EARTHQUAKE: Earthquake is caused Volcanic eruption

PPT on Earthquake

1. EARTHQUAKE Prepared by:- Ms Nilza Angmo Assistant Professor Department of Disaster Managemet Kargil campus , University of Ladakh

2. EARTHQUAKE ? An earthquake in simple words is the shaking of the earth. It is a natural event. It is caused due to release of energy, which generates waves that travel in all directions. The vibrations called seismic waves are generated from earthquakes that travel through the Earth and are recorded on instruments called seismographs or seismometer. The location below the earth’s surface where the earthquake starts is called the hypocenter, and the location directly above it on the surface of the earth is called the epicenter.

3. OCURRENCE OF EARTHQUAKE During an earthquake, the movement of rock blocks along the fault or line of weakness gives rise to seismic waves spreading outwards along the surface of the earth, in all directions simultaneously. These waves are grouped into two main types: Body waves P-Wave S-Wave 2.Surface Waves Rayleigh Love Waves

4. TYPES OF WAVES

5. The point where the energy is released is called the focus of an earthquake, alternatively, it is called the hypocentre. The energy waves travelling in different directions reach the surface. The point on the surface, nearest to the focus, is called epicentre . It is the first one to experience the waves. It is a point directly above the focu s.

6. CAUSES OF EARTHQUAKES FAULT ZONES PLATE TECTONICS VOLCANIC ACTIVITY HUMAN INDUCED

7. FAULTS

8. PLATE TECTONICS

9. STRUCTURE OF THE EARTH

10. Volcanic Earthquake Earthquakes produced by stress changes in solid rock due to the injection or withdrawal of magma are called volcano earthquakes. These earthquakes can cause land to subside and can produce large ground cracks. Volcano-tectonic earthquakes don't indicate that the volcano will be erupting but can occur at any time.

11. Human Induced Earthquakes In the areas of intense mining activity, sometimes the roofs of underground mines collapse causing minor tremors. These are called collapse earthquakes. Ground shaking may also occur due to the explosion of chemical or nuclear devices.Such tremors are called explosion earthquakes.

12. MEASUREMENT OF EARTHQUAKE The energy from an earthquake travels through Earth in vibrations called seismicwaves. Scientists can measure these seismic waves on instruments called seismometer. A seismometer detects seismic waves below the instrument and records them as a series of zig-zags. Scientists can determine the time, location and intensity of an earthquake from the information recorded by a seismometer. This record also provides information about the rocks the seismic waves traveled through.

13. SEISMOMETER

14. RICHTER SCALE THE FIRST SCALE FOR MEASURING EARTHQUAKE MAGNITUDES, DEVELOPED IN 1935 BY CHARLES F.RICHTER AND POPULARLY KNOWN AS THE " RICHTER " SCALE, IS ACTUALLY THE LOCAL MAGNITUDE SCALE . HE SCALE REPRESENTS THE MAGNITUDE OF THE EARTHQUAKE. THE MAGNITUDE IS EXPRESSED IN ABSOLUTE NUMBERS FROM 1-10.

15. MAGNITUDE

16. MERCALLI SCALE The scale represents the intensity of earthquake , named after Mercalli, an Italian seismologist. The intensity scale takes after effects like how many people felt it, how much destruction occurred etc. The range of intensity scale is from 1-12.

17. MERCALLI VS RICHTER

18. Seismic Zones of India Earthquake-prone regions of the country have been identified on the basis of scientific inputs related to seismicity, earthquakes that occurred in the past and the tectonic setup of the region. On the basis of these inputs, the Bureau of Indian Standards (BIS) has grouped the country into four seismic zones viz. zones V, IV, III and II . Zone V expects the highest level of seismicity whereas Zone II is associated with the lowest level of seismicity.