scholarly journals Seismic tomography and earthquake locations in the Nicaraguan and Costa Rican upper mantle

2008 ◽  
Vol 9 (7) ◽  
pp. n/a-n/a ◽  
Author(s):  
Ellen M. Syracuse ◽  
Geoffrey A. Abers ◽  
Karen Fischer ◽  
Laura MacKenzie ◽  
Catherine Rychert ◽  
...  
Keyword(s):  
Seismic Tomography ◽  
Upper Mantle ◽  
Costa Rican ◽  
Earthquake Locations

scholarly journals Comparing global tomography-derived and gravity-based upper mantle density models

2020 ◽  
Vol 221 (3) ◽  
pp. 1542-1554 ◽  
Author(s):  
B C Root
Keyword(s):  
Seismic Tomography ◽  
Upper Mantle ◽  
Seismic Data ◽  
Gravity Data ◽  
Heterogeneous Data ◽  
Clear Correlation ◽  
Data Sets ◽  
Satellite Gravity ◽  
Similar Density ◽  
Similar Peak

SUMMARY Current seismic tomography models show a complex environment underneath the crust, corroborated by high-precision satellite gravity observations. Both data sets are used to independently explore the density structure of the upper mantle. However, combining these two data sets proves to be challenging. The gravity-data has an inherent insensitivity in the radial direction and seismic tomography has a heterogeneous data acquisition, resulting in smoothed tomography models with de-correlation between different models for the mid-to-small wavelength features. Therefore, this study aims to assess and quantify the effect of regularization on a seismic tomography model by exploiting the high lateral sensitivity of gravity data. Seismic tomography models, SL2013sv, SAVANI, SMEAN2 and S40RTS are compared to a gravity-based density model of the upper mantle. In order to obtain similar density solutions compared to the seismic-derived models, the gravity-based model needs to be smoothed with a Gaussian filter. Different smoothening characteristics are observed for the variety of seismic tomography models, relating to the regularization approach in the inversions. Various S40RTS models with similar seismic data but different regularization settings show that the smoothening effect is stronger with increasing regularization. The type of regularization has a dominant effect on the final tomography solution. To reduce the effect of regularization on the tomography models, an enhancement procedure is proposed. This enhancement should be performed within the spectral domain of the actual resolution of the seismic tomography model. The enhanced seismic tomography models show improved spatial correlation with each other and with the gravity-based model. The variation of the density anomalies have similar peak-to-peak magnitudes and clear correlation to geological structures. The resolvement of the spectral misalignment between tomographic models and gravity-based solutions is the first step in the improvement of multidata inversion studies of the upper mantle and benefit from the advantages in both data sets.

Seismic Tomography Of The Upper Mantle Beneath Se Brazil

2001 ◽  
Author(s):  
Christian Escalante ◽  
Martin Schimmel ◽  
Marcelo Assumpção
Keyword(s):  
Seismic Tomography ◽  
Upper Mantle ◽  
Se Brazil

scholarly journals Seismic Structure of the Upper Mantle Beneath Eastern Asia From Full Waveform Seismic Tomography

2018 ◽  
Vol 19 (8) ◽  
pp. 2732-2763 ◽  
Author(s):  
Kai Tao ◽  
Stephen P. Grand ◽  
Fenglin Niu
Keyword(s):  
Seismic Tomography ◽  
Upper Mantle ◽  
Seismic Structure ◽  
Eastern Asia ◽  
Full Waveform

scholarly journals Upper mantle structure beneath the Azores hotspot from finite-frequency seismic tomography

2006 ◽  
Vol 250 (1-2) ◽  
pp. 11-26 ◽  
Author(s):  
T YANG ◽  
Y SHEN ◽  
S VANDERLEE ◽  
S SOLOMON ◽  
S HUNG
Keyword(s):  
Seismic Tomography ◽  
Upper Mantle ◽  
Mantle Structure ◽  
Finite Frequency ◽  
Upper Mantle Structure

Structure of the upper mantle in the Circum-Arctic region from regional seismic tomography

2012 ◽  
Vol 53 (10) ◽  
pp. 963-971 ◽  
Author(s):  
A.V. Jakovlev ◽  
N.A. Bushenkova ◽  
I.Yu. Koulakov ◽  
N.L. Dobretsov
Keyword(s):  
Seismic Tomography ◽  
Upper Mantle ◽  
Arctic Region

