NATURAL DISASTERS 2EARTHQUAKe & Earthquakes are among nature’s most terrifying forces. There will be one today. TSUNAMI Definitely. And it could strike in our region. InTRODUCTION A power unleashed, all too frequently ORE than 80 per cent of quakes happen along the Pacific Ocean rim, also called the Pacific Ring of Fire because of Mthe many volcanoes also found here. Today’s earthquake could be so small that no one will feel it. But it may be one of the estimated 700 quakes a year big enough to cause death and damage. If it occurs at sea, it may trigger a tsunami. Large earthquakes have more than played their part in global natural hazards that in 2010* forced more than 42 million people to flee their homes. A large insurance company that tracks natural disasters says the 10 worst catastrophes of the past 30 years killed 1,089,570 people. Of this number, 654,570 died in earthquakes and tsunamis. Recent years have seen major disasters in Haiti, New Zealand, Chile, China and Japan. The deadliest occurred in poor, unprepared Haiti, where estimates of the death toll varied from 222,570 to more than 310,000. But it was the graphic television pictures of an exploding nuclear power plant and massive tsunami swells swallowing Japanese towns in March 2011 that sharpened our understanding of what destruction nature can unleash. Australia has quakes regularly, and large ones about once every five years, but they are often in remote and sparsely populated areas. An exception was Newcastle in 1989 when an earthquake killed 13 and cost the community $4.5 billion. The damage done by an earthquake depends on where it strikes. Australia, for example, had a big quake in remote Tennant Creek in 1988. It caused damage of about $2.5 million. It was larger than a 1994 earthquake near Los Angeles, California. This one struck a built-up area, killed 60 people, injured 7000, left 20,000 homeless and caused $15 billion in damage. Collapsing buildings claim most lives, but people are killed, too, in mud and rock slides, fires and, of course, through the shocking power of tsunamis that sweep away everything in their paths. What causes earthquakes? Can we predict when they will happen? Why do some trigger tsunamis and others not? How do you measure their strength? Why does a massive quake in Chile kill a fraction of the numbers of a less powerful quake in Haiti? Nature does not always offer definitive answers to these kinds of questions. *Latest compiled figures Can earthquakes and tsunamis be predicted? OT YET. Professor James Goff, of the Australian Tsunami Research Centre, says that you can say where they will most likely occur, but Nnot when. There will, for example, certainly be a big earthquake at a point off Indonesia within “tens” of years, he says. “That might be one year or 15 years, we can’t tell.” What’s more, not all underwater earthquakes generate tsunamis, even the big quakes. “It has to be the right movement of plates,” Professor Goff says. “Tsunamis occur when sea water is displaced, and for this to happen, the sudden movement of the tectonic plates have to either lift up or drop down. If the plates slip past each other sideways, you don’t get a tsunami.” Scientists can calculate the probability of big earthquakes in particular places. Professor John McCloskey, a research geophysicist and expert on seismic activity off Indonesia, is quoted as saying the risk of a major earthquake off Sumatra, possibly bigger than the one that devastated South A case study … At 2.43pm on March 11, 2011, a magnitude 9 earthquake off the east coast of Honshu, Japan’s main island, triggered a catastrophic tsunami. Japan is surrounded by tectonic plate boundaries and is highly prone to earthquakes. East Asia on Boxing Day, 2004, is extremely high. The rupture of a fault about 130 kilometres off the coast was caused by the strain of the Pacific tectonic plate being subducted under part of the Eurasian Plate, which lies beneath Japan. ¶ Tsunami warnings went out three minutes after the start of the quake, and the “It’s just like slowly drawing a bow. For hundreds of years the energy first wave reached the mainland 17 minutes later. The tsunami eventually affected 2000 kilometres of coast. It inundated more than 400 square kilometres of land. The highest ‘‘run-up’’ height, or the inundation height above normal sea level, was 38.9 metres. is stored as the two tectonic plates bend and deform. Then, in just a few seconds all this energy is released, generating a massive earthquake and Images, such as the one above, showed the severity of destruction; the world watched footage of water swamping protective sea walls, sweeping away cities and towns, cars and trucks, boats, bridges, roads and people. ¶ We saw explosions at the Fukushima nuclear