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The isolated ∼680 km deep 30 May 2015 M_W 7.9 Ogasawara (Bonin) Islands earthquake

Ye, Lingling and Lay, Thorne and Zhan, Zhongwen and Kanamori, Hiroo and Hao, Jin-Lai (2016) The isolated ∼680 km deep 30 May 2015 M_W 7.9 Ogasawara (Bonin) Islands earthquake. Earth and Planetary Science Letters, 433 . pp. 169-179. ISSN 0012-821X. http://resolver.caltech.edu/CaltechAUTHORS:20160114-115759902

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Abstract

Deep-focus earthquakes, located in very high-pressure conditions 300 to 700 km below the Earth's surface within sinking slabs of relatively cold oceanic lithosphere, are mysterious phenomena. The largest recorded deep-focus earthquake (M_W 7.9) in the Izu–Bonin slab struck on 30 May 2015 beneath the Ogasawara (Bonin) Islands, isolated from prior seismicity by over 100 km in depth, and followed by only a few small aftershocks. Globally, this is the deepest (680 km centroid depth) event with M_W≥7.8 in the seismological record. Seismicity indicates along-strike contortion of the Izu–Bonin slab, with horizontal flattening near a depth of 550 km in the Izu region and rapid steepening to near-vertical toward the south above the location of the 2015 event. This event was exceptionally well-recorded by seismic stations around the world, allowing detailed constraints to be placed on the source process. Analyses of a large global data set of P, SH and pP seismic phases using short-period back-projection, subevent directivity, and broadband finite-fault inversion indicate that the mainshock ruptured a shallowly-dipping fault plane with patchy slip that spread over a distance of ∼40 km with a multi-stage expansion rate (∼5+ km/s down-dip initially, ∼3 km/s up-dip later). During the 17 s total rupture duration the radiated energy was ∼3.3×10^(16) J and the stress drop was ∼38 MPa. The radiation efficiency is moderate (0.34), intermediate to that of the 1994 Bolivia and 2013 Sea of Okhotsk M_W 8.3 deep earthquakes, indicating that source processes of very large deep earthquakes sample a wide range of behavior from dissipative, more viscous failure to very brittle failure. The isolated occurrence of the event, much deeper than the apparently thermally-bounded distribution of Bonin-slab seismicity above 600 km depth, suggests that localized stress concentration associated with the pronounced deformation of the Izu–Bonin slab and proximity to the 660-km phase transition likely played a dominant role in generating this major earthquake.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.epsl.2015.10.049DOIArticle
http://www.sciencedirect.com/science/article/pii/S0012821X15006858PublisherArticle
ORCID:
AuthorORCID
Ye, Lingling0000-0002-8739-2072
Lay, Thorne0000-0003-2360-4213
Kanamori, Hiroo0000-0001-8219-9428
Additional Information:© 2015 Elsevier B.V. Received 23 August 2015; Received in revised form 19 October 2015; Accepted 28 October 2015; Available online 9 November 2015. The IRIS DMS (http://www.iris.edu/hq/) and Orpheus (http://www.orfeus-eu.org) data centers were used to access the seismic data from Global Seismic Network and Federation of Digital Seis-mic Network stations, and the Hi-net data center (http://www.hinet.bosai.go.jp/about_data/?LANG=en) of NIED was used to ac-cess Hi-net recordings. The Data Management Centre of China National Seismic Network at Institute of Geophysics, China Earth-quake Administration, provided waveform data in China. This work made use of GMT and SAC software. K. Koper provided access to and training with his back-projection software. We thank an anonymous reviewer and H. Houston for helpful comments on the manuscript. This work was supported by NSF grant EAR1245717 (T.L.).
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
NSFEAR-1245717
Subject Keywords:deep earthquakes; Izu–Bonin slab; rupture process; slab deformation; transformational faulting
Record Number:CaltechAUTHORS:20160114-115759902
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20160114-115759902
Official Citation:Lingling Ye, Thorne Lay, Zhongwen Zhan, Hiroo Kanamori, Jin-Lai Hao, The isolated ∼680 km deep 30 May 2015 MW 7.9 Ogasawara (Bonin) Islands earthquake, Earth and Planetary Science Letters, Volume 433, 1 January 2016, Pages 169-179, ISSN 0012-821X, http://dx.doi.org/10.1016/j.epsl.2015.10.049. (http://www.sciencedirect.com/science/article/pii/S0012821X15006858)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:63688
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:14 Jan 2016 20:08
Last Modified:02 Oct 2017 20:12

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