Taiwan Earthquake

Why in news?

• Recently, Taiwan experienced its strongest earthquake of 7.2 magnitude in nearly 25 years.

About:

• Taiwan has a long history of earthquakes due to its location along the ‘Pacific Ring of Fire’, a line of seismic faults encircling the Pacific Ocean where most of the world’s earthquakes occur.
• The tension accumulated from the interactions of two tectonic plates, the Philippine Sea Plate and the Eurasian Plate, may lead to sudden releases in the form of earthquakes.
• The first recorded earthquake in Taiwan was in 1624.

Earthquake:

• It is a natural event caused due to release of energy, which generates waves that travel in all directions.
• The release of energy occurs along a fault, which is a sharp break in the crustal rocks, moving in opposite directions.
• The point where the energy is released is called the focus of an earthquake, alternatively, it is called the hypocentre.
• The point on the surface, nearest to the focus, is called epicentre. It is the first one to experience the waves. It is a point directly above the focus.

Measure of Earthquake:

• By seismographic networks, which are made of seismic stations, beneath the earth.
• It is possible to convert the measured wave amplitude into the energy released for that earthquake (magnitude of the earthquake).
• It is measured in the Richter scale.

Seismic waves:

• When an Earthquake occurs, the elastic limit of the earth breakdown and energy is released in the form of elastic waves (known as Seismic waves).

Types:

• Body waves: Generated due to the release of energy at the focus and move in all directions. Travel only through the interior of the earth. It is faster than surface waves.
• Types of Body Waves: P – Primary waves (all medium) and S – secondary waves (travel only through solid materials).
• Surface Waves: Body waves interact with surface rocks, and a new set of waves is formed called surface waves.
• These are transverse waves in which particle movement is perpendicular to the wave propagation. (formed crests and troughs).
• 2 common surface waves are Love waves and Rayleigh waves.
• Speed of different Waves in descending order: Primary Waves > Secondary Waves > Love Waves > Rayleigh Waves.

Why Are There Frequent Earthquakes in the Pacific Region?

• The ‘Pacific Ring of Fire’ is one of the most seismically and volcanically active zones in the world.
• It is primarily due to the movement of tectonic plates in this region.
• Much of the volcanic activity occurs along subduction zones, which are convergent plate boundaries where two tectonic plates come together.

Socio – Environmental Consequences of Earthquakes:

• Earthquakes are often associated with fear and horror due to the scale, magnitude and suddenness.
• It becomes a calamity when it strikes the areas of high density of population. It not only damages and destroys the settlements, infrastructure, transport and communication network, industries and other developmental activities but also robs the population of their material and socio-cultural gains that they have preserved over generations.
• It renders them homeless, which puts an extra-pressure and stress, particularly on the weak economy of the developing countries.

Glacial Lake Floods

Why in news?

• The Uttarakhand government has constituted two teams of experts to evaluate the risk posed by five potentially hazardous glacial lakes in the region. These lakes are prone to Glacial Lake Outburst Floods (GLOFs).

What are GLOFs?

• GLOFs are disaster events caused by the abrupt discharge of water from glacial lakes — large bodies of water that sit in front of, on top of, or beneath a melting glacier.
• As a glacier withdraws, it leaves behind a depression that gets filled with meltwater, thereby forming a lake.
• The more the glacier recedes, the bigger and more dangerous the lake becomes.

Reasons for GLOFs:

• GLOFs can be triggered by various reasons, including
• Glacial calving, where sizable ice chunks detach from the glacier into the lake,
• Inducing sudden water displacement
• Incidents such as avalanches or landslides can also impact the stability of the boundary around a glacial lake, leading to its failure, and the rapid discharge of water.
• In recent years, there has been a rise in GLOF events in the Himalayan region as soaring global temperatures have increased glacier melting.
• Rising surface temperatures across the globe, including India, have increased the risk of GLOFs
• Rapid infrastructure development in vulnerable areas has also contributed to the spike in such incidents.

Impacts:

• GLOFs can unleash large volumes of water, sediment, and debris downstream with formidable force and velocity.
• The floodwaters can submerge valleys, obliterate infrastructure such as roads, bridges, and buildings, and result in significant loss of life and livelihoods.
• It has resulted in several disasters in the Himalayan states in recent years.

Geographical Distribution:

• Commonly associated with glacial regions, especially in mountainous areas with significant glacial activity. Examples include the Himalayas, Andes, and Alps.
• Since 1980, in the Himalayan region, particularly in southeastern Tibet and the China-Nepal border area, GLOFs have become more frequent
• The National Disaster Management Authority (NDMA), which operates under the Union Ministry of Home Affairs, has identified 188 glacial lakes in the Himalayan states that can potentially be breached because of heavy rainfall.
• Thirteen of them are in Uttarakhand.

Way Forward:

• There is a need to know more about the dynamics of glaciers and glacial lakes
• Therefore,It is important to learn as much as possible about past events and the dynamics behind them and to assess the overall GLOF risk in the region for better planning and implementation of disaster risk reduction measures and climate change adaptation in the region.
• There is a need to Utilise satellite imagery and remote sensing technology to monitor changes in glacial lakes and identify potential threats.
• Develop and communicate emergency preparedness plans to communities at risk.