Sharpness of the 410-km discontinuity from the P410s and P2p410s seismic phases

2019 ◽  
Author(s):  
Lev Vinnik ◽  
Yangfan Deng ◽  
Grigoriy Kosarev ◽  
Sergey Oreshin ◽  
Zhou Zhang ◽  
...  
Keyword(s):  
Transition Zone ◽  
Southern Africa ◽  
Amplitude Ratio ◽  
Southern China ◽  
Broad Band ◽  
Receiver Functions ◽  
P Wave ◽  
Seismic Model ◽  
Yangtze Craton ◽  
Zone Water

Summary Sharpness of the 410-km boundary is of interest because it is sensitive to water content in the transition zone. We evaluate the width of the 410-km discontinuity with a new seismic method. Our estimates are inferred from the amplitude ratio of the P2p410s and P410s seismic phases that are detected in P-wave receiver functions. We applied this method to seismic recordings from arrays of broad-band stations deployed in central Fennoscandia, southern Africa and southern China. The obtained estimates of width of the 410-km discontinuity range from 10 to 22 km and always exceed the width of 7 km which is expected for anhydrous conditions. The enlarged width may be interpreted in terms of hydrous conditions, but we have found only one region (the eastern Yangtze Craton in China) where the broad 410-km discontinuity, as expected, is accompanied by a broad transition zone. Water in the transition zone may be a kind of a global phenomenon, but evidence of the enlarged width of the transition zone may be missing in most of our data because the reference seismic model is affected by water, as well.

Seismic images of the mantle transition zone beneath Northeast China and the Sino-Korean craton from P-wave receiver functions

2016 ◽  
Vol 675 ◽  
pp. 159-167 ◽  
Author(s):  
Ruiqing Zhang ◽  
Zhanyong Gao ◽  
Qingju Wu ◽  
Zhenxing Xie ◽  
Guangcheng Zhang
Keyword(s):  
Transition Zone ◽  
Northeast China ◽  
Receiver Functions ◽  
P Wave ◽  
Mantle Transition Zone ◽  
Seismic Images

Integrated teleseismic studies of the southern Alberta upper mantle

2002 ◽  
Vol 39 (3) ◽  
pp. 399-411 ◽  
Author(s):  
J Shragge ◽  
M G Bostock ◽  
C G Bank ◽  
R M Ellis
Keyword(s):  
Upper Mantle ◽  
Velocity Structure ◽  
Broad Band ◽  
Receiver Functions ◽  
P Wave ◽  
Crustal Thickening ◽  
Plate Motion ◽  
Moho Depth ◽  
Hydrous Minerals ◽  
South Central

This paper presents results from a teleseismic experiment conducted across the Hearne Province in south-central Alberta. Data from an array of nine portable broad-band seismographs deployed along a 500 km NW–SE array have been supplemented with recordings from two Canadian National Seismograph Network stations. P-wave delay times from 293 earthquakes have been inverted for upper-mantle velocity structure below the array. The recovered model reveals high velocities beneath much of the southern Hearne Province to depths of 200–250 km, which are interpreted as deep-seated lithospheric structure. Contrary to recent tectonic models, these results suggest that the Hearne lithosphere has remained intact. In particular, it appears unlikely that evidence for extensive, lower crustal melting derives from lithospheric delamination. However, the results admit the possibility that high mantle conductivity, as revealed in magnetotelluric studies, originates through small volumes of connected hydrous minerals or other conductive species introduced during subduction. Decreased upper-mantle velocities at the northern end of the Medicine Hat block also pose challenges for the interpretation of differential subsidence across the region which may manifest distant forcing due to more recent subduction. Multievent SKS-splitting analysis yields an average polarization direction that is broadly consistent with both the orientation of fossil strain fields, related to ~ 1.8 Ga NW–SE shortening, and North American absolute plate motion. Moho depth estimates from receiver functions are fairly uniform (~ 38 km) beneath northern stations but show crustal thickening (>40 km) within the Medicine Hat block to the south and are consistent with values from active-source profiling.

