Reservoir Induced Seismicity

The phenomenon of dam-triggered earthquakes is known as Reservoir Induced Seismicity.
Reservoir Induced Seismicity is not well-understood, but basically what happens is this:
When a dam is built and the reservoir filled with water, the amount of pressure exerted on the earth in that area changes dramatically. When the water level of a reservoir is raised, pressure on the underlying ground increases; when the water level is lowered, the pressure decreases. This fluctuation can stress the delicate balance between tectonic plates beneath the surface, possibly causing them to shift.
Another factor is the water itself. When the water pressure increases, more of it is forced into the ground, filling cracks and crevices. All of this water pressure can expand those cracks and even create new, tiny ones in the rock, causing greater instability below ground. What’s more, as the water sinks deeper, it can act as sort of a lubricant for rock plates that are being held in place by friction alone. The lubrication can cause those plates to slip.
Koyna Deep Drilling project
A major national project involving deep drilling in the earthquake-prone Koyna intra-plate seismic zone in Maharashtra has been initiated by the central government for conducting scientific studies related to earthquakes – international project to be led by Indian scientists – the total cost of the project is Rs.472.3 crore for five years.
The proposed scientific deep drilling investigation in Koyna region will provide a unique opportunity to better understand the mechanism of reservoir-triggered earthquakes, developing a forecast model and assessing earthquake hazard in a stable continental region.
The main objective of the project is to undertake a deep borehole (6-8 kms) investigations in the Koyna-Warna region of Maharashtra where small and micro-earthquakes of varying magnitude have been occurring in a restricted area of 20 x 30 sq. km. for the past five decades, including the largest earthquake of magnitude 6.3 in December 1967. Past studies have clearly demonstrated that the Koyna-Warna area is a natural laboratory to study reservoir-triggered earthquakes, perhaps the best site anywhere in the world.
The project will also provide crucial insights into Deccan volcanism and mass extinction; thermal structure and state of stress in the lithosphere; geothermal potential of the West Coast Belt as well as the geothermal record of climate change in the region.

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