1976 Moro Gulf earthquake

Earthquake in the Philippines December 2022 December 2022 1976 Moro Gulf earthquake Tsunami hit lebak.jpg Tsunami damage at Lebak, Mindanao 1976-08-16 16:11:08 709878 iscgem709878 1976 08 17 00:11:07 Philippines 1 6.29 124.09 Bullseye1.png 40 bottom 290 none 8.0 w y 20 km mi 0 on 6.29 N 124.09 E type:event_region:PH inline,title Philippines Megathrust 15 m 8 PEIS 7 5,000–8,000 dead 10,000 injured 90,000 homeless The 1976 Moro Gulf earthquake and tsunami occurred on August 17, 1976, at 00:11 local time August 16 at 16:11 UTC near the islands of Mindanao and Sulu, in the Philippines. It measured 8.0 on the moment magnitude scale occurring at a depth of 20 km.ISC-GEM Global Instrumental Earthquake Catalogue (1904–2018) http://www.isc.ac.uk/iscgem/index.php ISC 2022 International Seismological Centre Version 9.1 The earthquake was accompanied by a destructive tsunami that resulted in a majority of the estimated 5,000 to 8,000 fatalities. It was the deadliest earthquake in Philippines history and strongest earthquake in the Philippines in 58 years since the 1918 Celebes Sea earthquake. Tectonic summary 250px|left|thumbnail|Tsunami damage at Barangay Tibpuan, Lebak, Mindanao Several fault zones in the region are capable of producing major earthquakes and destructive local tsunamis. The two major fault zones that are most dangerous are the Sulu Trench in the Sulu Sea and the Cotabato Trench, a region of subduction that crosses the Celebes Sea and the Moro Gulf in Southern Mindanao. According to the PHIVOLCS historical catalog of earthquakes for the last 100 years, this region of the southern Philippines is characterized by moderate to high seismicity. The most recent earthquake along the Cotabato Trench region of subduction being the March 6, 2002, earthquake in Southern Mindanao.March 2022 Earthquake thumb|USGS ShakeMap The earthquake occurred in an region where typical seismicity originates at 500 km depth on the Wadati–Benioff zones associated with subduction along the Sangihe and Mindanao islands. The Philippines is characterised by several complex and active subduction zones. The most geologically dominant in the region is the Philippine Trench located east of Mindanao. It dips to the west as represented by the Wadati–Benioff zone which can be detected to at least 200 km.Stewart Gordon S. Cohn Stephen N. The 1976 August 16, Mindanao, Philippine earthquake (Ms = 7.8) – evidence for a subduction zone south of Mindanao Geophysical Journal International 1979 57 1 51–65 10.1111/j.1365-246X.1979.tb03771.x free 1979GeoJ...57...51SBeck Susan L. Susan L. Beck Ruff Larry. J. The rupture process of the 1976 Mindanao Earthquake Journal of Geophysical Research: Solid Earth 1985 90 B8 6773–6782 10.1029/JB090iB08p06773 1985JGR....90.6773B The mainshock had a shallow focal depth and represented thrust faulting along a plane dipping northeast at a shallow angle. The shock in the North Celebes Sea was associated with the smaller Cotabato Trench; a north–south bathymetric feature along the island's coast where it meets the Moro Gulf. Geologists have interpreted the earthquake as evidence for east–northeast-dipping subduction beneath Mindanao. The feature is also thought to be geologically young due to the absence of an active volcanic arc. In 1918, a major earthquake and tsunami ruptured a segment of the subduction zone south of the 1976 earthquake; both earthquakes ruptured a combined 300 km of the trench. The rupture propagated northward from the epicenter along the Cotabato Trench, evident from the aftershock zone. However, the strongest aftershock, measuring s y 6.8, was the result of strike-slip faulting and occurred away from the aftershock zone. Impact left|thumb|250px|The Cotabato Trench in southern Mindanao and the Philippine Mobile Belt. Mindanao right 270 Earthquakes in Mindanao Near the Cotabato Trench, two of the largest 20th century Philippine earthquakes: the 1918 Celebes Sea earthquake (8.3 Mw) and the 1976 Moro Gulf earthquake (8.0 Mw). Also included is the 2002 Mindanao earthquake (7.5 Mw) and 2026 Mindanao earthquake (7.8 Mw). The Moro Gulf, part of the Celebes Sea, is labeled for context. Mindanao 6.50 123.00 left Moro Gulf Mindanao 6.29 124.09 left 1976 Mindanao 5.97 124.38 left 1918 Mindanao 6.03 124.25 right 2002 Mindanao 5.592 125.047 left 2026 The initial earthquake was widespread and was felt as far as the central Philippine islands of the Visayas. A massive tsunami devastated 700 kilometers of coastline bordering the Moro Gulf in the North Celebes Sea, resulting in destruction and death in the coastal communities of the Sulu Archipelago, southern Mindanao particularly the provinces of Sultan