The Sunda plate is a minor tectonic plate straddling the equator in the Eastern Hemisphere on which the majority of Southeast Asia is located.
The Sunda plate was formerly considered a part of the Eurasian plate, but the GPS measurements have confirmed its independent movement at 10 mm/yr eastward relative to Eurasia.
In the geology of the Philippines, the Philippine Mobile Belt is a complex portion of the tectonic boundary between the Eurasian plate and the Philippine Sea plate, comprising most of the Philippine archipelago. It includes two subduction zones, the Manila Trench to the west and the Philippine Trench to the east, as well as the Philippine fault system. Within the Belt, a number of crustal blocks or microplates which have been shorn off the adjoining major plates are undergoing massive deformation.
Most segments of the Philippines, including northern Luzon, are part of the Philippine Mobile Belt, which is bounded by the Philippine Sea plate to the east, the Molucca Sea Collision Zone to the south, Sunda plate to the southwest, and the South China Sea Basin to the west and north-west. To the north it ends in eastern Taiwan, the zone of active collision between the North Luzon Trough portion of the Luzon Volcanic Arc and South China. The Philippine Mobile Belt has also been called the Philippine Microplate and the Taiwan–Luzon–Mindoro Belt.
Southeast Asia is the geographical southeastern region of Asia, consisting of the regions that are situated south of China, east of the Indian subcontinent, and northwest of mainland Australia, which is part of Oceania. Southeast Asia is bordered to the north by East Asia, to the west by South Asia and the Bay of Bengal, to the east by Oceania and the Pacific Ocean, and to the south by Australia and the Indian Ocean. Apart from the British Indian Ocean Territory and two out of 26 atolls of the Maldives in South Asia, Maritime Southeast Asia is the only other subregion of Asia that lies partly within the Southern Hemisphere. Mainland Southeast Asia is entirely in the Northern Hemisphere. Timor-Leste and the southern portion of Indonesia are the parts of Southeast Asia that lie south of the equator.
The region lies near the intersection of geological plates, with both heavy seismic and volcanic activities. The Sunda plate is the main plate of the region, featuring almost all Southeast Asian countries except Myanmar, northern Thailand, northern Laos, northern Vietnam, and northern Luzon of the Philippines, while the Sunda plate only includes western Indonesia to as far east as the Indonesian province of Bali. The mountain ranges in Myanmar, Thailand, Peninsular Malaysia, and the Indonesian islands of Sumatra, Java, Bali, Lesser Sunda Islands, and Timor are part of the Alpide belt, while the islands of the Philippines and Indonesia as well as Timor-Leste are part of the Pacific Ring of Fire. Both seismic belts meet in Indonesia, causing the region to have relatively high occurrences of earthquakes and volcanic eruptions, particularly in the Philippines and Indonesia.
The Burma plate is a minor tectonic plate or microplate located in Southeast Asia, sometimes considered a part of the larger Eurasian plate. The Andaman Islands, Nicobar Islands, and northwestern Sumatra are located on the plate. This island arc separates the Andaman Sea from the main Indian Ocean to the west.
To its east lies the Sunda plate, from which it is separated along a transform boundary, running in a rough north–south line through the Andaman Sea. This boundary between the Burma and Sunda plates is a marginal seafloor spreading centre, which has led to the opening up of the Andaman Sea (from a southerly direction) by "pushing out" the Andaman-Nicobar-Sumatra island arc from mainland Asia, a process which began in earnest approximately 4 million years ago.
The Yangtze plate, also called the South China block or the South China subplate, comprises the bulk of southern China. It is separated on the east from the Okinawa plate by a rift that forms the Okinawa Trough which is a back-arc basin, on the south by the Sunda plate and the Philippine Sea plate, and on the north and west by the Eurasian plate. The Longmenshan Fault on the latter border was the site of the 2008 Wenchuan earthquake.
The Yangtze plate was formed by the disaggregation of the Rodinia supercontinent 750 million years ago, in the Neoproterozoic era. South China rifted away from the Gondwana supercontinent in the Silurian. During the formation of the great supercontinent Pangaea, South China was a smaller, separate continent located off the east coast of the supercontinent and drifting northward. In the Triassic, the Yangtze plate collided with the North China plate, thereby connecting with Pangaea, and formed the Sichuan basin. In the Cenozoic, the Yangtze plate was influenced by the collision of the Indian plate and Eurasian plate creating the uplifting of the Longmen Mountains. Its southward motion is accommodated along the Red River fault.
The Sunda Trench, earlier known as and sometimes still indicated as the Java Trench, is an oceanic trench located in the Indian Ocean near Sumatra, formed where the Australian-Capricorn plates subduct under a part of the Eurasian plate. It is 3,200 kilometres (2,000 mi) long with a maximum depth of 7,290 metres (23,920 feet). Its maximum depth is the deepest point in the Indian Ocean. The trench stretches from the Lesser Sunda Islands past Java, around the southern coast of Sumatra to the Andaman Islands, and forms the boundary between the Indo-Australian plate and Eurasian plate (more specifically, Sunda plate). The trench is considered to be part of the Alpide belt as well as one of oceanic trenches around the northern edges of the Australian plate.
In 2005, scientists found evidence that the 2004 earthquake activity in the area of the Java Trench could lead to further catastrophic shifting within a relatively short period, perhaps less than a decade. This threat has resulted in international agreements to establish a tsunami warning system in place along the Indian Ocean coast.