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The 2018 Fiji M_w 8.2 and 7.9 deep earthquakes: One doublet in two slabs

Jia, Zhe and Shen, Zhichao and Zhan, Zhongwen and Li, Chenyu and Peng, Zhigang and Gurnis, Michael (2020) The 2018 Fiji M_w 8.2 and 7.9 deep earthquakes: One doublet in two slabs. Earth and Planetary Science Letters, 531 . Art. No. 115997. ISSN 0012-821X. doi:10.1016/j.epsl.2019.115997.

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The cold Fiji-Tonga subduction zone accounts for >75% of cataloged deep earthquakes but none of the largest ten in the last century. On 19 August 2018 and 06 September 2018, a deep earthquake doublet with moment magnitude (M_w) 8.2 and 7.9 struck the Fiji area, providing a rare opportunity to interrogate the behaviors of great deep earthquakes in cold slabs. While the aftershock productivity of the 2018 M_w 8.2 event is similar to the 2013 Okhotsk M_w 8.3 event in a cold slab, the inferred compact rupture dimensions of both the M_w 8.2 and 7.9 events appear to be similar to the 1994 Bolivia earthquake in a warm slab. This seems to contradict the traditional view that slab temperature controls deep earthquakes. However, we find that neither event was confined within the cold Tonga slab core: the M_w 8.2 ruptured mostly in the warmer rim of the Tonga slab and the M_w 7.9 occurred in a warm relic slab leaning on top of the Tonga slab. The Fiji doublet demonstrates local slab temperature as the critical factor for deep earthquakes, and reveals complex interaction of subducted slabs in Tonga.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Jia, Zhe0000-0003-0652-2646
Shen, Zhichao0000-0003-0458-5264
Zhan, Zhongwen0000-0002-5586-2607
Li, Chenyu0000-0002-0442-6928
Peng, Zhigang0000-0002-0019-9860
Gurnis, Michael0000-0003-1704-597X
Additional Information:© 2019 Elsevier B.V. Received 18 February 2019, Revised 18 November 2019, Accepted 28 November 2019, Available online 9 December 2019. We thank Yunyi Qian for sharing the Multitel3 code. We thank Stephen C. Myers and Douglas Wiens for sharing the aftershock catalog of 1994 Bolivia and 1994 Tonga earthquakes, and Lingsen Meng for sharing their unpublished result. We thank Hiroo Kanamori, Chen Ji and Robert Clayton for helpful discussions. We thank three anonymous reviewers and editor Miaki Ishii for their helpful comments. Seismic recordings are from the IRIS data management center. The earthquake catalogs are from the U.S. Geological Survey (USGS) National Earthquake Information Center (NEIC) and the International Seismological Center (ISC). This work is supported by USGS grant G19AP00030. C.L. and Z.P. are partially supported by NSF grants EAR-1818611 and EAR-1925965.
Group:Seismological Laboratory
Funding AgencyGrant Number
Subject Keywords:deep earthquakes; rupture process; earthquake doublet; Tonga slab; slab temperature
Record Number:CaltechAUTHORS:20191209-101229706
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Official Citation:Zhe Jia, Zhichao Shen, Zhongwen Zhan, Chenyu Li, Zhigang Peng, Michael Gurnis, The 2018 Fiji Mw 8.2 and 7.9 deep earthquakes: One doublet in two slabs, Earth and Planetary Science Letters, Volume 531, 2020, 115997, ISSN 0012-821X, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:100236
Deposited By: Tony Diaz
Deposited On:09 Dec 2019 18:29
Last Modified:16 Nov 2021 17:52

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