Elastoplastic Modeling of the Unusual Uplift of the Papatea Block in the 2016 M7.8 Kaikoura Earthquake

Session: Exploring Rupture Dynamics and Seismic Wave Propagation Along Complex Fault Systems
Type: Oral
Date: 4/29/2020
Time: 05:00 PM
Room: 110 + 140
Description: 

The largest surface uplift (~8m) in the 2016 M_W7.8 Kaikoura Earthquake occurred on a hanging wall block of the previously considered inactive reverse-sinistral Papatea fault (approximately north-south striking and 19-km long). The deformation across the steeply-dipping Papatea fault is surprisingly asymmetric with multimeter uplift on the hanging wall and only tens of centimeters of subsidence on the footwall, contradicting with elastic dislocation models (that would predict ~ 3 – 4 m subsidence on the footwall). The block is further bounded in the northwest by northwest-dipping Jordan Thrust and Kekerengu Fault and in the south by the north-dipping Hope fault. Hamling et al. (2017) and Diedrichs et al. (2019) suggest that the Papatea block is a pop-up structure due to inelastic deformation by slip on the bounding faults. Here we extend the model of Klinger et al. (2018) to 3D by modeling dynamic rupture propagating from south to north on the Papatea fault and jumping to Jordan Thrust and Kekerengu Fault. We also include the Hope fault in the model suggested by the aftershock relocations (Lanza et al., 2019). We show that the dynamic stress field by slip on these bounding faults cause inelastic deformation (modeled by the Drucker-Prager yield criterion) that can reproduce the asymmetry of vertical displacement and counter-clockwise rotation of the Papatea block and damage pattern in the field. The general southward (seaward) decrease of the uplift on the block is due to rupture directivity and the fault junction enhancing inelastic deformation toward the north.

Presenting Author: William Donnelly

Authors