of the low velocity anomaly behind the subduction zone and its relationship with the high-relief&#160;topography.&#160;This study uses data collected from 293 permanent and temporary broadband seismic stations (e.g., CIFALPS). Teleseismic events are selected from 30o&#160;to 90o epicentral distrance with magnitudes (Mw) between 5.3 and 9.0. Data are carefully checked&#160;by automated&#160;and manual&#160;procedures to to give a total of 24904&#160;receiver functions. Both 1D velocity model of the IASP91 and 3D velocity model of the EU60 (Zhu et al., 2015) are used for time-to-depth migration. The results show that&#160;using 3D velocity model to image the two discontinuities may obtain a more accurate structure image of the mantle transition zone.In the northern part of the study area, along the alpine orogenic belt, we find a localized arc-shaped thinning area&#160;with a depressed&#160;410 discontinuity, which is attributed to hot mantle upwellings.&#160;The uplift&#160;is&#160;hardly&#160;seen on the 660 discontinuity, suggesting that&#160;the thermal anomaly is unlikely to be interpreted as a mantle plume. The uplift of the 410-km can be interpreted as the European plate subducting to the depth of the upper transition zone. The depression of the 660-km &#160;is likely attributed&#160;to the remnants from the oceanic mantle lithosphere that detached from the Eurasian plate after closure of the Alpine Tethys.&#160;Our results show&#160;a good agreement&#160;between the thinning area of MTZ and the area of topographic uplift, the mantle upwelling promotes the temperature increase which is conducive to the uplift of topographic.ReferenceZhao L , Paul A , Marco G. Malus&#224;, et al. Continuity of the Alpine slab unraveled by high-resolution P-wave tomography. Journal of Geophysical Research: Solid Earth, 2016, 121.Hua, Y., D. Zhao, and Y. Xu (2017), P wave anisotropic tomography of the Alps, J. Geophys. Res. Solid Earth, 122, 4509&#8211;4528, doi:10.1002/2016JB013831.Zhu H,Bozdag E and Tromp J.Seismic structure of the European upper mantle based on adjoint tomography.Geophys. J. Int. 2015, 201, 18&#8211;52

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Mantle transition zone discontinuities beneath the Indochina Peninsula: Implications for slab subduction and mantle upwelling

Geophysical Research Letters ◽

10.1002/2017gl073528 ◽

2017 ◽

Vol 44 (14) ◽

pp. 7159-7167 ◽

Cited By ~ 15

Author(s):

Youqiang Yu ◽

Stephen S. Gao ◽

Kelly H. Liu ◽

Ting Yang ◽

Mei Xue ◽

...

Keyword(s):

Transition Zone ◽

Mantle Upwelling ◽

Indochina Peninsula ◽

Mantle Transition Zone

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Receiver function imaging of the mantle transition zone beneath the S outh C hina B lock

Geochemistry Geophysics Geosystems ◽

10.1002/2015gc005978 ◽

2015 ◽

Vol 16 (10) ◽

pp. 3666-3678 ◽

Cited By ~ 13

Author(s):

Haibo Huang ◽

Nicola Tosi ◽

Sung‐Joon Chang ◽

Shaohong Xia ◽

Xuelin Qiu

Keyword(s):

Transition Zone ◽

Receiver Function ◽

Mantle Transition Zone

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Topography of the Mantle Transition Zone Discontinuities Beneath Alaska and Its Geodynamic Implications: Constraints From Receiver Function Stacking

Journal of Geophysical Research Solid Earth ◽

10.1002/2017jb014604 ◽

2017 ◽

Vol 122 (12) ◽

pp. 10,352-10,363 ◽

Cited By ~ 5

Author(s):

Haider H. Dahm ◽

Stephen S. Gao ◽

Fansheng Kong ◽

Kelly H. Liu

Keyword(s):

Transition Zone ◽

Receiver Function ◽

Mantle Transition Zone

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Foundered lithospheric segments dropped into the mantle transition zone beneath southern California, USA

Geology ◽

10.1130/g46889.1 ◽

2019 ◽

Vol 48 (2) ◽

pp. 200-204

Author(s):

Youqiang Yu ◽

Stephen S. Gao ◽

Kelly H. Liu ◽

Dapeng Zhao

Keyword(s):

