Earthquakes and volcanoes are not randomly distributed over the globe At the boundaries between plates, friction causes them to stick together. When built up energy causes them to break, earthquakes occur. Figure showing the distribution of earthquakes around the globe Where do earthquakes form?
Rocks on both sides of a fault are pressed together tightly locked by friction When they finally, slip, vibrations occur A movement or trembling of the ground that is caused by a sudden release of energy when rocks move along a fault line
Figure showing the tectonic setting of earthquakes
The location within the Earth along a fault at which the first motion of an Earthquake occurs Focus:
The point on the Earth’s surface above the focus Epicenter:
Primary Wave Motion is back and forth in the direction of travel Fastest of the waves and can travel through solids, liquids, and gases Compression wave P-Wave
Secondary Wave Motion is side to side compared to direction of travel Second fastest and can only travel through solids Shear Waves S-Wave:
A seismic wave that travels along the surface and has a stronger effect; converted P and S wave, causes the most damage Surface Waves: http://www.youtube.com/watch?v=gl4FvHKzAlU
Led to more in depth knowledge of the Earth’s interior Various densities and phases are shown by wave deflection S waves blocked by liquid outer core P waves change direction as they pass through the cores Waves in the Interior of the Earth
Finding the earthquake location Seismograms – a record written by a seismograph in response to an earthquake, explosion, or other ground-motion sources. Seismograph – An instrument used to detect and record earthquakes. http://www.wwnorton.com/college/geo/an imations/how_seismograph_works.htm
The longer the time difference between the arrival of the P and S waves, the farther from the epicenter Once you have the distance to the epicenter, using readings from three stations, you can determine the location by creating circle with that distance as the radius. The point where the three circles meet is the location of the epicenter Determining the Location
Earthquake Detection To find the exact location of an earthquake, you need to have (3) different stations reporting the results of their respective seismograms. The scientists then create a VENN DIAGRAM to see where all of the data INTERSECTS. http://news.bbc.co.uk/2/hi/science/na ture/7498840.stm http://vimeo.com/7172545
Earthquake Exit Slip Focus Epicenter Fault Wave Fronts B
Earthquake Exit Slip S-Wave P-Wave Surface Waves Seismograph Seismogram F. G. H. I. Fastest of the waves and can travel through solids, liquids, and gases J. Waves that can only travel through solids E.