The 2016 Kaikōura earthquake: Simultaneous rupture of the subduction interface and overlying faults

The 2016 Mw 7.8 Kaikoura earthquake triggered widespread slow slip events (SSEs) in the northern Hikurangi subduction zone, providing a unique opportunity to study the mechanism of dynamic triggering of SSEs. Here we simulate SSEs near Gisborne, New Zealand, in the framework of rate‐and‐state friction. Low effective normal stress (~0.4 MPa) on the shallow subduction interface is needed to reproduce the observed repeating, spontaneous SSEs. Dynamic stress perturbations from the Kaikoura mainshock are adequate to trigger SSEs with characteristics similar to observation. SSE propensity to dynamic triggering mainly depends on the timing of perturbation with respect to the SSE cycle and the maximum Coulomb stress change. Once the perturbation amplitude exceeds an initial threshold, prolonged stress perturbations tend to decrease the triggering threshold hence promote dynamic triggering of SSEs. Therefore, shallow SSEs are more likely to be dynamically triggered than their deep counterparts because of enhanced stress perturbation (magnitude and duration) from the sedimentary wedge.

Section: Dynamic Perturbationmentioning

confidence: 78%

Numerical Modeling of Dynamically Triggered Shallow Slow Slip Events in New Zealand by the 2016 M_w 7.8 Kaikoura Earthquake

Wei

Kaneko

Shi

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). 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).…”

Section: Mechanisms Behind the Triggered Slow Slip And Afterslipmentioning

confidence: 99%

“…We also tried the coseismic model of Wang et al (2018) who suggest up to 14 m of coseismic slip on the subduction interface; the forward model from this scenario produces a similar slip distribution as Figure 5a, but with larger afterslip (up to 1-2 m in 2 months). We also tried the coseismic model of Wang et al (2018) who suggest up to 14 m of coseismic slip on the subduction interface; the forward model from this scenario produces a similar slip distribution as Figure 5a, but with larger afterslip (up to 1-2 m in 2 months).…”

Section: Geophysical Research Lettersmentioning

confidence: 99%

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

Wallace

Hreinsdóttir

Ellis

et al. 2018

111

The 2016 MW7.8 Kaikōura earthquake ruptured a complex sequence of strike‐slip and reverse faults in New Zealand's northeastern South Island. In the months following the earthquake, time‐dependent inversions of Global Positioning System and interferometric synthetic aperture radar data reveal up to 0.5 m of afterslip on the subduction interface beneath the northern South Island underlying the crustal faults that ruptured in the earthquake. This is clear evidence that the far southern end of the Hikurangi subduction zone accommodates plate motion. The MW7.8 earthquake also triggered widespread slow slip over much of the subduction zone beneath the North Island. The triggered slow slip included immediate triggering of shallow (<15 km), short (2–3 weeks) slow slip events along much of the east coast, and deep (>30 km), long‐term (>1 year) slow slip beneath the southern North Island. The southern Hikurangi slow slip was likely triggered by large (0.5–1.0 MPa) static Coulomb stress increases.

“…The 2016 Kaikoura earthquake in the northern South Island of New Zealand was one of the most complex faulting events ever observed. The geometrical complexity of the faults ruptured during the earthquake was captured by field surveys (Clark et al, ; Litchfield et al, ; Nicol et al, ), kinematic inversions using interferometric synthetic aperture radar, and GPS data (Hamling et al, ; Xu et al, ) and strong motion records (Y. F. Bai et al, ; Cesca et al, ; Holden et al, ; Kaiser et al, ; Wang et al, ), suggesting that the rupture was initiated near the southwestern end, propagated through a large number of subparallel and conjugate faults extending over 150 km, and terminated at the northeastern end. Although the involvement of the Hikurangi subduction interface is still debated (e.g., Y. F. Bai et al, ; Cesca et al, ; Holden et al, ; Wang et al, ; Xu et al, ), the source models of the Kaikoura earthquake show heterogeneous slip distributions with the maximum slip on Kekerengu fault (Hamling et al, ; Holden et al, ; Xu et al, ).…”

Section: Introductionmentioning

confidence: 99%

Dynamic Rupture Simulation Reproduces Spontaneous Multifault Rupture and Arrest During the 2016 M_w 7.9 Kaikoura Earthquake

Ando

Kaneko

2018

The 2016 Kaikoura (New Zealand) earthquake is characterized as one of the most complex multifault rupture events ever observed. We perform dynamic rupture simulations to evaluate to what extent relatively simple forward models accounting for realistic fault geometry can explain the characteristics of coseismic observations. Without fine parameter tuning, our model reproduces many observed features including the multifault rupture, overall slip distribution, and the locations of the maximum slip and rupture arrest. In particular, our model shows spontaneous arrest of dynamic rupture at the both ends of the ruptured fault system due to smaller prestress levels expected from a regional tectonic stress field. Both the simulated and the observationally inferred source time functions show similar double peaks with a larger second peak. The results illuminate the importance of the 3‐D fault geometry in understanding the dynamics of complex multifault rupture.