Blog

1. Answer the following in your own words.

a. Explain the relation between continuous rains and landslide. Give reasons.

Answer: Continuous rain is a primary trigger for landslides. The relationship is direct and causal for the following scientific reasons:

• Increase in Pore Water Pressure: Rainwater seeps into the soil and bedrock on a slope. This adds weight and, more critically, increases the pressure of water trapped between soil particles (pore pressure). High pore pressure reduces the friction that holds the soil and rock together, effectively acting as a lubricant.
• Loss of Cohesion: Water saturates the soil, reducing the cohesive forces that bind soil particles. Materials like clay become heavy and plastic, losing their structural integrity.
• Added Weight: The sheer weight of the absorbed water adds a significant load to the slope, increasing the gravitational pull downwards.
• Erosion: Continuous runoff can erode the base or toe of a slope, removing its natural support and making the upper material unstable.
  In essence, prolonged rain compromises the shear strength of slope material while simultaneously increasing the driving force (weight), creating a perfect condition for slope failure, i.e., a landslide.

b. Prepare a chart showing ‘Do’s’ and ‘Don’ts’ at the time of an earthquake.

Answer:

Do’s (Correct Actions)	Don’ts (Actions to Avoid)
DROP, COVER, and HOLD ON. Drop to your hands and knees, take cover under a sturdy piece of furniture (like a table), and hold on until shaking stops.	Do NOT run outside or move to another room during shaking. You are more likely to be injured by falling debris.
If no cover is nearby, crouch against an interior wall, away from windows, tall furniture, and hanging objects.	Do NOT stand in a doorway. Modern doors are no stronger than other parts of the house and do not protect from falling objects.
Stay indoors until the shaking stops and it is safe to exit.	Do NOT use elevators. You could become trapped if power fails.
If you are outdoors, move to an open area away from buildings, trees, streetlights, and utility wires.	Do NOT go near hillsides or cliffs due to the risk of landslides and rockfalls triggered by the quake.
If you are in a vehicle, pull over to a clear location, set the parking brake, and stay inside.	Do NOT panic or crowd exits. Stay calm to think clearly and avoid stampedes.

c. What are the specifications of an earthquake-proof building?

Answer: Earthquake-proof or seismic-resistant buildings are designed to absorb and dissipate seismic energy, preventing collapse. Key specifications include:

• Strong and Flexible Foundation: Use of deep piles and reinforced concrete foundations. Base Isolation is a advanced technique where the building rests on flexible bearings (pads of steel, rubber, and lead) that separate it from the ground motion.
• Diaphragm Floors and Roofs: Floors and roofs act as rigid yet flexible horizontal diaphragms that distribute shear forces to the vertical elements (walls and columns).
• Shear Walls and Braced Frames: Reinforced concrete or steel shear walls provide major resistance to lateral forces. Steel-braced frames offer additional support.
• Moment-Resisting Frames: Beam-column connections in the building’s frame are specially designed to be ductile (flexible), allowing them to bend without breaking.
• Use of Lightweight Materials: Reducing the overall mass of the structure decreases the inertial forces during shaking.
• Continuous Load Path: The building is tied together from the roof to the foundation, ensuring forces travel through a designed path without causing failure at connections.

d. Explain the effects of a landslide.

Answer: Landslides have wide-ranging destructive effects:

• Loss of Life and Injury: Direct impact from debris can cause fatalities and severe injuries.
• Property and Infrastructure Damage: They can destroy homes, buildings, roads, railways, bridges, and communication lines, leading to massive economic losses.
• Blockage of Rivers and Floods: Landslide debris can dam rivers, creating temporary lakes. The sudden breach of these dams can cause catastrophic downstream flooding.
• Loss of Agricultural Land and Forests: Fertile topsoil is stripped away, and forests are destroyed, impacting livelihoods and ecosystems.
• Secondary Hazards: Can trigger other disasters like tsunamis (if into a water body) or disrupt water sources, leading to contamination.
• Psychological and Social Impact: Displacement of communities, loss of heritage sites, and long-term trauma.

e. Is there any relation between dam and earthquake? Explain.

