EARTHQUAKE
AND TSUNAMI OF NOVEMBER 26, 1999 IN VANUATU
George Pararas-Carayannis
INTRODUCTION 
 A 7.3 earthquake struck Vanuatu,
a group of about 80 islands in the Southwest Pacific that has
a population of about 190,000 people. Worst-hit was Pentecost,
an island with a population of about 12,000.
This was the strongest
earthquake recorded in the Vanuatu archipelago in the past 30
years. A tsunami was generated which was particularly destructive
on the southern part of Pentecost.
The Pacific Tsunami
Warning Center in Hawaii was correct in not issuing a Pacific-wide
tsunami warning. Historically, earthquakes from this area have
generated only local tsunamis. Additionally, only small tsunami
wave heights were reported from stations outside the immediate
area..
THE EARTHQUAKE
The large earthquake
occurred shortly after midnight on Saturday morning, 26 November
1999, at 12:21 a.m. local time ( 13:21:15.43 GMT). The Strasbourg
Earth Sciences Observatory in France reported the earthquake's
magnitude as 7.3 on the Richter scale. The U.S. National Earthquake
Information Center (NEIC) in Golden Colorado reported it as 7.1
on the Richter scale. The quake' s epicenter was at given as
16.452 South, 168.183 East, approximately 90 miles north of Port
Vila. Its depth was shallow at 33km (NEIC). The quake was felt
throughout the islands of Vanuatu. Numerous aftershocks of decreasing
intensity continued in the days following the main event.
 TECTONIC SETTING
The entire region
where Vanuatu 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 islands of Vanuatu are close
to the New Hebrides trench,where there is active contact and
interaction between the Australian and Pacific tectonic plates.
The tectonic plates move at speeds averaging between 1 cm and
10 cm per year in this region. The Australian plate also shares
boundaries with the Philippine Plate, the Indian Plate, the Somali
Plate, the Eurasian plate and the Antarctic plate.
The 26 November 1999
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.
RECENT EARTHQUAKES
IN THE AREA
Since August 1998,
there has been a flurry of earthquake activity in the Southwest
Pacific region. The increased level of seismic activity begun
on July 17, 1998 when a 7.1 undersea earthquake off the coast
of Papua-New Guinea caused a huge tsunami which wiped away whole
villages in the Aitape coastal area of Papua New Guinea, killing
more than 3,000 people. Subsequently, NEIC has documented several
large earthquakes in the New Ireland and New Britain regions,
the Santa Cruz Islands and the region of Papua New Guinea, just
to the north of Vanuatu.
In recent months there
have been a series of other big earthquakes in the region of
Papua New Guinea in the area just to the north of Vanuatu and
in the region to the south. On 22 August 1999, an earthquake
measuring 6.5 on the Richter scale struck the very same region
of Pentecost Island. Its epicenter was located at about 200 kilometers
(120 miles) south of Pentecost. On 17 November 1999 there was
a 6.0 quake in Vanuatu Islands with epicenter at 5.97 South 148.81
East. On 18 November 1999 a severe earthquake with magnitude
6.9 on the Richter scale struck the New Britain region. The epicenter
of this earthquake was initially determined to be 420 kilometers
(252 miles) west-southwest of Rabaul, to the north of the Vanuatu
Islands at 5.97 South, 148.81East. The New Britain Region, was
again struck on 19 November 1999 by a magnitude 6.9 earthquake.
The epicenter of this event was at 6.431 South 148.670 East.
THE VANUATU EARTHQUAKE
WAS EXPECTED - MOST LIKELY EARTHQUAKE ACTIVITY IN THE AREA WILL
CONTINUE
The frequency of large
earthquakes in this region of the southwest Pacific is not a
mere coincidence. For example, one week before the Papua New
Guinea earthquake in August 1998, a large quake was recorded
to the west of Western Samoa, and another one occurred in Vanuatu.
Given the number of
large earthquakes which have been occurring in the region in
the last few months, the earthquake at Vanuatu was to be expected.
A quake measuring 6.5 on the Richter scale had struck the very
same region three months earlier on August 22. The epicenter
of this earthquake also was located about 200 kilometers (120
miles) south of Pentecost Islands. IRD (the French Research Institute
for Development) had warned about an impending major quake. The
present trends indicate that the seismic activity will continue
in the next few months and that other large earthquakes can be
expected in this region of the Southwest Pacific.
THE TSUNAMI
Near field Effects: Shortly after midnight on Saturday
morning of 26 November 1999, a destructive tsunami struck the
villages of Ena and Vemagely, on the southern tip of Pentecost,
a island in Vanuatu with population of about 12,000 people. The
tsunami arrived in southern Pentecost island about half an hour
after the earthquake.
 Tsunami waves were estimated
to be about 2-3 meters in height in the immediate offshore area,
but these estimates have not been confirmed. The waves washed
away many of the homes along the southern coast of Pentecost
island and, in some areas, purportedly surged two kilometers
inland.
At Vanuatu's Port
Vila station, the closest to the earthquake's origin, the gauge
recorded tsunami waves of 1.2 m approximately. The gauge recorded
height does not represent the maximum height of the tsunami observed
elsewhere in Vanuatu.
Far Field Effects: The tsunami was recorded by
numerous tide gauge stations in the immediate area and throughout
the Pacific, stations operated by NOAA/National Ocean Survey
and the National Tidal Facility of Flinders University of South
Australia.
A small tsunami was
recorded further away from the source. The following tsunami
heights were recorded: t Lautoka, Fiji ( Approx. 25cm); Apia
- Western Samoa (Approx. 10cm); Pago Pago - American Samoa (20cm);
Niue Is.(15cm); Chatham I., New Zealand (10cm); Pt. San Luis,
California (10cm). At Funafuti, Tuvalu, ; Nauru, Kwajalein -
Marshall Is., Papeete, Tahiti and Wake I., the recorded tsunami
was less than 10cm.
In the Hawaiian Islands,
the small tsunami was recorded by NOAA tide stations as follows:
Hilo, Hawaii, Hawaii (10cm); Kawaihae, Hawaii, Hawaii (< 10cm);
Kahului, Maui, Hawaii (20cm); Honolulu, Oahu, Hawaii (10cm) and
Nawiliwili, Kauai, Hawaii (20cm).
DEATH TOLL AND DAMAGES
The earthquake and
resulting tsunami caused extensive destruction, particularly
on Pentecost island where a church and many houses were destroyed.
Damage also occurred on the islands of Ambryn, Ape and Malacoula.
The Vanuatu provinces of Penama and Malempa were declared disaster
areas. Ten people died on Pentecost, two were missing and four
were seriously injured by the earthquake and the tsunami. Five
of the death were attributed to the earthquake and the other
five when the tsunami hit. Most of the deaths occurred at the
villages of Ena and Vemagely on Pentecost . About 100 people
were injured, most by the earthquake. Thousands of people were
left homeless and lost virtually everything in the disaster.
There was significant damage to the infrastructure of the country,
as landslides blocked roads and communication to some parts in
the central and southern parts of Pentecost Island. Water catchment
tanks were totally destroyed.
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