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概要

MAT TOOLBOX 2018

Modeling tectonic processesat convergent marginsIuse numerical simulations to understand what controls the formationof tectonic structures and styles and to identify the conditionsthat dictate the transition from one tectonic style to another. I alsoapply these methods to understand the formation of specific geologicalstructures such as nappes in Switzerland or the plate boundary inJapan. This knowledge is critical to understand the formation of mountainbelts and subduction zones, the distribution of natural resourcesor the distribution of seismicity.Initial and final stages of two numerical thermo-mechanical simulations of the shortening of a passive margin. Different basement rheologies are usedwhich leads to deformation being expressed by two different tectonic styles, either thin- or thick-skinned. The final stage corresponds to a shortening of35 %. The crystalline basement is represented in red with crosses. All other colors correspond to sediments whose properties are homogeneous (colors andpatterns are passive markers of the deformation). Modified after Bauville et al., 2015Thick- vs thin-skinned tectonicsin the AlpsThe Helvetic zone is a fold-and-thrustbelt that constitutes the outer part ofthe Alps in Switzerland. It resulted fromthe compressive deformation of previouslyextended continental margin. Kilometer-scaletectonics structures canbe classified as thin- or thick-skinneddepending on whether deformationaffects only the sedimentary cover oralso involves the crystalline basement,respectively. We used two-dimensionalnumerical simulations to study thedeformation style and the formation ofnappes during the shortening of basement?coversystems with half-grabens.The result suggests that the transitionfrom thin- to thick-skinned tectonics iscontrolled by strength contrast at thesediment-cover interface and the baseof the crystalline basement. The numericalsimulation were also applied toparticular structures in the Alps to betterunderstand their formation process.Plate interface formationin JapanAt some subductive margins, sedimentare accreted to the upper plate(e.g. Nankai Trough) while at otherssediment are entrained with the subductingplate (e.g. Japan Trench).Furthermore, the interplay betweenthe shallow decollement and deepersections of the plate boundary is stillincompletely understood. I hypothesizethat the plate interface largely controlsthe dynamics of the subduction zone.The aim of this project is, therefore, tosimulatetheformationandevolution20計地算球科学