模型実験によるリフトの断層の雁行配列について

Experimental configurations fall into two groups; rifting associated with previous uplift (Model U) and rifting following lithospheric extension (Model E). The tests of Model U were carried out on a rubber sheet pushed up by a motor-driven block, while the tests of Model E were achieved on the conveyer belts of cloth spread to both sides.
Results of the model experiments are summarized as follows: The crustal uplift (Model U) produces a narrow rift zone consisting of faults arranged in en echelon of two orders. The first order arrangement is composed of minor faults each of which strikes in the direction of the uplift axis. Right- and left-handed en echelon faults are cyclically alternated and they develop asymmetrically with respect to the rift axis, so that they evolve into a sigmoidal fault. This sigmoidal fault is an element of the second order en echelon arrangement. The rift floor is tilted due to asymmetrical growth of boundary faults. The spreading of the crust (Model E) produces a wide rift floor bounded by meandering faults. The second order en echelon arragement is not observed in Model E.