THE EARTHQUAKE
OF 25 JANUARY 2001 IN 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
23.40N 70.32E, 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 asftershocks (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 earhtquake,
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 $5.5 billion and rising.
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 Indias 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 seismotectonic coupling in this
particular region is not conducive to tsunamigenesis.
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© 2001 George Pararas-Carayannis
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