Compliant Volcanic Arc and Backarc Crust in Southern Kurile Suggested by Interseismic Geodetic Deformation

In 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.