Metastable olivine wedge beneath the Japan Sea imaged by seismic interferometry

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Authors

Zhichao Shen , Zhongwen Zhan

Abstract

The metastable olivine wedge (MOW) within subducted slabs has long been hypothesized to host deep-focus earthquakes (>300 km). Its presence would also rule out hydrous slabs being subducted into the mantle transition zone. However, the existence and dimensions of MOW remain controversial. Here, we apply inter-source interferometry, which converts deep earthquakes into virtual seismometers, to detect the seismic signature of MOW without influence from shallow heterogeneities. With data from the Hinet, we confirm the existence of MOW beneath the Japan Sea and constrain its geometry to be ~30 km thick at 410-km depth and gradually diminishing to a depth of 610 km at least. Our result supports transformational faulting of metastable olivine as the initiation mechanism of deep earthquakes, although large events (M7.0+) probably rupture beyond the wedge. Furthermore, the slab core must be dehydrated at shallower depth and only transports negligible amount of water into the transition zone.

DOI

https://doi.org/10.31223/osf.io/d5r6t

Subjects

Earth Sciences, Geophysics and Seismology, Physical Sciences and Mathematics

Keywords

interferometry, deep earthquake, metastable olivine, Subduction process

Dates

Published: 2019-10-08 07:51

License

CC BY Attribution 4.0 International

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