How prepared is Delhi for a 7 intensity earthquake?

The apprehension that whether Delhi would withstand an earthquake of 7 magnitude similar to that occurred in Turkey this year needs to be pondered upon seriously

A K Jain worked as Commissioner (Planning), Delhi Development Authority and as a member of the Committee of the Ministry of Housing and Urban Affairs on the DDA (2015). He was a member of UN Habitat (2007- 12). Author of several books, he is visiting faculty in planning and architecture. He was awarded 2nd Urban Professional Award 2014 at World Urban Forum in Medellin, Colombia, IBC Lifetime Achievement Award (2023), Living Legend Award by the Indian Institute of Architects (2022) and the Lifetime Achievement Award by the Smart Habitat Foundation (2022).

The devasting and deadly earthquake of 7.8 on the Richter Scale hit Southern Turkey and Syria on 6th February 2023 sent shivers in Delhi. It left 50,399 dead and 1,07,000 injured. Approximately 2.4 million people were shifted in temporary shelters, including 5,25,000 tents and 36,000 containers. Earlier, the Gujarat earthquake, also known as Bhuj earthquake on 26th January 2001, with an intensity of 6.9, left over 20,000 dead and more than 1,65,000 people injured (Fig. 1).

The Tejendra Khanna Committee in its report (2006) sent a warning stating that 70 to 80% of the structures in Delhi were violative of building and development control regulations. The unsafe buildings are mostly more than 50 years old, nonengineered, and dilapidated, like those in the Old City, villages and unauthorised colonies. The Ministry of Urban Development and Poverty Alleviation issued a Gazette notification dated 21.3 2001, for safety of buildings to withstand the earthquake and incorporating such provisions in the Building Byelaws and Master Plan for Delhi 2021 (Fig. 2).

The Building Materials and Technology Promotion Council (BMTPC) prepared a vulnerability atlas indicating seismic zone map of India (Figs. 3 , 4 and 5) and guidelines for earthquake and disaster prevention, preparedness, and mitigation. As per this Atlas, Delhi falls under Seismic Zone IV. Figs 6 and 7 show the Seismic Hazard Micro Zonation map of NCT Delhi which categorises the areas under low, moderate and high risks.

In 2005, the Parliament enacted the National Disaster Management Act under which the National Disaster Management Authority (NDMA), NDRF, and National Institute of Disaster Management (NIDM) were established. The National Disaster Response Force (NDRF) has been commended for many successful rescue and relief operations in india, as well as in Turkieye and Syria earthquake recently.

Earthquake preparedness in Delhi

The Master Plan for Delhi 2021, notified in Feb. 2007 recognises that Delhi falling in Seismic Zone IV, in the past, had several earthquakes (Fig.8). Two major lineaments, namely DelhiHaridwar ridge and Delhi-Muradabad faults pass through it, which have the potential of generating earthquakes of the magnitude up to 6.5 to 6.7. To mitigate the danger, areas of vulnerability be identified by micro zonation.

The MPD 2021 stipulates that the local bodies should update the building byelaws, besides adopting the following strategies:

a. Micro-zonation surveys should be referred for land use planning and be considered while preparing the Zonal Plans and Layout Plans.

• Seismic micro-zonation for selected areas having high growth rates should be taken up on priority.

• On the basis of vulnerability studies and hazard identification, which includes soil conditions, probable intensity of earthquake, physiographic conditions of the area, fault traces, etc., local level land use zoning and planning should be undertaken.

• Building bye-laws should incorporate the aspects of Multi Hazard Safety, and Retrofitting.

• Priority should be given to public buildings (such as hospitals /tertiary health care centres], educational, institutional, power stations, infrastructure, heritage monuments, lifeline structures and those which are likely to attract large congregation) for their ability to withstand earthquake of the defined intensity.

• Suitable action should be taken for retrofitting and strengthening of structures identified as vulnerable as per earthquake manuals and National Building Code. A techno-legal regime has to be adopted for provisions on Multi Hazard Safety aspects.

b. Delhi Fire Services being the nodal agency for disaster management should identify vulnerable areas such as areas with high density and poor accessibility in the city and propose suitable measures. Proposed Disaster Management Centres should be established in every zone to deal with the disasters, including bio-chemical and nuclear disasters. The key communication centres should be protected from natural disasters, i.e. flood, fire and earthquake etc. and services restoration should be taken up on top priority.

c. Sensitize people, particularly school children, about after effects of disaster.

d. Make people aware through media campaigns and advertisements about emergency procedures and location of emergency shelters etc.

According to MPD 2021, ‘Special Area Building Regulations be framed for Special Area, unauthorized regularized colonies and village abadis. Owners in Special Area, unauthorised regularized colonies and village abadi shall register themselves with the Local Body within the next six months (i.e. by August 2007). They will also submit a certificate of structural safety by qualified engineers. Owners / occupiers of properties beyond 15 m height may bring the structure within prescribed height by 30th June, 2009’.

