Affiliation:
1. Department of Earth and Planetary Sciences Yale University New Haven CT USA
Abstract
AbstractUltralow velocity zones (ULVZs) and seismic anisotropy are both commonly detected in the lowermost mantle at the edges of the two antipodal large low velocity provinces (LLVPs). The preferential occurrences of both ULVZs and anisotropy at LLVP edges are potentially connected to deep mantle dynamics; however, the two phenomena are typically investigated separately. Here we use waveforms from three deep earthquakes to jointly investigate ULVZ structure and lowermost mantle anisotropy near an edge of the Pacific LLVP to the southeast of Hawaii. We model global wave propagation through candidate lowermost mantle structures using AxiSEM3D. Two structures that cause ULVZ‐characteristic postcursors in our data are identified and are modeled as cylindrical ULVZs with radii of ∼1° and ∼3° and velocity reductions of ∼36% and ∼20%. One of these features has not been detected before. The ULVZs are located to the south of Hawaii and are part of the previously detected complex low velocity structure at the base of the mantle in our study region. The waveforms also reveal that, to first order, the base of the mantle in our study region is a broad and thin region of modestly low velocities. Measurements of Sdiff shear wave splitting reveal evidence for lowermost mantle anisotropy that is approximately co‐located with ULVZ material. Our measurements of co‐located anisotropy and ULVZ material suggest plausible geodynamic scenarios for flow in the deep mantle near the Pacific LLVP edge.
Funder
Yale University
National Science Foundation
Publisher
American Geophysical Union (AGU)
Subject
Geochemistry and Petrology,Geophysics
Cited by
2 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献