Abstract

The paleoseismicity of a historic seismic gap on the Alpine fault of New Zealand has been estimated from an analysis of vertical movements along the fault. The average earthquake recurrence interval is based on 14C-dated terraces that record river downcutting across the fault, and earthquake displacements are determined from young scarps along the fault. Large earthquakes with an average recurrence interval of 500 yr, a rupture length of 270 km, a maximum displacement of 9 m, and magnitudes of ∼8 are indicated for the central part of the Alpine fault. In addition to the coseismic movement, displaced and deformed surfaces indicate that some of the movement is by continuous, aseismic slip within hot schists to the southeast of the fault. When the aseismic part is considered, the earthquake throws and recurrence intervals are consistent with the rate of compressional movement between the Indian and Pacific plates.

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