On shaky ground

Sunday, 05 July 2020 | Shalini Saksena

On shaky ground

Sunday, 05 July 2020 | Shalini Saksena

The Capital region lies on tectonic faultlines. That’s common knowledge. What's more alarming than ever is the frequency with which NCR has shaken. Eighteen times in three months. Is it another Christchurch in the making? SHALINI SAKSENA explores

On July 3, an earthquake of magnitude 4.7 on the Richter scale hit Delhi-NCR. However, this was not the first one. There have been 17 earthquakes in Delhi-NCR between the magnitudes of 3 to 4.5 on the Richter Scale lately, but it is no cause for panic even though some of these lasted longer and caused a bit of worry for Delhiites. Experts say that India is highly vulnerable to earthquakes since the entire Himalayan belt falls on the tectonic plates. But the real cause of alarm is that Delhi falls in the Zone IV (severe intensity) of seismic activity. This means that if an earthquake of even a 6 on the Richter hits the metro, most buildings will flatten and an unimaginable number of people will die.

What makes this region vulnerable is that it has not seen any activity in over 200 years and now, experts insist, a shaker is long overdue. What’s causing them to be anxious is that while some plates in the region have shown some activity, the major plates which were locked thus far, can move any time. This, they tell you, is like a ticking bomb. Unlike a cyclone, which can now be predicted, there can be no forewarning for an earthquake.

Professor TG Sitharam, Director, IIT Guwahati tells you that the than 10 earthquakes in Delhi have caused panic. “Knowing the seismic history of Delhi, the occurrence of minor earthquakes in the vicinity of Delhi is not very unusual,” he says.

Seismotectonics of the Delhi region indicates the presence of several lineaments and faults in the region, which are responsible for earthquake activity in the region. The outcrops of Alwar quartzites in south Delhi, are generally highly jointed and folded. Some activity near the junction of Delhi-Hardwar ridge and the Lahore-Delhi ridge. Most of the area of Delhi is covered by alluvium due to Yamuna river.

“Earthquakes happen in and around Delhi-NCR because of its several faultlines. Maybe lockdown had an impact on the people (who are at home) to feel these vibrations and shocks. The Indian Plate is at present moving North-east at five cm (2.0 in) per year. Due to this movement, the intra fault lines around Delhi are subjected to movements and these shocks are very common. Most of these shocks are shallow focus and very small intensity (with only the quake occurring at Rohtak was above 4 which falls under the medium intensity quake). Also, note the nearest point from the Main Boundary Thrust (MBT) to Delhi is at around 200 km. The MBT is a plate boundary on which large earthquakes greater than 7 can happen,” Sitharam explains.

The Himalayas is known for its high seismic activities. When it shears there, the shocks travel to Delhi and can cause damages. If any quake occurs in the Himalayas or even the Hindukush, the impact could be felt in Delhi-NCR. The 2015 Nepal earthquake which was felt across the Indo-Gangetic belt including Delhi is one such example. Delhi lies on the Indo-Gangetic belt which has sediments and these sediments amplify the earthquake motion and thus its impact is much more. No one can say when earthquakes can happen and it is not possible to predict earthquakes. Science of prediction of earthquakes has not progressed much, one is told.

There is a reason why India is prone to disasters like floods, cyclones and earthquakes. The collision zone between the Indo-Australian plate and Eurasian plate in the Northern and Northeastern part of India makes it more vulnerable for hazards. Floods, cyclones and earthquakes are natural hazards. When there are natural hazards, they can't be prevented. These natural hazards are termed as disasters when they occur in places that are heavily inhabited areas. Factors that are manmade which will help in turning a hazard into a disaster. Disaster risks in India are further compounded by increasing vulnerabilities related to high population density, changing demographics and construction quality.

The main reason for India being more prone to so many hazards floods, earthquakes and cyclones is ignorance and lack of knowledge. People are not aware of the serious effects and scale of these disasters until they are affected by it. People are also complacent and assume that it is not going to hit us. It is not that only India faces a large number of disasters and many countries face more disasters than we do. But, India's population and density of urban areas are the major reason for being prone to disasters. Earthquakes do not kill people it is the buildings. The quality of construction also plays a major role.

Interestingly, while, it is easy to map the entire Gujarat region by testing the soil strength and the areas that have been showing seismic activity, it will take a long time to do the same in North India.

