Magnitude 6.2 Earthquake off the west coast of Sumatra.

The Indonesian Meteorological, Climatological, and Geophysical Agency recorded a Magnitude 6.2 Earthquake at a depth of about 29 km, off the West coast of Aceh Province, Sumatra, Indonesia slightly after 6.00 pm Western Indonesian Time (slightly after 11.00 am GMT) on Tuesday 31 January 2025. There have been no reports of any damage or casualties following this event, but people have reported feeling  tremors  across Aceh Province and parts of North Sumatra.

The approximate location of the 31 January 2025 Aceh Province Earthquake. USGS.

The Indo-Australian Plate, which underlies the Indian Ocean to the west of Sumatra, is being subducted beneath the Sunda Plate, a breakaway part of the Eurasian Plate which underlies Sumatra and neighbouring Java, along the Sunda Trench, passing under Sumatra, where friction between the two plates can cause Earthquakes. As the Indo-Australian Plate sinks further into the Earth it is partially melted and some of the melted material rises through the overlying Sunda Plate as magma, fueling the volcanoes of Sumatra.

The Subduction zone beneath Sumatra. NASA/Earth Observatory.

This does not happen at a 90° angle, as occurs in the subduction zones along the western margins of North and South America, but at a steeply oblique angle. This means that as well as the subduction of the Indo-Australian plate beneath the Sunda, the two plates are also moving past one-another. This causes rifting within the plates, as parts of each plate become stuck to the other, and are dragged along in the opposing plate's direction. The most obvious example of this is the Sumatran Fault, which runs the length of Sumatra, with the two halves of the island moving independently of one-another. This fault is the cause of most of the quakes on the island, and most of the island's volcanoes lie on it.

The movement of the tectonic plates around Sumatra. NASA/Earth Observatory.

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Evacuations ordered after increase in activity from Mount Ibu on Halmahera Island, Indonesia.

Authorities in North Maluku Province, Indonesia, have ordered the evacuation of six villages close to Mount Ibu, a 1325 m stratovolcano on the northwest coast of Halmahera Island, following a series of eruptions in the first two weeks of 2025. Mount Ibu began its current eruptive cycle in June 2024, but January has seen a significant rise in activity, with more than a thousand eruptions have been recorded on the volcano this year, with the largest producing ash columns reaching as high as 4 km over the summit of the volcano. However, to date only one village, with a population of 517 people, has been evacuated, with about 2500 people in the remaining five villages reluctant to leave without first harvesting crops.

An eruption on Mount Ibu, Halmahera Island, on Wednesday 15 January 2024. Azzam/AFP.

The Halmahera Island chain is a volcanic arc formed where the Halmahera Plate, a northeaster extension of the Molucca Sea Plate is being subducted beneath Philippine Plate from the east and the Eurasian Plate from the west, with the underlying plate being melted by the heat of the Earth's interior, and lighter minerals bubbling up through the overlying plate to form volcanoes. The Halmahera volcanoes are located where the Philippine Plate is overriding the Molucca Sea Plate; to the west the Sangihe Islands lie where the Molucca Sea Plate is being overridden by the Eurasian Plate.

Diagrammatic representation of the subduction zones beneath Halmahera (middle), plus the Philippines (top) and Sulawesi (bottom), with the Eurasian Plate to the left, the Molucca Sea Plate in the middle, and the Philippine Plate to the right.  Hall & Wilson (2000).

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Magnitude 6.9 Earthquake off the east coast of Kyūshū Island, Japan.

The Japan Meteorological Agency recorded a Magnitude 6.9 Earthquake at a depth of about 30 km, beneath the Hyūganada Sea, off the coast of Miyazaki Prefecture on Kyūshū Island, Japan, slightly before 9.20 pm Japan Standard Time (slightly before 12.20 pm GMT) on Monday 13 January 2025. One person was slightly injured by the event, due to falling on some stairs, minor damage to several buildings reported, and train services stopped temporarily while lines were checked. A tsunami warning was issued after the initial event, with concerns a wave as high as one metre could be triggered, although in the event a wave only 20 cm high was reported in Miyazaki Port.

The approximate location of the 13 January 2025 Hyūganada Sea Earthquake. USGS.

Japan has a complex tectonic situation, with parts of the country on four different tectonic plates. Kyūshū Island lies on the margin where the the Eurasian Plate is overiding the Philipine Plate, with the Pacific Plate being subducted beneath the Okhotsk Plate to the east. This is not a smooth process; the rocks of the two plates constantly stick together, only to break apart again as the pressure builds up, causing Earthquakes in the process.

The movement of the tectonic plates beneath Japan. University of Wisconsin Eau Claire.