Kudarat and Sarangani (formerly part of South Cotabato), and in the Zamboanga Peninsula including Zamboanga City and Pagadian City.March 2022 The maximum height of the waves reached 9 meters at Lebak on the isla; 4.3 meters at Alicia; 3 meters at Resa Bay on the eastern coast of Basilan; and at the islands of Jolo and Sacol.Department Commerce Dunbar Paula K. Pacific Tsunami Warning System: A Half Century of Protecting the Pacific, 1965–2015 April 24, 2015 46–47 https://books.google.com/books?id=Hb9w5gzoN1QC&pg=PA47 August 22, 2017 Government Printing Office 978-0-9962579-0-9 A field investigation revealed that the maximum height of the tsunami was approximately 15 m ft on.Perez Jeffery Lagunsad Kristine Burgos Leslie Verano Kim Tabigue Milo Villegas Ma 1 December 2023 Revisiting the 1976 Magnitude 8.1 Moro Gulf Earthquake and Tsunami: The East Side Story https://www.researchgate.net/publication/377813631_Revisiting_the_1976_Magnitude_81_Moro_Gulf_Earthquake_and_Tsunami_The_East_Side_Story January 28, 2026 ResearchGate At least 5,000 people died during the earthquake and tsunami, with thousands more remaining missing.http://www.ringsurf.com/online/2412-tsunamis_through_history.html History of Tsunami Devastation July 13, 2008 July 4, 2008 https://web.archive.org/web/20080704165837/http://www.ringsurf.com/online/2412-tsunamis_through_history.html dead Some reports say that as many as 8,000 people lost their lives in total, with ninety percent of all deaths the result of the following tsunami. Initially over 8,000 people were officially counted as killed or missing, 10,000 injured, and 90,000 homeless, making it one of the most devastating disasters in the history of the Philippine Islands.Catalog of Tsunamis in the Pacific 1969–1982 https://books.google.com/books?id=umZ--INFYEEC&pg=PA103 Staff of the Academy of Sciences of the USS Diane Pub 978-0-7881393-1-4 103, 104 1997 After the initial earthquake the people were unaware of the need to move to higher ground; when the tsunami hit it sucked most of the victims out to sea. Based on the investigation on the affected region it was confirmed that the waves reached up to 4 to 5 m when they hit the areas. There were reports of weak tsunami activity as far as Japan. In Zamboanga City, 14 buildings were partially damaged. The city was spared from serious damage of the tsunami triggered by this earthquake because the Basilan Island and the Santa Cruz Islands served as a buffer and deflected waves.http://www.phivolcs.dost.gov.ph/html/update_SOEPD/2012_Earthquake_Bulletins/Destructive_Earthquake/1976MoroGulfEQ/index-moro.html Moro Gulf Earthquake – 17 August 1976 Philippine Institute of Volcanology and Seismology October 15, 2013 October 15, 2013 https://web.archive.org/web/20131015062653/http://www.phivolcs.dost.gov.ph/html/update_SOEPD/2012_Earthquake_Bulletins/Destructive_Earthquake/1976MoroGulfEQ/index-moro.html dead +Intensity distribution by locationhttps://www.phivolcs.dost.gov.ph/phivolcs-earthquake-intensity-scale-2/ PHIVOLCS Earthquake Intensity Scale (PEIS) Philippine Institute of Volcanology and Seismology 2018 November 13, 2019Intensity scalesLocationVIICotabato City; Jolo-Sulu; Zamboanga CityVIBasilan City; Pagadian City; Dipolog City; Malaybalay-BukidnonVCagayan de Oro City; Davao City; General SantosIVDumaguete; Hinatuan Surigao del Sur; Tagbilaran-Bohol; Cebu City; Surigao-Surigao del NorteIIRoxas City; Iloilo City; Tacloban City; Legaspi City; Palo-Leyte; Catbalogan-Samar See also List of earthquakes in 1976 List of earthquakes in the Philippines References International Handbook of Earthquake & Engineering Seismology Part A, Volume 81A Global seismicity: 1900–1999 E. R. Engdahl A. Vallaseñor 2002 https://earthquake.usgs.gov/data/centennial/centennial.pdf Academic Press First 978-0124406520 683 Further reading Eadillo Victor Astilla Zinnia Moro Gulf Tsunami of 17 August 1978 1978 Special Committee on Tsunami Warning System, National Committee on Marine Sciences, National Science Development Board Quezon City https://www.mindanews.com/wp-content/uploads/2019/08/MoroGulf_1976complete.pdf 10 September 2024 External links Philippines Institute of Volcanology and Seismology https://web.archive.org/web/20100129060134/http://www.phivolcs.dost.gov.ph/ January 29, 2010 The Earthquake and Tsunami of August 16, 1976, in the Philippines – The Moro Gulf Tsunami" – George Pararas-Carayannis 709878 1976 Moro Category:1976 in the Philippines Category:August 1976 in Asia Category:1976 earthquakes Moro Category:History of Zamboanga del Sur Category:History of Maguindanao del Norte Category:History of Maguindanao del Sur Category:1976 disasters in the Philippines Category:Tsunamis in Asia