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- Title
Three‐Dimensional S Velocity Structure of the Mantle Transition Zone Beneath Central America and the Gulf of Mexico Inferred Using Waveform Inversion.
- Authors
Borgeaud, Anselme F. E.; Kawai, Kenji; Geller, Robert J.
- Abstract
Travel time tomography studies have reported various modes of subduction of slabs around the mantle transition zone, but the causes of this variability are still controversial. In order to place additional constraints on the style of subduction in and near the mantle transition zone, we apply waveform inversion to S wave triplications due to the 410‐ and 660‐km discontinuities, and infer the regional three‐dimensional S velocity structure in the depth range 370–820 km beneath Central America and the Gulf of Mexico. We use ~3,400 transverse component records at epicentral distances 17–30° from 20 intermediate focus earthquakes beneath Central America recorded at stations of the USArray and other smaller networks. We filter the records between 20 and 100 s, and use the portions of the waveforms from 10 s before to ~40–80 s after the arrival of the direct S wave, thereby including the S wave triplications while excluding the sS depth phase. We correct the data for the structure above our target region using previous S velocity models, and we show that the results of the inversion do not depend heavily on which correction is used. Resolution tests confirm that we can resolve small‐scale structure in the target region. Our inferred models show that the Cocos slab penetrates into the lower mantle, but with important variations along the Middle America Trench in the subduction style of the slab. We suggest that this variability could be due to the thermal structure of the Cocos slab, and to the interaction of the slab with a possible lower mantle plume. Key Points: We infer detailed 3‐D S velocity structure of the mantle transition zone using waveform inversion of S wave triplications from the USArrayOur images suggest variations in subduction style along the trench related to change in Cocos plate velocity at ~10 MaSubduction style of the Cocos slab might be controlled by variation in plate age along the trench, and a lower mantle plume
- Subjects
TOMOGRAPHY; SUBDUCTION; DISCONTINUITIES (Geology); CONSTRUCTION slabs; MANTLE plumes
- Publication
Journal of Geophysical Research. Solid Earth, 2019, Vol 124, Issue 9, p9664
- ISSN
2169-9313
- Publication type
Article
- DOI
10.1029/2018JB016924