Heat flow in the Bushveld Complex, South Africa: implications for upper mantle structure

2017 ◽  
Vol 120 (3) ◽  
pp. 351-370 ◽  
Author(s):  
M.Q.W. Jones
Keyword(s):  
South Africa ◽  
Thermal Conductivity ◽  
Heat Flux ◽  
Heat Flow ◽  
Seismic Tomography ◽  
Upper Mantle ◽  
Bushveld Complex ◽  
Kaapvaal Craton ◽  
Flow Measurements ◽  
Witwatersrand Basin

Abstract Geothermal measurements in South Africa since 1939 have resulted in a good coverage of heat flow observations. The Archaean Kaapvaal Craton, in the central part of South Africa, is the best-studied tectonic domain, with nearly 150 heat flow measurements. The greatest density of heat flow sites is in the Witwatersrand Basin goldfields, where geothermal data are essential for determining refrigeration requirements of deep (up to 4 km) gold mines; the average heat flow is 51 ± 6mWm-2. The Bushveld Complex north of the Witwatersrand Basin is an extensive 2.06 Ga ultramafic-felsic intrusive complex that hosts the world’s largest reserves of platinum. The deepest platinum mines reach ~2 km and the need for thermal information for mine refrigeration engineering has led to the generation of a substantial geothermal database. Nearly 1000 thermal conductivity measurements have been made on rocks constituting the Bushveld Complex, and borehole temperature measurements have been made throughout the Complex. The temperature at maximum rock-breaking depth (~2.5 km) is 70°C, approximately 30°C higher than the temperature at equivalent depth in the Witwatersrand Basin; the thermal gradient in the Bushveld Complex is approximately double that in the Witwatersrand Basin. The main reason for this is the low thermal conductivity of rocks overlying platinum mines. The Bushveld data also resulted in 31 new estimates for the heat flux through the Earth’s crust. The overall average value for the Bushveld, 47 ± 7 mW m-2, is the same, to within statistical error, as the Witwatersrand Basin average. The heat flow for platinum mining areas (45 mW m-2) and the heat flux into the floor of the Witwatersrand Basin (43 mW m-2) are typical of Archaean cratons world-wide. The temperature structure of the Kaapvaal lithosphere calculated from the Witwatersrand geothermal data is essentially the same as that derived from thermobarometric studies of Cretaceous kimberlite xenoliths. Both lines of evidence lead to an estimated heat flux of ~17 mW m-2 for the mantle below the Kaapvaal Craton. The estimated thermal thickness of the Kaapvaal lithosphere (235 km) is similar to that defined on the basis of seismic tomography and magnetotelluric studies. The lithosphere below the Bushveld Complex is not significantly hotter than that below the Witwatersrand Basin. This favours a chemical origin rather than a thermal origin for the upper mantle anomaly below the Bushveld Complex that has been identified by seismic tomography studies and magnetotelluric soundings.

Deep Mantle Dynamics in East Asia: Numerical Simulation of Mantle Convection Based on Seismic Tomography

2020 ◽  
Author(s):  
Huai Zhang ◽  
Qunfan Zheng ◽  
Zhen Zhang
Keyword(s):  
East Asia ◽  
Seismic Tomography ◽  
Upper Mantle ◽  
Continental Collision ◽  
Indian Plate ◽  
Mantle Flow ◽  
Lithospheric Deformation ◽  
Mantle Dynamics ◽  
Asthenospheric Mantle ◽  
Deep Mantle

