EarthquakeEarthquake EngineeringEngineering ResearchResearch InstituteInstitute TheThe GreatGreat SumatraSumatra EarthquakeEarthquake andand IndianIndian OceanOcean TsunamiTsunami ofof DecemberDecember 26,26, 20042004 An illustrated description of their causes and effects PrefacePreface This presentation was developed to explain the origins of the Sumatra earthquake of December 26, 2004 and the ensuing tsunami, and to document the damages caused by the earthquake and tsunami in so many countries around the Indian Ocean. ¾ The presentation was created largely by Widianto, a doctoral candidate in civil engineering and president of the EERI student chapter at the University of Texas at Austin. ¾ Other contributors include Sarah Nathe, Craig Comartin, and Heidi Faison. This project was supported by funds from the National Science Foundation through EERI’s Learning From Earthquakes Program under grant # CMS-0131895 “The 26th December 2004 Sumatra-Andaman earthquake is the fourth largest earthquake in the world since 1900 and is the largest since the 1964 Prince William Sound, Alaska earthquake.” United States Geological Survey (USGS) “The tsunami that struck Southeast Asia on December 26, 2004 has been confirmed as the most devastating in modern history.” Guinness Book of World Records Contents ¾ Introduction: Plate tectonics, earthquakes ¾ Sumatra Earthquake - Tectonic activity - Observations - Damage ¾ Indian Ocean Tsunami - Basic mechanism - Videos: before and after giant wave arrival - Damage ¾ Tsunamis in the USA ¾ Tsunami Risk Reduction ¾ The Earthquake Engineering Research Institute Introduction – Plate Tectonics ¾ The Earth is characterized by a small number of lithospheric plates that float on a viscous underlayer called the asthenosphere. ¾ Geological evidence shows that plates undergo constant, gradual change. Magma is continually upwelling at the mid-oceanic ridges and rises as the seafloor spreads apart. ¾ In some areas, large sections of plates are forced to move beneath other plates (surface layers of rocks are absorbed into the earth’s interior). These areas are called subduction zones. Ø A plate being subducted beneath another Introduction – Plate Tectonics Source: Earthquakes by Bruce A. Bolt Introduction – Plate Tectonics 95% of earthquakes occur along the edges of the interacting plates Source: Earthquakes by Bruce A. Bolt World’s Largest Magnitude Earthquakes Earthquake Magnitude Year Approx. casualties 1. Chile 9.5 1960 >2000 2. Prince William 9.2 1964 ≅ 125 Sound, Alaska 3. Andreanof 9.1 1957 Not reported Islands, Alaska 4. Kamchatka 9.0 1952 Not reported Peninsula 5. Sumatra 9.0 2004 >283,100 (>173,000 in Indonesia) Source: United States Geological Survey (USGS) Earthquake Energy Sumatra-Andaman (2004) Source: Earthquakes by Bruce A. Bolt Sumatra Earthquake Magnitude: 9.0 Date-time: Sunday, December 26, 2004 at 7:58:53 AM (local time) Depth: 30 km (18.6 miles) Distances: * 250 km (155 miles) SSE of Aceh, Sumatra, Indonesia * 310 km (195 miles) W of Medan, Sumatra, Indonesia * 1260 km (780 miles) SSW of Bangkok, Thailand * 1605 km (990 miles) NW of Jakarta, Java, Indonesia Source: United States Geological Survey (USGS) Tectonic Summary ¾ It occurred on the interface of the India and Burma plates: an interplate earthquake. ¾ India plate subducts beneath the overriding Burma plate at the Sunda Trench. ¾ In the region of the earthquake, the India plate moves toward the northeast at a rate of about 6 cm/year relative to the Burma plate. ¾ Thrust faulting caused the 6 cm/yr earthquake (slip directed perpendicular to the trench). ¾ Fault rupture propagated to the northwest from the epicenter with a width ≅ 100 km and an average displacement on the fault Source: United States Geological Survey (USGS) plane ≅ 20 meters. Felt Shaking Reports ¾Modified Mercalli Intensity Scale: Source: United States Geological Survey (USGS) Banda Aceh, Sumatra: IX Medan, Sumatra: IV Port Blair, Andaman Islands: VII ¾ Subsidence and landslides were observed in Sumatra. ¾ A mud volcano near Baratang, Andaman Islands began erupting on December 28, 2004. ¾ Intensity vs. Distance from Epicenter Plot : AftershockAftershock ZoneZone ¾ Extends from Northern Sumatra to the Andaman Islands, ~ 1300 km to the north. ¾ Largest aftershock directly following the main shock was M = 7.1 in the Nicobar Islands. ¾On March 28, 2005, a M = 8.7 earthquake occurred in a region of Epicenter of mainshock, the fault southeast of 28 Mar 2005 the Dec 26th mainshock and its rupture zone. EarthquakeEarthquake DamageDamage Location: Banda Aceh, Sumatra, Indonesia Banda Aceh epicenter Photo: Jose Borrero Structural damage to concrete frame building. EarthquakeEarthquake DamageDamage Location: Banda Aceh, Sumatra, Indonesia Banda Aceh epicenter Photo: