Page 1 - Lesson Notes
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SAI INTERNTIONAL SCHOOL
                                                        Class 8
                                                    Lesson notes

                                                 Subject- Physics
                                        Ch- Some Natural Phenomena
                                   Subtopic- Terms related to earthquake



                   Terms related to earthquake:


                         Seismic zone: The boundaries of tectonic plates are weak zones which
                          are prone to earthquake. These weak zones are called seismic zone or
                          fault zone.
                              o  Fault zones in India: Western and central Himalayas
                              o  Whole North-East region
                              o  Rann of kutch
                              o  Rajasthan
                              o  Indo-Gangetic Plane.
                         Richter scale: It is a scale in which power of Earthquake is expressed
                          as a number. It is a logarithmic scale. The earthquake with value more
                          than 7 is destructive in nature.
                         Seismograph or seismometer: It is an instrument used to detect and
                          record earthquakes. It measures the intensity of an Earthquake.
                         Seismic waves: It is the wave produced due to disturbance below the
                          Earth’s surface, which travels to the earth and give rise to tremors.
                         Mercalli scale: It is another scale used to measure an earthquake. It is
                          based on observed effect of any earthquake.
                         Focus  (Hypocentre):  It  is  the  point  below  the  Earth’s  crust  where
                          earthquake originates.
                         Epicentre: It is the point just above the focus, on Earth’s Surface.
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