sometimes flexing the seafloor to create a tsunami. Off western Sumatra, the power plant as the reactors failed. Radioactive leaks were confirmed in the following days and weeks. Tsunami waves propagated across the Pacific, reaching Hawaii, then the west coast of the United States. ¶ More than 15,700 people were confirmed dead and bow is drawn tight. thousands more missing. ¶ The region, right on the Pacific Ring of Fire, was on alert and prepared for tsunamis, with sea barriers, well-designed buildings and tsunami evacuation training. But this was not enough to stop it becoming the costliest natural disaster ever. “A massive earthquake is due there and could happen any day.” Counting the costs Colliding plates + strain + energy Fact file n In Australia an earthquake of the Sun, Moon and Earth. A tsunami magnitude 5.5, almost as big as can cross oceans and is caused OW can you count the cost of an earthquake? Is it by loss of life, released = earthquake Newcastle’s 1989 quake, occurs by an underwater earthquake (or property damage, the number of communities destroyed, or ruined every 15 months on average. landslide) suddenly displacing the Hlivelihoods? Earthquakes and tsunamis inflict massive tolls. arthqUakes are the speeds over the molten mantle to big earthquakes. The country sea water. The earthquake and monstrous tsunami that struck Japan in 2011 became shaking and rolling of solid below. They collide, grind past each is located where the Nazca Plate n The hypocentre of an earthquake the most expensive natural disaster of all time, even more costly than Eground. They are caused by other or pull apart. They are being is being forced under the South is the place beneath the earth’s Hurricane Katrina, according to leading insurers. the sudden release of strain that has compressed and bent, crumpled American Plate at 8 centimetres surface where the rupture of the Munich Re, a worldwide reinsurance company that keeps natural disaster built up by movement in and under and pushed up. Rough edges get a year. Chile recorded an 8.8 fault begins. The epicentre is on records, estimates the economic loss in Japan at $US210 billion. Hurricane the Earth’s crust. The Earth’s outer stuck or “locked” with another plate magnitude quake in 2010. The the surface directly above the Katrina’s losses were about $US125 billion. layer, the lithosphere, which is the moving in a different direction. One strongest earthquake ever recorded hypocentre. Geoscience Australia Earthquakes and tsunamis have brought a terrible death toll over the past crust and the uppermost part of plate can be forced, or subducted, was in Chile in 1960 measuring 9.5 n The world’s greatest mountain 30 years. The quake that struck Haiti in 2010 topped the list as the deadliest the mantle, is made of huge, rigid under the other and into the molten and killing 2000. range on land is the Himalaya- natural disaster, with at least 222,570 people killed. Next was the 2004 pieces called tectonic plates. They mantle below. When the pressure The infamous San Andreas Karakoram. The longest range is Boxing Day quake and tsunami in South East Asia, in which some 220,000 are a bit like giant pieces of a jigsaw becomes too great, plates can crack fault system that runs through the 7564-kilometre Andes in South people died. In the past 100 years, the only quake to have claimed more lives puzzle. The continent of Australia or “fault”, releasing energy in what California is located along a plate America. Both were created by the was in Tangshan, China, in 1976, when about 242,000 people perished. sits in the middle of the Australian are called seismic waves. boundary. The Pacific Plate and the movement of tectonic plates. Australia’s only disastrous earthquake, in Newcastle in 1989, killed 13 Plate. There are many other plates, Moving edges of plates can get North American Plate grind past n There is no such thing as people and cost about $A4.5 billion. Historically, earthquakes make up about including the Pacific Plate (the stuck against each other for years, each other in opposite directions. l Australian earthquakes in 2010. “earthquake weather”. Quakes occur 13 per cent of the cost of natural disasters in Australia, with an average biggest), the Indian, African, North with stresses building up along Geologists say that one day Los in all conditions. Weather cannot yearly cost of $A145 million. American and South American sections. When they suddenly jerk Angeles could end up in Alaska. n Seismic waves travel fast, from affect the huge forces kilometres The estimate in the United States for damage to buildings through plates. Oceanic plates are on the forward, the released strain energy San Francisco suffered a 1 to14 kilometres a second, under the surface.