Implications of the great M_w 9.0 Tohoku-Oki earthquake on the understanding of natural hazard in Taiwan and New Zealand

The great M_w 9.0 Tohoku-Oki earthquake was a sobering reminder that earthquake prediction is not currently possible and that estimating seismic hazard in subduction zones remains a nascent science (e.g., Morikawa and Fujiwara, 2016). Many aspects of the earthquake, including the rupture area, magnitude, and large displacement near to the trench, were surprising. The complex rupture involving rupture propagation through numerous patches that have experienced recent displacement dictates that current efforts to define earthquake hazard in subduction zones solely through interpretation of the historical earthquake record needs to be carefully scrutinized. Resulting from discussion during the 2015 meeting of the 3rd Annual Joint Workshop of the Japan/New Zealand/Taiwan Seismic Hazard Programs (Gerstenberger and Fry, 2016), we use the Tohoku-Oki earthquake as a coarse analog to explore potential consequences of great (or giant) events on the Hikurangi and Ryukyu subduction zones. We suggest that M_w 9+ earthquakes are possible on the Ryukyu and Hikurangi megathrusts that would produce damaging ground motions over most of Taiwan and the North Island, New Zealand. Furthermore, given the orientation of crustal faults in both New Zealand and Taiwan, stress changes as a result of megathrust rupture could also produce sequences of upper-plate fault earthquakes.