In the past month, the Coronavirus has not been the only big news emerging from Assam and other Northeast states. A few days ago, we witnessed a strong earthquake that shook everyone and everything. The Northeast region is no stranger to earthquakes but can we learn more about this phenomenon? What makes this region so susceptible to earthquakes? What can we do to protect ourselves? Is there a way to predict earthquakes? EastMojo spoke with Soumitra Dasgupta, Geologist, Geological Survey of India to understand more on the matter.
Will it be safe to say that North East India is most susceptible to frequent earthquakes?
The short answer is Yes. All of the Northeast, not just Assam, comes under the Seismic zone V, which makes it extremely susceptible to frequent, recurring earthquakes. The tectonic set-up makes it a region of high seismicity.
The one we experienced recently measured over 6 on the Richter scale but thankfully the damage was nowhere near catastrophic. What explains this phenomenon?
The photos of building damages in Guwahati and a few other places showed that while there was some damage, it was neither extensive nor considerable. However, that is what our eyes saw. Immediately after the earthquake, our team of experts went to Assam and started collating information and field data: both visible and the one which needs measurements. As of now, the work is ongoing. The Richter scale is only a measure of the strength of an Earthquake. The attenuating properties of the soil, rocks; potential for liquefaction etc all contribute to the damage inflicted by an earthquake. Was it a strong earthquake? Yes. Does this mean future earthquakes of similar ferocity will also not cause much damage? No. Each earthquake is different, and the latest Assam one was no different.
Experts have talked about the Kopili Fault in light of the recent quakes. Could you explain the concept and why it remains such a curious phenomenon for experts? Do we have examples similar to the Kopili Fault in other parts of India or the world?
The Kopili Fault is a unique tectonic feature which is regarded as an important active Fault in the north-eastern region. It has been measured that the Indian plate is on an average moving at approximately 5 cm per year in the Northeast direction. This results in an oblique collision between the Indian and Eurasian plates in the North-eastern Region. However, along the length of the collision zones, the rate of the convergence may not be uniform due to number of factors such as rheological properties, local structural heterogeneity etc. The differential rate of convergence may attribute to formation of strike-slip fault or may activate existing ones. Kopili represents one such Fault. Given that it is an active Fault in one of the most seismically active regions of the country, of course, it is of extreme interest to us geologists.
In terms of what we want to learn from it, primarily we want to understand the nature of this fault, the level of hazard it poses, its seismological nature, etc. And of course, as researchers, it is imperative that we perform long-term observations of the Fault. You see, an earthquake is a few seconds long, but that is what the common people feel and see. We never stop studying these phenomena.
Even though we are in a seismic zone, it seems there is little on the part of the government in terms of planning urban spaces keeping that in mind. How, according to you, should a city, a state or a region adapt to ensure that the seismic threat is well and truly accounted for?
I disagree with the first part of the question. As early as 2005, the Disaster Management Act was enacted which led to the formation of the National Disaster Management Authority. There are numerous awareness campaigns that the government has run and continues to do so at every level. The Bureau of Indian Standards has in place the building code for Earthquake resistant design. The implementation of these laws, yes, that one might argue with but I am not the best person to speak on/against that. My suggestion is this: if you are constructing in a Seismic V Zone, it is most essential to ensure your structures can withstand earthquakes. Sure, it will cost more to construct, but it will also remain to stand. People need to understand what is at stake here. Awareness is a 24*7/365 affair, not just about a workshop or an online session.
Over the past decade, there has been a lot of focus on building mega-dams in the Northeast. As a Geology expert, how safe do you think such dams would be in the case of a major earthquake? What kind of potential damage can be caused if things do go wrong?
I do not work on dams, we have a separate division: the Engineering Geology division which assesses each project vis-a-vis the earthquake threat. They carry out geotechnical investigation for feasibility studies, pre-construction and detailed investigations and also construction stage investigations.
Is it a risk to make mega-dams in Seismic V Zones? Yes, if they are not earthquake resistant! Is there a way to protect them from even the strongest earthquakes or at least limit the damage? Of course. Dams can be built in a way to withstand the effect of an earthquake.
There is no way to predict an earthquake, yes. But what are the ways we can improve our “shield” if an earthquake does strike?
This is an interesting question. My experience has shown that we have come a long way in terms of creating awareness. However, you see, an earthquake will always be sudden: no matter how much you prepare, what if you are having a cup of coffee on a roof? You will run no matter what your training is. Awareness building is stage one, now we must aspire to build resilience. Japan is a great example to emulate.
Last, has there been any study that seeks to explain if climate change has/is having an impact on earthquakes? I ask this because climate change has been linked to the occurrence of cyclones, storms, and floods. But can one say the same about earthquakes?
For now, there is no visible corelation to suggest that climate change is linked with earthquakes.