Earthquakes along subductive margins are particularly prone to causing tsunamis, since these often occur when the overlying plate has stuck to the underlying plate, being pulled out of shape by its movement. Eventually the pressure builds up to far and the overlying plate snaps back, causing an Earthquake and a tsunami. 

Simplified graphic showing tsunami generation along a convergent margin. NASA/JPL/CalTech.

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Magnitude 6.8 earthquake in southern Tibet kills at least 126 people.

The China Earthquake Networks Center recorded a Magnitude 6.8 Earthquake at a depth of 10 km beneath Tingri County in southern Tibet, close to Mount Everest and the border with Tibet at about 9.05 am local time on Tuesday 7 January 2025 (about 1.05 am, GMT). The Earthquake was felt across southern Tibet, eastern Nepal, western Bhutan, northeastern India and northern Bangladesh. More than 150 aftershocks have been recorded since the original event.

The approximate location of the 7 January 2025 Tibet Earthquake. USGS.

At the time of writing rescue workers have reported 126 deaths and 188 people injured in Tibet and another five injuries in Nepal. However, the number of casualties is likely to rise significantly, as the population in the area around the epicentre of the Earthquake largely live in small, remote villages, largely cut off from the outside world, and which are subsequently difficult for rescue workers to reach. To make matters worse, daytime temperatures in the area average -8°C at this time of year, falling to -18°C at night. More than a thousand homes have been damaged or destroyed in areas that rescue workers have managed to reach, so is likely that in other areas people may have lost  their homes or be trapped beneath debris, vulnerable to the cold.

Rescue workers in Tingri County, Tibet, following a Magnitude 6.8 Earthquake on Tuesday 7 January 2024. Xinhua/AP.

Earthquake activity in the area is caused by the uplift of the Tibetan Plateau, due to the impact of India into Eurasia to the south. he Indian Plate is moving northwards at a rate of 5 cm per year, causing it to impact into Eurasia, which is also moving northward, but only at a rate of 2 cm per year. The collision of the Indian and Eurasian plates has led to the formation of the Himalayan Mountains, the Tibetan Plateau, and the mountains of southwest China, Central Asia and the Hindu Kush.

Block diagram showing how the impact of the Indian Plate into Eurasia is causing uplift on the Tibetan Plateau. Jayne Doucette/Woods Hole Oceanographic Institution.

Much of Tibet and neighbouring areas of Central Asia and the Himalayas, are prone to Earthquakes caused by the impact of the Indian Plate into Eurasia from the south. When two tectonic plates collide in this way and one or both are oceanic then one will be subducted beneath the other (if one of the plates is continental then the other will be subducted), but if both plates are continental then subduction will not fully occur, but instead the plates will crumple, leading to folding and uplift (and quite a lot of Earthquakes). The collision of the Indian and Eurasian plates has lead to the formation of the Himalayan Mountains, the Tibetan Plateau, and the mountains of southwest China, Central Asia and the Hindu Kush.

The movement of India into Eurasia over the last 71 million years. USGS.

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Magnitude 5.2 Earthquake in Buzău County, Romania.

The Centre Sismologique Euro-Méditerranéen recorded a Magnitude 5.2 Earthquake at a depth of 131 km, roughly 16 km to the north of the town of Nehoiu in Buzău County, in southeast the Muntenia region of Romania, at about 6.40 pm local time (about 2.40 pm GMT) on Monday 16 September 2024. There are no reports of any damage or injuries arising from this event, but it was felt over much of eastern Romania, Moldova, and western Ukraine. This pattern of causing little damage but being felt a considerable distance from the epicentre is typical of deep Earthquakes, the energy of which is dispersed over a wide distance before reaching the surface.

The approximate location of the 16 September 2024Buzău County, Earthquake. USGS.

The Carpathian Mountains of Romania form part of the suture formed when the Tethys Ocean closed during the Mesozoic, joining the continents of Laurasia (to the north) and Gondwana (to the south). The area is now internal to the Eurasian continent, but the area to the south, known as the Moesian Platform, has a separate origin to the rest of Europe. This system is once again being stressed by the impact of Africa into Eurasia from the south, with the Anatolian Plate (which underlies Anatolian Turkey), Aegean Plate (which underlies southern Greece) and Adriatic Plate (which underlies eastern Italy and the western Balkan Peninsula) caught between the two larger units, leading to a more complex interplay of stresses across southeastern Europe. The Anatolian and Aegean Plates are located to the south of the Moesian Platform, and are being pushed to the west, while the Adriatic Plate lies to the west of the Aegean Plate and Moesian Platform, and is being pushed to the northeast.

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