From CK Nayak
New Delhi: Eight new cities including five from the North East region have been added to a Union government list of urban areas vulnerable to earthquakes of ‘very severe intensity’.
In all, 81 new towns and cities were added to the ‘list of areas prone to earthquakes’, bringing the total to 107, according to government data released recently.
The latest list included Jorhat, Sadiya, Tezpur, Imphal and Kohima (all in the North East) and Bhuj, Darbhanga and Mandi.
It is not clear whether Shillong has been named in the old or new list since the hill city is neither in the old list nor in the new entries even though the city has been affected by many earthquakes in the past and lies in the same seismic zone of the Himalayan belt. In 2002, only Guwahati and Srinagar were marked earlier in what is called a “very severe intensity zone” or Zone V, the highest risk seismic zone.
The panic spread by last week’s (April 14) earthquake is a continuing warning that India has vast areas of vulnerability.
Nearly 60 per cent of the sub-continental landmass is vulnerable to earthquakes, according to data released last year by IndiaSpend, an organisation that deals with data journalism, noting 38 earthquake prone cities (with over half a million population in seismic zones III, IV and V), based on 2002 data from the National Disaster Management Authority.
A big Himalayan earthquake – more than 500 years overdue – is expected, although no one can predict when this might be, IndiaSpend had reported.
The Himalayas and north India are on particularly shaky ground and in the geological past, before humans, India had broken off from an ancient supercontinent called Gondwana (a name still used for what is now Chhattisgarh).
The Indian and Eurasian plates have been in conflict for 50 million years at this collision zone, with the Indian plate diving, northward, under the Eurasian plate. This is why the Himalayas, including Mount Everest are still growing, the report said.
As many as 392 earthquakes of magnitude greater than 3.0 were located in and around India in 2015, the seismological network operated by Earth System Science Organisation-National Centre for Seismology reported. Of these, 136 earthquakes occurred in India, 114 in Zone-V, 14 in Zone-IV, five in Zone-III and three in Zone-II, respectively.
An analysis of the past 30 years of earthquake data suggests that there is no increase or decrease in seismicity rate. The only serious earthquake that modern India remembers is the temblor that killed about 20,000 in Gujarat in 2001, the report said.
The 2004 tsunami, which resulted from the third-most most severe quake ever recorded at 9.3 on the
Richter scale occurred when the Indian plate slid with greater violence than it normally does under the neighbouring Burma plate, upon which rest the Andaman and Nicobar islands. It caused a 100-km-long rupture in the crust, thrusting the seafloor upwards and pushing up masses of water, setting off tsunamis that killed 230,000 people in 14 countries.
No Indian metropolis has witnessed a serious earthquake, although Delhi lies in high-risk seismic zone
4. Mumbai, Chennai and Kolkata lie in zone 3, the report said. The 1950 Assam earthquake may have geologically set the stage for a really big one in the Himalayas, according to geologists.
The Northeastern part of the country continues to experience moderate to large earthquakes at frequent intervals including the two great earthquakes and since 1950, the region, on an average, experiences an earthquake with a magnitude greater than 6.0 every year, NDMA sources said.
The increase in earthquake risk is due to a spurt in developmental activities driven by urbanization, economic development and the globalization of India’s economy. The increase in use of high-technology equipment and tools in manufacturing and service industries has also made them susceptible to disruption due to relatively moderate ground shaking, the report added.