What is an earthquake.pptx 4 6575378357853

Earthquake

1. EARTHQUAKE Mr. SUMIT JOHAR CSIR-NET (JRF),GATE,JKSET Assistant Professor Department of Geology GDC Udhampur Jammu & Kashmir

2. What is an earthquake? An earthquake is a shaking of the Earth’s crust caused by a release of energy.

3. Geological Faults A fault is a planar fracture in a volume of rock, across which there has been significant displacement.

4. What Causes Earthquakes? Before an earthquake, the buildup of stress in the rocks on either side of a fault results in gradual deformation. Eventually, this deformation exceeds the frictional force holding the rocks together, and sudden slip occurs along the fault. This releases the accumulated stress and the rocks on either side of the fault return to their original shape (elastic rebound) but are offset on either side of the fault.

5. The point where an earthquake starts is termed the focus or hypocentre and may be many kilometres deep within the earth. The point at the surface directly above the focus is called the earthquake epicentre .

6. Types of Seismic Waves Earthquakes generate different kinds of waves that move through the Earth: Body waves Primary waves (P-waves) are the fastest. They compress and expand the ground like sound waves and are the first to be detected. Secondary waves (S-waves) move slower than P-waves and shake the ground up and down or side to side. Surface waves travel along Earth’s surface and cause the most damage. They move more slowly but with greater amplitude, making them especially destructive near the epicenter.

7. Earthquakes based on the depth of focus The earthquakes are divided into three zones: Shallow earthquakes  have a focus of 0 – 70 km deep. Intermediate earthquakes  have a focus 70 – 300 km deep. Deep earthquakes  have a focus 300 – 700 km deep.

8. How do we measure seismic waves? A seismograph, is an instrument used to detect and record seismic waves . 

9. Determing Epicentre Readings at different seismographic stations reveal the location of the earthquake epicentre.

10. Scales used in Earthquake Richter Scale : The Richter scale, developed by Charles F. Richter , measures the magnitude of an earthquake based on the amplitude of seismic waves recorded by seismographs. It is a logarithmic scale, meaning each whole number increase represents a tenfold increase in amplitude and roughly a 32-fold increase in energy released . For example, an earthquake measuring 6.0 on the Richter scale has waves ten times the amplitude of a 5.0 earthquake and releases about 32 times more energy.

11. Mercalli Scale : The Mercalli scale measures the intensity of an earthquake based on its observed effects on people, the environment, and structures. It uses Roman numerals from I to XII to describe the intensity, with I being barely felt and XII indicating total destruction. Intensity is affected by factors such as distance from the epicenter, ground conditions, and building construction.

12. Plate Boundaries & Earthquakes Small Extreme Mag >9 Very large Mag ~ 7-8 Large Mag ~ 7

13. Potential destructive effects of an earthquake :

14. Earthquake Safety Tips Before an earthquake: Anchor heavy furniture and appliances. Prepare an emergency kit. Identify safe spots in each room, like under study tables or against interior walls. During an earthquake: Drop to the ground, take cover under furniture, and hold on until shaking stops. Stay indoors if already inside—do not run outside. If outside, move to an open area away from buildings, trees, and power lines. After an earthquake: Check yourself and others for injuries. Be alert for aftershocks. Avoid using elevators and inspect your surroundings for hazards like gas leaks. Listen to emergency broadcasts and follow official instructions.

15. THANK YOU …….