Disaster Risk Reduction (DRR)

At the international level, India has been playing a leading role in the field of disaster risk reduction and has committed a contribution of $ 6 billion for DRR mitigation and $ 23 billion for preparedness, response and recovery during 2021-25. This was announced at the Sendai framework review meeting at the United Nations in May 2023. India has also set the priorities of DRR for G 20 Nations, viz. early warning for all, resilient infrastructure, improving finances and capacities for DRR response and eco-system-based approaches to DRR.

The gaps

In spite of extensive techno-legal and institutional work, Delhi is still precarious and unsafe. Out of 46 lakh odd buildings, the MCD has identified only 4655 buildings for structural audit, retrofitting or demolition. The MCD notice for submission of structural safety certificate, issued after High Court Order (2020) has not been implemented (Fig. 9). There is no comprehensive documentation of the buildings in the city. The responsibility of structural audit on the owner has not worked. The incentives of FAR /TDR and subsidy/loans are not available for redevelopment, retrofitting and repair of dangerous, dilapidated and non-engineered structures. This also raises the issue of political interventions, and whether the enforcement of the building regulations can be made a quasi-judicial process.

Strengthening basic data and leveraging new technologies

A major barrier is lack of up-to-date geospatial data of the buildings. The records of the ULBs are chaotic and inaccessible. These need to be organised by using new technologies, keeping in view the earthquake and disaster risk reduction, as given below:

It is generally not the natural hazards per se that kill people, rather unsafe buildings and construction that leads to loss of life and property. Both the Spatial and non-spatial data are abstracted and synthesised to prepare a comprehensive District Hazard Risk Map. This also helps to frame earthquake hazard in a comprehensive perspective (Fig. 10).

Risk assessment

Various engineering organisations and academic institutions, such as IIT (Kanpur), CBRI (Roorkee), SERC (Chennai), BMPTC, etc. have worked extensively to provide useful guidelines to safeguard the buildings from seismic damage. Table 2 details out the earthquake loss susceptibility for different construction types. Table 3 indicates the categories of seismic damages and suggests the empirical measures.

ABCDE of safe construction

The basic principle of safe construction can be summed up as ABCDE, as given below (Fig. 11):
A – Anchorage
B – Bracing
C – Connections
D – Detailing
E – External Environment

The critical action areas for safer buildings encompass the following:
i. Incentives for public and private sectors, such as, adjustment of insurance premia, loan or loan–cum–subsidy schemes.
ii. Technology Transfer for nonengineered structures.
iii. Buildings should be constructed on solid ground, preferably a frame structure with interlocked walls and floors that can withstand the lateral forces during an earthquake.
iv. Materials must have sufficient ductility to withstand the stresses during earthquake shaking.
v. Reinforcement of structure and columns must contain sufficient transverse, tied or spiral arrangements to withstand repeated distortion during earthquakes.
vi. Retrofitting of existing buildings and structures should be undertaken along with essential Services, water supply, transportation and communication.

Usually, in old buildings due to rust and dampness, the steel may get corroded, and concrete may lose strength and become prone to damage because of ageing, fires, structural failure, overloading, vibrations and earthquakes. As such, it is necessary that structural audit is undertaken for the structures older than 50 years. For repair of concrete pillars, beams, slabs, balconies, chajjas, staircases, etc., whenever necessary, reinforcement steel may be replaced, along with strengthening of the joints, supports, walls, pillars, etc.

Base isolation and seismic dampers

To protect buildings from damaging earthquake effects, Base Isolation Devices and Seismic Dampers can be adopted to detach (isolate) the building from the ground. These act as the shock absorbers and prevent building damage from an earthquake (Figs. 12 & 13).

Stone masonry is vulnerable against earthquake forces unless it is used with necessary earthquake resistant features, in accordance with the BIS 154326:1993 code of Practice for Earthquake Resistant Buildings, IS 4326 and IS 1597(part 2): 1992. Besides slenderness ratio of the wall (height or length / thickness), eccentricity of vertical load and openings affect the performance of masonry. The masonry units must conform to IS 1077:1992 and IS 2185(Part I). Use of through stones, bond stones and steel reinforcement are recommended for earthquake resistant masonry (Figs. 14 and 15).

Many of the key adaptations to earthquake risks require individual and collective action at the community-level, which are undertaken incrementally.

Conclusions

Delhi has a large numbers of unsafe structures all over (fig: 16,17). The apprehension that whether Delhi would withstand an earthquake of 7 magnitude similar to that occurred in Turkey and Syria this year needs to be pondered upon seriously. No doubt that since Gujarat earthquake, 2001 much has been done on the technical and legal fronts and organisational capacity building, still two major gaps exist:

i. Database of each and every structure and

ii. The enforcement of building/ structural Standards.

In spite of the court orders, Delhi has failed on these counts. This may cause a catastrophe unless rapid action is taken on this front and it may be considered whether the enforcement of the building regulations can be made a quasi-judicial process.

 

 

References

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BIS, IS:1893 Part (I) – 2002, Criteria for Earthquake Resistant Design of Structures (fifth Revision)”, BIS, New Delhi

BIS, IS:13920–1993, Ductile Detailing of Reinforced Concrete Structure subjected to seismic forces– code of practice, BIS, New Delhi

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