TsunamiTsunami sourcesource mechanismsmechanisms inin thethe PhilippinePhilippine archipelagoarchipelago Carla B. Dimalanta1, Graciano P. Yumul, Jr.1,2, Edanjarlo J. Marquez3 and Bart Bautista4 1National Institute of Geological Sciences, University of the Philippines, Diliman, Quezon City, Philippines 2Department of Science and Technology, Bicutan, Taguig, Philippines 3Department of Physical Sciences and Mathematics, University of the Philippines-Manila, Philippines 4Philippine Institute of Volcanology and Seismology – Department of Science and Technology, Diliman, Quezon City, Philippines TectonicTectonic settingsetting ~6 mm/yr ~7 mm/yr ~9 mm/yr Philippine Trench http://phivolcs.dost.gov.ph East Luzon Trough Negros Manila Trench Cotabato Trench Trench h c Earthquake generators n Earthquake generators e r T u l u S TsunamigenicTsunamigenic earthquakesearthquakes • generatedgenerated byby shallowshallow earthquakesearthquakes • largelarge tsunamistsunamis likelylikely toto bebe generatedgenerated byby earthquakesearthquakes withwith magnitudemagnitude >> 7.07.0 1981-2005 Wong & Chan, 2006 120o 125o Philippine Sea Tsunami Vulnerability Map 15o South China Sea 10o Sulu Sea Celebes Sea http://phivolcs.dost.gov.ph 120o 125o Philippine HIGHER VULNERABILITY Sea 15o South 9 lack of knowledge China Sea 9 high population density 9 improper land use 10o Sulu Sea 9 fatalistic attitude Celebes Sea http://phivolcs.dost.gov.ph EarthquakesEarthquakes (M(M >> 7.0)7.0) http://neic.usgs.gov/neis/epic/epic.html Tsunamigenic earthquake events www.phivolcs.dost.gov.ph 19761976 MoroMoro GulfGulf EarthquakeEarthquake QuickTime?and a TIFF (Uncompressed) decompressor are needed to see this picture. Area north of Zamboanga 9Magnitude: 7.9 9Cotabato Trench 9 ~6 m tsunami, peak velocity: 720 km/hr QuickTime?and a TIFF (Uncompressed) decompressor 9Tsunami affected 700 km of the are needed to see this picture. coastline bordering the gulf (Pagadian City, Cotabato City and Zamboanga City) Zamboanga City) Bongo Island www.phivolcs.dost.gov.ph 19901990 BoholBohol EarthquakeEarthquake 9 Magnitude: 6.8 9 Offshore thrust fault, east of Bohol Island 9 0.2-2 m tsunami 9 affected the municipalities of Jagna, Duero, Guindulman, Garcia Hernandez, Valencia as well as Camiguin Island (Besana et al., 2004) 19921992 EasternEastern MindanaoMindanao EarthquakeEarthquake 9 Magnitude:Magnitude: 6.86.8 9 PhilippinePhilippine TrenchTrench 9 SeveralSeveral cmcm upup toto ~6~6 mm 9 AffectedAffected thethe easterneastern coastlinescoastlines (Besana et al., 2004) 19941994 MindoroMindoro EarthquakeEarthquake 9 Magnitude: 7.1 9 Aglubang River Fault (dextral) 9 Vertical run-up: 0.5-8.5 m; Horizontal run-up: 4-250 m 9 Tsunami affected 40 km of the northern and eastern shoreline of Mindoro (Puerto Galera to Pinamalayan) plus the Verde and Baco Islands PHIVOLCS Special Report No. 2 TsunamigenicTsunamigenic earthquakeearthquake eventsevents Date Affected Areas Magnitude November 9, 1828 Manila Bay 6.6 June 3, 1863 Manila Bay 6.5 August 15, 1918 Southern Mindanao 8.0 November 11, 1921 Manay, Davao Oriental 7.5 April 14, 1924 Mati, Davao Oriental 8.3 August 1, 1968 Casiguran Bay 7.3 April 7, 1970 Baler, Aurora 7.0 October 31, 1975 Borongan, Eastern Samar 7.2 July 16, 1990 Luzon 7.8 SummarySummary 9 TsunamisTsunamis inin thethe PhilippinesPhilippines werewere generatedgenerated byby • TrenchTrench systemssystems surroundingsurrounding thethe archipelagoarchipelago • FaultsFaults ThankThank you!you!.