Three-dimensional coseismic deformation of the 2016 MW7.8 Kaikuora, New Zealand earthquake obtained by InSAR and offset measurements

The 2016 MW7.8 Kaikoura earthquake struck the northern part of south Island, New Zealand, within the active and complex Australia-Pacific plate boundary system. Firstly, we used the InSAR method to obtain coseismic LOS deformation fields based on SAR images and applied offset tracking methods to obtain offset measurements based on optical satellite images. The maximum displacement of about 6 m is detected in the direction away from the satellite on the south-west side and also towards the satellite on the north-east side. The 3D deformation field is then resolved by the combination of these measurements with a least-square solve method, and comparisons with 3 components of GPS stations show good consistency. Despite complex features demonstrated in the 3D deformation field, there are still clear spatial correlations between surface deformation and faults distribution. It reveals that more than ten faults were ruptured during the earthquake, including some faults were previously understudies for their tectonic activities. The maximum horizontal deformation of about 10 m occurs along the Kekerengu fault with the vertical deformation up to 2 m. The 3D deformation shows that the mainshock is a multisegments faulting with a rupture process of strike-slip, compression, transpressional rupture and strike-slip in space along the NE direction.