evidence: The VSZ (10–23∘ S, 165–173∘ E), including from south to north the French, Matthew, and Hunter volcanic islets, Vanuatu and Eastern Solomon Islands, is among the world's fastest moving plate boundaries, with a convergence rate of up to 16–17 cm yr−1 in the northern part (around latitude −11∘; not shown in Fig. 1) between the Australian plate on the west and several Vanuatu micro-plates on the border of the Pacific plate to the east (Louat et Pelletier, 1989; Pelletier et al., 1998; Calmant et al., 2003). It has a history of producing numerous moderate to strong earthquakes (Louat and Baldassari, 1989; Cleveland et al., 2014; Ioualalen et al., 2017). The largest events recorded during the instrumental period (since 1900) have moment magnitudes of between Mw 7.8 to 8.0 and are located in both the northern (Mw 7.8 on 7 October 2009 and Mw 8.0 on 6 February 2013 events) and the southern parts (Mw 7.9 on 9 August 1901, Mw 7.9 on 20 September 1920 and Mw 7.9 on 2 December 1950 events) of the subduction zone.