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1933 Sumatra earthquake

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Coordinates: 5°11′S 104°50′E / 5.18°S 104.83°E / -5.18; 104.83
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1933 Sumatra earthquake
1933 Sumatra earthquake is located in Sumatra
1933 Sumatra earthquake
1933 Sumatra earthquake is located in Indonesia
1933 Sumatra earthquake
UTC time1933-06-24 21:54:49
ISC event905657
USGS-ANSSComCat
Local dateJune 25, 1933 (1933-06-25)
Local time04:54:49 WIB
Magnitude7.5–7.7 Ms [1][2]
Depth20 km (12 mi)
Epicenter5°11′S 104°50′E / 5.18°S 104.83°E / -5.18; 104.83
FaultGreat Sumatran fault
TypeStrike-slip
Areas affectedIndonesia
Max. intensityMMI IX (Violent) [3]
AftershocksMultiple
Casualties788+ dead

The 1933 Sumatra earthquake or Liwa earthquake occurred in West Lampung Regency, Lampung Province, Indonesia on June 25. The earthquake had an estimated surface-wave magnitude (Ms ) of 7.7 occurring at a shallow depth of 20 km. It had an epicenter onshore, devastating the city of Liwa. At least 788 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 also triggered a nearby volcanic eruption two weeks later, killing some people.

Tectonic setting

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Great Sumatra fault

The west coast of Sumatra is dominated by the Sunda megathrust; a 5,500 km (3,400 mi)[4] long convergent boundary where the Australian Plate subducts beneath the Burma Plate and Sunda Plate at a rate of 60 mm (2.4 in) per year.[5] Convergence along this plate boundary is highly oblique, severely deforming the overriding Sunda Plate,[5] where it is accommodated by strike-slip motion along the Great Sumatran fault.[5] The Great Sumatran fault is a 1,900 km (1,200 mi) strike-slip fault system located on the island of Sumatra. The fault is divided into about 20 segments.[6] 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 Ms  7.8.[7] Most recently, a 6.2-magnitude event struck in 2022.

Earthquake

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The earthquake was caused by a strike-slip rupture on southern portion of the Great Sumatran Fault. A study by Hurukawa and others relocated the epicenter to 5°11′S 104°50′E / 5.18°S 104.83°E / -5.18; 104.83 from 5°14′S 104°36′E / 5.23°S 104.60°E / -5.23; 104.60 by the International Seismological Centre.[1] Its epicenter was located between two segments; the Semangko segment located 50 km (31 mi) southeast, and the Kumering 60 km (37 mi) north. Based on the reports of damage, the earthquake ruptured in a northwesterly direction along the Kumering segment for approximately 130 km (81 mi). The total length of the Kumering segment is 150 km (93 mi), indicating partial failure on the segment. An average slip of 2.7 m (8 ft 10 in) was estimated.[8] Five moderate aftershocks were recorded, two of which were located 100 km (62 mi) and 130 km (81 mi) 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. Its epicenter is not far from that of the Mw  6.8 earthquake in 1994.[2] No large magnitude 6.0 earthquakes would strike this portion of the Great Sumatran Fault until 1994.[9] Ground fissures were reported in Negeri Ratu and near Wai Uluhan stream, however it is unclear of the fissures were continuous or separated by their 16 km (9.9 mi) distance. These fissures were located on the Kumering sement and may represent surface rupture.[10]

Damage

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Suwoh which erupted two weeks later

Major destruction was widespread along an area that stretched from Lake Ranau to Suwoh (approximate length of the Kumering segment rupture[2]). The earthquake had a maximum Modified Mercalli intensity of VIII–IX (Severe–Violent).[3] Many buildings and other human infrastructures in the western portion of southern Sumatra were damaged. Large fissures and ground subsidence were reported; these effects were observed from Kota Agung to Makaka.[11] 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.[12] An aftershock on June 26 caused several fatalities in Bengkulu.[11]

About 424 people died in the south Bengkulu area while another 364 people died in Liwa. At least 50 people were badly injured in addition to 600 others with minor injuries.[13] The total number of fatalities is not known, possibly several hundred or thousands, although the National Geophysical Data Center earthquake database only attributed 76 deaths with the event.[11] An early statement by Reuters said at least 20 Europeans were among the 60 people dead which they later retracted.[14] Officials took strong measures to ensure food, medication and hygiene was adequate.[13]

Two weeks after the earthquake, geothermal activity at Suwoh increased, and a series of phreatic eruptions occurred,[15] bringing ash to settlements. The eruption rated 4 on the VEI scale and also caused some deaths.[16] On Lake Ranau, at the entrance of the Wai Warduk in Kotabatu, a "co-seismic flood wave" inundated ten paddy fields by up to 0.5 m (1 ft 8 in).[10]

See also

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References

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  1. ^ a b International Seismological Centre. Bulletin of the ISC. Thatcham, United Kingdom. [Event 905657].
  2. ^ a b c Hurukawa, Wulandari & Kasahara 2014.
  3. ^ a b "Katalog Gempabumi Signifikan dan Dirasakan" [Catalog of Significant and Felt Earthquakes]. bmkg.go.id (in Indonesian). Meteorology, Climatology, and Geophysical Agency. Retrieved 14 March 2022.
  4. ^ Sieh 2007.
  5. ^ a b c Philibosian et al. 2014.
  6. ^ Natawidjaja et al. 2007.
  7. ^ ISC-OB Event 899872 [IRIS].
  8. ^ Rafie, Muhammad Taufiq; Sahara, David P.; Cummins, Phil R.; Triyoso, Wahyu; Widiyantoro, Sri (April 2023). "Stress accumulation and earthquake activity on the Great Sumatran Fault, Indonesia". Natural Hazards. 116 (3): 3401–3425. doi:10.1007/s11069-023-05816-2. ISSN 0921-030X.
  9. ^ Widiwijayanti et al. 1996.
  10. ^ a b Martin, Stacey S.; Cummins, Phil R.; Meltzner, Aron J. (2022). "Gempa Nusantara: A Database of 7380 Macroseismic Observations for 1200 Historical Earthquakes in Indonesia from 1546 to 1950" (PDF). Bulletin of the Seismological Society of America. 112 (6): 2958–2980. doi:10.1785/0120220047.
  11. ^ a b c National Geophysical Data Center / World Data Service (NGDC/WDS): NCEI/WDS Global Significant Earthquake Database. NOAA National Centers for Environmental Information. doi:10.7289/V5TD9V7K
  12. ^ Ahmad Arif; Agung Setyahadi; Prasetya Eko P; Ingki Rinaldi; Wawan H Prabowo; Rustiono Andri (15 January 2019). "Hidup dan Maut Bertaut Erat di Liwa". Kompas (in Indonesian). Jelajah Kompas. Retrieved 14 March 2022.
  13. ^ a b "Mounting death roll in Sumatra". The Straits Times. 3 July 1933. Retrieved 25 June 2024.
  14. ^ "Sumatra Quake". Reuters. Malaya Tribune. 28 June 1933. p. 13. Retrieved 25 June 2024.
  15. ^ "Suoh". Global Volcanism Program. Smithsonian Institution. Retrieved 2006-12-28.
  16. ^ Sieh & Natawidjaja 2000.

Sources

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