A series of earthquakes hit the Zenda Jan district in Herat province, western Afghanistan, on Sunday October 8, 2023. The strongest earthquake–with a 6.3 magnitude according to the USGS–was also felt in the neighboring countries of Iran, Turkmenistan and Uzbekistan. At least 2,500 people were killed and more than 9,000 injured in Afghanistan, local authorities said. It’s one of the deadliest earthquakes to strike the country in two decades.
Earthquakes are common in the Alpine-Himalayan orogenic belt–a major mountain belt stretching from the Mediterranean through Anatolia, Iran, Afghanistan, Pakistan and Central Asia into South-East Asia–so seismologist Simon Redfern in an article for The Conversation. Around a fifth of the world’s largest earthquakes happened here.
The seismic activity is linked to the collision between the Eurasian tectonic plate to the north and the Indian plate to the south. The area marks the scar of the closure of an ancient ocean, the Tethys, which once separated the continents of Gondwana, including most of the landmasses in today’s southern hemisphere, and Laurasia, made up of most of the countries that are today in the northern hemisphere. The Tethyan Ocean closed around 40 million years ago. For a long time geologists assumed that as the plates continue to be pushed together, the accumulating energy is released from time to time in the form of earthquakes.
Research published in 2008 suggested a different mechanism to explain why seismic activity in the region seem to be linked to deep-seated fault-lines. According to this model, the earthquakes can be explained by the tearing off of sections of ancient ocean floor sinking into the Earth’s mantle beneath east Afghanistan-Pakistan-India. As large portions of rock break off, the stretched crust rebounds and moves up. These movements also deform a superficial fault network stretching west, triggering earthquakes. In combination with poor construction standards, most building in rural areas are made of mud bricks, such shallow earthquakes can cause widespread devastation.
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