GR8

• An earthquake occurs when two blocks of rock move past one another, releasing energy that travels through the earth as seismic waves.
• The Richter scale is used to measure the magnitude of an earthquake.
• Seismic waves are vibrations that travel outwards from the focus (hypocenter) of an earthquake at different speeds depending on their type.
• The focus is where the earthquake originates from
• Fault is a break on the Earth's crust where significant movement has taken place
• S-waves are secondary waves which are slower than P-waves but have higher amplitudes
• P-waves are primary waves which are fast but have low amplitude
• Epicentre is the point directly above the focus
• Fault plane

  • The flat surface which there is slip (fault) during an earthquake.

  Fault line

  • The trace of the fault or a geological fracture where in the movement of masses of rocks has displaced parts of Earth's crust
• Types of fault:Reverse fault, surface-slip fault, Normal fault

  1. Reverse fault —The block above the fault moves up relative to the block below the fault.
  2. Surface-slip fault —A fault in which rock strata are displaced in a horizontal direction parallel to the line of the fault.
  3. Normal fault —Where the block have shifted vertically.
• TYPES OF GEOLOGICAL STRESS: 1.COMPRESSION STRESS

  - where a rock is pressed together into itself

  2. TENSION STRESS

  A stress which stressed rocks

  in two opposite directions

  3.SHEAR STRESS

  -Rocks lengthen or break apart

  -Forces are parallel but moving

  in opposite directions

  4 CONFINING STRESS

  -Stress is applied to all sides of the rust where it can cause a sinkhole
• Seismographs measure seismic waves generated by earthquakes and volcanic eruptions.
• Earthquake waves include P-waves (compressional), S-waves (shear), surface waves (Love and Rayleigh).
• Magnitude of an earthquake is measured using the RICHTER SCALE. The higher the number, the more powerful the quake.
• •A SEISMOMETER detects the vibrations caused by an earthquake which are plotted by a seismograph.

  ・ The magnitude of an earthquake is measured using the RICHTER SCALE numbered 0-10.
• Earthquake is the sudden shaking of the Earth that occurs when energy is released when it's lithospheric crust or tectonic plates move.
• FOCUS -Is the point within the Earth where seismic waves originate. -It is the part of the fault that has the greatest movement. -The fault plate is the flat surface along which there is slip(fault) during an earthquake.
• EPICENTER -Is a location on the earth's surface directly above the focus.
• Seismometer - A device used to measure ground motion due to earthquakes.
• Active faults:

  -Have moved in the past and are expected to move in the future.

  Inactive faults:

  -Have moved in the past and are not expected to move in the future.
• TSUNAMI -A sudden' push from an under water fault that produces a wave -Is very destructive because the force of the whole ocean is behind it. •When a fault suddenly moves on land, Earthquake occurs. But if a fault suddenly moves in or near a body of water, Tsunami occurs. •These faults that move in a horizontal direction or sideways will not result a tsunami, the fault has to move vertically.