Small- to Large-Scale Rock Fracture Patterns as Indicators of Shock-Related Fragmentation

Shock-fragmentation of the Ries impact crater forms characteristic and complex fracture patterns from micro- to kilometre-scale. Outside the crater rim, prominent fractures are mainly vertical to sub-vertical, either in radial or tangential orientation to the crater. The traces of radial fractures from various outcrops around the Ries consistently point towards impact centre and, consequently, represent an excellent tool for locating the crater centre. The presence of prominent fractures in numerous outcrops outside the Ries crater indicates that impact-induced brittle deformation reaches as far as 70 km away from the crater centre. Time series analyses of fracture frequency reveals regularly spaced, ca. 3-4 m interval elongate vertical to sub-vertical zones of high deformation. This periodicity of increased fragmentation appears typical of impact fragmentation. The cyclic repetition of intensely fractured zones and their variations with distance are most likely the results of the interaction of rapidly evolving impact-induced shock waves.