<p>East Asia is a tectonically active area on earth and has a complicated lithospheric deformation due to the western continental collision from the cratonic Indian plate and the eastern oceanic subduction mainly from Pacific plate. Studies have suggested that the Indo–Asian continental collision may have driven significant lateral mantle flow, but the velocity, range and effect of the mantle flow remain uncertain. Hence, a series of 3-D numerical models are conducted in this study to reveal the impacts of the Indo–Asian collision on mantle dynamics beneath the East Asia, especially on the asthenospheric mantle. Global model domain encompasses the lithosphere, upper mantle and the lower mantle with different viscosity for each layer. A global temperature structure built from seismic tomography and absolute plate field are applied subsequently to get a better constraint of the initial temperature condition and surficial velocity boundary condition. Thus, the reasonable velocity and temperature distributions of upper mantle beneath East Asia at different depths are retrieved based on our 3-D global mantle flow simulations, and the key controlling parameters in shaping the present-day observed mantle structure are investigated. The results show different scales of convection beneath East Asia.</p><p>Our results suggest that Indo–Asian collision may have induced mantle flow beneath the Indian plate and the different velocity structures between the asthenosphere and lithosphere indicate the shear drag of asthenospheric mantle. That may explain the reason that Indo–Asian collision has occurred since 50 Ma, and this collision can still continue to accelerate in the Tibetan Plateau. The simulation results also show the lithospheric delamination and the induced mantle upwelling, which is consistent with the general understanding from previous observations. The Indian lithosphere and its asthenosphere move northward, while the Yunnan lithosphere and its asthenosphere move southward, that may reflect the differences in deep mantle dynamics between the eastern and western Himalayan Syntaxis.</p>

Unraveling the upper mantle heterogeneity from integrated multi-observable inversions

2020 ◽  
Author(s):  
Javier Fullea ◽  
Sergei Lebedev ◽  
Zdenek Martinec ◽  
Nicolas Celli
Keyword(s):  
Seismic Tomography ◽  
Upper Mantle ◽  
Plate Tectonics ◽  
Seismic Velocity ◽  
Gravity Data ◽  
Density Field ◽  
Seismic Velocities ◽  
Satellite Gravity ◽  
The Earth ◽  
Multiple Data Sets

<p>The lateral and vertical thermochemical heterogeneity in the mantle is a long standing question in geodynamics. The forces that control mantle flow and therefore Plate Tectonics arise from the density and viscosity lateral and vertical variations. A common approach to estimate the density field for geodynamical purposes is to simply convert seismic tomography anomalies sometimes assuming constraints from mineral physics. Such converted density field does not match in general with the observed gravity field, typically predicting anomalies the amplitudes of which are too large. Knowledge on the lateral variations in lithospheric density is essential to understand the dynamic/residual isostatic components of the Earth’s topography linking deep and surface processes. The cooling of oceanic lithosphere, the bathymetry of mid oceanic ridges, the buoyancy and stability of continental cratons or the thermochemical structure of mantle plumes are all features central to Plate Tectonics that are dramatically related to mantle temperature and composition.</p><p><br>Conventional methods of seismic tomography, topography and gravity data analysis constrain distributions of seismic velocity and density at depth, all depending on temperature and composition of the rocks within the Earth. However, modelling and interpretation of multiple data sets provide a multifaceted image of the true thermochemical structure of the Earth that needs to be appropriately and consistently integrated. A simple combination of gravity, petrological and seismic models alone is insufficient due to the non-uniqueness and different sensitivities of these models, and the internal consistency relationships that must connect all the intermediate parameters describing the Earth involved. In fact, global Earth models based on different observables often lead to rather different, even contradictory images of the Earth.</p><p><br> Here we present a new global thermochemical model of the lithosphere-upper mantle (WINTERC-grav) constrained by state-of-the-art global waveform tomography, satellite gravity (geoid and gravity anomalies and gradiometric measurements from ESA's GOCE mission), surface elevation and heat flow data. WINTERC-grav is based upon an integrated geophysical-petrological approach where all relevant rock physical properties modelled (seismic velocities and density) are computed within a thermodynamically self-consistent framework allowing for a direct parameterization of the temperature and composition variables.</p>

Seismic Tomography of the Crust and Upper Mantle Structure Underneath the Chinese Tianshan

2006 ◽  
Vol 49 (6) ◽  
pp. 1543-1551 ◽  
Author(s):  
Biao GUO ◽  
Qi-Yuan LIU ◽  
Jiu-Hui CHEN ◽  
Da-Peng ZHAO ◽  
Shun-Cheng LI ◽  
...  
Keyword(s):  
Seismic Tomography ◽  
Upper Mantle ◽  
Mantle Structure ◽  
Crust And Upper Mantle ◽  
Upper Mantle Structure ◽  
Chinese Tianshan
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