EDITORIAL 2: The Kamchatka quake
Context
An 8.8 magnitude earthquake, one of the strongest on record, struck the Kamchatka Peninsula, in Russia’s far-east, recently triggering a tsunami.
Rare but not unusual
- The earthquake in Kamchatka was the strongest since the 9.1 magnitude quake that had struck Japan in 2011.
- That quake too had caused a major tsunami which then led to the nuclear disaster at Fukushima.
- Only five earthquakes of magnitude 8.5 and above have occurred in the past 20 years — but it occurred in a region that is one of the most earthquake prone in the world.
Kamchatka Peninsula
- Kamchatka Peninsula lies on the Circum-Pacific seismic belt, more popularly known as the “Ring of Fire”, that witnesses the maximum number of earthquakes and volcanic eruptions on Earth.
- This seismically active belt encircles almost the entire Pacific Ocean — on its eastern side is the western coast of the Americas, and on its western side lies the Far East and Oceania.
- It touches countries like the United States, Mexico, Chile, Peru, New Zealand, Australia, Indonesia, the Philippines, Japan and Russia.
- According to the United States Geological Survey (USGS), the Ring of Fire accounts for more than 80% of the planet’s largest earthquakes.
- The nearly 2,000-km long region extending from Kamchatka Peninsula in the north to northern Japan in the south, and including the volcanically-active Kuril Islands of Russia, has witnessed more than 130 earthquake events of 7-plus magnitude since 1900.
Process of subduction
- The Circum-Pacific seismic belt is home to multiple subduction processes, in which the Pacific tectonic plate is clashing against continental land.
- Subduction is a geological process in which one tectonic plate — put simply, a large section of the Earth’s crust — presses against another.
- Usually, the heavier or denser plate, that is, the one with more mass per unit of area, tends to go below the lighter plate.
- But this process results in deformities and creates a huge stress at the plate boundaries. It is this stress that is released in the form of earthquakes.
- The Himalayas were created due to subduction, as a result of the Indian plate pushing against the Eurasian plate. This is also the reason why the Himalayan region is one of the most earthquake-prone in the world.
- The Pacific plate is denser, and is subducting under the continental plate at several places on both sides.
- There is no other place on Earth where so many subduction processes are happening. And this is why the region produces so many earthquakes.
Other active regions
- The Circum-Pacific seismic belt is one of the three large earthquake zones of the Earth. The Alpide belt — spanning from Indonesia through the Himalayas and further to Afghanistan, Iran, and Turkey — which runs mostly over the land, is the second-most earthquake-prone zone in the world.
- But unlike the Ring of Fire, which accounts for around 80% of all big earthquakes, the Alpide belt contributes only 15-17%, according to USGS.
- However, this belt traverses some of the most heavily populated areas on the planet, which makes earthquakes in the region extremely deadly.
- In general, while the strongest earthquakes often take place under the ocean, the ones on land, even if they are weaker, are often more deadly due to their proximity to population centres.
- The Kamchatka quake stuck off the coast of the peninsula, which is sparsely populated.
- The third most prominent seismic belt is what is known as the mid-Atlantic ridge, which runs north-south through the middle of the entire Atlantic Ocean, from the Arctic to the Antarctic region.
- The strength of an earthquake is, in part, dependent on the length of the faultline, that is, the extent of the plate boundaries that clash against each other. A larger faultline is more likely to produce a stronger earthquake.
Conclusion
To produce anything stronger, say an event of magnitude 10 or more, a faultline extending to almost the entire Earth would be required. No current faultline is capable of producing a quake that strong.