21 Feb

Earthquake

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Contents

• Introduction
• Different zones
• Causes of Earthquakes
• Consequences of Earthquakes
• NDMA Guidelines for Management of Earthquake
• Steps that needs to be taken
• Earthquake hazard Reduction and Mitigations

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Introduction

• India lies at the northwestern end of the Indo-Australian Plate, which encompasses India, Australia, a major portion of the Indian Ocean and other smaller countries.
• The major reason for the high frequency and intensity of earthquakes is that Indian plate is driving into Asia at a rate of approximately 47 mm/year.
• According to NDMA, about 59% of India’s land could face moderate to severe earthquakes.

Different zones

• Bureau of Indian Standards, based on the past seismic history, grouped the country into four seismic zones, viz. Zone-2, Zone-3, Zone-4 and Zone-5. Of these, Zone 5, is the most seismically active region, while zone 2 is the least.
• The Modified Mercalli (MM) intensity, which measures the impact of the earthquakes on the surface of the earth, broadly associated with various zones, is as follows :
  • Seismic Zone Intensity                       MM Scale

Zone – V ( Very High Intensity zone)     IX (or more)

Zone -IV (Severe Intensity Zone)           VIII

Zone – III (Moderate Intensity Zone)      VII

Zone – II (Low Intensity Zone)                 VI (or less)

• Zone 5: Areas with highest risk; suffers earthquakes of intensity MM IX or greater; IS code
  assigns zone factor of 0.36 for Zone 5.
  • Regions in India: Parts of J&K, Himachal Pradesh, Uttaranchal, Parts of North Bihar, Entire North eastern region, and Andaman and Nicobar Islands.
• Zone 4: Areas within High Damage Risk Zone and covered areas are liable to MM VIII; IS code assigns a zone factor of 0.36 for Zone 4
  • Regions in India: Parts of J&K and Himachal Pradesh, UT of Delhi, Northern Part of UP, Bihar and Bengal, Sikkim, Parts of Gujarat, Small Portion of MHA near the west coast and Rajasthan.
• Zone 3: Classified as Moderate Damage Risk Zone; liable to MM VII; IS code assigns zone factor of 0.16 for zone 3.
  • Regions in India: Kerala, Goa, Lakshadweep islands, and remaining parts of Uttar Pradesh, Gujarat and West Bengal, parts of Punjab, Rajasthan, MP, Bihar, Jharkhand, Chhattisgarh, Maharashtra, Orissa, Andhra Pradesh, Tamil Nadu an Karnataka.
• Zone 2: The region is assigned low damage risk. The IS code assigns zone factor of 0.10 (maximum horizontal acceleration that can be experienced by a structure in this zone is 10% of gravitational acceleration) for Zone 2.
  • Region: Rest of India.
• Zone 1
  • Since the current division of India into earthquake hazard zones does not uses Zone 1, no area in India is classed as Zone 1.

Causes of Earthquakes

• The important causes of earthquakes can be divided into two categories: Natural and Manmade
  i. Natural Causes

1. Tectonic Movements

2. Volcanic Activities

3. Adjustment in the inner rocks beds (Plutonic Earthquakes)

• • • • Adjustment between Sima and Sial in the interior of the earth’s crust.

4. Pressure of Gases in the interior

• • • • The expansion and contraction of gases in the interior of the earth sometimes cause a sudden shake on the earth’s surface

5. Other causes

• • • • Landslides and avalanches
      • Denudation of landmasses and deposition of materials

ii. Man-made causes

1. Dams: Impounding of large quantity of water behind the dams disturb the crustal balance and can cause earthquakes

2. Nuclear Bombs

• • • The shockwaves through the rocks set up by underground testing of Atom bombs or Hydrogen bombs may be severe enough to cause an earthquake.

iii. Causes which make India very vulnerable

• • • Fragile built environment (Similar sized earthquake in Japan or USA will cause much smaller damage).

Consequences of Earthquakes

• Human and livestock loss
• Damage to Property
• Tsunamis
• Change in river course – floods
• Fountain of muds
• Landslides

NDMA Guidelines for Management of Earthquake: Six Pillars of Earthquake Management in India

a. Ensure the incorporation of earthquake resistant design features for the construction of new structures.

b. Facilitate selective strengthening and seismic retrofitting of existing priority and lifeline structures in earthquake-prone areas.

c. Improve the compliance regime through appropriate regulation and enforcement.

d. Improve the awareness and preparedness of all stakeholders.

e. Introduce appropriate capacity development interventions for effective earthquake management (including education, training, R&D, and documentation).

f. Strengthen the emergency response capability in earthquake-prone areas

Earthquake hazard Reduction and Mitigations

• Earthquake is a natural phenomenon which is difficult to prevent and therefore we can only prepare for the earthquake and post-earthquake response. The foreknowledge of potential
  danger areas can help mitigate the impact of a disaster.

Steps that needs to be taken

• Short Term Steps:
  1. Preparing Vulnerability Map of the country
  • Establishing infrastructure for early warning system in vulnerable areas.

2. Strengthening Early Waring Infrastructure -> for providing those crucial extra seconds of a minute in disaster scenario.

3. Strengthening Institutional Framework -> Shortage of manpower in SDRF and NDRF should be rectified. Local governments, NGOs etc also need to be prepared for post disaster response especially in vulnerable areas.

4. Implementing Building Codes -> Municipalities need to ensure that BIS codes and
guidelines are properly being followed in new buildings.

• • The lifeline buildings which have been built in the past and are not earthquake resistant needed to be upgraded by retrofitting techniques

5. Improving building code through a new architecture regime and this be made mandatory for all builders and developers.

6. Educating people through dissemination of information about the ways and means of minimizing the adverse impacts of earthquakes. Dissemination of techniques such as ‘Drop, Cover and Hold’ is very important reducing the loss of life during earthquakes.

• • Community preparedness is very important for dealing with earthquake. Though we have NDRF and other bodies to do search and rescue operations, but experience shows that most of the time it is the community which plays the first hand role in disaster situation and therefore they have to be given proper training regarding search and rescue as well.
    • Community should have a disaster emergency kit ready for disaster situation
    • Community also needs to participate in planning, implementation and monitoring process of any method being used.
• Long Term steps:

1. International Collaboration

• • We should collaborate with other countries in development of earthquake resistant infrastructure. Our collaboration with countries like Japan will be very crucial in enhancing our preparedness for earthquakes.

2. Decongesting of Cities to reduce risk and vulnerabilities

Conclusion

• Earthquake may not yet be predictable and certainly not preventable, still if effective and timely steps are taken, the adverse impact of Earthquakes can be considerably blunted.