Why the Location of China’s Earthquake Matters

Sub: Geo

Sec: Disaster Management

Why in News

On January 7, a magnitude 7.1 earthquake struck Tibetan China and Nepal. The epicentre was located near Mt. Everest, causing significant loss of life and property.

Key Details:

Epicentre: Located 10 km below the surface, approximately 80 km north of Mt. Everest.
Location: Tingry County in the Shigatse region, Tibet, 4-5 km above sea level.
Lhasa Terrane: The epicentre may have been located in this fragment of the Earth’s crust.
Himalayan Region: Known as the ‘third pole’ due to its vast water reserves in rivers, glaciers, and lakes.

Tingry County:

Situated in the southwestern part of the Tibet Autonomous Region, China; lies at the northern foot of Mount Everest in the middle section of the Himalayas.
Serves as a gateway for expeditions to Mount Everest and other Himalayan peaks; popular among trekkers and mountaineers.

Shigatse Region:

Second-largest city in Tibet, located in the southwestern part of the Tibet Autonomous Region.
Traditional seat of the Panchen Lama, a key figure in Tibetan Buddhism; houses the Tashilhunpo Monastery, an important religious site.
Agriculture is predominant, with vast grasslands and fertile river valleys; also known for semi-tropical jungles and snowfields at high altitudes.

Lhasa Terrane:

A geological terrane, or fragment of crustal material, that forms present-day southern Tibet; sutured to the Eurasian Plate during the Cretaceous period.
The northern part may have originated in the East African Orogeny, while the southern part appears to have been part of Australia; these parts joined and later attached to Asia.
The collision of the Indian Plate with the Eurasian Plate impacted the Lhasa Terrane, contributing to the formation of the Himalayas.
Home to the Gangdese Batholith, a major geological structure formed around 100 million years ago due to subduction-related volcanism; experienced two stages of plutonism in the Late Cretaceous and early Paleogene periods.
Research suggests that the Lhasa Terrane’s drift history from Gondwana to Asia plays a crucial role in understanding Tethys evolution and true polar wander.

Earthquake:

An earthquake is shaking or trembling of the earth’s surface, caused by the seismic waves or earthquake waves that are generated due to a sudden movement (sudden release of energy) in the earth’s crust (shallow-focus earthquakes) or upper mantle (some shallow-focus and all intermediate and deep-focus earthquakes).
The point where the energy is released is called the focus or the hypocentre of an earthquake.
The point on the surface directly above the focus is called epicentre (first surface point to experience the earthquake waves).
A line connecting all points on the surface where the intensity is the same is called an isoseismic line.

Waves:

There are several different kinds of seismic waves, and they all move in different ways. The two main types of waves are body waves and surface waves.
Body waves can travel through the earth’s inner layers, but surface waves can only move along the surface of the planet like ripples on water
The first kind of body wave is the P wave or primary wave. This is the fastest kind of seismic wave, and, consequently, the first to ‘arrive’ at a seismic station. The P wave can move through solid rock and fluids, like water or the liquid layers of the earth. It pushes and pulls the rock it moves through just like sound waves push and pull the air.
The second type of body wave is the S wave or secondary wave, which is the second wave felt in an earthquake. An S wave is slower than a P wave and can only move through solid rock, not through any liquid medium. It is this property of S waves that led seismologists to conclude that the Earth’s outer core is a liquid.
S waves move rock particles up and down, or side-to-side–perpendicular to the direction that the wave is traveling in (the direction of wave propagation)

Measuring earthquake:

The Mercalli scale bases its measurement on the observed effects of the earthquake and describes its intensity. It is a linear measurement.
On the other hand, the Richter scale measures the seismic waves, or the energy released, causing the earthquake and describes the quake’s magnitude.