Sunda Trench

The Sunda Trench, earlier known as and sometimes still indicated as the Java Trench,[1] 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).[2] 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 on to the Andaman Islands, and forms the boundary between Indo-Australian Plate and Eurasian plate (more specifically, Sunda Plate). The trench is considered to be part of the Pacific Ring of Fire as well as one of a ring of oceanic trenches around the northern edges of the Australian Plate.

Map showing earthquake activity in the vicinity of the Java Trench around the time of the 2004 Indian Ocean earthquake. Prepared by the United States Geological Survey

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 of time, perhaps less than a decade.[3] This threat has resulted in international agreements to establish a tsunami warning system in place along the Indian Ocean coast.[4]

Characteristics
Main article: Geology of the Sumatra Trench

For about half its length, off of Sumatra, it is divided into two parallel troughs by an underwater ridge, and much of the trench is at least partially filled with sediments. Mappings after the 2004 Indian Ocean earthquake of the plate boundary showed resemblance to suspension bridge cables, with peaks and sags, indicative of asperity and locked faults, instead of the traditional wedge shape expected.[5]

Exploration

Some of the earliest exploration of the Trench occurred in the late 1950s when Robert Fisher, Research Geologist at the Scripps Institution of Oceanography, investigated the trench as part of a worldwide scientific field exploration of the world's ocean floor and sub-oceanic crustal-structure. Bomb-sounding, echo-train analysis and manometer were some of the techniques used to determine the depth of the trench. The research contributed to an understanding of the subduction characteristic of the Pacific margins.[6] Various agencies have explored the trench in the aftermath of the 2004 earthquake, and these explorations have revealed extensive changes in the ocean floor.[7]

Manned descent
Deep Submersible Support Vessel DSSV Pressure Drop and DSV Limiting Factor at its stern

On 5 April 2019 Victor Vescovo made the first manned descent to the deepest point of the trench in the Deep-Submergence Vehicle DSV Limiting Factor (a Triton 36000/2 model submersible) and measured a depth of 7,192 m (23,596 ft) ±13 m (43 ft) by direct CTD pressure measurements at 11°7'44" S, 114°56'30" E,[8][9] about 500 km (310 mi) south of Bali. The operating area was surveyed by the support ship, the Deep Submersible Support Vessel DSSV Pressure Drop, with a Kongsberg SIMRAD EM124 multibeam echosounder system. The gathered data will be donated to the GEBCO Seabed 2030 initiative.[10][11] The dive was part of the Five Deeps Expedition. The objective of this expedition is to thoroughly map and visit the deepest points of all five of the world's oceans by the end of September 2019.[12]

To resolve the debate regarding the deepest point of the Indian Ocean, the Diamantina Fracture Zone was surveyed by the Five Deeps Expedition in March 2019, recording a maximum water depth of 7,019 m (23,028 ft) ±17 m (56 ft) at 33°37'52" S, 101°21'14" E for the Dordrecht Deep.[8] This confirmed that the Sunda Trench was indeed deeper than the Diamantina Fracture Zone.

Associated seismicity

The subduction of the Indo-Australian Plate beneath a bloc of the Eurasian Plate is associated with numerous earthquakes. Several of these earthquakes are notable for their size, associated tsunamis, and/or the number of fatalities they caused.

Sumatra segment

Java segment

See also

References
  1. Sunda Trench (4°30' S 11°10' S 100°00' E 119°00' Accredited by: SCGN (Apr. 1987) The trench was studied in some detail in 1920s-1930s by Dutch geodesist F.A. Vening Meinesz, who made classic pendulum gravity measurements in a Dutch submarine. Shown as Java Trench in ACUF (Advisory Committee on Undersea Features Gazetteer). see also: http://www.gebco.net/
  2. Heather A. Stewart, Alan J. Jamieson: The five deeps: The location and depth of the deepest place in each of the world's oceans. In: Earth-Science Reviews 197, October 2019, 102896, doi:10.1016/j.earscirev.2019.102896.
  3. Davis, Katharine. "Asia primed for next big quake". New Scientist.
  4. IOC: Towards a Tsunami Warning System in the Indian Ocean Archived 1 February 2006 at Archive.today
  5. "Press Release: Folded sediment unusual in Sumatran tsunami area". Penn State University. 2 February 2007.
  6. "Presentation of the Drake Medal to Dr Robert L. Fisher" (PDF). National Geophysical Data Center. 30 April 2006. Archived from the original (PDF) on 30 April 2006.
  7. "The underwater survey of the SUMATRA earthquake source area". www.jamstec.go.jp.
  8. Hydro International.com (18 June 2019). "Exploring the Deepest Points on Planet Earth". hydro-international.com. Retrieved 20 June 2019.
  9. Five Deeps Expedition (16 April 2019). "Deep sea pioneermakes history again as first human to dive to the deepest point in the Indian Ocean, the Java Trench" (PDF). fivedeeps.com. Retrieved 20 June 2019.
  10. "Nippon Foundation-GEBCO Seabed 2030 Project". seabed2030.gebco.net.
  11. "Major partnership announced between The Nippon Foundation-GEBCO Seabed 2030 Project and The Five Deeps Expedition". gebco.net. 11 March 2019. Retrieved 19 June 2019.
  12. "Home". fivedeeps.com. Retrieved 9 January 2019.

Further reading
  • Špičák, A., V. Hanuš, and J. Vaněk (2007), Earthquake occurrence along the Java trench in front of the onset of the Wadati–Benioff zone: Beginning of a new subduction cycle?, Tectonics, 26, TC1005

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