Wallace, L.M.; Jacobs, K.M.; Palmer, N.G.; Warren-Smith, E.; Chin, S-J.; Fell, S.; Juarez-Garfias, C.; Mengesha, D.; TAN2108 Science Party; TAN2110 Science Party 2026. Voyage Report TAN2108 and TAN2110: physical processes underlying slow earthquakes II (PULSE II). Lower Hutt, NZ: Earth Sciences New Zealand. GNS Science report 2025/13. 63 p.; doi: 10.21420/Y064-8J05
Abstract
The PULSE deployment is a multi-institutional, international, seafloor geodetic and seismological investigation of shallow slow-slip events on the Hikurangi subduction thrust offshore of New Zealand’s North Island’s east coast. Continuously operating Global Navigation Satellite System (GNSS) sites in the North Island reveal the shallowest, well-documented slow-slip events anywhere on Earth. As part of the previous Hikurangi Ocean Bottom Investigation of Tremor and Slow Slip (HOBITSS) experiment, we have deployed (TAN1405), then recovered and re-deployed (RR1507, TAN1607, TAN1705, TAN1809, TAN1907, TAN2013) ocean-bottom instruments belonging to GNS Science (now part of Earth Sciences New Zealand), as well as United States of America and Japanese institutions, to document deformation and seismicity during large slow-slip events offshore the North Island’s east coast. The current PULSE experiment is expected to have captured vertical crustal deformation and seismicity related to a low-slip event offshore from the Pōrangahau region of southern Hawke’s Bay / northern Wairarapa that was observed by the onshore GeoNet continuously operating GNSS network at the end of May 2021. Previous Pōrangahau slow-slip events have occurred on a five-yearly basis in 2006, 2011 and 2016. The offshore deployment was complemented by an extensive onshore deployment of seismometers and temporary GNSS instruments, starting in May 2021. As part of the PULSE experiment, TAN2108 retrieved 16 ocean bottom pressure recorders (belonging to GNS Science, the University of Texas and Tohoku University), and 10 ocean bottom seismometers (belonging to the University of Tokyo) that had been deployed on voyages TAN2013 and TAN2102. On TAN2110, we subsequently deployed 15 bottom pressure recorders and nine ocean bottom seismometers offshore of Gisborne to monitor slow slip. Work undertaken on TAN2108 and TAN2110 is supported under the Ministry of Business, Innovation & Employment Endeavour-funded project ‘Diagnosing peril posed by the Hikurangi subduction zone’ (Contract C05X1605) and a Marsden Fund Grant awarded to GNS Science (‘Tipping the balance: What makes slow earthquakes Episodic’). (auths)
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