Numerical modelling of large scale asteroid impact events: Crater formation on continental and oceanic targets, environmental pertubations and code development

小行星与地球的碰撞贯穿于地球的整个历史，给区域地质和全球环境带来了灾难。对地球和生命演变的影响，以及未来这类事件的威胁，使得重建陨石坑形成过程成为一项至关重要的工作。在项目的第一阶段，通过数值模拟分析了陨石撞击海洋目标和海啸波的产生和传播，以评估这类事件的后果，同时，在现有的二维版本的基础上开发了一个新的三维水程序来模拟撞击过程。必须建立三维模型，以调查撞击角度和目标不均匀性（潜水员材料特性的倾斜层）对陨石坑形成过程的影响。尽管撞击结构的整体形状是圆形的，但事实上陨石的撞击碰巧是倾斜的。对撞击坑效率作为撞击角度函数的参数研究的初步结果产生了新的有希望的结果，将导致改进撞击动能与撞击坑大小之间重要关系的比例律。在撞击事件期间，由于冲击波载荷和剪切变形，在撞击坑结构下面的岩石中的损害的建模方面取得了很大进展，目前，只有可能对破碎状态进行定性描述（破碎区的大小和范围）;然而，为了与地球物理异常和撞击结构进行直接比较，计划对由于剪切膨胀（膨胀）而导致的孔隙空间增加进行量化。出于这个原因，开发了一个孔隙度模型，并在代码中实现。到目前为止，可以计算孔隙空间的压实，并计划开发一个模型来确定剪切和应变产生的开放孔隙空间。解决这两个问题，影响的影响角度和目标的不均匀性，以及地下目标修改的定量描述将大大提高我们对撞击坑的理解，并将有助于估计大小，因此，the consequences后果of impact影响events事件in past过去and future未来.

Asteroid collisions with the Earth have occurred throughout the entire history of our planet andbrought catastrophe to the regional geology and global environment. The importance of pastimpacts on the evolution of Earth and life as it exists today and the threat of future such eventsmake the reconstruction of the cratering process a crucial endeavour. In the first phase of theproject meteorite impact on marine targets and the generation and propagation of tsunami-likewaves were analysed by numerical modelling to evaluate the consequences of such events.Concurrently, a new 3D hydrocode to simulate impact processes was developed based on theexisting 2D version. 3D modelling is mandatory to investigate the effect of the angle of impact,and target heterogeneities (inclined layers of divers material properties) on the craterformation process. Despite the overall circular shape of impact structures it is a matter of factthat meteorite impact happens to be oblique. Preliminary results of a parameter study of craterefficiency as a function of impact angle yielded new promising results that will lead to refinedscaling laws for the important relation between the kinetic impact energy and resulting cratersize. Much progress was achieved in modelling the damage in rocks underneath craterstructure due to the shock wave loading and shear deformation during an impact event.Currently, only a qualitative description of the fragmentation state is possible (size and extent of fragmentation zone); however, for a direct comparison with geophysical anomalies atimpact structures a quantification of the increase in pore space due to shear bulking(dilatancy) is planed. For this reason a porosity-model was developed and implemented in thecode. So far, the compaction of pore space can be calculated and the development of a modelto determine the production of open pore space by shearing and straining is planed.Resolving these two issues, the effect of impact angle and target heterogeneities, and aquantitative description of subsurface target modifications will greatly improve ourunderstanding of impact cratering and will help to estimate size and, thus, the consequencesof impact events in past and future.