16:30 〜 16:45
[J02-4-01] Postseismic deformation following the 2016 Mw 7.8 Kaikoura earthquake, New Zealand
The November 14 2016 Mw 7.8 Kaikoura earthquake in New Zealand ruptured at least 12 major crustal faults and caused widespread damage across the northern South Island. In response to the earthquake several new continuous and semi continuous GPS stations were installed in the region to augment the GeoNet CGPS network. In addition, InSAR data acquired by ALOS-2 and Sentinel-1A/B, which are acquired every 6-12 days, are used to measure post-seismic deformation across the region.
We will present the first few months of the postseismic deformation following the Kaikoura earthquake. The most rapid early postseismic deformation is observed in the region of Cape Campbell, coinciding with a large cluster of aftershocks, with about 24 cm NE motion and 26 cm uplift observed at CGPS site CMBL by the end of 2016. Sites NW of Cape Campbell have a similar NE trend and uplift with decreasing rate NW from the Needles fault. Coastal sites, south of the Clarence fault move in a more easterly direction, with the site KAIK moving 8.5 cm ESE and insignificant vertical change.
A simple postseismic deformation model based on the best-fit coseismic fault planes and assuming a 30-km-thick elastic layer overlying a Maxwell viscoelastic mantle is able to broadly reproduce the direction of postseismic deflections from north to south, but predicts maximum displacements too far inland. Adding in the dipping Pacific plate slab as an elastic body reduces the magnitude of postseismic displacement in the model but does not change directions or the location of maximum displacements significantly. We also undertake time-dependent inversions of the afterslip, solving for slip on the crustal faults that ruptured in the earthquake, as well as the underlying subduction interface. The best-fit postseismic models have afterslip on the crustal faults that ruptured in the earthquake, as well as on the subduction interface beneath the northern South Island, in addition to a component of mantle relaxation.
We will present the first few months of the postseismic deformation following the Kaikoura earthquake. The most rapid early postseismic deformation is observed in the region of Cape Campbell, coinciding with a large cluster of aftershocks, with about 24 cm NE motion and 26 cm uplift observed at CGPS site CMBL by the end of 2016. Sites NW of Cape Campbell have a similar NE trend and uplift with decreasing rate NW from the Needles fault. Coastal sites, south of the Clarence fault move in a more easterly direction, with the site KAIK moving 8.5 cm ESE and insignificant vertical change.
A simple postseismic deformation model based on the best-fit coseismic fault planes and assuming a 30-km-thick elastic layer overlying a Maxwell viscoelastic mantle is able to broadly reproduce the direction of postseismic deflections from north to south, but predicts maximum displacements too far inland. Adding in the dipping Pacific plate slab as an elastic body reduces the magnitude of postseismic displacement in the model but does not change directions or the location of maximum displacements significantly. We also undertake time-dependent inversions of the afterslip, solving for slip on the crustal faults that ruptured in the earthquake, as well as the underlying subduction interface. The best-fit postseismic models have afterslip on the crustal faults that ruptured in the earthquake, as well as on the subduction interface beneath the northern South Island, in addition to a component of mantle relaxation.