Geophysicist:quake 8.1 magnitude

[Guest guest]

Geophysicist insists quake

was of 8.1 magnitude

 

Fresh seismological analysis has revealed that the January 26

earthquake in Gujarat was of 8.1 magnitude on the Richter Scale, and

not 6.9 or 7.9 as stated earlier. And had its epicentre been

Ahmedabad, at least two million people would have perished.

 

On Thursday, US experts had said the quake measured 7.7, but

according to eminent geophysicist Dr J G Negi, the Bhuj-centred quake

was equivalent in magnitude to the one which ravaged Mexico on

September 19, 1985. The Bhuj tremor was about 1,000 times more life-

threatening than the Latur quake of September 30, 1993, which

measured 6.3 on the Richter Scale.

 

Dr Negi, who was awarded the prestigious Shanti Swaroop Bhatnagar

Award for studies on the Koyna quake of 1969, said that the Bhuj

quake had ''softened up'' Ahmedabad, making its parts brittle and

shattered like the windscreen of a car and rendered it more

vulnerable to quakes.

 

The aftershocks are still being felt in various parts of Gujarat, and

tremors measuring up to 6.5 could not be ruled out. ''No one can

predict an earthquake correctly. The only precaution we can have is

to be prepared to face it,'' he added.

 

Speaking to UNI over the telephone from Hyderabad, Dr Negi said

Ahmedabad and Mexico city were nearly 450 km from the epicentre of

the quake. Although Jamnagar was only about 110 km from Bhuj,

destruction in this coastal city was less than Ahmedabad because the

latter had an alluvial, sedimentary four-km thick surface, while the

former had a besalt hard-rock topography.

 

This difference in topography created a wave from Bhuj to Jamnagar,

which was reflected towards Ahmedabad in an amplified intensity. The

Bhuj quake was one of the greatest quakes in the continental shield

area ever recorded, and the biggest ever in 189 years in this

category.

 

In fact, just two seconds before the major quake, at about 0845 hours

on Republic Day, a small, preparatory quake in Bhuj was also

recorded, as if making way for the killer one. This created a ''dual

event'' effect in Gujarat.

 

Discounting the controversy over the actual magnitude of the quake,

Dr Negi, who retired as a director-grade scientist from the National

Geophysical Research Institute and was also a former director-general

of the Madhya Pradesh Council for Science and Technology, said had it

been of the 6.9 intensity, the Indian tectonic plate would not have

been trembling like a pendulum. The energy released in Bhuj was

nearly 1,000 times than that of the Latur case, the energy having a

potential to shake the entire Indian sub-continent.

 

''In fact, Ahmedabad is the typical case of a 'partial collapse' zone

due to the Bhuj quake, vis-à-vis Latur which made little impact on

Bombay.''

 

Reports from Kutch and Saurashtra now corroborate Dr Negi's

observations. In the Rann of Kutch, off Khawda, 60 km from Bhuj,

shining, red-hot or golden lava and a nearly 100-metre-high fountain

of hot, marine water were reported by eye-witnesses, on the day of

the quake. Besides, a mysterious black, sticky liquid oozed out at a

number of freshly-appearing apertures in the area. Several areas in

the district appeared to have sunk, while others rose.

 

Many areas in Kutch district have become undulated: valleys have

replaced hillocks and vice-versa. Saline water turned sweet and some

oases have been replaced by arid zones and vice-versa.

 

Even the course of the Indus river's tributaries is reported to be

affected slightly in neighbouring Pakistan. In the arid district

facing a perpetual drought, water levels have suddenly gone up or

down.

 

This is what was reported to have taken place after the June 16,1819

Kutch quake. Besides, in its north-west, a 90-km-long, a five metre

high and 20 metre deep 'dam', later christened as Allahbund, suddenly

appeared, pushing towards Baluchistan the course of the Indus and its

tributaries. Due to this geological change, the famous ancient port

of Lakhpat was destroyed and later deserted.

 

This led to the then British rulers developing Karachi as an

alternative port for geopolitical reasons in the Persian Gulf.

 

After the 1819 quake, the Indus river's surface flow in the Kutch

region was stopped but the subterranean flow continued. Due to this,

there still remained some oases and sweet-water resources in Kutch

and even in the desert of Rann. The subterranean flow of the Indus

into Kutch district would, according to satellite studies, continue

for five centuries.

 

According to Dr Negi, such geological changes naturally occur after

massive earthquakes. The Kutch quake of 1819 was of 7.9 magnitude.

The only other area in which such mega-quakes can occur is the

Himalayan range, from Kashmir in northern-most India to Arunachal

Pradesh in the northeast. Like the folded Himalayas, the Kutch region

is also a folded zone, rubbing against the stable continental shield.

It was due to similar reasons that the 1811 and 1812 quakes in New

Madrid, USA, both with an intensity of 8.3, had occurred. The Indian

plate's tectonic movement leads to its rubbing against the Himalayas

and then with the Eurasian plate, causing enormous energy release.

 

It was due to these developments that the 1897 quake on the India-

China border (8.6), 1905 Kangda-Himachal Pradesh quake (8.1), the

1934 Munger quake (8.3), the 1950 quake of Assam (8.4) and the 1970

quake of Anjar-Kutch (7.0) had also occurred. The magnitude of the

1819 Kutch quake was 7.9.

 

The latest quake was an example of ''triple junction activity'' as

well. The two rift zones of the gulfs of Kutch and Cambay and

the ''Delhi train'' of seismic wave created the complex phenomenon.

 

According to Dr Negi, the 1819 quake had caused submergence of about

5,000 sq km, which went below the ground level. About 1500 sq km was

raised in the process, which led to the emergence of Allahbund by

five to eight metres. This is a typical activity of folds, which push

the earth's surface up in some places and down in others, like the

Himalayas.

 

UNI