“Gujarat region and Northern India region are not comparable. Seismic activity is much higher in Northern India due to its close proximity to the MBT and Main Central Thrust (MCT). Himalayas — the mountain belt of complex geo-tectonic set-up stretching about 2,400 km long in an East-West direction with variable width of 230 to 320 km is formed due to the convergent movement of two plates of the earth's lithosphere. The Indo-Gangetic belt and the deposited sediments make hazards much more significant in this area. These alluvium sediments amplify the earthquake motion and thus its impact is much more in northern India. Many microzonation projects have been done in Northern Indian cities, which have mapped the seismic activity and the soil shear strength profiles with depth,” Sitharam tells you.

Very few people know that when an earthquake occurs, it is not one point but in an area of say 150 to 200 km which is considered as its epicentre. The area it covers and the depth at which it occurs determine the extent of damage. In the Hindu Kush area, the depth is at 210 km. So, a quake here will have little impact on life and property. Also, the farther one is from the point of impact, the less the damage. Usually cites that are more than 500 km away are safe. Unfortunately, Delhi is only 250 km or so away from the frontal Himalayan region.

India is the 13th most vulnerable country to climate change in the world. As per the National Disaster Management Authority of India, 58.6 per cent of India's landmass is prone to earthquakes; over 40 million hectares (12 per cent) of its land is prone to floods and river erosion; 5,700 km of the 7,516 km long coastline is prone to cyclones and tsunamis; 68 per cent of its cultivable area is vulnerable to droughts and its hilly areas are at risk from landslides and avalanches. Therefore, teams like the National Disaster Response Force (NDRF), under the aegis of National Disaster Management Authority, are in place.

According to Professor CP Rajendran at the geodynamics unit of the Jawaharlal Nehru Centre for Advanced Scientific Research in Bengaluru the recent seismic activity in the Capital should not lead to any cause of worry among the people because this kind of sequence has happened in the region before.

“There is no need for panic. What happened in Delhi-NCR is a normal activity due to the stress that are being built due to the structure of the faultlines. The construction that is happening in the Himalayas should be of more concern than what happened in Delhi. The Himalayas can generate large big earthquakes and places in Delhi-NCR can be impacted but it should not lead to panic,” Rajendran says.

He tells you that the sequences of events that took place in the area may not necessarily lead to bigger earthquakes and the reason why Delhi is vulnerable is because out the city’s proximity to the Himalayas.

“The reason why our country makes it prone to disasters due though floods, cyclones and typhoons are due to climate but earthquakes are caused due to shift in plates. But yes, due to our positioning, we are in the middle of the ocean and changes in the oceans due to global warming makes us more vulnerable. As for earthquakes, again we are more prone to them due to the Himalayas,” Rajendran tells you.

He says because we have had a history of earthquakes, we today, have more instruments that can help us better understand and study earthquakes especially after Latur disaster. But whether, on is better prepared, especially whether Delhi is prepared is not very clear. “We must take a leaf out of what Japan and Taiwan have done — learnt to live with earthquakes. There is need for public awareness and education and also in terms of building proper structures. This can’t be done in one day. It is a continuous process and should be built into and collapse system where people should be made aware to bring down casualties and collapse of buildings. For the already constructed buildings, one must strengthen them,” Rajendran says.

Also, where the country is lacking are the doers. One is told that while we have the theoretical aspect down to a perfect T, the practicalities need to be worked on. What is on paper needs to trickle down to the people at the grassroots level with required training so that they are able to carry out the disaster instructions and rescue operations.

What is missing is the last link that of connectivity. It has been found that during a disaster, the local administration has largely been unable to give the exact location to the Air Force to drop food packages, leading to a delay in trying to find out the longitude and latitude of the maximum damage area.

According to Sitharam the solution lies in understanding our buildings subjected to earthquakes not really earthquakes. It is important to put an emphasis on sensitising people and taking precautionary measures. “There is a strong need to prepare the community for earthquake disaster. Earthquakes don’t kill, it is the buildings that do. Thus, awareness on earthquake resistant design and earthquake preparedness is important to the community at large and it is critical to prepare the community for an eventuality,” he says.

Also, earthquake preparedness is not a part of the public consciousness even in the vulnerable regions of India. There are many things that individuals and communities residing in seismically active regions can do that will reduce the havoc and loss during a quake. These steps can be a complementary measure, alongside other activities that focus on the overall development of the community; with a team spirit. There is a need to bring this spirit of togetherness and solidarity well before a disaster so that a community can be prepared well to face the disaster and thus reduce the loss of life and properties.

