Delhi

Delhi’s vulnerability to severe quakes: Analysis of a 6.5 magnitude event

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Delhi QuakeBy Sushil Gupta
General Manager, Risk Modeling and Insurance, RMSI, India

In the wake of the recent Nepal earthquake that caused a shaking of about intensity II-III on Modified Mercalli Intensity (MMI) scale in Delhi, even being about 735 km away from the epicenter, it was a daunting situation in the city with many people standing out of their houses and cracking up of buildings in Trilokpuri, days later to the aftershocks. This event is a grim reminder of the structural safety of several Lakhs of buildings/ houses in the capital city, which falls in a high seismic zone IV, as per Bureau of Indian Standards Code, IS: 1893, 2002.

RMSI, an India based catastrophic risk modeling firm, recently conducted an impact analysis for the city, considering a situation where an earthquake of 6.5  magnitude hits in proximity of the city. RMSI applied its Earthquake Risk Estimation Model to estimate the intensity of earthquake across Delhi. The modeled earthquake intensities are applied to the buildings across Delhi to estimate the impact of the earthquake on Delhi. Delhi’s building exposure was estimated using RMSI’s proprietary building exposure data developed at cluster level using space based technologies and remote sensing techniques.

Earthquake-Intensity

Figure 1: Earthquake hazard Intensity Map for Delhi

Hazard Scenario

RMSI experts studied a scenario where Delhi is hit by an earthquake of 6.5 magnitude in its vicinity.  Delhi lies in seismic zone IV and thus has a potential for experiencing earthquakes with magnitude up to 6.5 to 7 on Richter scale. RMSI experts simulated this earthquake using its computer based Earthquake Risk Estimation model. The primary output from the model is the spatial distribution of earthquake ground shaking across Delhi. The earthquake model estimates the ground shaking in terms of acceleration of the shaking in the ground due the earthquake. The model also takes into account the effect of local soil conditions and geology (local soil-amplification) on ground shaking. Figure-1 shows the distribution of the earthquake intensity across Delhi.

Exposure

To estimate exposure RMSI used its proprietary building exposure data at cluster level. The detailed building exposure database was created for the Residential, Commercial, and Industrial buildings using satellite imagery and remote sensing techniques. The building exposure data has been developed at cluster level for entire Delhi. In total, the city has been divided into 121,169 clusters (Figure-2). These clusters have been further categorized by occupancy (residential, commercial, and industrial) and building height (low, medium and high rise), i.e., all buildings having similar height and use have been grouped together in a cluster that is represented by a cluster footprint in a digital map. RMSI experts have also associated suitable building structural types to all these building clusters.

In terms of exposed population, the Census (2011) data has been considered at the base level. As per latest Census (2011), Delhi is home to 16.75 million people (actual numbers are expected to be much higher as Delhi also has a significant number of floating population), and the population is growing at a rate of 2% per year. The population data has been divided into 9 districts, and 27 sub-districts of Delhi.

The replacement value (just the cost of construction, and not including the cost of land or land filling or debris removal or the cost of contents) of all residential buildings within Delhi is estimated at about INR 12.5 trillion ($ 200 billion), while that of the commercial and industrial buildings is estimated at about INR 3.8 trillion ($60 billion) and about INR 850 billion ($13.5 billion) respectively.