Answer: Yes, there is a scientifically recognized relation. The construction and operation of large dams can induce earthquakes, a phenomenon known as Reservoir-Induced Seismicity (RIS). The reasons are:

• Increased Load: The immense weight of the water in the reservoir adds significant stress to the underlying and surrounding rock strata.
• Increased Pore Pressure: Water seeps deep into cracks and faults in the bedrock. This increases pore pressure, which reduces friction along pre-existing fault lines, effectively “lubricating” them and allowing them to slip more easily.
• Hydro-Seismic Effect: The combination of static load stress and dynamic pore pressure changes can alter the local tectonic stress regime, potentially triggering earthquakes in seismically active or even stable regions. Notable examples include the 1967 Koynanagar earthquake in India, linked to the Koyna Dam.

2. Give Scientific reasons.

a. It is safer to find shelter under things like a bed or table at the time of an earthquake.

Answer: The primary danger during an earthquake is injury from falling and flying objects (e.g., ceiling plaster, light fixtures, glass, bookshelves). A sturdy piece of furniture like a bed or table acts as a protective shield, creating a “survivor space” or a “triangle of life” by taking the impact of the collapsing load. It prevents direct hits to the body, reducing the risk of fatal head injuries and crush wounds.

b. In monsoon, don’t take shelter near a hillside.

Answer: Hillsides become extremely unstable during the monsoon due to prolonged rainfall. The soil becomes saturated, heavy, and loses its cohesive strength, significantly increasing the probability of landslides, mudflows, or rockfalls. Taking shelter near or at the base of a hillside puts one directly in the path of such rapid, destructive mass movements, leading to high risk of being buried or injured.

c. Don’t use lifts at the time of an earthquake.

Answer: During an earthquake, power grids are highly vulnerable to failure, leading to immediate and unpredictable power outages. If an elevator loses power, it will stop abruptly, trapping occupants inside. Furthermore, elevator shafts can be damaged or deformed by seismic forces, causing the elevator car to jam or even fall. Stairs are the only safe means of vertical evacuation during and immediately after a quake.

d. The foundation of an earthquake-proof building is separated from other land.

Answer: This describes the Base Isolation technique. The foundation is not rigidly attached to the ground but is separated by layers of flexible pads (elastomeric bearings). These isolators act as a shock absorber. When seismic waves travel through the ground, the isolators deform, absorbing and dissipating a large portion of the energy. This dramatically reduces the amount of shaking transferred to the superstructure above, allowing the building to sway gently rather than violently, preventing structural damage.

3. If a crowd gathers at the place of an earthquake, what would be the difficulties in relief work?

Answer: The convergence of crowds, known as convergence behavior, creates severe impediments to effective disaster relief:

• Blocked Access: Essential routes for emergency vehicles (ambulances, fire trucks, rescue equipment) become impassable, causing critical delays.
• Impeded Search & Rescue: Crowds can trample on potential survivor locations, damage unstable structures further, and create noise that drowns out calls for help from trapped victims.
• Secondary Casualties: The gathering often occurs near damaged buildings, putting people at risk from aftershocks that could cause further collapse.
• Logistical Chaos: It becomes difficult to establish triage areas, set up field hospitals, or distribute aid (food, water, medicine) in an orderly manner.
• Spread of Misinformation: Panic and rumors can spread quickly in a crowd, leading to irrational behavior and hindering official communication.
• Security Challenges: Managing large, distressed crowds requires significant law enforcement resources, which could be deployed for direct rescue operations.

4. Make a list of the institutes and organizations who provide help for disaster management. Collect more information about their work.

Answer:

Organization	Key Area of Work (Information to Collect)
National Disaster Management Authority (NDMA)	National level policy & planning. Formulates guidelines, ensures preparedness, and coordinates response to major disasters in India.
National Disaster Response Force (NDRF)	Specialized response force. Trained for chemical, biological, radiological, nuclear, and natural disaster response. Conducts rescue operations domestically and internationally.
State Disaster Management Authority (SDMA)	State-level implementation. Implements NDMA policies, prepares state-level plans, and coordinates resources at the state level.
Indian Meteorological Department (IMD)	Early warning for cyclones, floods, etc. Provides critical weather forecasts, rainfall data, and cyclone tracking that form the basis for early evacuation.
Indian Red Cross Society (IRCS)	Humanitarian aid and community preparedness. Focuses on first aid, blood banks, shelter management, and long-term community-based disaster risk reduction programs.
United Nations Office for Disaster Risk Reduction (UNDRR)	International coordination & framework. Leads the global effort to implement the Sendai Framework, promoting policies to reduce disaster risk and losses.
World Food Programme (WFP)	Emergency food assistance. Provides life-saving food aid and logistical support during and after disasters to affected populations.