Dr Kalachand Sain, director, Wadia Institute of Himalayan Geology in Dehra Dun tells you that there is no way that onecan predict when the next earthquake will hit nor can we predict what will be the magnitude.

“The Delhi-NCR is a path through which the strain energy needs to come out. Without a path, it won’t happen. Due to the weak zones and faults and paths in this region, there is activity. Since, we have not had a major activity in a long time, there is a chance that the energy may release. But there is no way earthquakes in this area can be predicted. In order to predict we need three things — epicentre, magnitude and when. This is not possible. We can only have conjectures based on studies,” Sain explains. What can be said with certainty is that there is a lot of strain energy in this region.

“If say 4 magnitude energy has been released, it doesn’t mean that all energy has expanded because this area has also seen strain energy release of 6 magnitude in the past. For an earthquake of 6 on the Richter Scale to occur, to release that amount of energy we need 1,000 earthquakes to release that much energy. Till now, this region has seen 17 earthquakes but still there is no accurate prediction that is at work here. We make these calculations on the basis of what has taken place in the past,” Sain says.

The kind of disaster that will take place will depend on the kind of energy that will be released. Also, the destruction will depend on the depth of the epicentre. If the epicentre is at 32 km with magnitude of 6 the destruction will be less as compared to disaster that will occur at a depth of 5 km of the same magnitude. The shallower energy release will have a greater impact and there is no way that the surface will not be affected and besides building collapse, there will be cracks on the surface as well.

“There are three things that we can say with certainty. First, Delhi is vulnerable. Second, we can tell up to what depth the earthquake can occur only after a thorough in-depth study. Third, we can’t predict the amount of strain that will be released but we can find out the lelve of strain but it doesn’t help to predict the earthquake. Though there is some study and maybe with technological advancement we may be able to predict them in the future,” Sain says.

TIMELINE

Earthquakes Delhi-NCR 2020

April 12: Delhi — Richter Scale 3.5

April 13: Delhi — Richter Scale 2.7

April 16: Delhi — Richter Scale 2.0

May 3: Delhi — Richter Scale 3.0

May 6: Faridabad — Richter Scale 2.3

May 10: Delhi — Richter Scale 3.4

May 15: Delhi — Richter Scale 2.2

May 28: Faridabad —Richter Scale 2.5

May 29: Rohtak — Richter Scale 4.5 and 2.9

June 1: Rohtak — Richter Scale 1.8 and 3

June 3: Faridabad — Richter Scale 3.2

June 4: Rohtak — Richter Scale 2.1

June 8: Delhi-Gurgaon border — Richter Scale 2.1

June 18: Rohtak — Richter Scale 2.1

June 19: Rohtak — Richter Scale 2.3

July 3: Near Gurugram — Richter Scale 4.7

Earthquakes India

Sep 18, 2011: 6.8-magnitude quake hits northern and eastern India.

Sep 7, 2011: 4.2-magnitude quake jolts Delhi and adjoining areas, with its epicenter near Sonepat, Haryana.

Oct 8, 2005: 7.6-magnitude quake strikes Indian and Pakistani-held Kashmir and Himachal Pradesh, killing over 80,000 people, mostly in Pakistan.

Dec 26, 2004: Over 200,000 die when a 9.3 magnitude temblor rattled Indonesia's Sumatra island, unleashing a tsunami that hit India, Sri Lanka, Thailand and the Maldives.

Jan 26, 2001: 7.7-magnitude earthquake kills over 20,000 in Gujarat, mainly in Kutch, Ahmedabad and Bhuj.

Sep 30, 1993: 6.4-magnitude quake leaves 7,928 people dead in Latur, Maharashtra.

Oct 20, 1991: 6.6-magnitude in Uttarakashi region of Uttar Pradesh.

Aug 21, 1988: 6.4-magnitude quake on Bihar-Nepal border.

Aug 6, 1988: 6.6-magnitude quake on Manipur-Myanmar border.

Jan 19, 1975: 6.2-magnitude quake in Kinnaur, Himachal Pradesh.

Dec 10, 1967: 6.5-magnitude quake in Koyna, Maharashtra.

July 21, 1956: 7-magnitude quake in Anjar, Gujarat.

Aug 15, 1950: 8.5-magnitude quake on India-China border in what is now Arunachal Pradesh

Biggest Earthquakes Globally

Valdivia, Chile, May 22, 1960 — Richter Scale 9.5

Prince William Sound, Alaska, March 28, 1964 — Richter Scale 9.2