FEATURE
SUBOPTIC 2023 BEST ORAL PRESENTATION AWARD
WHAT CAN WE LEARN ABOUT VOLCANIC HAZARDS FOR SUBSEA CABLES FROM THE 2022 HUNGA TONGA-HUNGA HA’APAI ERUPTION? By Michael Clare, Isobel Yeo, James Hunt (National Oceanography Centre, UK), Sally Watson Richard Wysoczanski, Sarah Seabrook, Michael Williams, Emily Lane, Kevin Mackay (National Institute of Water and Atmospheric Research, New Zealand), Peter Talling, Edward Pope (Durham University, UK), Shane Cronin (University of Auckland, New Zealand), Marta Ribó (Auckland University of Technology, New Zealand), Taaniela Kula (Tonga Geological Services, Kingdom of Tonga), David Tappin (British Geological Survey, UK), Samiuela Fonua, James Panuve (Tonga Cable Ltd), Dean Veverka (Southern Cross), Ronald Rapp (SubCom), Valey Kamalov (Google)
ABSTRACT
The 15th January 2022 Hunga Tonga-Hunga Ha’apai volcanic eruption was the most explosive on Earth in more than a century. Here, we present findings from surveys performed only months after the large eruption to show how powerful pyroclastic flows plunged into the ocean, scouring deep gullies, and causing extensive damage to international and domestic cables, cutting communication links to the Kingdom of Tonga. These powerful flows travelled at high speeds (up to 122 km/hour) over >100 km. We share lessons learned from this event and discuss how to better understand the hazards posed by other volcanoes to subsea cables.
INTRODUCTION
impacts of both human and natural hazard-related cable damage[4]; however, islands that have few connections will be more vulnerable[5]. In this paper, we discuss the case of the January 2022 Hunga Tonga-Hunga Ha’apai volcanic eruption that led to extensive damage to the Kingdom of Tonga’s only subsea international telecommunications cable, severed it from the global network at a critical time for disaster response.
Subsea cables provide critical communications links, carrying >99% of all intercontinental digital data traffic worldwide[1]. While geological hazards only account for <15% of reported subsea cable faults globally[2], such events can be particularly significant as they can affect very large areas of seafloor, damaging multiple cable systems synchronously[3]. Remote island nations are particularly reliant on submarine cables; however, they are often located in regions that are prone to natural hazards, such as earthquakes, tropical storms, underwater landslides and volcanic activity[1]. Diversity in cable routes and landing station locations Figure 1: Photograph of the erupting plume from Hunga Tonga-Hunga Ha’apai ensures that most regions are volcano on January 14th 2022 (the day before the main eruption). Image courtesy sufficiently resilient to the of Tonga Geological Services.
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AIM AND OBJECTIVES
Our overarching aim is to share results of recent surveys that reveal the seafloor impacts of the largest volcanic eruption in the last century and provide new insights for cable routing and resilience. We address the following questions. 1) What explains the unusually exten-