[S-CG51] 広域観測・微視的実験連携による沈み込み帯地震研究の新展開

[SCG51-06] Thermal maturity observations depend on the structural history of the wedge

*Utsav Mannu¹、David Fernández-Blanco²、Ayumu Miyakawa³、Taras Gerya⁴、Masataka Kinoshita⁵ (1.Indian Institute of Science Education and Research Pune、2.Barcelona Center of Subsurface Imaging, Institut de Ciències del Mar (ICM-CSIC), Barcelona、3.Geological Survey of Japan, AIST、4.Institute of Geophysics, ETHZ Zurich、5.Earthquake and Volcano Information, Earthquake Research Institute, Tokyo-U)

キーワード：Accretionary Wedge, Thermal maturity, Geodynamic modeling

Estimations of the thermal evolution of sediments from thermal maturity proxies like vitrinite reflectance overlook the influence of fault patterns in wedge evolution. Our numerical study uses conservative 2D finite-difference thermomechanical models of subduction to show that the distribution of faults in the wedge, and particularly, the location of the frontal thrust, is critical to providing feasible inferences for thermal maturity observations. Given that the fault patterns that occur during wedge evolution are influenced by external factors, such as sedimentation, erosion, incoming sediment thickness, the topographic gradient in the slab, etc., these factors also control the thermal maturity of wedge sediments. Our observations support the existence of low and high maturity paths in the wedge, and more relevantly, constraint the conditions of preference of specific pathways. Our results also show that the thermal maturity distribution inside the wedge is most robust in the shallower part of the wedge for sediments at the highest structural locations and that thermal maturity inferences ought to account for the structural patterns of wedge evolution.