中科大地球与行星物理学术报告通知-焦利青
报告地点：腾讯会议：894-640-878
报告时间：星期五,2022-11-11 15:00 - 16:30
报告人：焦利青 （中国地质科学院）
报告人简介：
焦利青，中国地质科学院研究员；曾在新加坡南洋理工大学土木与环境工程学院项目工作员以及在南洋理工大学新加坡地球观测研究所博士与博士后，法国巴黎地球物理研究所合同研究员与教师研究员。曾受邀在法国科学院里昂一大，格勒诺布尔阿尔卑斯山大学，南希洛林大学，道达尔石油公司研究院多次访问并给了多个受邀报告。主要研究领域为运用数值方法研究印亚板块碰撞下的大陆构造变形以及火山喷发过程中断裂变形；运用数值方法研究印尼苏门答腊俯冲带区域的地震周期；以及走滑断层地表破裂数值模拟研究与力学分析。部分研究成果发表于EPSL, GRL, PNAS, Tectonophysics, Acta Geologica Sinica 等国内外知名杂志。
报告题目：Discrete Element Modeling of Continental Deformation, Volcanic Spine Extrusion, and fault rupture
报告内容简介
The discrete element method is anumerical approach to be generally used in large dynamic deformation. The approach permits mega-fault generationand evolution without pre-arranged initial settings. The results provideinsight into fault birth, propagation and rupture. We use this method in three different types ofdeformation from large-scale continental deformation, relatively small-scalevolcanic extrusion and short time scale fault rupture process.
First, we use the India-Asian collisionas an example, the Indiancollision has deformed the eastern Asian continent in a multifaceted way,uplifting Tibet and surrounding mountains, activating ≥ 1000 km-longstrike-slip faults, and opening Tertiary rifts and oceanic basins up to ≈ 3000km away from the Himalayas. We use Discrete Element Modelling to simulate andfurther understand the evolution of 3D strain across east Asia since the onsetof collision, ≈ 55 Ma ago. The planar, 50 million km2, 125 km-thickmodels, scaled for gravity corroborate that continental crustal thickeningalternated with the extrusion of large blocks that rifted apart in the farfield.
In volcanic silicic spine extrusion, seismicity involves recurrentexcitation of similar sources at stationary depth beneath the crater. We assessstress, strain and faulting in ascending magma which, although hot, behaves asa solid. Earthquake fault-plane solutions during the 09/2004-08/2005 eruptionsof Mount St. Helens imply shrinking of magma rising across a conduit“bottle-neck”. Constriction across the neck and vertical shear along theconduit walls thus predominate. Dynamic Discrete Element Modeling successfully reproduces repetitive nucleation of thrust faults within the neck. Furthermore,the pressure drop across the neck boosts crack opening and hence gas extraction(natural “fracking”).
During large earthquake fault rupture, seismic sources tendto split in several sub-events that rupture neighboring fault segments. Usingnumerical modelling, we demonstrate that when a pristine layer of brittlematerial is sheared, the first oblique Riedel fractures nucleate with regularspacing controlled by the thickness of that layer. During later localization,modelling results show that initial fractures control the spatial structurationof the entire fault system.