Building-Height-Class

Figure 2: Low, medium, and high-rise building clusters in Delhi

FINDINGS

Damage

As per the scenario, it was estimated that on an average 33% (about 35% residential, 26% commercial, and 35% industrial) of the buildings will be damaged in Delhi in such an event. The locality/areas, where most of the fatalities/major-injuries would occur are: (a). Areas with unplanned construction and slums, viz., Mandawali, West Vinod Nagar, New Ashok Nagar and Railway Colony in Preet Vihar subdistrict; Pooth Kalan in Saraswati Vihar; Ambedkar Basti and Maujpur in Seelam Pur; Murad Nagar and Ansari Road in Gandhi Nagar; Subhash Park, New Jaffrabad, and Babarpur in Shahdara; Prem Nagar in Seema Puri; State Bank Colony and Meera Bagh in Punjabi Bagh; Okhla, Sanjay Colony, and Tughlakabad in Kalkaji; and Palam Colony in Najafgarh.  (b). Jagatpur Khadar village and the neighboring regions in Civil Lines (esp. Bagiabad, Bengali Colony and Milan Vihar). (c). Villages in Eastern part of Narela (viz. Tiggipur, Hamidpur, Ibrahimpur, Tajpur Kalan, Jhangola, Sungarpur, Nathupura, Fatehpur Jat, Mohammadpur, Cullakpur, Akbarpur Majra, Bhaktawarpur etc.)

The analysis of low rise residential buildings further revealed that in localities such as Lakshminagar, Shakarpur, Mandavali (in East Delhi District), and Sonia Vihar, Usmanpur, Rajiv Nagar in North East district, having mostly unplanned construction, about 55-60 percent of the houses are going to be damaged, about one-third of these 55 – 60 percent houses  have a high likelihood to collapse. On the other hand, unplanned areas, such as Sheik-Sarai, Ashoka Bindu Sher Camp (in South Delhi District) are likely to suffer damage to 30-40 percent of the houses, out of which 20 percent of houses are likely to collapse. This difference is mainly because the soil. East and North East Delhi is mainly very soft-soil whereas South Delhi has a mix of soft and hard rock. Areas having very soft soil experience an amplified shaking during an earthquake that causes more damage.

A lot of the mid-rise and high-rise buildings in Delhi have ground floors that are being used for parking. The Bhuj, Gujarat earthquake damage in Ahmadabad city proved that such structures suffered much more damage than the structures which do not have ground floor as parking floor.  As a result in several areas such as Dwarka (in West Delhi) about 30-45 percent of the buildings are likely to be damaged, out of which about 10 percent of buildings have a high chance of collapsing.

There are areas in New Delhi district, such as Chanakypuri, which are better planned and constructed. These areas are likely to suffer damage to 15-20 percent of the buildings, out of which 2-3 percent of buildings/houses are likely to collapse.

There is a large inventory of commercial buildings in different parts of Delhi. Some areas are highly congested and have unplanned construction, such as Chandni Chowk market, Karol Bagh market, Gaffar Market, Azmal Khan Road market. Commercial establishments in these areas are likely to suffer 45-50 percent of damage, and with a strong possibility of about half of those damaged finally collapse.

Commercial buildings in areas such as Saket, Nehru Place, and Connaught place have planned constructions. About 10-15 percent buildings are likely to suffer damage in these areas, and 2-4 percent of these have a likelihood of collapsing.

The analysis revealed another interesting aspect. Many areas of North and North-West Delhi are going to suffer high damage. This is because, unlike the popular perception, these areas also lie on soft soil though not as soft as compared to Eastern Delhi. This amplifies the seismic waves, resulting in higher damages. The losses are lowest in South Delhi owing to relatively stiffer soil and better construction.

Casualties

Deaths-per-million-people

Figure 3: Structural losses, across the sub-districts

The total affected population would be close to 5 million with over 11,000 immediate fatalities, 70,000 people trapped under collapsed buildings and close to 2 Lakhs injured. These estimates of casualties are an average of casualties from a day time, commute time and night time earthquake. Out of injured population, over 40,000 people would require life saving/paramedics medical facilities. Out of the 70,000 people trapped in collapsed buildings, anywhere from 10% to 50% could loose their lives depending upon the efficiency of the rescue effort.

Most of the deaths are likely to occur from collapsed buildings in sub-districts such as Narela, Seelam Pur, Saraswati Vihar, Seema Puri, Preet Vihar, Shahdara, Civil Lines, and Gandhi Nagar, where there are lots of unplanned constructions with low-quality materials. Figure 3 shows the distribution of casualties across various sub-districts of Delhi. Once again South Delhi performs much better than the rest of the city except for Kalkaji area that is closer to the eastern belt as well as includes localities like Govindpuri, Sanjay Colony, and Tughlakabad. In north Delhi, Model Town performs better than the rest of the area due to lesser unplanned construction. Civil lines will have higher casualties due to Jagatpur Khadar village, Bagiabad, Bengali Colony and Milan Vihar.

