[J02-3] Recent large earthquakes III

[J02-3-04] Complex rupture of the 2016 Kaikoura earthquake, New Zealand

^○Simone Cesca¹, Joachim Saul¹, Yong Zang², Rongjiang Wang¹, Sebastian Hainzl¹, Vasiliki Mouslopoulou¹, Onno Oncken¹, Torsten Dahm¹ (1.GFZ German Research Centre for Geosciences, Potsdam, Germany, 2.Peking University, Beijing, China)

The M7.8 Kaikoura earthquake struck New Zealand on November 13, 2016 at 11:02:58, followed by a significant aftershock sequence. This was the largest event instrumentally recorded in the region. It took place in a complex tectonic environment, controlled by the subduction of the Pacific plate offshore the East coast of New Zealand and the Alpine transform fault. The seismic waveforms footprint indicates a complex rupture process. The seismic moment tensor computed by GEOFON shows a strong non-double-couple term, as also depicted by other global moment tensor catalogues, suggesting the complex rupture of one or multiple faults. Similarly, the hypocentral distribution of aftershocks appears distributed and clusters along lineaments with different orientations. The surface expression of rupture processes confirms the activation of mutiple faults with different orientations either during the main shock or the early postseismic phase. Finally, the surface deformation is characterized by a distributed uplift, but includes smaller scale anomalies, such as localized coseismic extrusion of more than 5 meters. We perform a broad seismological analysis, combining regional and teleseismic seismic data, to determine the rupture process of the main shock and tens of aftershocks. The main shock is analysed by combining InSAR, GPS and seismic data to resolve the slip distribution on a finite fault, both revealing strong rupture directivity and slip heterogeneity along the rupture area. The aftershock are investigated through a full waveform regional moment tensor inversion, revealing a combination of different rupture styles, including thrust, strike-slip and very shallow near vertical faulting, characteristic of different spatial clusters. Combining this information with the kinematic source analysis of the main shock, we propose a multiple rupture process for the Kaikoura earthquake rupture process.