Palaeoslab and plume signatures in the mantle transition zone beneath Eastern Himalaya and adjoining regions

2020 ◽  
Vol 221 (1) ◽  
pp. 468-477
Author(s):  
Dipankar Saikia ◽  
M Ravi Kumar ◽  
Arun Singh
Keyword(s):  
Transition Zone ◽  
Broad Band ◽  
Receiver Functions ◽  
Eastern Himalaya ◽  
Bengal Basin ◽  
Southern Tibet ◽  
Data Set ◽  
Mantle Transition Zone ◽  
Tomographic Images ◽  
Indian Lithosphere

SUMMARY A comprehensive data set of 73 876 high quality receiver functions computed using waveforms recorded by 327 broad-band seismic stations is used to investigate the mantle transition zone (MTZ) structure beneath the eastern Himalaya, southern Tibet, Assam valley and the previously unexplored Burmese arc and Bengal basin regions. A highly variable and perturbed mantle transition zone, with depressed 410 and 660 km discontinuities, is observed beneath the Bengal basin and to the east of the eastern Himalayan syntaxis. The 410 is elevated by ∼10 km along the Himalayan collision front, while it deviates in the range of ±5 km beneath most parts of Tibet and the Himalayan Foredeep. In northern Tibet and along the Red River Fault, delayed conversions from the 410 reveal a deepening of more than 10 km. The 410 and 660 km discontinuities are uplifted by nearly 10 km beneath the Arunachal Himalaya, due to the presence of a subducting Indian lithosphere, as evident in the regional tomographic images. We observe a thick (>20 km) transition zone beneath the Burmese Arc and close to the Tengchong volcano. An uplifted 410 together with a depressed 660 km discontinuity requires presence of lithospheric slabs within the MTZ. Delayed P-to-s conversions from the 410 and 660 km discontinuities in the proximity of the Jinsha suture zone seem to be consistent with the earlier results that invoke flow of a hot Tibetan asthenosphere into the mantle transition zone, as an explanation. Interestingly, results from the Bengal basin reveal a deepening (∼10 km) of both the 410 and 660 km discontinuities. Similar results from other plume affected regions prompt us to interpret this as a signature of the Kergulean plume.

Location and characteristics of the X-discontinuity beneath SW Morocco and the adjacent shelf area using P-wave receiver functions

2020 ◽  
Vol 223 (3) ◽  
pp. 1780-1793
Author(s):  
Theresa Rein ◽  
Katrin Hannemann ◽  
Christine Thomas ◽  
Michael Korn
Keyword(s):  
Phase Transitions ◽  
Transition Zone ◽  
Receiver Functions ◽  
P Wave ◽  
Small Scale ◽  
Depth Range ◽  
Shelf Area ◽  
Seismic Velocities ◽  
Mantle Transition Zone ◽  
Study Region

SUMMARY Receiver function approaches have proven to be valuable for the investigation of crustal and upper mantle discontinuities whose sharp changes in seismic velocities cause wave conversions. While the crustal and mantle transition zone discontinuities are largely understood, the X-discontinuity at 250–350 km depth is still an object of controversial debate. The origin and global distribution of this structure with a velocity jump of 1.5–4.8 % for compressional and shear waves is still unexplained. Although the crustal and mantle transition zone discontinuities beneath SW Morocco and surroundings have been investigated, only a few studies observed the X-discontinuity and place the depth at 260–370 km beneath the region of western Morocco. In order to better locate and characterize the X-discontinuity beneath southwest Morocco, we create P-wave receiver functions using data recorded by the Morocco–Münster array and detect the X-discontinuity at apparent depths of 285–350 km. In the western part of our study region we find apparent depths of ∼ 310–340 km. The eastern part of the study area appears more complex: we locate two velocity jumps at apparent depths of around 285–295 km and 330–350 km in the northeast, and in the southeast we find a discontinuity at apparent depths of 340–350 km. Due to the large depth range and the twofold appearance of the X-discontinuity, we suggest that two different phase transitions cause the X-discontinuity beneath SW Morocco. The velocity contrasts at larger depths likely point to the coesite–stishovite phase transition occurring in deep eclogitic pools. The shallower depths can be explained by the transition from orthoenstatite to high-pressure clinoenstatite which requires the reaction between eclogite and peridotite to form orthopyroxene-rich peridotite. This reaction is likely related to previously proposed small-scale mantle upwellings beneath SW Morocco. Since both phase transitions require eclogite occurrence, the location of the X-discontinuity in this region can be used to indicate the location of recycled oceanic crust.

scholarly journals Post-collisional mantle delamination in the Dinarides implied from staircases of Oligo-Miocene uplifted marine terraces

