What is an earthquake and what causes them to happen? An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel. In California there are two plates - the Pacific Plate and the North American Plate. The Pacific Plate consists of most of the Pacific Ocean floor and the California Coast line. The Pacific Plate grinds northwestward past the North American Plate at a rate of about two inches per year.Parts of the San Andreas Fault system adapt to this movement by constant "creep" resulting in many tiny shocks and a few moderate earth tremors. Learn more: "Earthquakes".
Animations Each series of animations below contains text, graphics, animations, and videos to help teach Earth Science fundamentals. Click links or scroll down to view the available animations. Check out our Earth Science Videos pages. Animations Hazards Orphan tsunami How will 3 buildings, engineered equally, on different bedrock react to an earthquake? Plate Tectonics Tectonics & earthquakes of Alaska—More than just plate boundaries NEW! GPS - Understanding Future Earthquakes in the Pacific Northwest Solomon Islands Regional Tectonics Gulf of California tectonics Sumatran Tectonics What is a hotspot? How do Earth's tectonic plates interact? Do subducting plates slide smoothly past one another? How is stress stored between tectonic plates? Do faults break all at once, or in many short segments? What are the 4 basic classes of faults? What happens when the crust is stretched? GPS -- Measuring Plate Motion Earth Structure Stratigraphy Same earthquake, different stations; why do the seismograms look different? Volcanoes
How Are Earthquake Magnitudes Measured? Unfortunately, many scales, such as the Richter scale, do not provide accurate estimates for large magnitude earthquakes. Today the moment magnitude scale, abbreviated MW, is preferred because it works over a wider range of earthquake sizes and is applicable globally. The moment magnitude scale is based on the total moment release of the earthquake. Moment is a product of the distance a fault moved and the force required to move it. It is derived from modeling recordings of the earthquake at multiple stations. Magnitudes are based on a logarithmic scale (base 10). Magnitude scales can be used to desribe earthquakes so small that they are expressed in negative numbers. Here's a table describing the magnitudes of earthquakes, their effects, and the estimated number of those earthquakes that occur each year. Some things that affect the amount of damage that occurs are: Figures 1 and 2 from Walker, 1982.
De Geobronnen » Aardrijkskunde in het nieuws What is an Earthquake Introduction to Earthquakes & Tsunamis Turn on the TV or read the newspapers and almost always there is something devastating happening somewhere as a result of sheer nature's power. Examples of such natural occurrences are hurricanes, tornados, wildfires, volcanic eruptions, flooding, earthquakes and tsunamis. These are usually not caused directly by humans, but their effects live with us for a long time. In this lesson we shall look at one of such natural occurrences...earthquakes! What is an Earthquake? Simply, earthquakes are the rumblings, shaking or rolling of the earth's surface. Earthquakes come in many forms. Foreshocks, Mainshocks and Aftershocks: Sometimes, there are smaller shocks that occur before (foreshock) and after (aftershock) a main earthquake (mainshock). Earthquakes are also called temblors. It is important to understand the earth’s makeup to help understand earthquakes better. The Mantle is semi-molten rock, also called magma.
Shaking Intensity It is a modern human tendency to focus on the number of an earthquake—specifically, the magnitude, or what people used to call the “Richter scale.” But the destruction from a quake usually has more to do with location and timing. Such was the case with the earthquake in Christchurch, New Zealand, on February 22, 2011. A September 2010 earthquake centered 40 kilometers (25 miles) west of Christchurch, in the plains near Darfield, struck at 4:35 a.m., had a magnitude of 7.1, and caused some structural damage and one death (by heart attack). The earthquake in February 2011 occurred at 12:51 p.m. and just 10 kilometers (6 miles) from the center of Christchurch. The natural-color image above was captured on March 4, 2011, by the Advanced Land Imager (ALI) on NASA’s Earth Observing-1 (EO-1) satellite. The deeper the red color of the circle, the more intense the “peak ground acceleration,” or shaking of the earth. There are two forms of energy that cause the shaking in an earthquake.
