| アブストラクト |
Impact craters are the most common landform on planetary surfaces; however, the mechanics of the end stages of the formation of large craters is not fully understood. The final stage of crater formation involves the collapse of a hemispherical transient cavity. Around small craters, the limited amount of collapse preserves a bowl-shaped cavity. In contrast, the observed shallow depths and complex inner morphologies of large craters require very low shear strength in the collapsing material. Because the observed amount of collapse cannot be reproduced using quasi-static (laboratory) values for the frictional strength of fractured rock, a temporary weakening mechanism is necessary. I will present simulations that investigate the hypothesis that craters collapse along a network of impact-generated faults that weaken during long displacements at high slip velocities via, for example, frictional melting. The model reproduces the major geologic features observed around the largest terrestrial craters (Vredefort, Sudbury, and Chicxulub), including shallow depths, fault structures, frictional melt distributions, and deep-seated central uplifts. Finally, I will raise open questions related to the formation of multi-ring impact basins.
Reading:
Senft, L. E., and S. T. Stewart.
Dynamic Fault Weakening and the Formation of Large Impact Craters.
Earth and Planetary Science Letters, 287, 471-482,
doi:10.1016/j.epsl.2009.08.033, 2009. |
