The 1933 Sumatra earthquake or Liwa earthquake occurred in

West Lampung Regency West Lampung Regency is a regency of Lampung Province, Sumatra, Indonesia. Until 2012 it had an area of 4,950.4 km2 of which forests occupied some 57% of the total area (as of 2011). It had a population of 418,560 people at the 2010 census. Ho ...

, Lampung Province, Indonesia on June 25. The earthquake had an estimated surface-wave magnitude () of 7.7 occurring at a shallow depth of 20 km. It had an epicenter onshore, devastating the city of Liwa. At least 76 people were reported killed, although the death toll may have been in the thousands. Aftershocks followed, including one which was strong enough to cause additional fatalities. The

mainshock In seismology, the mainshock is the largest earthquake in a sequence, sometimes preceded by one or more foreshocks, and almost always followed by many aftershocks. Foreshock A foreshock is an earthquake that occurs before a larger seismic eve ...

also triggered a nearby

volcanic eruption Several types of volcanic eruptions—during which lava, tephra (ash, lapilli, volcanic bombs and volcanic blocks), and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are oft ...

two weeks later, killing some people.

Tectonic setting

The west coast of Sumatra is dominated by the Sunda megathrust; a 5,500 km long convergent boundary where the

Australian Plate The Australian Plate is a major tectonic plate in the eastern and, largely, southern hemispheres. Originally a part of the ancient continent of Gondwana, Australia remained connected to India and Antarctica until approximately when India broke ...

subducts beneath the

Burma Plate 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 ...

and Sunda Plate at a rate of per year. Convergence along this plate boundary is highly oblique, severely deforming the overriding Sunda Plate, where it is accommodated by strike-slip motion along the

Great Sumatran fault The Indonesian island of Sumatra is located in a highly seismic area of the world. In addition to the subduction zone off the west coast of the island, Sumatra also has a large strike-slip fault, the Great Sumatran Fault also known as Semangko ...

. The Great Sumatran fault is a -long strike-slip fault system located on the island of Sumatra. The fault is divided into about 20 segments. The Great Sumatran fault was the source of the 1994 Liwa and 1995 Kerinci earthquakes. It produced its largest earthquake during the 1943 Alahan Panjang sequence; measuring 7.8. Most recently, a 6.2-magnitude quake struck in 2022.

Earthquake

The earthquake was caused by a strike-slip

rupture Rupture may refer to: General * Rupture (engineering), a failure of tough ductile materials loaded in tension Anatomy and medicine * Abdominal hernia, formerly referred to as "a rupture" * Achilles tendon rupture * Rupture of membranes, a "wate ...

on southern portion of the Great Sumatran Fault. A study by Hurukawa and others relocated the epicenter to from by the

International Seismological Centre The International Seismological Centre (ISC) is a non-governmental, nonprofit organisation charged with the final collection, definitive analysis and publication of global seismicity. The ISC was formed in 1964 as an international organisation ...

. Its epicenter was located between two segments; the Semangko segment located 50 km southeast, and the Kumering 60 km north. Based on the reports of damage, the earthquake ruptured in a northwesterly direction along the Kumering segment for approximately 130 km. The total length of the Kumering segment is 150 km, indicating partial failure on the segment. An average slip of 2.7 meters was estimated. Five moderate aftershocks were recorded, two of which were located 100 and 130 km northwest of the epicenter, respectively. There is a possibility that the fault rupture may have initiated on the northeastern portion of the Semangko segment, and progressed northwest to rupture the Kumering segment. A secondary branch away from the main strand of the Great Sumatran Fault may have also ruptured during the quake. Its epicenter is not far from that of the 6.8 earthquake in 1994. A

surface rupture In seismology, surface rupture (or ground rupture, or ground displacement) is the visible offset of the ground surface when an earthquake rupture along a fault affects the Earth's surface. Surface rupture is opposed by buried rupture, where th ...

extended to Lake Ranau. No large magnitude 6.0 earthquakes would strike this portion of the Great Sumatran Fault until 1994.

Damage

Major destruction was widespread along an area that stretched from Lake Ranau to

Suwoh Suoh or Suwoh is an 8 × 16 km wide volcano-tectonic depression in the southern part of Sumatra, Indonesia. Historical maars and silicic lava domes are found along the Great Sumatran fault line. Phreatic eruptions occurred during the major ...

(approximate length of the Kumering segment rupture). The earthquake had a maximum Modified Mercalli intensity of VIII–IX (''Severe–Violent''). Many buildings and other human infrastructures in the western portion of southern Sumatra were damaged. Large

fissure A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes. Ground fissure ...

s and ground subsidence were reported; these effects were observed from Kota Agung to Makaka. Damage in Sebarus, a village in Lampung, was so severe that it forced all of its residents to leave. In Pasirah, every home was destroyed and rice fields were ruined. In Liwa and Banding Agung, the quake razed all buildings to the ground. Landslides were widespread, seen in the

Barisan Mountains The Bukit Barisan or the Barisan Mountains are a mountain range on the western side of Sumatra, Indonesia, covering nearly 1,700 km (1,050 mi) from the north to the south of the island. The Bukit Barisan range consists primarily of volca ...

. An aftershock on June 26 caused several fatalities in

Bengkulu Bengkulu is a province of Indonesia. It is located on the southwest coast of Sumatra. It was formed on 18 November 1968 by separating out the former Bencoolen Residency area from the province of South Sumatra under Law No. 9 of 1967 and was fi ...

. The total number of fatalities is not known, possibly several hundred or thousands, although the

National Geophysical Data Center The United States National Geophysical Data Center (NGDC) provided scientific stewardship, products and services for geophysical data describing the solid earth, marine, and solar-terrestrial environment, as well as earth observations from spac ...

earthquake database only attributed 76 deaths with the event. Two weeks after the earthquake, geothermal activity at Suwoh increased, and a series of phreatic eruptions occurred, bringing ash to settlements. The eruption rated 4 on the VEI scale and also caused some deaths.

References

Sources * * * * * * *

External links

* {{Earthquakes in Indonesia 1933 earthquakes Earthquakes in Indonesia Earthquakes in Sumatra 1933 in the Dutch East Indies West Lampung Regency History of Lampung 20th-century volcanic events VEI-4 eruptions Bengkulu Strike-slip earthquakes Landslides in Indonesia 1933 disasters in Asia 1933 disasters in Oceania 20th-century disasters in Indonesia

Tectonic setting

Earthquake

Damage

See also

References

External links