Flume experiments on the horizontal stream offset by strike-slip faults

Flume experiments, in which the middle section of an erosion channel is displaced horizontally, have been conducted to assess the response of streams to horizontal displacement by a strike-slip fault. The experimental erosion channel was developed in a mixture of sand and clay, which provided relatively stable banks with its cohesiveness. Horizontal displacement of a strike-slip fault perpendicular to the channel is expected to add a flat section to its longitudinal profile along the fault line. The experimental stream eliminated this flat section with downstream degradation, upstream aggradation, and lateral channel shift. As a result, a roughly continuous longitudinal profile was maintained. This maintenance of a continuous longitudinal profile along channel is considered to be the principle of stream response to horizontal displacement by a strike-slip fault. Downstream degradation was the dominant process of this stream response in the overall tendency of erosion without sand supply. When the rate of fault displacement was low (long recurrence interval), the experimental stream eroded the fault surface, jutting laterally into the channel like a scarp, and deflected the channel within the recurrence interval. This lateral channel shift gave some gradient to the reach created by fault displacement (offset reach), and the downstream degradation occurred as much as completing the remaining longitudinal profile adjustment. When the rate of fault displacement was high (short recurrence interval), the lateral erosion on the first fault surface was interrupted by the next fault displacement.