Tonga Slab Morphology and Stress Variations Controlled by a Relic Slab: Implications for Deep Earthquakes in the Tonga‐Fiji Region
Abstract
Deep focus earthquakes within the Tonga‐Fiji subduction system account for about two‐thirds of the global total and provide significant constraints on slab deformation. The factors controlling the intense deformation remain unclear. Here, we use two‐dimensional, time‐dependent geodynamic models to study the morphology, stress state, and thermal structure of the Tonga‐Fiji subduction zone. The results, consistent with tomographic images and focal mechanisms, demonstrate that collision between a relic slab from the Vanuatu Trench and the Tonga slab may control the steeper dip of the Tonga slab and earthquakes in the mantle transition zone. We suggest that the magnitude 8.2 and 7.9 earthquakes in 2018 mostly ruptured within the warm rim of the Tonga slab and occurred beneath the folding relic slab with high temperatures of at least ∼900°C and ∼1100°C, respectively. The findings support the hypothesis that local slab temperature likely controls rupture of deep earthquakes.
Additional Information
© 2021 American Geophysical Union. Issue Online: 09 April 2021; Version of Record online: 09 April 2021; Accepted manuscript online: 22 March 2021; Manuscript accepted: 07 March 2021; Manuscript revised: 08 February 2021; Manuscript received: 19 October 2020. H. Liu's visit to Caltech was supported by the Strategic Priority Research Program of Chinese Academy of Sciences, Grant No. XDB 41000000 and the China Scholarship Council. Additional support provided by the National Science Foundation through award EAR‐1645775, and National Natural Science Foundation of China (41774105 and 41820104004). Data Availability Statement: The mantle convection code Citcom and the P wave tomography models are available at https://geodynamics.org/cig/and https://www.earth.ox.ac.uk/∼smachine/cgi/index.php, while model data files will be available at https://data.caltech.edu/Attached Files
Published - 2020GL091331.pdf
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Additional details
- Eprint ID
- 108522
- Resolver ID
- CaltechAUTHORS:20210323-070959264
- XDB 41000000
- Chinese Academy of Sciences
- China Scholarship Council
- EAR-1645775
- NSF
- 41774105
- National Natural Science Foundation of China
- 41820104004
- National Natural Science Foundation of China
- Created
-
2021-03-23Created from EPrint's datestamp field
- Updated
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2021-10-16Created from EPrint's last_modified field
- Caltech groups
- Seismological Laboratory, Division of Geological and Planetary Sciences