An earthquake measuring over 7 on the Richter Scale occurred very early Saturday morning 27 November, in the area close to Pentecost and Ambrym islands in Vanuatu. It was followed by several after-shocks one of which appears to have generated a tsunami or seismic sea wave. A large number of landslides were also triggered on Pentecost, Ambrym and nearby Paama. It also appears that ground deformation included permanent uplift of northern Ambrym by up to 80 centimetres, with subsidence in the southern part of Pentecost. Ambrym is an active volcano, both crater lakes have emptied discharging mud and debris down the flanks of the island.
A total of ten dead were reported, five at Ena Village in the north of Pentecost and five drowned by the tsunami at Baie Marteli at the southern tip of Pentecost. Several hundred others attending a wedding escaped death from the tsunami as when the seawater receded the villages knew what to do and fled to high ground. There is much damage on the islands from ground shaking and/or landslides. Houses and communal buildings have collapsed, roads disrupted, and many homes relying on roof catchments for water supply have lost their tanks through collapse.
At the request of the Vanuatu Government, SOPAC has coordinated the organisation of an international team of nine to survey the recent earthquakes and associated tsunami in Vanuatu. It is particularly important that survey of the effects of the tsunami take place as soon after immediate disaster response work is completed as much of the evidence of water damage and inundation by the sea does not last. Detailed survey on the ground of the landslides will follow the studying of satellite photographs taken after the event, together with air photographs taken by the Royal New Zealand Airforce Orion surveillance aircraft. At this time detailed seabed bathymetry collected during SOPAC cruises in the mid-1980's is being reviewed together with the epicentre locations for the earthquakes to assist with determining the location and nature of any seabed rupture.
The Joint Japan-US-Vanuatu-SOPAC international survey team includes professional scientists from the United States and Japan, and will be joined by their Vanuatu colleagues on arrival in Port Vila on 14 December.
The team is led by Prof Costas Synolakis of the University of Southern California assisted by his Japanese colleague Prof Hideo Mastutomi of Akita University. Other team members include University of Southern California colleagues Utku Kanoglu and Christophe Ruscher, Tomoyuki Takahashi of Kyoto University, and Andrew Moore and Shun-ichi Koshimura of Tohoku University. The Ni-Vanuatu colleagues are Charlie Douglas and Morris Stephen. Stanley Temakon, Director General of Lands and SOPAC's National Representative in Vanuatu, and Jean Sese, Chair of the Disaster Council will meet with the team on their arrival.
The team is likely to split into two groups for field survey purposes with the hiring of a helicopter as road access on Pentecost has been cut from the Lonorore airstrip nearest to but 10km away from Baie Marteli, the area worst affected by the tsunami.
Since the major earthquakes there has been increased volcanic activity on Ambrym and confirmation of new arcuate cracks on the north third of Ambrym. These are potentially very significant if there is any question that they may be active and propogating such that rupture of the upper magma chamber takes place. In other words seawater gets into contact with the hot magma, an extremely explosive event could ensue with regional as opposed to national impact. Such an event has occurred in the past in Vanuatu.