Administrative set-up
- Delhi is the capital of India as well as a State in itself.
- Both national and state governments are based in Delhi
- Different agencies are controlled by State or National governments/administrators.
- Lt.Governor and Chief Minister are the highest authorities.
Disasters management strategies must consider interaction between different agencies.
Risk management
- Disaster management plan should consider the following factors;
- Hazard
- Vulnerability
- Exposure
- External context (Economic impact)
- Earthquake risk of Delhi is the intersection of all these factors.
Disaster management should consider cost benefit of different options for risk reduction.
Seismic hazard
- Seismological studies
- Geological studies
- Historical data
Objective - probability of earthquake exceeding a particular intensity in a given number of years.
Current status - maximum level of earthquake acceleration that is likely during the life of the structure (IS: 1893-1994)
Site effects
- Effect of soil condition and topology is typically reflected through seismic microzonation maps.
- Areas of city with likelihood of local amplification of seismic waves are identified.
- Soft soils and hilly terrains both lead to amplification of seismic waves.
Structures in these areas need to be designed for higher seismic forces.
Structural vulnerability
- Estimation of likely level of damage to buildings due to postulated earthquake.
- Estimation of likely economic loss due to postulated earthquakes.
- Estimation of casualty levels.
Information from vulnerability evaluation is very useful for planning relief and recovery measures after an earthquake.
Seismic vulnerability
- Depends on type of structures (structure category) and their age.
- Depends on land use in city (space between adjacent buildings, height of buildings etc.)
- Depends on month and time (buildings may be weaker during the rainly season, and residential building more fully occupied during nights).
- Depends on population density (impact of damage of a building to number of people)
Example of Mumbai
2.76 million buildings (1991)
Engineered constructions
- 9.08% reinforced concrete buildings
- 31.35% brick masonry buildings with RCC roof
Non -engineered constructions
- 31.49% informal masonry buildings.
- 28.08% other non-engineered buildings using light weight materials.
Vulnerability
- Influence of old constructions on vulnerability needs to be considered.
- Recent studies show significant deficiency in design and/or construction practice even fir engineered constructions.
Vulnerability index for different construction types is established based on observed behaviour of similar constructions in past earthquakes.
Seismic vulnerability Index
| |
MSK |
MSK VI |
MSK VII |
MSK VIII |
Reinforced concrete
building |
0.00 |
0.05 |
0.25 |
0.50 |
Engineered masonry
Building |
0.05 |
0.25 |
0.50 |
0.75 |
Non-engineered
masonry building |
0.05 |
0.25 |
0.50 |
0.75 |
Non-engineered
constructions using
other materials |
0.10 |
0.50 |
0.75 |
0.95 |
Casualty model
Consistent morbidity model based on conditional probability can be used to determine casualty levels.
Ks
b = D5
b x [ M1
b x M2
b x M3
b x M4
b]
| B |
is building type |
| Ks |
is estimated number of people killed in b |
| D5 |
is total number of damaged buildings |
| M1 |
is number of occupants per building |
| M2 |
is probability of occupation of building |
| M3 |
is probability of occupants getting injured |