The Zone of Earthquake

 Sucheta Mullick

An earthquake is a phenomenon that involves shaking of earth's crust and release of energy due to the movement of tectonic plates in Asthenosphere.

Asia is a hotbed of earthquake activity in which Tibet is marked as one of the major earthquake zone. There occurred almost 2046 earthquakes with a maximum magnitude of 7.4 in this region between February 2018 to February 2024.

In India, major earthquake zones are observed in the northern part along the Himalayan mountain range mainly Ladakh, Himachal Pradesh , Uttarakhand , Sikkim, Northern part of UP, Arunachal Pradesh.

The origin of this region is about 40 to 50 million years ago, when the Indian and Eurasian plates started to collide which caused the edges of the plates to fold, forming Himalayas and Tibetan plateau.

Now the question arise that, why only this particular region within the whole plate boundary only facing frequent earthquakes?

To determine the true cause of this, the Geologists of Stanford University, USA, had measured the boundary in the Tibet region through an unusual way by collecting Helium 3 and Helium 4, isotopes released by the Hot springs found in the frozen plateau of Tibet.

But why only Helium isotopes? As only Helium 3 are observed in magma and it turned into Helium 4 by reacting with Uranium in the crust. These features indicates when the quantity of He3 is higher, the crust is thin. But when the concentration of He4 is greater indicates thick crust layer. 

To verify the truth scientists used 225 Hot springs in Tibet region. And the shocking part is that, the Indian plate, which is typically 100 km thicker was discovered to be only 80 to 85 km thick in this specific zone.

To gain more detailed information and further analysis on this topic, the Ocean University of China presents the first SRS & SWS results from 94 Broadband seismic stations shown west east area of southern Tibet in greater detail.

Interestingly, the P & S waves that originated from the center of the earthquakes, propagates more rapidly in the liquid than solid. In the Tibet region the artificially generated primary and secondary waves travels faster in shallow depth from crust that indicates presence of magma in shallow depth. However, there are instances when the speed of waves decreased again in greater depth indicates existence of crust zone. So, the formation is more like Crust - magma - crust.

 So the geologist announced that there should be a crack in Indian plate in Tibetan part where the gap is filled by magma. This process is termed as Delamination by geologists.

On the other side, the American Geophysical Union Conference in San Francisco, 2023 summit highlighted ongoing complex geological processes in the Himalayas where Indian plate is showing the dual movement simultaneously. As it is underplating into Eurasian plate as well as uplifting that give continuous rise in height of the Himalayan mountain range which disturbing the stability.

This tear & peeling of tectonic plate could effect on the basis of intensity and space of stress and thus the potential for quakes.

 

So there are several points of views upon the destructive earthquakes frequently takes place in the Northern part of India and Tibetan plateau. Now the question is that, What is the destiny of Himalayas?

 *Student, Semester V