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From Slab Coupling to Slab Pull: Stress Segmentation in the Subducting Nazca Plate
Author(s) -
Bloch Wasja,
Schurr Bernd,
Kummerow Jörn,
Salazar Pablo,
Shapiro Serge A.
Publication year - 2018
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2018gl078793
Subject(s) - slab , geology , subduction , seismology , stress field , slab window , stress (linguistics) , fault (geology) , episodic tremor and slip , coupling (piping) , geophysics , tectonics , materials science , finite element method , oceanic crust , linguistics , physics , philosophy , thermodynamics , metallurgy
We investigate the stress field that the Nazca slab experiences during subduction beneath the South American plate by determining the focal mechanisms of moderate subduction‐related earthquakes continuously from 20‐ to 120‐km depth and inverting for the stress directions of four slab regions. Our results show the sharp termination of the coupling zone, which is characterized by compressional stresses, uplift of the overlying mountain range, and likely the activation of preexisting slab structures. Beyond and below this zone slab pull is the dominant stress. Near the slab surface, we also find signatures of the activation of inherited structures. Deeper in the slab, fault orientations are more likely controlled by the stress field alone. Along the subduction pathway, we find indication for an increase of the absolute slab pull component of the stress field that correlates with an increase in event rate and the occurrence possibility of M > 7 intermediate depth earthquakes.