seismicity
- Created by: Sharon
- Created on: 30-12-15 15:26
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- Seismicity
- Earthquakes
- When energy stored in elastically strained rocks suddenly released.
- causes waves of energy sent through the earth.
- Causes
- rocks subject to forces tend to bend. when they bend they deform. Forces "stress&strain"
- Tensional - Stretches
- Compressional - squash
- Shear - slippage
- How
- elastic energy sends out vibrations "seismic waves"
- Focus - point where fault rupture starts
- Epicenter - point on surface directly above focus.
- P waves, primary travel with velocity depending on elasticity or rock. move compressing and expanding material
- S waves, secondary velocity depending on rigidity and density of material. 0 in liquid,
- Surface waves parallel to earth surface up/down/side2side
- Measuring
- Seismometers - instrument records vibrations resulting in a graph called "seismogram"
- moves with vibrations part of it is stationary.. pen attached to large mass suspended by spring spring and mass move less than paper (attached to earth)
- Seismometers - instrument records vibrations resulting in a graph called "seismogram"
- Size
- Richter scale - max ground shaking one area of epicenter (ENERGY)(SEISMOGRAPH)
- Better to measure energy released.
- Mercalli scale - intensity and ground shaking & building damage over large area, (EFFECT)(OBSERVATION
- amplitude of largest recorded wave at specific distance from earth.
- During
- Ground shaking - depends on intensity and bedrock underlying.(wood/steel flexible)(Concrete brittle)
- Ground rupture - along fault zone moves during quake, structures across collapse
- Fire - secondary effect, power lines knocked/ natural gas. if water supply broken no extinguish.
- Landslides - mountainous regions mass-wasting events of lose debris.
- Liquefaction - occurs in water when completely surrounds all grains and eliminates contact = flows like fluid (requires shaking)
- Aftershocks - further earthquakes after main event.cause further damage
- Tsunami - giant ocean waves, disturbance of water by any means. larger cause=greater distance
- Earthquakes
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