|
|
EARTHQUAKE AND TSUNAMI OF JANUARY 2, 2002 IN VANUATU
George
Pararas-Carayannis
------------------------------------------
© 2002 George Pararas-Carayannis - All Rights Reserved
INTRODUCTION
On January 2, 2002 (UTC -3 January,
local date), a powerful earthquake struck Vanuatu, a group of
about 80 islands in the Southwest Pacific with a population of
about 190,000 people. The earthquake caused extensive damage
in the capital, Port-Vila, (a town of about 19,400) and surrounding
areas on the island of Efate. A small tsunami was generated.
This was the most destructive event in the Vanuatu Archipelago
since the 26 November 1999 earthquake and tsunami struck the
northern island of Pentecost, a town of about 12,000 people.
The 1999 tsunami left thousands of people homeless.
THE EARTHQUAKE
The earthquake occurred at 17:22:49 on 2 January 2002 (UTC)(or 04.22 hrs on 3 January, local time and date). Its magnitude was 6.3mb (7.5MS) and its focal depth about 21 km. The epicenter was at at 17.78S, 167.88E (USGS), approximately 45 km West of of Port Vila. A number of aftershocks were recorded.
TECTONIC SETTING OF THE REGION
The
entire region where Vanuatu island group is located is characterized
by high volcanic and seismic activity and is part of what is
often referred to as the " Pacific Rim of Fire" - an
area notorious for frequent earthquakes and volcanic eruptions.
This region of the Southwest Pacific Ocean is presently responsible
for about ten per cent of the total energy released by earthquakes
in the world.
The 2 January 2002 earthquake occurred along a zone where tectonic plate convergence and subduction take place, as the Pacific tectonic plate submerges beneath the Australian plate. In the Vanuatu area this process of subduction has formed the New Hebrides Trench and is the cause of major earthquakes and locally destructive tsunamis. The tectonic plates move at speeds averaging between 1 cm and 10 cm per year. As shown the adjacent map, the Australian plate also shares boundaries with the Philippine Plate, the Indian Plate, the Somali Plate, the Eurasian plate and the Antarctic plate.
THE TSUNAMI
Historically, only local tsunamis are generated by earthquakes in the region. The January 2, 2002 quake generated a local tsunami. It took 14 minutes after the quake for the first wave to reach the Port Vila tide gauge station, the closest to the earthquake's origin. The maximum recorded tsunami wave was 0.8 m (trough to crest). The average period was about 11 minutes.
However, as with the November 1999 event, the Port Vila gauge tsunami recorded height does not represent the maximum runup observed elsewhere in the harbor or along the open coasts. According to eyewitness reports the maximum tsunami runup at different parts of PortVila , was about 3.0 meters - large enough to cause damage. However, most of the local damage was caused mainly by the earthquake.
A large aftershock on the following day generated another small local tsunami, which was recorded by the Port Vila tide gauge to be less than 10 cm. Its height on the open coast is not known.
Map showing the New Hebrides Trench and the epicenter of the November 26, 1999 earthquake.
Several people were injured but
there were no reported deaths. Fearing a tsunami, hundreds of
residents had fled to higher ground. Damage at Port Vila and
other areas on Efate Island was widespread but was caused primarily
by the earthquake and resulting landslides. Access
to the wharf was blocked by rockslides. Buildings in the business
district of the town were damaged and shops had broken windows.
Ground liquefaction was responsible for most of the damage to
homes, buildings, structures and embankments. Three bridges were
reported damaged or destroyed.
Now available from Amazon, Barnes and Noble and other major bookstores.
