Paleotsunamis on the Southern Hikurangi Subduction Zone, New Zealand, Show Regular Recurrence of Large Subduction Earthquakes

Abstract Geological records of subduction earthquakes, essential for seismic and tsunami hazard assessment, are difficult to obtain at transitional plate boundaries, because upper-plate fault earthquake deformation can mask the zone signal. Here, we examine unusual shell layers within a paleolagoon Lake Grassmere, transition between Hikurangi Marlborough system. Based on biostratigraphic sedimentological analyses, interpret as deposits. These dated 2145–1837 1505–1283 yr B.P., most likely source these tsunamis was ruptures southern interface. Identification two large earthquakes brings total record four in past 2000 yr. For first time, it is possible geologically constrained recurrence interval zone. We calculate 500 (335–655 yr, 95% confidence interval) coefficient variation 0.27 (0.0–0.47, interval). The probability 26% next 50 find no consistent temporal relationship faults.