Achraf Koulali

Slow slip events and the 2016 Te Araroa Mw 7.1 earthquake interaction: Northern Hikurangi subduction, New Zealand

Following a sequence of three Slow Slip Events (SSEs) on the northern Hikurangi Margin, between June 2015 and August 2016, a Mw 7.1 earthquake struck ~30 km offshore of the East Cape region in the North Island of New Zealand on the 2nd September 2016 (NZ local time). The earthquake was also followed by a transient deformation event (SSE or afterslip) northeast of the North Island, closer to the earthquake source area. We use data from New Zealands continuous Global Positioning System (cGPS) networks to invert for the SSE slip distribution and evolution on the Hikurangi subduction interface. Our slip inversion results show an increasing amplitude of the slow slip towards the Te Araroa earthquake foreshock and mainshock area, suggesting a possible triggering of the Mw 7.1 earthquake by the later stage of the slow slip sequence. We also show that the transient deformation following the Te Araroa earthquake ruptured a portion of the Hikurangi Trench northeast of the North Island, further north than any previously observed Hikurangi margin SSEs. Our slip inversion and the coulomb stress calculation suggest that this transient may have been induced as a response to the increase in the static coulomb stress change downdip of the rupture plane on the megathrust. These observations show the importance of considering the interaction between slow slip events, seismic and aseismic events, not only on the same megathrust interface, but also on faults within the surrounding crust.

Lineaments and earthquake ruptures on the East Japan megathrust

Additional support derived from Australian Research Council Discovery Project DP120103554 and Linkage Project LP130100134. EJR acknowledges Australian Laureate Fellowship FL120100050