Dynamically triggered slip on a splay fault in the M_w 7.8, 2016 Kaikoura (New Zealand) earthquake

Abstract

We investigate the Mw 7.8, 2016 Kaikoura (New Zealand) earthquake by using optical satellite imagery and seismology to reveal the main features of the rupture process. Correlation of Landsat8 images reveals a 30–40 km surface rupture on the Kekerengu Fault and Jordan Thrust, with up to 12 m of right‐lateral slip. A previously unrecognized conjugate strike‐slip fault, the Papatea Fault, also slipped coseismically (3–4 m). The global centroid moment tensor (gCMT) centroid indicates both thrust and right‐lateral slip and is located ~100 km NE of the main shock epicenter. The significant non‐double‐couple component of the gCMT (25%) suggests that the main shock is not well represented by a single planar fault. Back projection of teleseismic P waves reveals two main bursts of seismic radiation: (1) at 10–20 s, near the main shock epicenter, and (2) at ~70 s, close to the observed surface ruptures. We determine a finite source kinematic model of the rupture from the inversion of seismic waveforms. We use two faults in our model, defined to match the observed slip on the Kekerengu Fault, and a deeper offshore fault with a lower dip angle to satisfy the long period seismological observations. We compute the equivalent moment tensor from our finite source model and find it to be remarkably consistent with the gCMT solution. Although little is known about the geometry of these faults at depth, if the Kekerengu Fault splays from the deeper thrust, then it provides a rare example where the contribution of slip on a splay fault can be clearly isolated in the seismological waveforms.

Self‐Entrainment Motion of a Slow‐Moving Landslide Inferred From Landsat‐8 Time Series

“…Previous studies have noted similar artifacts in correlations made with very high resolution satellite images, especially on steep slopes or near tree cover where there is dramatic variation in cast shadows (Delacourt et al, ; Lacroix et al, ). In medium‐resolution satellite data, similar artifacts have also been reported by Hollingsworth et al (), who suppressed the noise substantially by correlating images only acquired at the same point in the season, thereby minimizing differences in illumination properties. Bontemps et al () also report a substantial increase in noise when correlating images acquired at different seasons.…”

Triggered Slow Slip and Afterslip on the Southern Hikurangi Subduction Zone Following the Kaikōura Earthquake

“…Some suggest that rupture of the subduction interface contributed >50% of the earthquake's moment (Bai et al, 2017;Duputel & Rivera, 2017;Hollingsworth et al, 2017;Wang et al, 2018), while others suggest a much smaller contribution from the subduction zone (<30%; Clark et al, 2017;Hamling et al, 2017), if any (Cesca et al, 2017;Holden et al, 2017;Xu et al, 2018). Some suggest that rupture of the subduction interface contributed >50% of the earthquake's moment (Bai et al, 2017;Duputel & Rivera, 2017;Hollingsworth et al, 2017;Wang et al, 2018), while others suggest a much smaller contribution from the subduction zone (<30%; Clark et al, 2017;Hamling et al, 2017), if any (Cesca et al, 2017;Holden et al, 2017;Xu et al, 2018).…”

Coseismic and postseismic deformation associated with the 2016 Mw 7.8 Kaikoura earthquake, New Zealand: fault movement investigation and seismic hazard analysis

“…The earthquake rupture was initiated in North Canterbury and propagated more than 170 km northward along at least 12 separate faults (Bradley et al 2017;Hamling et al 2017;Kaiser et al 2017). Geological field investigations and seismological and geodetic constraints show that the Kaikoura earthquake was an extraordinarily complex multi-fault rupture incident (Duputel and Rivera 2017;Hamling et al 2017;Hollingsworth et al 2017;Shi et al 2017;Zhang et al 2017).…”