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TitleCompliant volcanic arc and backarc crust in southern Kurile suggested by interseismic geodetic deformation
AuthorItoh, Y; Wang, KORCID logo; Nishimura, T; He, J
SourceGeophysical Research Letters vol. 46, issue 21, 2019 p. 11790-11798,
Alt SeriesNatural Resources Canada, Contribution Series 20190304
PublisherAmerican Geophysical Union
Mediapaper; on-line; digital
File formatpdf; html
ProvinceOffshore region
AreaHokkaido; Pacific Ocean; Kurile Trench; Japan
Lat/Long WENS 139.0000 150.0000 46.0000 40.0000
Subjectstectonics; geophysics; Science and Technology; Nature and Environment; satellite geodesy; plate tectonics; subduction zones; deformation; models; crustal models; thermal analyses; seismology; seismic waves; lithosphere; crustal thickness; seismicity; seismic risk; earthquakes; earthquake risk; geodynamics; global navigation satellite systems (GNSS); Global positioning systems
Illustrationslocation maps; geoscientific sketch maps; schematic cross-sections; plots
ProgramPublic Safety Geoscience Assessing Earthquake Geohazards
Released2019 10 16
AbstractIn southern Kurile, interseismic contraction observed with Global Navigation Satellite Systems is faster in the volcanic arc than in the forearc. Here, we use a viscoelastic finite element model to investigate the physical process responsible for the localized deformation. On the basis of thermal and seismic observations that suggest the volcanic arc and backarc to be more compliant than a typical continental lithosphere, we assume a lower rigidity and/or smaller thickness for the arc and backarc. We find that the interseismic observations require the volcanic arc to be very compliant and the backarc to be moderately compliant. The trade-off between lower rigidity and smaller thickness cannot be resolved by interseismic observations alone, but coseismic observations can help to set a lower limit for the rigidity. Our results indicate that properly accounting for the long-wavelength lithospheric heterogeneity is important to accurately inferring megathrust locking state from geodetic observations.
Summary(Plain Language Summary, not published)
When the megathrust of a subduction zone is locked, the neighboring crust is shortened like a spring to build up energy for future earthquakes. GPS monitoring of the rate of shortening helps us identify the locked zone. In Hokkaido, however, the rate of shortening is larger in the area hosting a chain of volcanoes, called the volcanic arc. To explain what amplifies the shortening rate, we use computer models to investigate the effect of the lateral variations in the properties of the crust. We find that the faster shortening occurs because the arc area, and to a lesser degree the area farther away from the trench, is more compliant, that is, it offers less resistance to the lateral compression due to megathrust locking. The greater compliance is consistent with what can be inferred from heat flow and seismic imaging in this area. Our results indicate that, in order to accurately infer megathrust locking from GPS observations, we must include the greater compliance in our model.

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