The 7.9-magnitude earthquake that wreaked havoc in Nepal and parts of India has heightened interest in seismic activity of the region and the level of preparedness needed to meet any eventuality.
However, the land mass of Mysuru and most parts of the State are said to be stable and earthquakes if any, would be of moderate intensity.
S. Govindaiah, professor and chairman, Department of Studies in Earth Sciences, University of Mysore, told The Hindu that though there are fractures and fissures in Peninsular India, the basement rocks were formed more than 3,000 million years ago and are stable.
“Besides, the region here has Fractures (separation or break in rock formation) but no Folds (when a flat surface becomes curved owing to deformation caused by stress).
The Himalayas is an example of Fold Mountains formed by the collision of the Indian Plate with the Tibetan Plate. It was rising at the rate of approximately 2 cm per year. Hence, the region is geologically unstable and susceptible to high intensity seismic waves, Dr. Govindappa said.
However, Shear Zones in Mysuru belt are relatively weak zones in the Earth’s crust along which earthquakes can happen. Here a single land mass is broken into different parts and are on a collision course that can cause tremors.
The Shear Zones of the region are Bhavani-Moyar Shear Zone, Kollegal Shear Zone and Cauvery Shear Zone. However, test results prove that the crust is thick and hence, is stable, said Dr. Govindappa.
In the event of any seismic activity, it will be of a magnitude of 3 to 4 on the Richter Scale which can cause mild tremor causing cracks on buildings constructed on weak foundation. “However, there is no history of an earthquake of a magnitude 7 or 8 in this region,” he added.
The Chamundi Hill is an example of what was once a weak zone and is about 800 million years old, but is now stable, the geologist said.
