THE
EARTHQUAKE OF 25 JANUARY 2001 IN GUJARAT, INDIA
George
Pararas-Carayannis
Introduction
On 25 January 2001,
a major earthquake occurred in Gujarat, a prosperous industrial
and agricultural state on India's west coast, close to the border
with Pakistan.
The quake was the
most powerful to strike this region of India in the last fifty
years. It was also the most destructive in terms of lives lost
and property damage.
 Earthquake Epicenter,
Origin Time, Magnitude and Aftershocks
The preliminary magnitude
of the earthquake was initially reported as 7.9. It was later
revised to 7.7 Ms. According to the USGS, it occurred at 8:16
PM MST, Jan 25, 2001 (Jan 26 at 8:46 AM local time in India).
The epicenter was at 23.40 N 70.32 E, approximately 12.5 miles
northeast of the town of Bhachau and about 65 miles (110 km)
NNE of Jamnagar. The quake's depth was 23.6 km. Ground motions
lasted about 90 seconds. Its tensor solution is given below (source
USGS)
The quake was felt
in New Delhi, 600 miles (966 kilometers) away,  where
high rises swayed. It was also felt in Calcutta, 800 miles away,
in Nepal and in coastal Bangladesh 1,200 miles (1,931 kilometers)
away. Strong aftershocks (more than 300) continued to strike
the Kutch district of Gujarat, in the days and weeks following
the main shock. One aftershock with 5.3-magnitude had its epicenter
was 12.5 miles northeast of Bhachau, a town that was badly damaged
by the main quake. The aftershocks are expected to continue for
many weeks and even months.
 Death Toll and Damages
Because of its size
and location, this quake was very destructive in terms of lives
lost and damage to property. All the deaths occurred in India'a
western state of Gujarat, near the Pakistan border. Bhuj , a
coastal resort only 20 kilometers (14 miles) from the epicenter,
was the worse affected town.
As many as 15,000
-20,000 people were initially reported dead but within a few
days after the earthquake, the death toll kept on rising. As
of 3 February 2001, the official toll had climbed to more than
30,000. However, the final death toll may never be known with
certainty. At least 30,000 more people were reported as injured.
This too may be an underestimate.
The quake destroyed
90 percent of the homes in Bhuj, several schools, and flattened
the hospital. Considerable damage occurred also at Bhachau. In
Ahmedabad, Gujarat's commercial capital and a city of 4.5 million,
as many as 50 multistory buildings collapsed and several hundred
people were killed. Total property damage was estimated at more
than $5.5 billion.
 Recent Earthquakes
in India.
The Gujarat earthquake
was the most powerful to strike India since 15 August 1950, when
an 8.5 magnitude quake killed 1,538 people in the northeastern
Assam state. The recent quake was also very similar to the powerful,
8.3 magnitude earthquake which struck the Gujarat region in 1919
and killed about 2,500 people. The 1919 event had ruptured the
earth's surface for about 80 km long, creating a fault known
as Allah Bundh (a dam created by God). This fault is slightly
to the North West of the new rupture caused by the 25 January
2001 quake.
Tectonic
Setting - Geological Instability of the Region.
The quake of 25 January
2001 occurred along a tectonic boundary which, as the adjacent
USGS map illustrates, is characterized by high seismic activity.
This seismic
boundary has been formed by the movement of the Indian tectonic
plate in a north and northeast direction as it collides with
the Eurasian and Arabian tectonic plates.  This
process has continued for millions of years as the India plate
drifted northward.
Compression along
this boundary resulted in a thrust or reverse type of faulting
with the net result being an upward displacement of the Indian
plate and the formation of the Himalayan Mountain Range and the
Tibetan Plateau.
(USGS graphics)
 The more intense seismic activity
occurs by the thrust which is developing at the Himalayan foothills
of India's Uttar Pradesh state, to the east. In the last hundred
years eight earthquakes with magnitude of more than 6 have been
recorded in the Uttar Pradesh region. These quakes resulted by
the gradual shifting of the India tectonic plate beneath the
Tibetan plate in the geologically young Himalayan Mountain range
and along the Himalayan arc.
 Most
recently, on 29 March 1999, a destructive earthquake with magnitude
of 6.8 struck the Kumaon hills of Uttar Pradesh,185 miles (295
kilometers) northeast of New Delhi near India's border with China.
Another destructive earthquake in 1991, measuring 6.1, killed
more than 1,000 people near the town of Uttarkashi in the same
region.
Although not as frequent
as in Uttar Pradesh, earthquakes in India's western region of
Gujarat - as that of 25 January 2001 - have been more powerful
and extremely destructive.
 Tsunami Generation is not Possible
in this Region.
Although the earthquake
of 25 January 2001 was large and occurred near India's western
coastal zone, no significant tsunami activity was expected and
none was reported.
Earthquakes in this
region of India result from compression due to continental-continental
type of convergence, rather than from subduction of tectonic
plates. Large, destructive tsunamis are usually generated from
large earthquakes in zones of tectonic subduction. No subduction
takes place along this tectonic boundary in India because both
of the interacting blocks are continental have the same material
density. For subduction to occur there must be convergence between
oceanic and continental tectonic plates.
Subduction occurs
because the denser oceanic plate sinks below the less dense continental
plate. Most of the vertical crustal uplift from earthquakes in
India occurs primarily over land areas thus seismo-tectonic coupling
in this particular region is not conducive to tsunamigenesis.
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