The truth is, they can happen any time. But we are not certain when they will hit. There is no reliable way to predict earthquakes. So, there is no point to unnecessary panic. We should control what we can, and not think much about the uncontrollables.
It is well known historically and scientifically that J&K is prone to earthquakes. Most of its regions lie in Seismic Zones 4 and 5. It is being said that Radon gas could be an indicator of earthquake. If the concentration of Radon gas increases in the atmosphere or soil or in the groundwater, then there are chances of earthquakes occurring in the area.
Lately, numerous mild tremors were felt in the Chenab valley. Many people have apprehensions that the construction of dams across the Chenab valley could be the reason behind the tremors. Does that make sense?
First we must know what an earthquake is. An earthquake is the shaking of the earth’s surface due to a slip in the tectonic plates and it results in release of seismic energy. Or it may be due to a volcanic eruption or magma activity or other stress changes in the earth’s crust. We can say that any shaking of the earth could be termed as earthquake. Mostly, though, we are concerned with earth quakes which occur due to a slip on the fault along the plate boundaries, commonly called tectonic earthquakes.
Now coming to our question, could dams cause earth quakes? The answer in the simplest of terms is Yes. But for dams to cause earthquakes, the area should already be geologically weak and the dam must be constructed near the fault lines or in the area where fault lines are present. There is no way to predict even when the dam would induce an earthquake. Such earthquakes are termed as reservoir-induced seismicity (RIS). The Konya dam is said to be an example of RIS, where an earthquake of 6.5 magnitude on Richter scale occurred three years after the dam was constructed, killing 180 people.
The RIS, though, is not fully understood. When the dam is constructed and reservoirs are filled with the water, the stress on the earth in that area changes. The filling up of the reservoir with water increases the pressure on the rocks beneath and lowering the level of the water in the reservoir would decrease the pressure on the underlying rocks. The fluctuation of pressure on the underlying rocks could result in disrupting the delicate balance between the tectonic plates. That could make them shift, causing earthquakes.
An increase in water pressure would force the water to move downwards, sometimes resulting in further widening of the cracks or faults in the rocks or creating new tiny cracks altogether. The result would be enhanced instability of the rocks beneath, causing earthquakes. The water moving deeper could act as a lubricant for the rock plates that are being held together by friction alone. The lubrication would make the plates slip. These things could happen. But when the earthquake hits, it is not possible to say beyond doubt that the culprit was the dam. So, not constructing dams in seismic zones areas would be better. Though as of now there is no certainty that dams are a reason behind earthquakes. But they well could be.
What we are sure, though, is that dam collapses are more likely to occur in earthquake-prone areas. Because the shaking of the earth could result in the failure of the dam. That could cause immense loss of life and property. A dam saturates the soil beneath it, so there are chances of huge landslides in areas where dams are built. So, as far as possible, dam construction should not be undertaken in earthquake-prone areas.
The reality, however, is that dams are a must for energy generation. If we are to construct a dam, we must ensure that at least only small dams are built. The hazards of small dams are less. Build many small dams, instead of one large dam. That would be somewhat safer. Small dams are more eco-friendly than the larger ones. Large dam construction should be stopped altogether.
Panic can get us killed. We should learn to live with earthquakes or any other disaster. We should ensure that our buildings are earthquake resilient. That means we should follow the building codes of seismic zone areas. There should be mock drills related to earthquakes. The Dos and Don’ts must be strictly followed, in case an earthquake hits the area. Preparedness before the disaster would save us during the disaster.
The writer is a student at GDC Kargil (Sankoo Campus)