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Philipp Balling ◽  
Christoph Grützner ◽  
Bruno Tomljenović ◽  
Wim Spakman ◽  
Kamil Ustaszewski
Keyword(s):  
Balkan Peninsula ◽  
Receiver Functions ◽  
P Wave ◽  
S Wave ◽  
Slab Geometry ◽  
Surface Uplift ◽  
River Incision ◽  
Marine Terraces ◽  
Convergence System ◽  
Internal Dinarides

AbstractThe Dinarides fold-thrust belt on the Balkan Peninsula resulted from convergence between the Adriatic and Eurasian plates since Mid-Jurassic times. Under the Dinarides, S-wave receiver functions, P-wave tomographic models, and shear-wave splitting data show anomalously thin lithosphere overlying a short down-flexed slab geometry. This geometry suggests a delamination of Adriatic lithosphere. Here, we link the evolution of this continental convergence system to hitherto unreported sets of extensively uplifted Oligocene–Miocene (28–17 Ma) marine terraces preserved at elevations of up to 600 m along the Dinaric coastal range. River incision on either side of the Mediterranean-Black Sea drainage divide is comparable to the amounts of terrace uplift. The preservation of the uplifted terraces implies that the most External Dinarides did not experience substantial deformation other than surface uplift in the Neogene. These observations and the contemporaneous emplacement of igneous rocks (33–22 Ma) in the internal Dinarides suggest that the Oligo-Miocene orogen-wide uplift was driven by post-break-off delamination of the Adriatic lithospheric mantle, this was followed by isostatic readjustment of the remaining crust. Our study details how lithospheric delamination exerts an important control on crustal deformation and that its crustal signature and geomorphic imprint can be preserved for millions of years.

scholarly journals Reliable workflow for inversion of seismic receiver function and surface wave dispersion data: a “13 BB Star” case study

2019 ◽  
Vol 24 (1) ◽  
pp. 101-120
Author(s):  
Kajetan Chrapkiewicz ◽  
Monika Wilde-Piórko ◽  
Marcin Polkowski ◽  
Marek Grad
Keyword(s):  
Surface Wave ◽  
Inverse Problems ◽  
Receiver Function ◽  
Joint Inversion ◽  
Wave Dispersion ◽  
Receiver Functions ◽  
P Wave ◽  
Surface Wave Dispersion ◽  
Phase Velocity Dispersion ◽  
Wide Range

AbstractNon-linear inverse problems arising in seismology are usually addressed either by linearization or by Monte Carlo methods. Neither approach is flawless. The former needs an accurate starting model; the latter is computationally intensive. Both require careful tuning of inversion parameters. An additional challenge is posed by joint inversion of data of different sensitivities and noise levels such as receiver functions and surface wave dispersion curves. We propose a generic workflow that combines advantages of both methods by endowing the linearized approach with an ensemble of homogeneous starting models. It successfully addresses several fundamental issues inherent in a wide range of inverse problems, such as trapping by local minima, exploitation of a priori knowledge, choice of a model depth, proper weighting of data sets characterized by different uncertainties, and credibility of final models. Some of them are tackled with the aid of novel 1D checkerboard tests—an intuitive and feasible addition to the resolution matrix. We applied our workflow to study the south-western margin of the East European Craton. Rayleigh wave phase velocity dispersion and P-wave receiver function data were gathered in the passive seismic experiment “13 BB Star” (2013–2016) in the area of the crust recognized by previous borehole and refraction surveys. Final models of S-wave velocity down to 300 km depth beneath the array are characterized by proximity in the parameter space and very good data fit. The maximum value in the mantle is higher by 0.1–0.2 km/s than reported for other cratons.

scholarly journals Crustal Structure Along Sunda-Banda Arc Transition Zone from Teleseismic Receiver Functions

2016 ◽  
Vol 64 (6) ◽  
pp. 2020-2049 ◽  
Author(s):  
Syuhada Syuhada ◽  
Nugroho Dwi Hananto ◽  
Chalid I. Abdullah ◽  
Nanang T. Puspito ◽  
Titi Anggono ◽  
...  
Keyword(s):  
Transition Zone ◽  
Crustal Structure ◽  
Receiver Functions ◽  
Banda Arc

scholarly journals Crustal structure beneath Tierra del Fuego, Argentina, inferred from seismic P-wave receiver functions and ambient noise autocorrelations

