PTWC Procedures and PTWS Products for Hunga Tonga–Hunga Ha'apai Volcanic Tsunami Hazard Response

The massive 15 January 2022 explosion of the Hunga Tonga–Hunga Ha'apai (HTHH) volcano in Tonga – which generated a tsunami causing widespread damage locally, regionally and throughout the Pacific – was an unprecedented event not only for the Pacific Tsunami Warning Center (PTWC) but also for all Tsunami Warning Centers, whose warning procedures and products were designed for earthquake-generated tsunamis, accounting for almost 90% of past tsunami events worldwide.

The impact of the explosion and subsequent tsunami led the Intergovernmental Coordination Group (ICG) for the Pacific Tsunami Warning and Mitigation System (PTWS) to establish a Task Team on Hunga Tonga–Hunga Ha’apai Volcano Tsunami Hazard Response to address the possibility of future tsunamis originating from additional volcanic eruptions or associated processes at the HTHH. The Task Team prepared an Interim Volcanic Tsunami Alert Procedures Implementation Plan with a focus on the HTHH Interim Products and Procedures for responding to this possibility.

In September 2023, the ICG/PTWS at its thirtieth session (Nuku’alofa, Tonga) decided to establish the permanent HTHH monitoring and warning procedures based on the interim products and procedures in use by PTWC since March 2022. The ensuing user's guide is now available.

The finalisation of these products and procedures marks an important milestone in addressing the requirements of tsunami risk mitigation for tsunamis generated by non-seismic and complex sources in general, specifically for tsunamis generated by volcano-processes.

PTWS will continue its efforts to further explore options for developing alternative warning strategies for tsunamis generated by volcanoes through its Task Team on Tsunami Generated by Volcanoes (TGV) established at its 30th session.