Abstract

The Mw 7.8 Kaikōura earthquake ruptured at least 17 faults for a distance of approximately 165 km across the New Zealand plate boundary zone in the northeastern South Island. In the epicentral area, the earthquake produced displacement at the surface on The Humps, Leader, Conway‐Charwell, and Stone Jug faults, which are the primary focus of this article. Analysis of the surface rupture, aftershocks, focal mechanisms, and Interferometric Synthetic Aperture Radar (InSAR)–derived uplift from the earthquake provides new information on the dimensions, geometries, and kinematics of these faults, which was not previously available from the active faults or bedrock structure. Relocation of the mainshock indicates that it initiated on The Humps fault with rupture mainly propagating to the northeast. The resulting ground ruptures comprise two intersecting sets that strike east‐northeast with right‐lateral and reverse displacements, and north‐northwest to north‐northeast faults with left‐lateral reverse displacement. Reverse faulting was accompanied by folding associated with differential uplift and bedding‐parallel slip. On a regional scale, faulting accommodated transpression consistent with the oblique relative plate motion vector and Quaternary bedrock deformation. Whereas the kinematics of faults that ruptured during the earthquake was predictable, the fault‐rupture complexity could not have been anticipated or explicitly incorporated into seismic hazard models.

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