2019 ◽  
Vol 751 ◽  
pp. 41-53 ◽  
Author(s):  
Carolina Buffoni ◽  
Martin Schimmel ◽  
Nora Cristina Sabbione ◽  
María Laura Rosa ◽  
Gerardo Connon
Keyword(s):  
Crustal Structure ◽  
Ambient Noise ◽  
Receiver Functions ◽  
Tierra Del Fuego ◽  
P Wave

scholarly journals Triplicated P-wave measurements for waveform tomography of the mantle transition zone

Solid Earth ◽  
2012 ◽  
Vol 3 (2) ◽  
pp. 339-354 ◽  
Author(s):  
S. C. Stähler ◽  
K. Sigloch ◽  
T. Nissen-Meyer
Keyword(s):  
Transition Zone ◽  
Epicentral Distance ◽  
Body Wave ◽  
Source Parameters ◽  
Body Waves ◽  
P Wave ◽  
Theoretical Modelling ◽  
Finite Frequency ◽  
Mantle Transition Zone ◽  
Band Limited

Abstract. Triplicated body waves sample the mantle transition zone more extensively than any other wave type, and interact strongly with the discontinuities at 410 km and 660 km. Since the seismograms bear a strong imprint of these geodynamically interesting features, it is highly desirable to invert them for structure of the transition zone. This has rarely been attempted, due to a mismatch between the complex and band-limited data and the (ray-theoretical) modelling methods. Here we present a data processing and modelling strategy to harness such broadband seismograms for finite-frequency tomography. We include triplicated P-waves (epicentral distance range between 14 and 30°) across their entire broadband frequency range, for both deep and shallow sources. We show that is it possible to predict the complex sequence of arrivals in these seismograms, but only after a careful effort to estimate source time functions and other source parameters from data, variables that strongly influence the waveforms. Modelled and observed waveforms then yield decent cross-correlation fits, from which we measure finite-frequency traveltime anomalies. We discuss two such data sets, for North America and Europe, and conclude that their signal quality and azimuthal coverage should be adequate for tomographic inversion. In order to compute sensitivity kernels at the pertinent high body wave frequencies, we use fully numerical forward modelling of the seismic wavefield through a spherically symmetric Earth.

Sp phases from the transition zone between the upper and lower mantle

1980 ◽  
Vol 70 (2) ◽  
pp. 487-508
Author(s):  
Sonja Faber ◽  
Gerhard MÜller
Keyword(s):  
United States ◽  
Transition Zone ◽  
Lower Mantle ◽  
The United States ◽  
P Wave ◽  
Western United States ◽  
Nodal Plane ◽  
Transition Zones ◽  
Velocity Models ◽  
Long Period

abstract Precursors to S and SKS were observed in long-period SRO and WWSSN seismograms of the Romanian earthquake of March 4, 1977, recorded in the United States at distances from 68° to 93°. According to the fault-plane solution, the stations were close to a nodal plane and SV radiation was optimum in their direction. Particle-motion diagrams, constructed from the digital data of the SRO station ANMO (distance 89.1°), show the P-wave character of the precursors. Several interpretations are discussed; the most plausible is that the precursors are Sp phases generated by conversion from S to P below the station. The travel-time differences between S or SKS and Sp are about 60 sec and indicate conversion in the transition zone between the upper and lower mantle. Sp conversions were also observed at long-period WWSSN stations in the western United States for 2 Tonga-Fiji deep-focus earthquakes (distances from 82° to 96°). Special emphasis is given in this paper to the calculation of theoretical seismograms, both for Sp precursors and the P-wave coda, including high-order multiples such as sP4 which may arrive simultaneously with Sp. The Sp calculations show: (1) the conversions produced by S, ScS, and SKS at interfaces or transition zones between the upper and lower mantle form a complicated interference pattern, and (2) conversion at transition zones is less effective than at first-order discontinuities only if their thickness is greater than about half a wavelength of S waves. As a consequence, details of the velocity structure between the upper and lower mantle can only be determined within these limits from long-period Sp observations. Our observations are compatible with velocity models having pronounced transition zones at depths of 400 and 670 km as have been proposed for the western United States, and they exclude much smoother structures. Our study suggests that long-period Sp precursors from pure thrust or normal-fault earthquakes, observed at distances from 70° to 95° close to a nodal plane and at azimuths roughly perpendicular to its strike, offer a simple means for qualitative mapping of the sharpness of the transition zones between the upper and lower mantle.

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