2.3 Notes: Earthquake Damage Can Be Reduced

Transcription

1 2.3 Notes: Earthquake Damage Can Be Reduced Earthquakes can cause severe damage and loss of life Each year, there is about one earthquake with a magnitude of or higher-this is an extremely earthquake. 8.0 earthquakes (or bigger) can destroy all buildings near their epicenters and cause huge loss of. 9.0 Earthquake in Japan in 2011 lasted 6 minutes and killed people. Most deaths from earthquakes are caused by collapsing buildings and, not by the shaking of the ground. Earthquake magnitude The most powerful earthquakes can release more energy than weak earthquakes combined! Earthquake magnitude is described using a number scale from 0-10 (no real maximum possible value). The first number scale was developed in the 1930 s by Charles Richter and. o Describes an earthquake s magnitude based on how fast the ground moves at a seismic. Most scientists today prefer the moment magnitude scale (MMS), which measures the total amount of released by an earthquake. Both the Richter Scale and the MMS increase by 32 times with each whole number increase. o A magnitude 5 earthquake is times stronger than a magnitude 4 earthquake. o A magnitude earthquake is 1000 times stronger than a magnitude 4 earthquake! The MMS is more accurate and also allows scientists to measure the strength of earthquakes that occurred before seismographs were invented by measuring the strengths of rocks and length they moved along a fault. Damage from earthquakes Earthquakes can crack roads, buildings, damns, and any other structures that exist on top of a. Earthquakes can also raise, lower, or tilt the surface. An is a smaller earthquake that follows a more powerful earthquake in the same area. Sometimes aftershocks cause buildings that were weakened by an earthquake to collapse. Fire caused by earthquakes can cause significant damage. In the 1906 San Francisco Earthquake, fire caused more than of the damage. are a common side effect of earthquakes as soil is shaken loose. Liquefaction is a process in which shaking of the ground causes soil to temporarily act like a. Liquefaction can cause structures to down into the soil or flow away with it. Damage from tsunamis A tsunami is a water triggered by an earthquake, volcanic eruption, or landslide. Tsunamis can be taller than a building! A tsunami may be a single wave but can also be several waves that have different heights and arrive apart. In deep water, tsunamis can travel at km/hr (430 mi/hr)! p. 19

2 As tsunamis approach coastlines, they slow down and grow in. In 2004, an earthquake off the coast of Sumatra caused a tsunami. o people died. Scientists work to monitor and predict earthquakes We cannot predict the day or even that an earthquake will occur. Sometimes there are and sometimes there are none at all. Long term predictions can be generated. o Example: An area might have a chance of being hit by an earthquake with magnitude or higher in the next years. Scientists around the world work constantly to try to better predict earthquakes, by observing the following things: o Tilts or changes in the of the ground o Slow movements or stretching in rock o The development of small in the ground Structures can be designed to resist earthquake damage Review For safety during an earthquake, the best place to be is and away from any buildings. Scientists make of areas that have many earthquakes. Planners use these maps to develop for building in these areas. For small buildings (like houses): o Should be firmly fastened to the o Should have walls For large buildings (like skyscrapers): o Base : flexible material between building and foundation o Cross braces: X shaped braces added to a building to help a building keep its. 1. The moment magnitude scale is based on the A. Amount of ground movement at a seismic station B. Amount of building damage caused by an earthquake C. Number of human deaths caused by an earthquake D. Amount of energy released by an earthquake 2. One method of making a building earthquake resistant is to A. Add sand under the foundation C. Make the walls of brick B. Reduce the use of steel D. Use cross braces

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4 2.3 Notes: Earthquake Damage Can Be Reduced Earthquakes can cause severe damage and loss of life Each year, there is about one earthquake with a magnitude of 8 or higher-this is an extremely powerful earthquake. 8.0 earthquakes (or bigger) can destroy all buildings near their epicenters and cause huge loss of life. 9.0 Earthquake in Japan in 2011 lasted 6 minutes and killed 18,000 people. Most deaths from earthquakes are caused by collapsing buildings and fires, not by the shaking of the ground. Earthquake magnitude The most powerful earthquakes can release more energy than 1 million weak earthquakes combined! Earthquake magnitude is described using a number scale from 0-10 (no real maximum possible value). The first number scale was developed in the 1930 s by Charles Richter and Beno Gutenberg. o Describes an earthquake s magnitude based on how fast the ground moves at a seismic station. Most scientists today prefer the moment magnitude scale (MMS), which measures the total amount of energy released by an earthquake. Both the Richter Scale and the MMS increase by 32 times with each whole number increase. o A magnitude 5 earthquake is 32 times stronger than a magnitude 4 earthquake. o A magnitude 6 earthquake is 1000 times stronger than a magnitude 4 earthquake! The MMS is more accurate and also allows scientists to measure the strength of earthquakes that occurred before seismographs were invented by measuring the strengths of rocks and length they moved along a fault. Damage from earthquakes Earthquakes can crack roads, buildings, damns, and any other structures that exist on top of a fault. Earthquakes can also raise, lower, or tilt the ground surface. An aftershock is a smaller earthquake that follows a more powerful earthquake in the same area. Sometimes aftershocks cause buildings that were weakened by an initial earthquake to collapse. Fire caused by earthquakes can cause significant damage. In the 1906 San Francisco Earthquake, fire caused more than 90% of the damage. Landslides are a common side effect of earthquakes as soil is shaken loose. Liquefaction is a process in which shaking of the ground causes soil to temporarily act like a liquid. Liquefaction can cause structures to sink down into the soil or flow away with it. Damage from tsunamis A tsunami is a water wave triggered by an earthquake, volcanic eruption, or landslide. Tsunamis can be taller than a 20-story building! A tsunami may be a single wave but can also be several waves that have different heights and arrive hours apart. In deep water, tsunamis can travel at 700 km/hr (430 mi/hr)! As tsunamis approach coastlines, they slow down and grow in height. p. 19

5 In 2004, an earthquake off the coast of Sumatra caused a tsunami. o 280,000 people died. Scientists work to monitor and predict earthquakes We cannot predict the day or even year that an earthquake will occur. Sometimes there are signs and sometimes there are none at all. Long term predictions can be generated. o Example: An area might have a 60% chance of being hit by an earthquake with magnitude 7 or higher in the next 25 years. Scientists around the world work constantly to try to better predict earthquakes, by observing the following things: o Tilts or changes in the elevation of the ground o Slow movements or stretching in rock o The development of small cracks in the ground Structures can be designed to resist earthquake damage Review For safety during an earthquake, the best place to be is outside and away from any buildings. Scientists make maps of areas that have many earthquakes. Planners use these maps to develop rules for building in these areas. For small buildings (like houses): o Should be firmly fastened to the foundation o Should have strong walls For large buildings (like skyscrapers): o Base isolators: flexible material between building and foundation o Cross braces: X shaped braces added to a building to help a building keep its shape. 1. The moment magnitude scale is based on the A. Amount of ground movement at a seismic station B. Amount of building damage caused by an earthquake C. Number of human deaths caused by an earthquake D. Amount of energy released by an earthquake 2. One method of making a building earthquake resistant is to A. Add sand under the foundation C. Make the walls of brick B. Reduce the use of steel D. Use cross braces