The Formation Model of Multi-ring Basins Based on the Theory of Impact Tsunami

Adopting the theory of shallow water waves with an initial surface deformation of a parabolic crater, the tsunami model of the origin of multi-ring basins is discussed and an approximate formula for calculating the ring radius is obtained. From the computed ring spacings of three multi-ring basins on the moon (Orientale, Moscoviense and Serenitatis South), it is shown that the tsunami model can only be applied to the area within the main ring (the IV ring), which marks the end of fluidized region and the crater rim of the excavated basin. Besides this, by comparing the result of initial impulsive pressure disturbance with initial deformation disturbance under the condition of the same fluidized depth, it seems that the time of multi-ring basins required to reach its present status in the case of initial deformation disturbance is shorter than in the case of initial impulsive pressure disturbance. This time difference can be explained as the time required from the start of impact to the deformation of a parabolic crater.