2D stress rotation in the Tonga subduction region

Jakub Pokorný; Hana Čížková; Craig R. Bina; Arie van den Berg

doi:10.1016/j.epsl.2023.118379

2D stress rotation in the Tonga subduction region

Jakub Pokorný^*, Hana Čížková, Craig R. Bina, Arie van den Berg

^*Corresponding author for this work

Earth and Planetary Sciences

Research output: Contribution to journal › Article › peer-review

3 Scopus citations

Abstract

Despite their enigmatic origins, deep earthquakes provide unique information about the stress distribution in slabs. Down-dip compression is expected at depth, due to resistance from endothermic phase transition near 660 km and increasing viscosity. Focal mechanisms for ordinary deep (620-680 km) earthquakes in the Tonga subduction zone exhibit down-dip compressional stresses in agreement with this expectation, but unusually deep (≥ 680 km) earthquakes exhibit vertical tension and horizontal compression. Here we present a numerical modelling study of the Tonga slab focused on stress patterns in the transition zone. The subducting Pacific plate is one of the oldest and thus coldest plates in the world, so our parametric study tests the effects of rheology and phase transitions on stress evolution for an exceptionally cold subducting plate. Our results suggest that direct buoyancy effects from the endothermic phase transition at 660 km depth are overprinted by bending-related forces. A stress pattern best fitting seismogenic stresses is found for the coldest tested subducting plate (150 Myr old) and a viscosity interface decoupled from the 660-km phase transition and shifted to 1000-km depth. An abrupt change of stress orientations is observed when the slab, temporarily deflected by the phase transition, penetrates to the shallow lower mantle and the fold of the flat-lying part is tightening.

Original language	English (US)
Article number	118379
Journal	Earth and Planetary Science Letters
Volume	621
DOIs	https://doi.org/10.1016/j.epsl.2023.118379
State	Published - Nov 1 2023

Funding

We thank Michael Gurnis and an anonymous reviewer for comments that helped to improve the manuscript substantially. CRB is grateful to Prof. Yoshio Fukao for inspiring discussions during a visit in March 2014. This work was supported by the Charles University Grant Agency under grant number 36121 , grant SVV 260709 , The Netherlands Research Centre for Integrated Solid Earth Science , and by The Ministry of Education, Youth and Sports of the Czech Republic through the program INTER-EXCELLENCE II (grant LUAUS23233 ). Tomographic images were plotted with a SubMachine web tool ( https://www.earth.ox.ac.uk/~smachine/cgi/index.php ). Model stress figures were produced using the Generic Mapping Tool (GMT) software ( https://www.generic-mapping-tools.org ). We thank Michael Gurnis and an anonymous reviewer for comments that helped to improve the manuscript substantially. CRB is grateful to Prof. Yoshio Fukao for inspiring discussions during a visit in March 2014. This work was supported by the Charles University Grant Agency under grant number 36121, grant SVV 260709, The Netherlands Research Centre for Integrated Solid Earth Science, and by The Ministry of Education, Youth and Sports of the Czech Republic through the program INTER-EXCELLENCE II (grant LUAUS23233). Tomographic images were plotted with a SubMachine web tool (https://www.earth.ox.ac.uk/~smachine/cgi/index.php). Model stress figures were produced using the Generic Mapping Tool (GMT) software (https://www.generic-mapping-tools.org).

Keywords

Tonga subduction region
deep earthquakes
stress orientation
subduction dynamics
transition zone

ASJC Scopus subject areas

Geophysics
Geochemistry and Petrology
Space and Planetary Science
Earth and Planetary Sciences (miscellaneous)

Access to Document

10.1016/j.epsl.2023.118379

Cite this

@article{d1ce000fd97d426f875c6591f6bd63f0,

title = "2D stress rotation in the Tonga subduction region",

abstract = "Despite their enigmatic origins, deep earthquakes provide unique information about the stress distribution in slabs. Down-dip compression is expected at depth, due to resistance from endothermic phase transition near 660 km and increasing viscosity. Focal mechanisms for ordinary deep (620-680 km) earthquakes in the Tonga subduction zone exhibit down-dip compressional stresses in agreement with this expectation, but unusually deep (≥ 680 km) earthquakes exhibit vertical tension and horizontal compression. Here we present a numerical modelling study of the Tonga slab focused on stress patterns in the transition zone. The subducting Pacific plate is one of the oldest and thus coldest plates in the world, so our parametric study tests the effects of rheology and phase transitions on stress evolution for an exceptionally cold subducting plate. Our results suggest that direct buoyancy effects from the endothermic phase transition at 660 km depth are overprinted by bending-related forces. A stress pattern best fitting seismogenic stresses is found for the coldest tested subducting plate (150 Myr old) and a viscosity interface decoupled from the 660-km phase transition and shifted to 1000-km depth. An abrupt change of stress orientations is observed when the slab, temporarily deflected by the phase transition, penetrates to the shallow lower mantle and the fold of the flat-lying part is tightening.",

