THE FAULT LINES OF SAURASHTRA

The topography of the arid peninsula of Saurashtra has metamorphosed into lush green in the past two decades. Thanks to good monsoons resulting in healthy agriculture and forest cover.

- Jumana Shah

However, little did Kathiawar expect that this boon would eventually become a bane of sorts for the region. In the past two years, many regions in the peninsula have been experiencing seismic swarms—several small earthquakes measuring less than 3.4 on the Richter scale keep recurring for an extended period of time. Despite being low-intensity, their strange recurrence has left residents unnerved.

A study by the Institute of Seismological Research (ISR), Gandhinagar, indicates these quakes do not necessarily presage a bigger one. But it underlines that earthquakes cannot be predicted despite the leap in technology. ISR director Dr Sumer Chopra explains that Gujarat and the surrounding states rest on the Deccan Traps, a large area of volcanic lava cooled into rock, but with a lot of fractures. “The region is being subjected to hydrological loading in addition to tectonic loading. Amreli, for instance, has been experiencing above-average rainfall for the past few years. The region is prone to moderate and low-magnitude earthquakes within the depth range of ~ 3 to ~ 24 km,” Chopra tells India today.

A previous study has indicated that swarm earthquakes in Jamnagar were observed in the monsoon season, following heavy rains that drastically raised the water table by ~ 24 m, thereby increasing the pore pressure by ~ 2.0 bars. The stress changes are sufficient to trigger small earthquakes.