EARTHQUAKE
WHAT ARE EARTHQUAKES??? Earthquake refers to a sudden violent shaking and vibration of the earth surface resulting from underground movement along a fault plane or from volcanic activity. Earthquakes can cause serious destruction to property, injury to people and even kills. It happens when there is sudden movement or breaking of the tectonic plates. Tectonic plates are huge rock pieces within the earth’s crust. The plates are usually marked by fractures or fault lines formed when the plates tear apart or slide or collide past each other. This results in a change of the earth’s interior masses which send out powerful shock waves with enough force to alter the surface of the earth. The shock waves can thrust up cliffs and open huge cracks on the ground leading to an earthquake event.
OCCURRENCE OF EARTHQUAKES Although earthquakes are mainly concentrated in zones close to boundaries of tectonic plates of the Earth's lithosphere, infrequent events away from the main seismic regions can cause major disasters. The major cause of damage and injury following earthquakes is elastic vibration, rather than fault displacement. This vibration at a particular site will depend not only on the size and distance of the earthquake but also on the local soil conditions. Earthquake prediction is not yet generally fruitful in avoiding earthquake disasters, but much useful planning to reduce earthquake effects can be done by studying the general earthquake hazard in an area, and taking some simple precautions
CHARACTERISTICS OF EARTHQUAKES FOCUS : The point inside the earth from where the earthquake originates is called the focus. EPICENTRE : The point exactly above the focus on the surface of earth is called the epicentre . The maximum destruction takes place in the epicentre. SEISMIC WAVES : The tremors or vibrations produced during an earthquake are also called seismic waves. RITCHER SCALE : The Richter Scale is a scale of numbers used to tell the size of earthquakes. Charles Richter developed the Richter Scale in 1935. Seismograph : The instrument used for the measurement of earthquakes is called seismograph. Seismologists : The people who study geophysical science of earthquakes and the mechanical properties of the earth are called seismologists. The study of the geophysical science of earthquakes and the mechanical properties of the earth is called seismology.
FOCUS , EPICENTRE AND SEISMIC WAVES
RICHTER SCALE
SEISMOGRAPH
SEISMOLOGY
SEISMOLOGISTS
TIME FOR QUIZ 1.What are earthquakes? 2.what is the focus? 3.What is the epicentre? 4.How do earthquakes occur? 5.Define richter scale?
PRESENTED BY : Yaswanth Sri Vishnu Vardhan Nitin Maran Vishal Ragavendra SU.Asmita
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