Imperial College London
Alternate

Dr Ian Bastow

Faculty of Engineering, Department of Earth Science & Engineering

Senior Lecturer
 
 
 
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Contact

 

+44 (0)20 7594 2974i.bastow Website

 
 
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Location

 

4.45Royal School of MinesSouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Bernardino:2019:10.1130/GES02093.1,
author = {Bernardino, M and Jones, C and Levandowski, W and Bastow, I and Owens, T and Gilbert, H},
doi = {10.1130/GES02093.1},
journal = {Geosphere},
pages = {2018--2042},
title = {A multicomponent Isabella anomaly: Resolving the physical state of the Sierra Nevada upper mantle from Vp/Vs anisotropy tomography},
url = {http://dx.doi.org/10.1130/GES02093.1},
volume = {15},
year = {2019}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - The Isabella anomaly, a prominent upper-mantle high-speed P-wave anomaly located within the southern Great Valley and southwestern foothills of the Sierra Nevada, has been interpreted either as foundering sub-Sierranlithosphere or as remnant oceanic lithosphere. We used Vp/Vs anisotropytomography to distinguish among the probable origins of the Isabella anomaly.S waveforms were rotated into the Sierran SKSFast and SKSSlow directionsdetermined from SKS-splitting studies. Teleseismic P-, SFast-, SSlow-, SKSFast-, andSKSSlow-wave arrival times were then inverted to obtain three-dimensional(3-D) perturbations in Vp, Vp/VsMean, and percent azimuthal anisotropy usingthree surface wave 3-D starting models and one one-dimensional (1-D) model.We observed the highest Vp/Vs anomalies associated with slower velocitiesin regions marked by young volcanism, with the largest of these anomaliesbeing the Mono anomaly under the Long Valley region, which extends todepths of at least 75 km. Peak Vp/Vs perturbations of +4% were found at 40km depth. The low velocities and high Vp/Vs values of this anomaly couldbe related to partial melt.The high wave speeds of the Isabella anomaly coincide with low Vp/Vsvalues with peak perturbations of −2%, yet they do not covary spatially. TheP-wave inversion imaged the Isabella anomaly as a unimodal eastward-plungingbody. However, the volume of that Isabella anomaly contains three separatebodies as defined by varying Vp/Vs values. High speeds, regionally averageVp/Vs values (higher than the other two anomalies), and lower anisotropycharacterize the core of the Isabella anomaly. The western and shallowestpart has high wave speeds and a lower Vp/Vs values than the surroundingmantle. The eastern and deepest part of the anomaly also contains highspeeds and lower Vp/Vs values but exhibits higher anisotropy. We consideredcombinations of varying temperature, Mg content (melt depletion), or modalgarnet to reproduce our observations. Our results suggest t
AU  - Bernardino,M
AU  - Jones,C
AU  - Levandowski,W
AU  - Bastow,I
AU  - Owens,T
AU  - Gilbert,H
DO  - 10.1130/GES02093.1
EP  - 2042
PY  - 2019///
SN  - 1553-040X
SP  - 2018
TI  - A multicomponent Isabella anomaly: Resolving the physical state of the Sierra Nevada upper mantle from Vp/Vs anisotropy tomography
T2  - Geosphere
UR  - http://dx.doi.org/10.1130/GES02093.1
UR  - http://hdl.handle.net/10044/1/74090
VL  - 15
ER  -
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