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[SCG49-P08] 3D model of changes in the slab bending moments before and after the occurrence of M9 interplate earthquake at subduction zones
Keywords:subduction zone, M9 class interplate earthquake, bending moment of slab , inelastic deformation
In this study, we consider the slab deformation mode before and after the M9 class interplate earthquake at tightly coupled subduction zones, focusing on the bending moment.
For example, in the case of a subduction zone with the averaged relative plate motion rate of 10 [cm/y], the recurrence period of the M9 interplate event is considered to be approximately 1 x 103 [y]. In this case, total horizontal displacement due to relative plate motion during 1 x 103 [y] reaches 1x102 [m].
Early geophysical studies on bending stress changes within the oceanic lithosphere before and after a larger or greater interplate earthquake at subduction zones such as those by Eguchi et al. (1987a, 1987b), Eguchi (1987), Dmowska et al. (1988), Lay et al. (1989, 2009) and Eguchi (1998) were mainly based on mechanical models for a two- dimensional vertical cross-section in the trench-normal direction. However, these early studies are not sufficient to identify the three-dimensional spatiotemporal changes in bending moments in oceanic plates before and after the M9 interplate earthquake at (tightly) coupled subduction zones such as the Japan, western Java, and Chile trench systems.
We classify the three-dimensional slab bending moments as follows, according to the mechanical source(s) of the bending and the affected region(s). However, the classified bending moments are not always independent of each other.
(1) Bending moments related to the formation of outer rise terrain and trench axis due to the buckling of three-dimensional spherical shell.
(Affected areas; from the shallow area of plate interface to the outer rise area)
The dynamics of slab bending (spherical shell buckling) would depend on the age of the subducting ocean lithosphere (slab age), that is, the “effective elastic-layer thickness” (EET) of the ocean lithosphere, as well as the flexural rigidity, D, (depending on EET), etc.
(2) Spatiotemporal changes in bending moments within the slab before and after a M9 earthquake.
(Wide area including the plate interface of the slab and the entire outer rise)
2-1. Bending moment due to mechanical integration at the plate interface.
2-2. Local bending moment due to "horizontal indentation" of oceanic lithosphere into the forearc region.
2-3. Transient bending moment just below (deeper) side of the "fault plane of the forthcoming M9 class interplate earthquake".
2-4. Others. (Deflexing moments due to M8 interplate seismic events, etc.)
For example, in the case of a subduction zone with the averaged relative plate motion rate of 10 [cm/y], the recurrence period of the M9 interplate event is considered to be approximately 1 x 103 [y]. In this case, total horizontal displacement due to relative plate motion during 1 x 103 [y] reaches 1x102 [m].
Early geophysical studies on bending stress changes within the oceanic lithosphere before and after a larger or greater interplate earthquake at subduction zones such as those by Eguchi et al. (1987a, 1987b), Eguchi (1987), Dmowska et al. (1988), Lay et al. (1989, 2009) and Eguchi (1998) were mainly based on mechanical models for a two- dimensional vertical cross-section in the trench-normal direction. However, these early studies are not sufficient to identify the three-dimensional spatiotemporal changes in bending moments in oceanic plates before and after the M9 interplate earthquake at (tightly) coupled subduction zones such as the Japan, western Java, and Chile trench systems.
We classify the three-dimensional slab bending moments as follows, according to the mechanical source(s) of the bending and the affected region(s). However, the classified bending moments are not always independent of each other.
(1) Bending moments related to the formation of outer rise terrain and trench axis due to the buckling of three-dimensional spherical shell.
(Affected areas; from the shallow area of plate interface to the outer rise area)
The dynamics of slab bending (spherical shell buckling) would depend on the age of the subducting ocean lithosphere (slab age), that is, the “effective elastic-layer thickness” (EET) of the ocean lithosphere, as well as the flexural rigidity, D, (depending on EET), etc.
(2) Spatiotemporal changes in bending moments within the slab before and after a M9 earthquake.
(Wide area including the plate interface of the slab and the entire outer rise)
2-1. Bending moment due to mechanical integration at the plate interface.
2-2. Local bending moment due to "horizontal indentation" of oceanic lithosphere into the forearc region.
2-3. Transient bending moment just below (deeper) side of the "fault plane of the forthcoming M9 class interplate earthquake".
2-4. Others. (Deflexing moments due to M8 interplate seismic events, etc.)