Why the recent surge in earthquakes?
“There are many things about the inner workings of the Earth and earthquakes themselves that we do not yet understand,” says Vineet Gahalaut, director of the National Centre for Seismology (see ‘A promising start’,). It is still an actively developing field with several unknown variables under research.
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While some of the strain is released during the jerk, the movement of the plates causes other regions along the fault to get loaded with stress and results in a chain of seismic events that can unfold over millions of years.
But new research is challenging long-held beliefs and pointing at other processes that may be leading to earthquakes. For instance, a study published in Science in November 2016, says the curvature in a fault is a prominent factor responsible for the location, timing and magnitude of an earthquake. It states that the rupture threshold or stress-bearing capacity of surfaces is varied along curved faults. Hence, the stress released by one rupture is passed on to neighbouring surfaces and the impact of the temblor is restricted. On the other hand, the stress-bearing capacity is more homogeneous along flatter faults, giving rise to a higher likelihood of large simultaneous ruptures.
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It is the “floating” of lithospheric plates on the asthenosphere that affects tectonic plate movements, causing earthquakes.
In 2010, researchers from Monash University, Canada, appeared to have contradicted this theory when they suggested that plate tectonics was more of a “top-down” system than a “bottom-up” one. They stated that the rising and sinking of the Earth’s crust, and not what is below it, determines the motion of plates. Yet another study by a team from the University of Columbia, USA, published in Nature in July 2016, indicates that the system is not so simplistic. They found that tectonic plate movement is not restricted to activity in the lithosphere and may be influenced by small-scale convection in the lower, semi-molten layer of the asthenosphere.
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