Vanuatu

On the 26th of November, 1999, a magnitude 7.5 earthquake struck the islands of Vanuatu. The earthquake generated a tsunami which attacked the coast of Vanuatu, with runups of more than 5 meters. In particular, Baie Martelli, a village near the southern tip of Pentecost, was completely destroyed by the waves.

A survey team went to Vanuatu two weeks after the event to determine the extent of the damage. Here are a few photos of what we found.

Vanuatu is an island chain about two and a half hours flight from Australia. It became an independent country in 1980--before that it was ruled by the British an was called the New Hebrides.

Vanuatu is an island arc formed by the subduction of the Australian Plate under the Pacific Plate. The earthquake occurred on a thrust fault formed in the backarc of the subduction zone (big circle; little circles are aftershocks). Most of the damage occurred on Pentecost, the long skinny island just north of 16 degrees.

This is a pretty typical village on Pentecost. The houses are a mix of grass and concrete, and the area is generally grassy.

This is the village of Baie Martelli, after the tsunami. A few concrete houses (and the church) remain standing, although badly damaged. Sand covers the formerly grassy town, and debris from the town has collected behind the damage area.

Closeup of the debris zone. You can see how far inland the tsunami reached by the abrupt transition from sand and debris to green vegetation. Tsunamis commonly kill much of the vegetation they contact because the plants are not salt tolerant.

Sediment left by the tsunami. Residents of Baie Martelli reported that this tsunami consisted of three waves--the first quite small, followed by two larger waves. Here, the sediment records the passage of two waves. The light band in the middle is coarse sand marking the beginning of the second large wave.

Vanuatu is also home to many active volcanoes. This is Ambrym, visible to the south of Baie Martelli across the Selwyn Strait. In the foreground is a large scour pit dug by the tsunami.

Typical Pentecost architecture; a mix of old and new. The buildings are commonly grass, with a concrete pad floor, however, notice the solar panel to drive the village freezer! This is the town of Wali, whose residents graciously housed us during our stay.

One of the main consequences of the earthquake were many landslides that blocked roads, and may have contributed locally to wave damage. Here is a large slide near the town of Baie Martelli, visible in the background.

The people of Baie Martelli were one of our best resources in studying this event. The children helped collect sediment samples, and elders like Maxwell gave us a straightforward account of what happened that day. The residents should be praised for immediately recognizing the approach of a tsunami (the water receded here just before the waves struck), and evacuating the town. This action saved the lives of over 300 of the village's residents; the total loss of life from tsunami was 5.

This is the hill that people ran up to avoid the tsunami. The tsunami stopped about where Everyone is standing, as marked by the transition from debris to green grass.