![]() Nevertheless, tsunami waves are generated although the water depth is very small. If γ < 0.1, the presence of water can be neglected regarding the crater formation process, and the resulting morphology of the crater structures is similar to impact craters on continents ( Artemieva & Shuvalov 2002). The morphology of these craters differs in several respects from those on continents ( Gault & Sonett 1982 Ormö 2002 Shuvalov 2002). If γ is between 10 and 1, the water column has a strong influence on the crater formation in the ocean bottom. No crater structure is formed in the oceanic crust and only tsunami waves are generated. If γ > 10, the kinetic energy of the bolide is not sufficient to penetrate the water column. The ratio γ between the water depth H and the diameter of the projectile d(γ= H/ d) can be used to evaluate the influence of the water depth on the cratering process, if the impact velocity and density of the projectile are kept constant ( Artemieva & Shuvalov 2002). If the impact energy of the bolide striking the Earth's surface is assumed to be constant, the water depth is the controlling parameter to determine the characteristics and quantity of the induced waves ( Weiß 2003). Apparently the ratio of the water depth at the impact site to the size of the projectile is an important parameter assessing the magnitude of the generated waves ( Crawford & Mader 1998 Shuvalov 2002). Therefore, it is important to investigate the destructive force of these waves as a function of distance from impact, and the local bathymetry. Tsunami may cause extensive damage even several thousands of kilometres away from the point of impact. The most striking difference is the generation of tsunami waves ( Crawford & Mader 1998 Paine 1999 Ward & Asphaug 2000 Shuvalov 2002). Oceanic impacts have distinct consequences in comparison to the strike of a bolide on land due to the water masses involved in the cratering process. Depending on the size of the projectile (asteroid or comet), impact events are directly linked to environmental perturbations on local, regional and global scales. The probability of an asteroid or comet impacting on water is much higher than for continental sites because two-thirds of the Earth's surface is covered by oceans. Hydrocode modelling, impact cratering, long wave run-up, Oceanic impacts, tsunami wave propagation 1 Introduction Besides the model description we exemplify the capability of our modelling scheme by the simulation of the strike of an asteroid 800 m in diameter on a 5000-m-deep ocean at 10.2 km s −1, the subsequent propagation of the induced tsunami waves over an artificial bathymetry and the run-up of the wave on the coast. The run-up of the tsunami wave on the coastline is implemented as a special case of reflection and is realized by the well-established MOST code. For the simulation of the propagation of tsunami waves that are generated by the impact process we use a newly developed wave propagation model, which is based on the non-linear shallow water theory with boundary conditions derived from the impact model. Especially, the handling of different materials (water and solid rocks) is crucial as they are involved in the cratering process. The numerical simulation of oceanic impacts requires some changes and extensions to the original SALE code. We present a model, consisting of the well-known SALE impact model and a non-linear wave propagation model, to study the generation and subsequent spread out of the initial wave pattern caused by the strike of an asteroid or comet in the ocean. ![]() However, the characteristics of the induced waves are affected by these parameters. Hypervelocity impacts of asteroids in marine environments produce tsunami waves independent of the water depth and the diameter of the projectile. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |