Signature of remnant slabs in the North Pacific from P‐wave tomography

TLDR: In this article, a 3D ray-tracing technique was used in a global tomographic inversion in order to obtaintomographic images of the North Pacific, and the final data set, used for following the inversion, contained 523430 summary ray paths.

Abstract: SUMMARY A 3-D ray-tracing technique was used in a global tomographic inversion in order to obtaintomographicimagesoftheNorthPacific.ThedatareportedbytheGeophysical SurveyofRussia(1955‐1997)wereusedtogetherwiththecataloguesoftheInternational SeismologicalCenter(1964‐1991)andtheUSGeologicalSurveyNationalEarthquake Information Center (1991‐1998), and the recompiled catalogue was reprocessed. The final data set, used for following the inversion, contained 523430 summary ray paths. The whole of the Earth’s mantle was parametrized by cells of 2°◊2° and 19 layers. The large and sparse system of observation equations was solved using an iterative LSQR algorithm. Asubhorizontalhigh-velocityanomalyisrevealedjustabovethe660kmdiscontinuity beneaththeAleutiansubductionzone.Thishigh-velocityfeatureisobservedatlatitudes of up to~70°N and is interpreted as a remnant of the subducted Kula plate, which disappeared through ridge subduction at about 48Ma. A further positive velocity perturbation feature can be identified beneath the Chukotka peninsula and Okhotsk Sea, extending from~300 to~660km depth and then either extending further down to~800km (Chukotka) or deflecting along the 660km discontinuity (Okhotsk Sea). This high-velocity anomaly is interpreted as a remnant slab of the Okhotsk plate accreted to Siberia at~55Ma.