For Teachers - Met Office Education Resources to support the National Curriculum These items are designed for the teacher to use in the classroom or as background reference material. The lesson plans cover elements of the Geography, Science and Maths curriculum. Key Stage 2 Lesson Plans Keeping warm, Mountain environment, Water cycle, Weather around the world, Handling data, Tourism In depth Climate, Extreme weather, Understanding weather, The water cycle Weather Data Latest UK weather data, Latest world weather data, Historic weather data archive Videos Selection of our weatherbytes videos Weather Wiz Kids weather information for kids Earthquakes(Earthquakes are not associated with weather, but instead are natural disasters.) What is an earthquake?Earthquakes are the shaking, rolling or sudden shock of the earth’s surface. They are the Earth's natural means of releasing stress. More than a million earthquakes rattle the world each year. Click Here to learn more about earthquakes from USGS. What causes an earthquake? Click Here to see an animation of an earthquake. What are plate tectonics? What is a seismograph? Click Here to calculate the strength of earthquakes! Click Here to see an animation of an earthquake and the resulting tsunami. Know the Lingo EPICENTER - The point on the earth's surface directly above the source of the earthquake.SEISMIC WAVES - The energy created by the quake travels in waves from the epicenter, where they are the strongest. Richter Scale Click Here to learn about cool earthquake facts! Earthquake Safety Tips BEFORE AN EARTHQUAKE: Have a disaster plan. Earthquake Activities
How earthquakes generate tsunamis How do earthquakes generate tsunamis? Tsunamis can be generated when the sea floor abruptly deforms and vertically displaces the overlying water. Tectonic earthquakes are a particular kind of earthquake that are associated with the earth's crustal deformation; when these earthquakes occur beneath the sea, the water above the deformed area is displaced from its equilibrium position. Large vertical movements of the earth's crust can occur at plate boundaries. This simulation (2 MB) of the 1993 Hokkaido earthquake-generated tsunami, developed by Takeyuki Takahashi of the Disaster Control Research Center, Tohoku University, Japan, shows the initial water-surface profile over the source area and the subsequent wave propagation away from the source.
Earthquakes & Tsunamis: Causes & Information Almost every year, a large earthquake occurs somewhere in the world and captures the public's attention. Meanwhile, every day thousands of smaller tremors often go unnoticed by most people. Although we usually consider the ground to be solid and stable, the earth is, in fact, constantly shifting under our feet. What causes earthquakes? Earth's crust ranges from 3 to 45 miles deep (5 to 70 kilometers). The crust is a thin, hard shell that floats on the denser, hotter rock of the mantle. As they slide past one another, the tectonic plates snag on rough patches of rock. An earthquake occurs when the pressure built up along a fault becomes stronger than the pressure holding the rocks together. Even though the tectonic plates slide at a regular rate over time, the way that faults release stored energy is different with each earthquake, said Shimon Wdowinski, a geophysicist at the University of Miami's Rosentiel School of Marine & Atmospheric Sciences. Tsunamis Measuring earthquakes
Why do Some Earthquakes Cause Tsunamis When Others Don't? Damage caused by the 2011 Japanese tsunami. Photo by Tamaki Seto In the past decade, the devastating impact of major tsunamis has made the news on a number of occasions, most notably the 2011 Japanese tsunami and the notorious Boxing Day tsunami of 2004. But the earth experiences very many earthquakes each day, and each year sees on average around 15 major earthquakes of at least magnitude 7 (M7.0) and one of ≥M8.0 – and in this context, damaging tsunamis are few. What Causes a Tsunami? Tsunamis are not just large waves: they are generated by vertical displacement of sea water by some kind of submarine activity. The devastating impact of a major tsunami comes from the fact that, unlike the waves we normally see, they travel through the whole depth of the ocean. Which Earthquakes Cause Tsunamis? How a tsunami is generated. For an earthquake to cause a tsunami, certain conditions must be satisfied; size, depth of water, and type of movement must all be right to generate the huge waves.
Canterbury earthquake facts and figures 29 November 2010 What are earthquakes? New Zealand lies on the boundary of the Pacific and Australian tectonic plates. Tectonic plates are large plates of rock, about 100km in thickness, that make up the foundation of the earth's crust and the shape of the continents (like pieces of a giant jigsaw puzzle). There are ten major plates and many more minor ones. Tension builds up as they scrape over, under or past each other. Most (though not all) earthquakes occur at faults, which are breaks extending deep within the earth, caused by the movement of these plates. The fault that caused the Canterbury earthquake on 4 September 2010 has been named the Greendale Fault. Scientists from the Institute of Geological and Nuclear Sciences (GNS) think it is the first time this fault has moved in several thousand years, and it is unlikely that it will move again for another few thousand years. Measuring earthquakes The magnitude is a measure of the amount of energy released by the earthquake. Aftershocks