Speculations on the geometry of the initiation and termination processes of earthquake rupture and its relation to morphology and geological structure

Earthquake initiation and termination processes are commonly described in terms of barriers and asperities. Barriers fall into two classes: Geometric barriers are associated with places where the orientation of failure surface changes, and relaxation barriers, where stress is low because asesmic creep processes outpace tectonic loading. Geometric barriers fall into conservative and nonconservative subgroups, according to whether finite fault motion can proceed without the creation of new structures or whether it demands the creation of new faulting or void space. The multiple faulting, or ‘fragmentation’, associated with some nonconservative barriers can disrupt fault planes and form asperities. By means of selected examples it is shown that a description in terms of these barriers can help one to visualise the processes of earthquake rupture and its relation to the geological environment.

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