HYDERABAD: The recent bouts of highly localised tremors and sounds emerging from the earth in parts of Hyderabad are triggered by rapid and unsustainable urban growth, warn geophysicists. Unhindered construction activity, involving building of cellars and sub-cellars, and sinking borewells deep have further increased the vulnerability of Hyderabad to seismic events.
Besides human activity, natural phenomenon, including heavy rainfall in short spans of time, location of water bodies, and sudden increase in groundwater table are also responsible for tremors. One of the epicentres is located at Durgam Cheruvu, which has, of late, emerged as a major tourist destination.
Geophysicists have found a “trend”, a type of seismic line, running from KBR Park to Durgam Cheruvu. Incidentally, most of the seismic activity, though minor in nature, was recorded in Jubilee Hills area where KBR Park and Durgam Cheruvu are located. These areas have been witnessing construction boom with several multi-storeyed buildings coming up. Apart from Jubilee Hills, areas like Toopran, Gajwel, Medchal, Patancheru, Gandipet and Pratap Singaram — all around Hyderabad — have also recorded localised tremors.
Prof G Ramadass, retired professor of geophysics, Osmania University, said the increase in the frequency of seismic events could be attributed to rapid and unsustainable urban growth, which has further increased the vulnerability of Hyderabad to seismic events.
“Our study revealed, there is an increase in the frequency of micro earthquakes in Hyderabad in the last 47 years. They are localised swarm-type micro earthquakes, concentrated mostly around Gandipet and Jubilee Hills,” he said.
Prof Ramadass, who is also associated with the Centre of Exploration Geophysics, OU, said with increasing urbanisation, the occurrence of micro earthquakes is significantly increasing.
“Seismologists and urban experts should give a fresh thought based on the distribution of tremors,” he said, adding that as urban concentrations grow, there is a need to identify structurally weak zones to take up hazard management plans.
Hyderabad is also experiencing tremors following events of heavy rainfall. The unprecedented rains in October also triggered seismic activity in and around the city with reservoirs getting filled up.
For instance, in 1982 there were 48 micro seismic events and 16 in 2017. Jubilee Hills had witnessed 979 tremors between 1994 and 2017, the severest being 2.8 on the Richter scale. As heavy rains induce more percolation of rainwater into the water table, water fills up the gaps or air pockets created by digging of borewells and blasting of rocks for construction of cellars or sub-cellars.
As water seeps into the gaps, it creates sounds and vibrations. Such incidents were reported at Borabanda during the recent heavy rains, he said.