Taiwan Quake Resilience

Concept :

  • In the Taiwan region, the Philippine Sea plate is moving northwest towards the Eurasian plate at a velocity of about 7.8 cm per year, which is faster than the motion of the Indian plate.
  • Lying 160 km of the coast of China, Taiwan was formed at a convergent boundary of the Philippine and Eurasian plates in the western Pacifc Ocean. It is a country of strong earthquakes.
  • The latest one occurred near the city of Hualien on the eastern coast. In 1999, the Chi-Chiearthquake of magnitude 7.7 occurred in the central part of Taiwan and impacted the western region.
  • It killed more than 2,430 people and left 11,305 wounded. It caused more than 50,000 buildings to collapse and partially damaged as many.
  • The Hualien earthquake killed at least 13 people and injured about 1,000. Most of the deaths were caused by earthquake-triggered rockfalls and not by toppled buildings. Despite being of nearly comparable magnitude, the 2024 earthquake has caused minimal damage compared to the 1999 earthquake.
  • What is remarkable is that even in Hualien city, located within the epicentre of the latest earthquake, where shaking is expected to be most intense, only about 50 residential buildings and a nine-storey building partially collapsed.
  • In the capital city of Taipei, only 10 houses were severely damaged. These were reported to have been constructed before the implementation of stringent building codes following the 1999 Chi-Chi earthquake.

Earthquakes:

  • Violent shaking of the ground caused by the sudden release of energy within Earth’s lithosphere (upper mantle and crust).
  • Tectonic Plates: Earth’s surface is divided into rigid tectonic plates that move slowly over the underlying mantle.

Causes:

  • Plate Movements: Friction between plates at their boundaries (convergent, divergent, transform) can build up stress, leading to sudden release and earthquakes.
  • Fault Lines: These are zones of weakness within plates where movement and earthquakes are more likely.
  • Volcanic Activity: Movement of magma can cause tremors and minor earthquakes.

Key Earthquake Terminology:

  • Hypocenter (Focus): The point within Earth where the earthquake originates.
  • Epicenter: The point on the Earth’s surface directly above the hypocenter.
  • Seismic Waves: Vibrations radiating outward from the hypocenter, causing the ground to shake. These come in different types:
  • Primary (P) Waves: Travel fastest, compress and stretch rock layers.
  • Secondary (S) Waves: Travel slower, vibrate the ground side-to-side.
  • Surface Waves: Cause the most significant shaking and destruction at the surface.

Measuring Earthquakes:

  • Magnitude: Quantifies the energy released at the hypocenter using the Richter Scale (logarithmic scale, base 10).
  • Lower values indicate minor tremors, while higher values signify powerful earthquakes.
  • Intensity: Measures the effects of ground shaking at a specific location using the Modified Mercalli Intensity (MMI) scale (descriptive scale, I to XII).
  • Higher MMI values indicate more severe shaking and potential damage.

Impact of Earthquakes:

  • Ground Shaking: The primary cause of damage to buildings, infrastructure, and landslides.
  • Tsunamis: Undersea earthquakes can trigger massive waves that devastate coastal areas.
  • Liquefaction: Saturation of loose soil can cause it to behave like a liquid, leading to building collapse.
  • Fire: Damaged electrical lines and ruptured gas pipelines can ignite fires.

Earthquake-Prone Areas in India:

  • Himalayan Region: Located in Zone V (highest risk) due to the ongoing subduction of the Indian Plate under the Eurasian Plate.
  • North-East India: Part of Zone V due to active fault lines.
  • Gujarat: Prone to earthquakes due to the presence of the Cambay Graben Rift Valley.
  • Andaman and Nicobar Islands: Lying on the boundary of tectonic plates, highly vulnerable to earthquakes and tsunamis.

Government Initiatives for Earthquake Risk Reduction:

  • National Disaster Management Authority (NDMA): Develops policies, plans, and coordinates efforts for earthquake preparedness and mitigation.
  • Bureau of Indian Standards (BIS): Prescribes earthquake-resistant building codes.
  • National Centre for Seismology (NCS): Monitors seismic activity and issues earthquake warnings.

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