{"id":2802,"date":"2021-01-28T15:08:58","date_gmt":"2021-01-28T22:08:58","guid":{"rendered":"http:\/\/faculty.epss.ucla.edu\/~cbeghein\/?page_id=2802"},"modified":"2021-10-13T07:59:15","modified_gmt":"2021-10-13T14:59:15","slug":"upper-mantle-radial-anisotropy-under-the-indian-ocean","status":"publish","type":"page","link":"https:\/\/faculty.epss.ucla.edu\/~cbeghein\/research\/regional-tomography\/upper-mantle-radial-anisotropy-under-the-indian-ocean\/","title":{"rendered":"Upper Mantle Radial Anisotropy Under the Indian Ocean"},"content":{"rendered":"

Model Download: the distributions of velocity and radial anisotropy models obtained with a fully non-linear transdismensional model space search approach for the Indian Ocean can be found here<\/a>.<\/span><\/span><\/p>\n

Citation<\/b>: \"lnk\"<\/a><\/p>\n

Weidner, E., Beghein, C<\/strong>., Huang, Q., and Schmerr, N. (2021), Upper Mantle Radial Anisotropy Under the Indian Ocean from Higher Mode Surface Waves and a Hierarchical Transdismensional Approach, Geophys. J. Int.<\/em>,\u00a0228<\/b>(1), 78-101, doi:10.1093\/gji\/ggab340<\/a><\/p>\n

Summary:<\/strong><\/p>\n

In this project, we investigated the likelihood of radial anisotropy in the shallow and deep upper\u00a0mantle, including the mantle transition zone (MTZ) under the Indian Ocean. Seismic anisotropy can be an indicator of mantle deformation through lattice preferred\u00a0orientation of anisotropic crystals in the mantle. It has thus the potential to illuminate Earth’s dynamic interior, but previous seismic tomography studies have not\u00a0achieved consensus on the existence of radial anisotropy below \u00a0<\/span>250 km depth. We\u00a0developed a fully non-linear transdimensional hierarchical Bayesian Markov Chain\u00a0Monte Carlo approach to invert fundamental and higher mode surface wave dispersion data and applied it to a subset of a global Love and Rayleigh wave dataset.<\/p>\n

We obtained posterior model parameter distributions for shear-wave velocity (Vs)\u00a0and radial anisotropy \u00a0<\/span>under the Indian Ocean. These posterior model distributions were used to calculate the probability of having radial anisotropy at different\u00a0depths. We demonstrated that separate inversions of Love and Rayleigh waves yield\u00a0models compatible with the results of joint inversions within uncertainties. The\u00a0obtained pattern of Vs anomalies agrees with previous studies.\u00a0They display negative anomalies along ridges in the uppermost mantle, but those are stronger than\u00a0for regularized inversions. The Central Indian Ridge and the Southeastern Indian\u00a0Ridge present velocity anomalies that extend to \u00a0<\/span>200 km depth whereas the Southwestern Indian Ridge seems to have a shallower origin. Weaker, laterally variable\u00a0velocity perturbations were found at larger depths.<\/p>\n

The anisotropy models differ\u00a0more strongly from regularized inversion results, especially below 100 km depth.\u00a0Apart from a fast horizontally polarized shear-wave signal in the top 100 km, likely\u00a0reflecting the horizontal plate motion due to asthenospheric deformation, no clear\u00a0relation to surface geology was detected in the anisotropy models. We found that,\u00a0although the anisotropy model uncertainties are rather large, and lateral variations\u00a0are present, the data generally prefer at least 1% anisotropy in the MTZ with fast\u00a0vertically polarized shear waves, within errors. Incorporating group velocity data\u00a0did not help better constrain deep structure by reducing parameter trade-os. We\u00a0also tested the effect of prior constraints on the 410- and 660-km topography and\u00a0found that the undulations of these discontinuities had little effect on the resulting\u00a0models.<\/p>\n

 <\/p>\n","protected":false},"excerpt":{"rendered":"

Model Download: the distributions of velocity and radial anisotropy models obtained with a fully non-linear transdismensional model space search approach for the Indian Ocean can be found here. Citation: Weidner, E., Beghein, C., Huang, Q., and Schmerr, N. (2021), Upper Mantle Radial Anisotropy Under the Indian Ocean from Higher Mode Surface Waves and a Hierarchical … <\/p>\n

Read more “Upper Mantle Radial Anisotropy Under the Indian Ocean”<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"parent":66,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"inspiro_hide_title":false,"footnotes":""},"class_list":["post-2802","page","type-page","status-publish","hentry"],"jetpack_sharing_enabled":true,"featured_media_urls":[],"_links":{"self":[{"href":"https:\/\/faculty.epss.ucla.edu\/~cbeghein\/wp-json\/wp\/v2\/pages\/2802","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/faculty.epss.ucla.edu\/~cbeghein\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/faculty.epss.ucla.edu\/~cbeghein\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/faculty.epss.ucla.edu\/~cbeghein\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/faculty.epss.ucla.edu\/~cbeghein\/wp-json\/wp\/v2\/comments?post=2802"}],"version-history":[{"count":9,"href":"https:\/\/faculty.epss.ucla.edu\/~cbeghein\/wp-json\/wp\/v2\/pages\/2802\/revisions"}],"predecessor-version":[{"id":2933,"href":"https:\/\/faculty.epss.ucla.edu\/~cbeghein\/wp-json\/wp\/v2\/pages\/2802\/revisions\/2933"}],"up":[{"embeddable":true,"href":"https:\/\/faculty.epss.ucla.edu\/~cbeghein\/wp-json\/wp\/v2\/pages\/66"}],"wp:attachment":[{"href":"https:\/\/faculty.epss.ucla.edu\/~cbeghein\/wp-json\/wp\/v2\/media?parent=2802"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}