It is hard to forecast earthquakes with the current state of knowledge. Research is going on to predict the place, time and intensity of earthquakes.
Dr OP Mishra, Director, National Centre for Seismology, in a conversation with Jitendra Choubey, says we need sound technological solutions to address our development planning — no need to create a phobia against development.
Why Himalayan region has been experiencing frequent earthquakes?
Tectonic configuration of the Himalayas in a way that each Indian plate collides with the Eurasian plates. Around 50 million years ago, during the formation process of Himalayan ranges, Indian plates were subducted beneath the Eurasian plates. The dynamics of plates are in such a way that the Indian plate tries to move on further, while the Eurasian plate resists its movement. These frictional motions – resistive and forward – cause a collision of tectonics plate or collisional subduction in the Himalayan region.
It makes rocks subject to too much strain and energy accumulation. Finally, it reaches a point when the rock’s searing and bearing capacity is superseded by stress, resulting in rock ruptures and ultimate earthquakes happening everywhere in the Himalayan region. It makes this region quite dynamic. The measurement of the earthquake is in ‘magnitude’, which shows the total content of energy gets released. I see it as very similar to human anatomy that an earthquake is nothing but a heart attack of Earth.
How many seismogenic faults exist in the Himalayas?
An earthquake generates faults, and faults generate the earthquake. There are lots of partitioning of the seismogenic faults which give relative motion to the blocks. There are some regional faults, the main central thrust (MCT) fault which pushes further north. Indo-Gangetic plain is partitioned by Himalayan frontal thrust(HFT). So HFT is the boundary between the Gangetic alluvial and Shivalik.
Further north is another partition called Main Boundary Thrust (MBT). It is a boundary between Shivalik in the south and Sub-Himalayas and the lesser Himalayas in the North. Then there is the boundary of the main central thrust (MCT), which separates Greater Himalaya and Lesser Himalaya. Besides, there are many minor faults like Brahmaputra, Taapsee, Kangra, and Dhubri faults in Assam. However, some faults are already mapped while some faults are yet to be mapped, i.e. hidden faults.
Are we getting nearer to the forecast earthquake?
It is impossible to predict any earthquake with the present state of knowledge. Furthermore, the prediction has four stages – Anticipation, Expectation (increasing certainty), Justification, and Authentication regarding location, time and size.
We crossed all three forecast stages and demarcated the globe into different seismogenic zones. Based on it, today we can answer that there is a high possibility of an earthquake in the Himalayas. However, we can’t answer where, when, and at what depth and size. Globally, the study is going on to decipher the fourth stage.
Is there any need for some basic technology?
In studying seismology, there is a huge difference between laboratory experiments and the real action of the Earth. For instance, if we take a particular rock and apply measurable pressure and temperature to test its searing and bearing capacity. But in reality, it behaves differently at different sub-surface levels.
Though there are three crucial Earth layers, however, there are a lot of sub-layers and physical component varies from layer to layer. Seismologists are searching for the earthquake diagnostic precursors to tell about earthquake occurrence of time, place and intensity. Until now, we can warn you about the vulnerability of zones and prompt you to take precautions.
Is there any relation between climate change and earthquakes?
I wrote a scientific paper in 2014 arguing climate change vis-à-vis earthquakes. Climate change led to speeding up the melting of glaciers, so the reduction in ice thickness. So, now, a lot of the brittle failure is taking place because of the lessening of the ice thickness block, consequently reducing Earth’s crust load. It results in lower modulation seismicity of 3.5-4.1 magnitudes of earthquake at a micro level in the polar region and Himalayan glaciers.
The Himalaya ecosystem is shared among ten countries. But there is no holistic plan in place to manage the Himalayas to save its melting glaciers. Do you think managing of Himalayas in a holistic way to reducing the earthquake disaster?
Himalaya is regarded as a water tower and an immense resource zone for most Asian countries. Sustainable management of the Himalayan ecosystem to reduce the fast melting of glaciers is the need of an hour to save water wastage. If we do not intervene timely, earthquake impact would further aggravate as I mentioned, climate change cause mild tremors. These mild tremors cause rock cracks at the subsurface and surface levels. When the melting of the water or the water from the Himalayan starts percolating and gushing into those cracks, further widening and leading to instability. All of these are not visible to the naked eye. Take the example of Joshimath. Joshimath is located in the rupture zone of the Chamoli earthquake of 6.8 magnitude in 1999. Then after, there were over 2000 aftershocks (mild tremors) of magnitude between 5 - 5.6 in the next year.
Are the aftershocks major reasons behind the subsidence of Joshimath?
Over 2000 aftershocks happened between 1999-2000, which is the primary reason behind the subsiding of Joshimath instead of developmental work such as tunnelling. We are assessing the crack volume of the subsurface rock to suggest what will be long-term remedial measures such as how to get sustainable water passage and the possibility of the Joshimath.
Don’t you think developmental work accentuates the earthquake and subsidence of Joshimath?
Making a construction or development of infrastructures is a very localised phenomenon. It is true that sometimes developmental processes also cause ecological imbalances. However, they also make compensation through afforestation work or other bioengineering solutions. You only need competent and sound technological solutions to address development planning —no need to create a phobia against development. Japan is a great example.