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Source: Innovation Report

Context

According to a study published in Seismological Research Letters (2017), over 700 human-caused earthquakes have occurred around the world in the last 150 years.

What are human-caused earthquakes?

These are earthquakes caused by human activity rather than natural tectonic movements. Mining, groundwater extraction, dam construction, and fracking all affect the earth's crust, which causes seismic activity. Over 700 human-caused earthquakes have been documented worldwide in the last 150 years.

Delhi NCR: Prone to Human-Induced Earthquakes – Key Reasons

• Location of the Seismic Fault Line: Delhi sits in Seismic Zone IV, one of India's most earthquake-prone areas. The region is traversed by active fault lines, rendering it naturally exposed to seismic shocks.
• Excessive removal of groundwater for agriculture and consumption causes a decline in the water table. This lowers the subsurface pressure that supports the crust, perhaps causing tremors.
• For example, a study found that between 2003 and 2012, seismic activity increased when groundwater levels fell dramatically. After 2014, when water levels normalized, earthquake frequency decreased.

How does climate change affect seismic risks?

• Melting glaciers  Increase Uplift Pressure: Rapid glacial melt in the Himalayas (due to rising temperatures) lowers surface weight.  This causes isostatic rebound, in which the crust rises and shifts, potentially activating faults underneath.  For example, in Uttarkashi (Uttarakhand), greater seismic activity has been seen near the retreating Gangotri Glacier, which has been connected to glacier thinning and uplift.
• Changing Rainfall Patterns Lead to Landslides and Crustal Stress:  Intense rainfall and flash floods, exacerbated by climate change, induce fast groundwater recharge and erosion, threatening fault stability.  For example, in Kodagu (Karnataka), abnormally high rainfall in 2018 caused landslides and mild tremors as a result of destabilized slopes and crustal shifting.
• Sea-Level Rise and Coastal Seismic Pressure: Rising sea levels increase water pressure on coastal plates, particularly in delta zones.  This can either suppress or activate tectonic stresses along coastlines.  For example, in the Sundarbans (West Bengal), changes in sediment load and sea-level rise have generated worries about future seismic dangers in this low-lying, tectonically sensitive zone.

Source: The Hindu