Emergency Response

In light of the above estimates of damage and casualties it is very important that Delhi prepares now to handle an event of this scale. Such a future event will throw huge challenges in terms of response and recovery specially taking care of the injured, rescue of entrapped victims in time, arranging suitable shelter locations for such a large number of displaced households, debris removal and reconstruction. RMSI did a quick check on some of the most important needs in the aftermath of such an event.

The Fire and Emergency service (first responder) in Delhi has about 53 operational fire-stations with about 3300 fire-fighting and rescue personnel, which on an average serves more than 3 Lakhs people per fire station. It’s anybody guess that in such an earthquake scenario, Delhi Fire Services would not be able to rescue such a large number of trapped people.

Also considering that there could be about 70,000 people trapped under the rubble which will primarily brick and concrete, there is a strong need to identify where from the necessary equipment (like concrete breakers) for rescuing such a large number of people will come.

RMSI estimates indicate that the total numbers of Beds in all the hospitals of Delhi are about 30,000, which would be insufficient, even if we assume that no hospital would be damaged and all the bedsThe Fire and Emergency service in Delhi has about 53 operational fire-stations with about 3300 fire- fighting and rescue personnel, which on an average serves more than 3 Lakhs people per fire station. It’s anybody guess that in such an earthquake scenario, Delhi Fire Services would not be able to rescue such a large number of trapped people.

Also considering that there could be about 70,000 people trapped under the rubble which will primarily brick and concrete, there is a strong need to identify where from the necessary equipment (like concrete breakers) for rescuing such a large number of people will come.

RMSI estimates indicate that the total numbers of Beds in all the hospitals of Delhi are about 30,000, which would be insufficient, even if we assume that no hospital would be damaged and all the beds would be available, which is highly unlikely. So it is very important to plan ahead regarding how to provide first aid and treatment to the large number injured population.

Conclusions

The scenario of a strong to major earthquake in the near future can be catastrophic for Delhi and its inhabitants. In addition to tens of thousands of casualties, such an event would also result in INR 5.7 trillion (USD 90 billion) worth of structural and non-structural losses, which do not include content damage of buildings, infrastructure losses and business-interruption. Hence, economic losses of a high magnitude event are likely to exceed Delhi’s GDP. Moreover, the economic impact of the earthquake would not be limited just to Delhi and its surroundings, but also to the other parts of India as well and it will take several years to rebuild the regions affected by such a catastrophic event. It will require a herculean effort to respond to such an event that too if Delhi plans to equip itself today to face such an event in future.

Planning for such an event would require a huge effort in terms of detailed risk assessment and implementation of disaster risk reduction (DRR) measures. It’s high time that both Delhi Government and National Disaster Management Authority take suitable steps for risk mitigation planning and implementation of DRR measures in Delhi.

(Mr Sushil Gupta has over 23 years of professional experience in the field of catastrophic risk modelling, engineering seismology and earthquake engineering, and disaster risks management. He has executed several multi-hazard risk assessment projects related to disaster risk reduction  and climate adaptation projects as a team leader that were sponsored by the World Bank, UNISDR, UNDP and Govt. of India. An IITian having an M.Tech in Applied Geophysics with specialisation in Engineering Seismology and MBA with specialisation in Insurance management, Mr Gupta also obtained advance level certificates in the field of Disaster Risk Reduction from EPFL, Switzerland; the World Bank Institute, Washington DC and NIDM; and in the field of Earthquake Engineering of Nuclear facilities from ICTP, Trieste, Italy and Bhabha Atomic Research Centre, Mumbai. An author with 55 research publications to his credit, he was one of the ‘Peer Reviewer of UNISDR Global Risk Assessment, 2011’ and ‘UNISDR Expert of Week (2014)’. He is the recipient of many awards and honours including 2011 A.S. Arya – I I T R Disaster Prevention Award)

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