AGARTALA / GUWAHATI, Sep 26 (TIWN): An earthquake of moderate intensity jolted India's northeastern states and parts of Bhutan on Friday night, officials said. There were no immediate reports of casualties or damage to property."The quake, measuring 4.6 on the Richter Scale, occurred at 10.27 p.m. and had its epicentre in Assam's Darrang district bordering China," said an official of the meteorological department.The earthquake was felt in some parts of Assam, Tripura, Arunachal Pradesh, Meghalaya, and adjoining areas of northeastern region, besides parts of Bhutan. It lasted for about 10 to 12 seconds.India's northeast is considered the sixth major earthquake-prone belt in the world. Guwahati, Shillong and Agartala are the three Northeast Indian cities at highest risk of being devastated by an earthquake, with 36 other cities in areas prone to earthquakes, according to government data. Guwahati and Agartala fall in what is called “very severe intensity zone”, or zone V, the highest-risk earthquake zone. Tripura is very vulnerable to earthquakes as it is situated on seismic zone-V and has higher probability of occurrence of big earthquakes measuring magnitudes 8 and more on Richter scale.The capital of Tripura is having high risk potential in any major earthquake with possibilities of massive collateral damage in the form of casualties and mass injuries.

A recent exercise found that the city is to be uniquely positioned to render massive physical damage to the residents of the city in any case of major natural calamities like earthquakes above 6.5 magnitude on the Richter Scale. 

The exercise was conducted based on major earthquakes like Haiti and Californioa, the highly placed source placed in the state government said.    

Floods are recurrent and have potential for disaster. They occur every year during normal monsoon season and cause temporary floods in valley and plain-lands, and urban flooding in Agartala and other ULBs. So far as Cyclone vulnerability is concerned, wind speed in the State can go up to 55m/s (198km/h) which are occasionally reach the State after crossing Bangladesh. It also affects the State during “Kal Baishakhi” (April-May) of every year. Tripura also witnesses landslides during monsoon in hills and along NH-44. The earth/rocks in the hill range of Tripura comprise of immature formation which is more vulnerable to earthquake tremors, the source further mentioned. 

Besides initiating measures for fighting possible disasters likely to be caused by earthquakes, the state government has already identified 2,000 vulnerable buildings. These include Ujjayanta Palace, abode of former princely rulers of the state in the heart of Agartala town, Raj Bhavan, Neer Mahal, a lake palace built by Tripura’s last king Bir Bikram Kishore Manikya in 1933, MBB College and a large number of school buildings, the source added.

According to the records of the Indian Meteorological Department, 41 earthquakes of 5.6 or lower magnitude have occurred within the coordinates 23.00-25.00ºN and 91.00-93.00ºE encompassing Tripura during the period 1970 to 2000.

The city was severely damaged by an earthquake of 8.7 magnitudes in the year 1897 when the royal palace was also fully destroyed.

Earthquakes of high magnitude over the last 200 years in the region are :
Earthquake of 10 January 1869 (Magnitude 7.5), Sillong plateau earthquake of 12 June 1897 (8.7), Srimangal earthquake of 1918 (7.6), Dubri earthquake of 1930 (7.1), Assam earthquake of 15 August 1950 (8.5).

About 50 million years ago, India — then an island that had previously broken off from a supercontinent called Gondwana, a name still used for what is now Chhattisgarh — slammed into the Eurasian mainland, creating the Himalayas as it collided.

All land on earth rides on “plates”, which glide on the mantle, a rocky inner layer. The Indian plate continues to grind into the Eurasian plate, and as it does, the Himalayas and north India are on shaky ground.

India pushes northeast into Asia at roughly 5 cm every year, causing subterranean stresses that are released in the form of earthquakes every now and then.