Context:
Recently, a magnitude 7.3 earthquake struck off the coast of Vanuatu in the South Pacific Ocean.
About Vanuatu:
- Vanuatu is located in the Australasia Ecozone consisting of a chain of 13 principal and many smaller islands.
- There are many Active volcanoes including Séré’ama on Vanua Lava, Manaro on Aoba, Garet on Santa Maria, Benbow and Marum on Ambrym, and Yasur on Tanna, along with several submarine volcanoes.
- The nation faces an existential threat from climate change, impacting livelihoods, security, and overall well-being.
- Its sea level is rising at twice the global average rate and is expected to continue rising throughout the 21st century.
- Vanuatu’s vulnerability has consistently ranked it as the most at-risk country globally under the UN’s World Risk Index.
What is an earthquake?
- An earthquake is the sudden release of strain energy in the Earth’s crust, resulting in waves of shaking that radiate outwards from the earthquake source.
- When stresses in the crust exceed the strength of the rock, it breaks along lines of weakness, either a pre-existing or new fault plane.
- The point where an earthquake starts is termed the focus or hypocentre and may be many kilometers deep within the earth.
- The point at the surface directly above the focus is called the earthquake epicenter.
- The instrument used to measure earthquakes is called a seismograph
- There are several scales used to measure the size of an earthquake, including the Richter scale (does not provide accurate estimates for large magnitude earthquakes), the Mercalli scale, and the moment magnitude scale (applicable globally).
Types of earthquakes:
- Tectonic earthquake: Occurs when the Earth’s crust breaks due to geological forces on rocks and adjoining plates, causing physical and chemical changes.
- Volcanic earthquake: Triggered by tectonic forces associated with volcanic activity.
- Collapse earthquake: Small earthquakes in underground caverns or mines, caused by seismic waves from rock explosions on the surface.
- Explosion earthquake: Results from the detonation of nuclear or chemical devices.