2004 Indian Ocean earthquake and tsunami

Main article: Earthquakes

Shift of the Indian plate under Burma for 1.2 thousand km and giant rock collapses

The epicenter of the earthquake was located in the Indian Ocean, north of the island of Simyolue, located near the northwestern coast of the island of Sumatra (Indonesia).

The earthquake was unusually large in a geographical sense. There was a shift of about 1200 km (according to other estimates - 1600 km) of rock to a distance of 15 m along the subduction zone, as a result of which the Indian plate moved under the Burma plate.

The shift was not a one-time shift, but was divided into two phases within a few minutes. The first phase formed a fault measuring approximately 400 km per 100 km, located at a depth of 30 km under the seabed. The fault formed at a speed of about 2 km/s, starting from the coast of Ase towards the northwest for about 100 seconds. Then there was a pause of about 100 seconds, after which the fault continued to form north towards the Andaman and Nicobar Islands, which apparently shifted southwest about 1.25 meters and dropped 1 meter.

In February 2005, the British warship HMS Scott examined the seabed in the area of ​ ​ the earthquake, the depth of which varies from 1000 to 5000 m. A study conducted using a high-resolution multi-beam sonar system showed that the earthquake had a significant impact on the topography of the seabed. The 1,500-meter-high thrusts created by previous geological activity along the fault collapsed, causing landslides several kilometers wide. One of these landslides consisted of a solid block of rock about 100 meters high and 2 km long. The momentum of water displaced by the tectonic uplift also dragged massive blocks of rock, each weighing millions of tons, 10 km across the seabed. In the earthquake zone, an oceanic depression several kilometers wide was exposed.

Sea floor rise of several metres triggers largest tsunami in history

The 2004 Indian Ocean earthquake caused the seabed to rise several meters, displacing approximately 30 km3 of water and causing devastating tsunami waves. Waves spread outward over the entire 1600 km gap length (acting as a linear source). This greatly expanded the geographic area in which waves were observed, reaching as far as Mexico, Chile and the Arctic.

The rise of the seabed significantly reduced the volume of the Indian Ocean, which led to a constant increase in global sea level by about 0.1 mm.

Speed of movement of tsunami with indication of hours from the moment of its beginning

The tsunami reached the shores of Indonesia, Sri Lanka, southern India, Thailand, the Maldives, Somalia and other countries.

A few minutes before the tsunami, the sea sometimes temporarily retreats from the shore, which was observed in the fault zone in the east, for example, on the Aceh coast, on the islands of Phuket and Khao Lak in Thailand, on the island of Penang in Malaysia and on the Andaman and Nicobar Islands. The rare sight reportedly prompted people, especially children, to head to the coast to explore the space and collect beached fish.

Scientists who studied the damage caused in Aceh found evidence that the wave reached a height of 24 m when coming ashore on large sections of the coastline, and in some areas rose to 30 m when moving inland.

The highest tsunami height was recorded on a hill between Lhoknga and Leupung, on the west coast of the northern tip of Sumatra, near Banda Aceh, at 51 m.

Average wave height

Since the fault of 1200 kilometers was located approximately in the north-south direction, the largest force of the tsunami wave reached in the east-west direction. Bangladesh, located at the northern end of the Bay of Bengal, suffered the most minor damage, despite being located sufficiently low above sea level.

In many places, waves passed up to 2 km of land, and in some (in particular, in the coastal city of Banda Aceh) - 4 km.

Tsunami victims: more than 225 thousand people

According to various estimates, from 225 thousand to 300 thousand people died. The exact number of dead is unknown, as many people were carried away by water into the ocean.

Indonesia: 172 thousand dead

The death toll in Indonesia was 172,761.

Sri Lanka: 35,000 dead

In Sri Lanka, the tsunami first hit the east coast. Refracted tsunami waves then flooded the southwestern part of Sri Lanka after some of their energy was reflected from the Maldives.

A regular passenger train running between Maradana and Matara carrying more than 1,750 passengers derailed and overturned due to the tsunami, killing at least 1,000 people in the largest rail disaster in history. Based on the condition of the shoreline and the water level mark of a nearby building, estimates suggest that the tsunami rose 7.5-9 m above sea level and 2-3 m above the top of the train.

Civilian casualties in Sri Lanka were the second highest after Indonesia, with about 35,000 deaths. The country's eastern shores were hit hardest, while the southwestern shores were hit later, but the death toll there was just as significant.

Andaman and Nicobar Islands

The Andaman Islands suffered little damage, while Maly Andaman Island and the Nicobar Islands were hit hard by the tsunami.

On the island of South Andaman, according to local eyewitnesses, there were three tsunami waves, and the third was the most destructive.

Flooding was observed along the east coast and in the lowlands inside the island, which were linked to the open sea by streams.

Several coastal structures and numerous infrastructure such as breakwaters and a 20 MW diesel power plant in Bamboo Valley were destroyed. In Port Blair, the water receded before the first wave, and the third wave was the highest and caused the most damage.