Murat Saatcioglu, Ahmed Ghobarah, Ioan Nistor Partial collapse of concrete frame building due to column failure. EarthquakeEarthquake DamageDamage Location: Banda Aceh Sumatra, Indonesia Banda Aceh epicenter Photos: Murat Saatcioglu, Ahmed Ghobarah, Ioan Nistor Partial collapse of concrete frame building due inadequate column reinforcement. EarthquakeEarthquake DamageDamage Location: Banda Aceh, Sumatra, Indonesia Banda Aceh epicenter Architectural damage to the Photo: Jose Borrero Grand Mosque tower. EarthquakeEarthquake DamageDamage Location: Port Blair, Andaman Islands Port Blair epicenter Column of residential building damaged by ground motion. Source: Geological Survey of India EarthquakeEarthquake DamageDamage Longitudinal (50 m long) Location: Port Blair, crack on Kamraj Road after Andaman Islands the earthquake Port Blair epicenter Major crack showing a rupture width of 15 cm on Kamraj Road after the earthquake Source: Geological Survey of India Earthquake and Tsunami Not all earthquakes generate tsunamis. An earthquake must have certain characteristics in order to generate a tsunami: 1. Epicenter is underneath or near the ocean. 2. Fault causes vertical movement of the sea floor (up to several meters) over a large area (up to 100,000 km2). 3. Large magnitude ( > 7.5 ) AND shallow focus ( < 70 km). Source: Earthquakes by Bruce A. Bolt Basic Tsunami Mechanism ¾ An earthquake causes a vertical movement of the seafloor, which displaces the sea water. ¾ Large waves then radiate from the epicenter in all directions. Tsunami Explained ¾ A tsunami is series of traveling ocean waves of extremely long length generated primarily by earthquakes occurring below or near the ocean floor. ¾ Tsunami waves propagate across the deep ocean with a speed exceeding 800 km/h (≅ 500 mph) and a wave height of only a few tens of centimeters or less. ¾ As they reach the shallow waters of the coast, the waves slow down and their height increases up to tens of meters (30 ft) or more. Source: NOAA Tsunami Translated Japanese word: “Tsu“ means “harbor” English translation: “Nami“ means “Harbor wave” “wave” ¾ “Tidal wave” is a misnomer because the cause is unrelated to tides. ¾ “Seismic sea wave” is misleading because a tsunami can be caused by non-seismic events, and it is not dangerous in the open ocean. Water Recession: A Precursor Wave Generation Draw Down Effect From: Nature Publishing Group From: Nature Publishing Group Kalutara Beach, Sri Lanka From: Digital Globe TsunamiTsunami WaveWave AppearanceAppearance Source: www.waveofdestruction.org ¾ A tsunami wave crest has three general appearances from shore: Fast-rising tide Cresting wave A step-like change in the water level that advances rapidly (called a bore) A bore on the Qian Tang Jiang River, China ¾ Series of waves Most tsunamis come in a series of waves that may last for several hours The outflow of water back to the sea between waves can cause more damage than the original incoming wave fronts The first wave is rarely the largest Tsunami Propagation National Institute of Advanced Industrial Science and Technology, Japan TsunamiTsunami DamageDamage Location: Lhoknga, Indonesia Lhoknga Before Tsunami January 10, 2003 epicenter After Tsunami December 29, 2004 Source: National University of Singapore TsunamiTsunami DamageDamage Location: Lhoknga, Indonesia Lhoknga Exposed bridge piers of road that Photo: Jose Borrero washed away. epicenter High Water Mark Overturned ship Damage zone showing an overturned tanker, trees snapped in half, and the high water mark on islands Broken Trees where vegetation was stripped away. Photo: Jose Borrero TsunamiTsunami DamageDamage Location: Gleebruk, Indonesia Gleebruk Before Tsunami April 12, 2004 epicenter After Tsunami January 2, 2005 Source: Digital Globe TsunamiTsunami DamageDamage Gleebruk epicenter Before Tsunami April 12, 2004 After Tsunami January 2, 2005 Source: Digital Globe TsunamiTsunami DamageDamage Location: Banda Aceh, Indonesia Banda Aceh Before Tsunami June 23, 2004 epicenter After Tsunami December 28, 2004 Source: Digital Globe TsunamiTsunami DamageDamage Location: Banda Aceh, Indonesia Banda Aceh A boat was lifted on top of houses by the Photo: Jose Borrero waves. epicenter Damage was caused by both water and water-borne debris. Photo: Jose Borrero TsunamiTsunami DamageDamage Location: Banda Aceh & Lhoknga, Indonesia Banda Aceh epicenter The tsunami waves came from many directions and flowed across the tip of northeastern Sumatra. Graphic: Jose Borrero TsunamiTsunami DamageDamage Location: Thailand KeThailandrala Coast Damage to Kao Lak Resort from tsunami waves. epicenter Photo: Curt Edwards Despite the presence of debris, this naval base building had little structural damage due to a retaining wall at its frontage.