We present a new three‐dimensional S v wave speed and azimuthal anisotropy model for the upper mantle of eastern Asia constrained by analysis more than 17,000 vertical component multimode Rayleigh seismograms. This data set allows us to build an with horizontal resolution few hundred kilometers extending ∼400 km depth. At 75–100 depth, there is approximately ±9% perturbation from “smoothed PREM” reference used in our analysis, pattern complex. Both amplitude heterogeneity complexity decrease...

Abstract We present 3D2015_07Sv, an S wave model of the upper mantle based on waveform modeling 1,359,470 Rayleigh waves recorded since 1976. The use approximate forward theory and allows updating with new data a regular basis. 3D2015_07Sv contains azimuthal anisotropy, achieves lateral resolution ∼600 km, is consistent other recent models up to degree 60 in uppermost 200 km 15 transition zone. Although radial anisotropy has been found extend deeper beneath continents than oceans, we find no...

We present DR2012, a global SV‐wave tomographic model of the upper mantle. use an extension automated waveform inversion approach Debayle (1999) which improves our mapping transition zone with extraction fundamental and higher‐mode information. The new is fully has been successfully used to match approximately 375,000 Rayleigh waveforms. For each seismogram, we obtain path average shear velocity quality factor model, set dispersion attenuation curves. incorporate resulting models into...

In this study, we confirm the existence of a change in shear velocity spectrum around 1000 km depth based on new tomographic model Earth's mantle, SEISGLOB2. This is Rayleigh surface wave phase velocities, self- and cross-coupling structure coefficients spheroidal normal modes body traveltimes which are, for first time, combined inversion. SEISGLOB2 developed up to spherical harmonic degree 40 21 radial spline functions. The flattest (i.e. richest 'short' wavelengths corresponding degrees...

We present a new three‐dimensional model for the SV wave hetero‐geneities and azimuthal anisotropy in upper mantle of Australasian region. The is constrained by waveforms 2194 Rayleigh waves seismograms with dense ray coverage that ensure lateral resolution order few hundred kilometers. use higher modes allows structure down to depths at least 400 km. In 200 km model, seismic velocities are lower on eastern Phanerozoic margin continent compared Precambrian central western cratons, agreement...

This paper focuses on the upper-mantle velocity structure of African continent and its relationship to surface geology. The distribution seismographs earthquakes providing seismograms for this study results in good fundamental higher mode path coverage by a large number relatively short propagation paths, allowing us image SV-wave speed structure, with horizontal resolution several hundred kilometres vertical ∼50 km, depth about 400 km. difference mantle between Archean Pan-African terranes...

The Zagros of Iran form one the youngest collisional orogenic belts on Earth. At shallow depths, shortening across is accommodated by folding in sediments, high‐angle thrust faulting basement and thickening lower crust, but how lithospheric mantle has been uncertain largely because upper seismic structure poorly known. We map lateral variations shear wave speed beneath this region using a large, multimode surface data set. slow for most Middle East, high lid extending to ∼225 km depth exists...

Regional axial depths, mantle Bouguer anomaly values, geochemical proxies for the extent of partial melting and tomographic models along Southwest Indian Ridge (SWIR) all concur in indicating presence thicker crust hotter between Indomed Gallieni transform faults (TFs; 46°E 52°20′E) relative to neighbouring ridge sections. Accreted seafloor these TFs over past ∼10 Myr is also locally much shallower (>1000 m) corresponds (>1.7 km) than previously accreted same region. Two large outward facing...

A new scheme is proposed for the inversion of surface waves using a continuous formulation inverse problem and least squares criterion. Like some earlier schemes Gaussian priori covariance function controls horizontal degree smoothing in inverted model, which minimizes artifacts observed with spherical harmonic parameterizations. Unlike approach incorporates sophisticated geometrical algorithms dramatically increase computational efficiency render possible several tens thousands seismograms...

We present a regional surface waveform tomography of the Pacific upper mantle, obtained using an automated multimode inversion technique on fundamental and higher mode Rayleigh waves, to constrain VSV structure down ∼400 km depth. have improved previous implementations this by robustly accounting for effects uncertainties in earthquake source parameters tomographic inversion. furthermore path coverage South region including wave observations from French Polynesian Lithosphere Upper Mantle...

We present a new global study of the transition zone from Pds converted waves at 410‐ and 660‐km discontinuities. Our observations extend previous studies with larger data set, especially in oceanic regions where we have been able to measure travel times, sampling mantle (MTZ) beneath 26 hotspot locations. find significant lateral variations MTZ thickness. Both maximum (±35–40 km) long‐wavelength pattern are overall agreement SS precursors studies. The is generally thick subduction zones,...

Surface wave studies in the 1960s provided first indication that upper mantle was radially anisotropic. Resolving anisotropic structure is important because it may yield information on deformation and flow patterns mantle. The existing models are poor agreement. Rayleigh waves have been studied extensively recent show general Less work has focused Love do exist less well-constrained than models, suggesting responsible for agreement of We adapted waveform inversion procedure Debayle & Ricard...

Abstract Azimuthal anisotropy derived from multimode Rayleigh wave tomography in China exhibits depth‐dependent variations Tibet, which can be explained as induced by the Cenozoic India‐Eurasian collision. In west E‐W fast polarization direction at depths <100 km is consistent with accumulated shear strain Tibetan lithosphere, whereas N‐S greater aligned Indian Plate motion. northeast depth‐consistent NW‐SE directions imply coupled deformation throughout whole possibly also involving...

Abstract Inconsistencies between observations from long and short period seismic waves geochemical data mean craton formation evolution remains enigmatic. Specifically, internal layering radial anisotropy are poorly constrained. Here, we show that these inconsistencies can be reconciled by inverting cratonic Rayleigh Love surface wave dispersion curves for shear‐wave velocity using a flexible Bayesian scheme. This approach requires no explicit vertical smoothing only adds to layers where...

The details of heterogeneities in the lower mantle have increased considerably during last decades thanks to seismic imaging revealing ULVZs, D” layer, PERM anomaly and now mega-ULVZs. However, origin these anomalies is actively debated, as velocities alone cannot disentangle between thermal or compositional origins. Seismic attenuation can provide an additional perspective velocity for constraining physical properties heterogeneities. In this study, we aim develop first 3D global...