17:15 〜 19:15
[SCG61-P16] A multiscale viscoelastic model of mantle convection and great earthquake cycles in subduction zones
キーワード：マントル対流、粘弾性、数値モデル、沈み込み帯、地震の周期
Subduction zones exhibit diverse mechanical behaviors, influencing their ability to generate great earthquakes (Mw > 8.0). Uyeda and Kanamori (1979) classified them into Chilean type (strong coupling) and Mariana type (relatively weaker coupling). The Japan trench was historically considered to be an intermediate case between these two types (Huang and Zhao, 2013), and it was not expected to generate great earthquakes (Mw~9.0) prior to 2011. The great earthquake cycles in the Tohoku region remain poorly understood, with estimates varying from 500 years to millions of years (Ikeda et al., 2012). A critical distinguishing feature of the NE Japan is its fast subsidence rate, likely linked to the subduction of an old and cold slab (Wang, 2012). On the contrary, Cascadia, where a young and hot slab subducts, experiences higher megathrust stress, leading to greater potential for large seismic events (Wang 2012; Crisosto and Tassara, 2024). These variations suggest that mantle dynamics beneath subduction zones play a crucial role in their long-term evolution and seismic behavior. To address this, we will develop a viscoelastic finite-difference numerical model based on Tagawa et al. (2007) to investigate the role of slab geometry, mantle rheology, plate dynamics, and fluid interactions in controlling earthquake cycles. Our approach will involve a multiscale numerical framework. First, a long-term simulation that captures the evolution of mantle convection and subducting slab coupling. Second, a shorter-term high-resolution model that refines the grid and timestep to resolve stress accumulation and release along the megathrust, providing insights into the mechanics of earthquake recurrence.
By incorporating viscoelastic rheology, which accounts for both long-term mantle flow and short-term elastic deformation, we aim to bridge the gap between mantle-scale dynamics and seismic cycle processes. The findings will enhance our understanding of how subduction zones evolve over geological time and how earthquake cycles are modulated by subduction zone parameters, viscoelastic properties of real Earth materials and fluid interactions. Ultimately, this study aims to propose a new classification scheme based on the predicted properties of great earthquake cycles in different subduction zones, thus serving as a framework for seismic hazard assessment.
By incorporating viscoelastic rheology, which accounts for both long-term mantle flow and short-term elastic deformation, we aim to bridge the gap between mantle-scale dynamics and seismic cycle processes. The findings will enhance our understanding of how subduction zones evolve over geological time and how earthquake cycles are modulated by subduction zone parameters, viscoelastic properties of real Earth materials and fluid interactions. Ultimately, this study aims to propose a new classification scheme based on the predicted properties of great earthquake cycles in different subduction zones, thus serving as a framework for seismic hazard assessment.