Transition Zone ◽

Sierra Nevada ◽

Southern California ◽

Receiver Function ◽

Active Tectonics ◽

Mantle Transition Zone ◽

Diverse Range ◽

Transverse Ranges ◽

The Pacific ◽

Lateral Variations

Abstract The diverse range of active tectonics occurring in southern California, USA, offers an opportunity to explore processes of continental deformation and modification in response to the instability of the Pacific and Farallon plates. Here, we present a high-resolution receiver-function image of the mantle transition zone (MTZ). Our result reveals significant lateral heterogeneities in the deep mantle beneath southern California. Both seismic tomography and MTZ discontinuity deflections reveal foundered lithospheric segments that have dropped into the MTZ beneath the western Transverse Ranges, the Peninsular Ranges, and part of the southern Sierra Nevada. Water dehydrated from these foundered materials may contribute to the observed MTZ thickening. Our observations, combined with previous tomography and geochemical results, indicate that lithospheric foundering of fossil arc roots provides a way for geochemical heterogeneities to be recycled into the underlying mantle, and suggest that the foundered materials can play a significant role in inducing lateral variations of MTZ structure.

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Garnet-controlled very low velocities in the lower mantle transition zone at sites of mantle upwelling

Terra Nova ◽

10.1111/ter.12348 ◽

2018 ◽

Vol 30 (5) ◽

pp. 333-340 ◽

Cited By ~ 2

Author(s):

Thorsten J. Nagel ◽

Erik Duesterhoeft ◽

Christian Schiffer

Keyword(s):

Transition Zone ◽

Lower Mantle ◽

Mantle Upwelling ◽

Mantle Transition Zone

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Common reflection point mapping of the mantle transition zone using recorded and 3-D synthetic ScS reverberations

Geophysical Journal International ◽

10.1093/gji/ggz467 ◽

2019 ◽

Vol 220 (1) ◽

pp. 724-736

Author(s):

Samuel M Haugland ◽

Jeroen Ritsema ◽

Daoyuan Sun ◽

Jeannot Trampert ◽

Maria Koroni

Keyword(s):

Transition Zone ◽

Large Scale ◽

Receiver Function ◽

Wave Theory ◽

Shear Velocity ◽

Velocity Model ◽

Reflection Point ◽

Mantle Transition Zone ◽

Point Mapping ◽

Continental Scale

SUMMARY The method of ScS reverberation migration is based on a ‘common reflection point’ analysis of multiple ScS reflections in the mantle transition zone (MTZ). We examine whether ray-theoretical traveltimes, slownesses and reflection points are sufficiently accurate for estimating the thickness H of the MTZ, defined by the distance between the 410- and 660-km phase transitions. First, we analyse ScS reverberations generated by 35 earthquakes and recorded at hundreds of seismic stations from the combined Arrays in China, Hi-NET in Japan and the Global Seismic Network. This analysis suggests that H varies by about 30 km and therefore that dynamic processes have modified the large-scale structure of the MTZ in eastern Asia and the western Pacific region. Second, we apply the same procedure to spectral-element synthetics for PREM and two 3-D models. One 3-D model incorporates degree-20 topography on the 410 and 660 discontinuities, otherwise preserving the PREM velocity model. The other model incorporates the degree-20 velocity heterogeneity of S20RTS and leaves the 410 and 660 flat. To optimize reflection point coverage, our synthetics were computed assuming a homogeneous grid of stations using 16 events, four of which are fictional. The resolved image using PREM synthetics resembles the PREM structure and indicates that the migration approach is correct. However, ScS reverberations are not as strongly sensitive to H as predicted ray-theoretically because the migration of synthetics for a model with degree-20 topography on the 410 and 660: H varies by less than 5 km in the resolved image but 10 km in the original model. In addition, the relatively strong influence of whole-mantle shear-velocity heterogeneity is evident from the migration of synthetics for the S20RTS velocity model and the broad sensitivity kernels of ScS reverberations at a period of 15 s. A ray-theoretical approach to modelling long-period ScS traveltimes appears inaccurate, at least for continental-scale regions with relatively sparse earthquake coverage. Additional modelling and comparisons with SS precursor and receiver function results should rely on 3-D waveform simulations for a variety of structures and ultimately the implementation of full wave theory.

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