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Expert stresses on study of earthquake history

By AJIT PATOWARY

GUWAHATI, May 9 � Noted expert in earthquake engineering and geotechnical engineering, Dr Sarada Sarma of the Imperial College in London has underscored the need of studying historical earthquakes to save the people from earthquake-related tragedies.

Very large earthquakes may have recurrence periods of 500 years, 1,000 years, etc. If such earthquakes are properly studied, structures could be saved from the devastating impacts of such phenomena with preventive measures. Here lies the importance of studying the historical earthquakes, he said.

The late Professor Nicolas Ambraseys was an expert in the study of historical earthquakes and found information in the Middle East about earthquakes of Biblical periods. Prof Ambraseys was Dr Sarma�s guide during his PhD research in the Imperial College of London. The late Professor used to question Dr Sarma, now an Emeritus Reader at the Imperial College, about earthquakes in Assam. Dr Sarma used to tell him that it would be very difficult to find those records in India. For, the Indians are very much pessimistic about earthquakes. They blame the earthquakes on God and refrain from writing about them.

Within Assam, no place is really safe from large earthquakes. This also enhances the importance of studying the historical earthquakes, said Dr Sarma.

Further, he observed it is a fact that people tend to forget bad events of the past. �In the history of seismology, we tend to forget past damaging earthquakes very soon,� he said.

Recounting his post-2001 earthquake visit to Bhuj, he said he had found the Bhuj people bereft of any knowledge of their 1819 earthquake, which was far more damaging than that of the 2001. The same thing happens in other parts of the world as well. That is why, it is necessary to remind people of these events occasionally. There are mentions of past damaging earthquakes in EA Gait�s A History of Assam. And those included the ones occurring in 1548, 1626, etc. Some of these were very damaging.

�Now to get an idea of the size of those earthquakes, we need more information. For example, do we have any information about other places where those earthquakes were felt? From the geographical area where an earthquake is felt, we can get an approximate idea of the size. If we can get an idea of the epicentre of the earthquake and at the same time about the damage, then we can approximate the size. That is why, the historical information need to be detailed. But sadly, we do not have such details. The histories written during the Ahom period also lack such information,� he regretted.

Heritage structures: In reply to a question concerning the abilities of the structures of the Kamakhya temple, the Shiva Doul, the Rangghar, the Karengghar, etc., to withstand jolts of the major earthquakes, he said though it is commonly believed that these structures could survive the earthquakes of 1897 and 1950, in fact none of them were in the meizoseismal area (the area of maximum damage) of those earthquakes.

Kamakhya temple, located closer to the epicentre of the 1897 earthquake, which was on the Northern edge of the Shillong Plateau, suffered some damages under the impact of that earthquake. But during the occurrence of the 1950 earthquake, its distance from the epicentre of that seismic event was much, and hence it was not damaged.

On the other hand, the distance between the epicentre of 1897 earthquake and Sivasagar was much, while this historic town was within a relatively closer distance from the epicentre of the 1950 earthquake.

The impacts of the earthquakes reduce with the distances. But, nobody can claim that large earthquakes will not happen nearer to the above sites, asserted Dr Sarma.

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Expert stresses on study of earthquake history

GUWAHATI, May 9 � Noted expert in earthquake engineering and geotechnical engineering, Dr Sarada Sarma of the Imperial College in London has underscored the need of studying historical earthquakes to save the people from earthquake-related tragedies.

Very large earthquakes may have recurrence periods of 500 years, 1,000 years, etc. If such earthquakes are properly studied, structures could be saved from the devastating impacts of such phenomena with preventive measures. Here lies the importance of studying the historical earthquakes, he said.

The late Professor Nicolas Ambraseys was an expert in the study of historical earthquakes and found information in the Middle East about earthquakes of Biblical periods. Prof Ambraseys was Dr Sarma�s guide during his PhD research in the Imperial College of London. The late Professor used to question Dr Sarma, now an Emeritus Reader at the Imperial College, about earthquakes in Assam. Dr Sarma used to tell him that it would be very difficult to find those records in India. For, the Indians are very much pessimistic about earthquakes. They blame the earthquakes on God and refrain from writing about them.

Within Assam, no place is really safe from large earthquakes. This also enhances the importance of studying the historical earthquakes, said Dr Sarma.

Further, he observed it is a fact that people tend to forget bad events of the past. �In the history of seismology, we tend to forget past damaging earthquakes very soon,� he said.

Recounting his post-2001 earthquake visit to Bhuj, he said he had found the Bhuj people bereft of any knowledge of their 1819 earthquake, which was far more damaging than that of the 2001. The same thing happens in other parts of the world as well. That is why, it is necessary to remind people of these events occasionally. There are mentions of past damaging earthquakes in EA Gait�s A History of Assam. And those included the ones occurring in 1548, 1626, etc. Some of these were very damaging.

�Now to get an idea of the size of those earthquakes, we need more information. For example, do we have any information about other places where those earthquakes were felt? From the geographical area where an earthquake is felt, we can get an approximate idea of the size. If we can get an idea of the epicentre of the earthquake and at the same time about the damage, then we can approximate the size. That is why, the historical information need to be detailed. But sadly, we do not have such details. The histories written during the Ahom period also lack such information,� he regretted.

Heritage structures: In reply to a question concerning the abilities of the structures of the Kamakhya temple, the Shiva Doul, the Rangghar, the Karengghar, etc., to withstand jolts of the major earthquakes, he said though it is commonly believed that these structures could survive the earthquakes of 1897 and 1950, in fact none of them were in the meizoseismal area (the area of maximum damage) of those earthquakes.

Kamakhya temple, located closer to the epicentre of the 1897 earthquake, which was on the Northern edge of the Shillong Plateau, suffered some damages under the impact of that earthquake. But during the occurrence of the 1950 earthquake, its distance from the epicentre of that seismic event was much, and hence it was not damaged.

On the other hand, the distance between the epicentre of 1897 earthquake and Sivasagar was much, while this historic town was within a relatively closer distance from the epicentre of the 1950 earthquake.

The impacts of the earthquakes reduce with the distances. But, nobody can claim that large earthquakes will not happen nearer to the above sites, asserted Dr Sarma.