Velocity structure and relocated aftershocks in the Kaikōura to Palmerston region, New Zealand, from body-wave seismic tomography
Abstract
The rupture area of the 2016 Mw 7.8 Kaikōura earthquake is located in a region that straddles a complex tectonic setting at the transition from the subduction of the Pacific Plate beneath the Australian Plate (Hikurangi subduction zone) to strike-slip and continental collision along the Alpine Fault in the central South Island of New Zealand. The state of coupling of the Hikurangi megathrust and whether it was involved in the Kaikōura earthquake rupture process is the subject of ongoing debate. To identify the faults that failed seismically following the Kaikōura earthquake and illuminate those that may extend to the underlying subduction zone, we present aftershock relocations. These relocated events were obtained using a new 3D velocity model and high quality automatic phase-picks from an extended network, that includes a temporary seismic deployment in the northern South Island and southern North Island (Seismic Triggering Response for Earthquakes around Wellington NZ: STREWN). Results show clustering of aftershocks predominantly along mapped surface ruptures and a small cluster of five events with magnitude 3 to 4 on a deeper structure, possibly the subducting plate interface. This suggests that the majority of afterslip on the Hikurangi subduction zone did not directly result in seismic events. Additional insights into the architecture of this portion of the subduction zone will be presented through body-wave tomographic images of the seismic velocity structure beneath Kaikōura to Palmerston region.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.T51I0281L
- Keywords:
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- 1207 Transient deformation;
- GEODESY AND GRAVITYDE: 7230 Seismicity and tectonics;
- SEISMOLOGYDE: 8170 Subduction zone processes;
- TECTONOPHYSICSDE: 8185 Volcanic arcs;
- TECTONOPHYSICS