keywords = "Tonga subduction region, deep earthquakes, stress orientation, subduction dynamics, transition zone",

author = "Jakub Pokorn{\'y} and Hana {\v C}{\'i}{\v z}kov{\'a} and Bina, {Craig R.} and {van den Berg}, Arie",

note = "Publisher Copyright: {\textcopyright} 2023 Elsevier B.V.",

year = "2023",

month = nov,

day = "1",

doi = "10.1016/j.epsl.2023.118379",

language = "English (US)",

volume = "621",

journal = "Earth and Planetary Science Letters",

issn = "0012-821X",

publisher = "Elsevier",

}

TY - JOUR

T1 - 2D stress rotation in the Tonga subduction region

AU - Pokorný, Jakub

AU - Čížková, Hana

AU - Bina, Craig R.

AU - van den Berg, Arie

PY - 2023/11/1

Y1 - 2023/11/1

N2 - Despite their enigmatic origins, deep earthquakes provide unique information about the stress distribution in slabs. Down-dip compression is expected at depth, due to resistance from endothermic phase transition near 660 km and increasing viscosity. Focal mechanisms for ordinary deep (620-680 km) earthquakes in the Tonga subduction zone exhibit down-dip compressional stresses in agreement with this expectation, but unusually deep (≥ 680 km) earthquakes exhibit vertical tension and horizontal compression. Here we present a numerical modelling study of the Tonga slab focused on stress patterns in the transition zone. The subducting Pacific plate is one of the oldest and thus coldest plates in the world, so our parametric study tests the effects of rheology and phase transitions on stress evolution for an exceptionally cold subducting plate. Our results suggest that direct buoyancy effects from the endothermic phase transition at 660 km depth are overprinted by bending-related forces. A stress pattern best fitting seismogenic stresses is found for the coldest tested subducting plate (150 Myr old) and a viscosity interface decoupled from the 660-km phase transition and shifted to 1000-km depth. An abrupt change of stress orientations is observed when the slab, temporarily deflected by the phase transition, penetrates to the shallow lower mantle and the fold of the flat-lying part is tightening.

AB - Despite their enigmatic origins, deep earthquakes provide unique information about the stress distribution in slabs. Down-dip compression is expected at depth, due to resistance from endothermic phase transition near 660 km and increasing viscosity. Focal mechanisms for ordinary deep (620-680 km) earthquakes in the Tonga subduction zone exhibit down-dip compressional stresses in agreement with this expectation, but unusually deep (≥ 680 km) earthquakes exhibit vertical tension and horizontal compression. Here we present a numerical modelling study of the Tonga slab focused on stress patterns in the transition zone. The subducting Pacific plate is one of the oldest and thus coldest plates in the world, so our parametric study tests the effects of rheology and phase transitions on stress evolution for an exceptionally cold subducting plate. Our results suggest that direct buoyancy effects from the endothermic phase transition at 660 km depth are overprinted by bending-related forces. A stress pattern best fitting seismogenic stresses is found for the coldest tested subducting plate (150 Myr old) and a viscosity interface decoupled from the 660-km phase transition and shifted to 1000-km depth. An abrupt change of stress orientations is observed when the slab, temporarily deflected by the phase transition, penetrates to the shallow lower mantle and the fold of the flat-lying part is tightening.

KW - Tonga subduction region

KW - deep earthquakes

KW - stress orientation

KW - subduction dynamics

KW - transition zone

UR - http://www.scopus.com/inward/record.url?scp=85172379660&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85172379660&partnerID=8YFLogxK

U2 - 10.1016/j.epsl.2023.118379

DO - 10.1016/j.epsl.2023.118379

M3 - Article

AN - SCOPUS:85172379660

SN - 0012-821X

VL - 621

JO - Earth and Planetary Science Letters

JF - Earth and Planetary Science Letters

M1 - 118379

ER -

2D stress rotation in the Tonga subduction region

Abstract

Funding

Keywords

ASJC Scopus subject areas

Access to Document

Other files and links

Fingerprint

Cite this