Broadband converted phases from midmantle discontinuities

Vinnik, Lev; Niu, Fenglin; Kawakatsu, Hitoshi

doi:10.1186/bf03352193

Cited by 32 publications

(25 citation statements)

References 17 publications

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“…These reflectors may be related to the bottom of the subducted slab, or represent phase transitions in slab specific compositions. Deuss and Woodhouse (2002) found reflectors at 1,200 km depth in stacks for the Indonesian subduction zone region, at the same depth and location where receiver function studies have also found lower mantle reflectors (Vinnik et al 1998(Vinnik et al , 2001.…”

Section: Lower Mantle Reflectorsmentioning

confidence: 86%

Global Observations of Mantle Discontinuities Using SS and PP Precursors

2009

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SS and PP precursors are currently the only body wave data types that have significant coverage in both oceanic and continental regions to study the existence and characteristics of mantle discontinuities on a global scale. Here, the techniques used by global seismologists to observe SS and PP precursors are reviewed. Seismograms, aligned on SS or PP, are stacked using normal move out (NMO) techniques to obtain common depth point gathers. Bootstrap methods are employed to determine 95% confidence levels of the stacks and robustness of the observations. With these relatively simple techniques, a range of discontinuities has been found in the mantle up to 1,200 km depth. The stacks are dominated by the transition zone discontinuities at 410, 520 and 660 km depth, but additional discontinuities at 220, 300-350, 800-900 and 1,100-1,200 km depth are also seen in certain regions. An overview is given of the most recent observational results with a discussion of their mineral physical interpretation and geodynamical significance. Both seismology and mineral physics agree on the level of complexity at the transition discontinuities: a simple 410, a more complicated 520 and a highly complicated 660-km discontinuity are consistently found in both disciplines.

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Section: Lower Mantle Reflectorsmentioning

confidence: 86%

Global Observations of Mantle Discontinuities Using SS and PP Precursors

2009

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“…There are also widespread reports of seismic discontinuities between 800 and 1200 km depth (e.g. Kawakatsu & Niu 1994, 1996; Vinnik et al 1998), which could separate regions of somewhat different chemical composition. Interestingly, 1000 km also corresponds to the approximate depth of an order of magnitude increase in mantle viscosity inferred by Mitrovica & Forte (1997, 2002).…”

Section: Discussionmentioning

confidence: 99%

J362D28: a new joint model of compressional and shear velocity in the Earth's mantle

Antolik

Ekström

et al. 2003

Geophysical Journal International

104

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SUMMARY The discrimination between chemical and thermal heterogeneity in the Earth's mantle remains one of the most important and challenging questions to be answered by observational and theoretical geophysics. To answer this question requires a thorough knowledge of the ratio between compressional and shear velocity anomalies. We describe results of a joint inversion for compressional and shear velocity in the mantle using a large and diverse data set consisting of traveltimes, complete waveforms and surface wave dispersion measurements. A horizontal tessellation consisting of 362 spherical splines is used to parametrize the model, which is approximately equivalent to a spherical harmonic of degree 18 in resolution. The model contains peak variations (from PREM) of up to ±7 per cent in S velocity and ±2.5 per cent in P velocity in the upper mantle. These variations decrease to ±1.5 and ±0.6 per cent, respectively, at 1000 km depth and reach ±2.5 and ±1.0 per cent, respectively, in the D″ region. The rms ratio of S to P velocity perturbations is fairly constant between 2.0 and 2.5 in the lower mantle, but a local minimum in this ratio occurs at a depth of approximately 1700 km. Resolution tests show that the recovery of P and S velocity is not geographically uniform, but also show that this amplitude ratio is well resolved between 670 and 2700 km depth. We also observe a persistent negative correlation between bulk‐sound and shear velocity throughout the same region of the mantle. In addition, the model contains a minimum correlation between P and S velocity between 670 and ∼1100 km. This feature is supported by both the favourable outcome of resolution experiments and the poor fit provided by the starting model from the inversion (in which the P and S velocities are perfectly correlated) to our data set of P‐wave traveltimes. The power spectra of both P and S velocity heterogeneity are similar, although we note a slightly larger dominance of degree two in the spectra for P velocity in the mid‐mantle where resolution is highest.

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“…2000; Fukao et al . 2000) and with the depth of the mid‐mantle discontinuity (Kawakatsu & Niu 1994; Niu & Kawakatsu 1997; Vinnik et al . 1998).…”

Section: Discussionmentioning

confidence: 99%

Seismic evidence for a mantle plume oceanwards of the Kamchatka-Aleutian trench junction

Gorbatov¹,

Fukao²,

Widiyantoro³

et al. 2001

Geophysical Journal International

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Summary A non‐linear iterative P‐wave traveltime tomography has revealed a mantle plume originating at a depth of nearly 1000 km, rising across the 600 km discontinuity, and deflecting subhorizontally in the uppermost mantle presumably by shear flow due to the overlying moving plate. Data from the Geophysical Survey of Russia (1955–1997) were inverted jointly with the catalogues of International Seismological Centre and USGS National Earthquake Information Centre (1964– 1998). The result shows a 300–500 km‐wide cylindrical low‐velocity anomaly (∼ − 2 per cent) that extends from a depth of greater than 900 km to shallower than 200 km. The anomaly is almost vertical at depths up to ∼400 km and rises obliquely to the north up to ∼200 km under the ocean floor near the northern end of Emperor seamounts. Above ∼300 km depth a subsidiary anomaly extends subhorizontally to the NW in fair agreement with the direction of movement of the Pacific Plate. The overlying seafloor is characterized by anomalously high heat flow, which may be attributed to the thermal effect of the mantle plume.

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Broadband converted phases from midmantle discontinuities

Cited by 32 publications

References 17 publications

Global Observations of Mantle Discontinuities Using SS and PP Precursors

Global Observations of Mantle Discontinuities Using SS and PP Precursors

J362D28: a new joint model of compressional and shear velocity in the Earth's mantle

Seismic evidence for a mantle plume oceanwards of the Kamchatka-Aleutian trench junction

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