Earthquake and causes of earthquake

(1) Causes of earthquake
(2) Seismic waves
Body waves
Surface waves
(3)Locating and measuring Earthquakes
Determining the location of earthquake
Measuring the size of earthquake
Location and size of earthquake in United States

1. BISMILLAHIRRAHMANIRRAHIM Afnan Ullah

2. O bjectives (1) Causes of earthquake (2) Seismic waves Body waves Surface waves (3)Locating and measuring Earthquakes Determining the location of earthquake Measuring the size of earthquake Location and size of earthquake in United States

3. Earthquake A sudden violent shaking of the ground, typically causing great destruction, as a result of movements within the earth's crust or volcanic action

4. Causes of eartquake Earthquakes are caused by tectonic movements in the Earth's crust. The main cause is that when tectonic plates collide, one rides over the other, causing orogeny (mountain building), earthquakes and volcanoes. The boundaries between moving plates form the largest fault surfaces on Earth. When they stick, relative motion between the plates leads to increasing stress. This continues until the stress rises and breaks, suddenly allowing sliding over the locked portion of the fault, releasing the stored energy as shock waves.

5. Causes of the earthquakes fall into the following broad categories: 1. Volcanic activities 2. Folding and faulting 3. Plate tectonics

6. Volcanic activities Volcanic explosions are certainly the most common cause of earthquakes in the neighbourhood of active volcanoes. Such earthquakes are, therefore, known as volcanic earthquakes. This type of earthquake is caused either under the influence of the increasing pressure of volcanic gases or the subterranean movement of molten lava trying to come up on the earth's surface.

7. Folding and Faulting A fault is defined as a fracture plane along which the rocks have been displaced. There are vertical as well as horizontal displacements. Earthquakes are caused due to sudden movements of rocks along faults. Such earthquakes are called tectonic earthquakes. Remember that the horizontal as well as vertical movements of rocks result from the operation of endogenetic forces beneath the earth's surface. It is due to such movements that folds and faults are created.

8. Plate Tectonics According to the theory of plate tectonics, the surface of the earth consists of 15 plates comprising the rigid upper mantle, and the oceanic and continental crust. Out of the total number of plates, 6 are major plates and 9 are minor plates. These plates are always moving. Now, it is an established fact that practically all the tectonic, seismic and volcanic activities take place at the plate margins. That is why must of the earthquakes and volcanoes are found in narrow and semi-continuous belts mostly confined to the plate boundaries.

9. Seismic waves Energy moving outward from the focus of an earthquake OR A wave of energy that is generated by an earthquake or other earth vibration and that travels within the earth or along its surface.

10. Seismic Waves forms Body Waves:Waves travel through the earth interior,spreading outward from the focus in all directions There are two types of body waves P-waves: called compressional , or push-pull waves Propagate parralel to the direction in which the wave is moving Move through solids, liquids S-waves: Called shear waves Propagate the movement perpendicular to the direction in which the wave is moving

11. cont... 2. Surface Waves: Waves that travel on earth's surface away from the epicentre,like water waves spreading out from a pebble thrown into pond. There are two types of earthquake Love waves:The ground move side to side in a horizontal plane that is perpendicular to the direction the wave is traveling like S waves Rayleigh waves:They are consider to be more destructive b/c they produce more ground movement and take longer to pass.

12. Measuring earthquakes Seismometers: instruments that detect seismic waves Seismographs : R ecord intensity, height and amplitude of seismic waves

13. Locating the shaking Measure time between P and S waves on a seismogram Need at least 3 seismographs

14. Frequency of Occurrence of Earthquakes Descriptor Magnitude Average Annually Great 8 and higher 1 ¹ Major 7 - 7.9 17 ² Strong 6 - 6.9 134 ² Moderate 5 - 5.9 1319 ² Light 4 - 4.9 13,000 (estimated) Minor 3 - 3.9 130,000 (estimated) Very Minor 2 - 2.9 1,300,000 (estimated) ¹ Based on observations since 1900. ² Based on observations since 1990.

15. Recent Earthquake Activity in the World

16. Largest earthquake in the world Chile : 1960 May 22 19:11:14 UTC Magnitude 9.5 More than 2,000 killed, 3,000 injured, 2,000,000 homeless, and $550 million damage in southern Chile tsunami caused 61 deaths $75 million damage in Hawaii; 138 deaths and $50 million damage in Japan; 32 dead and missing in the Philippines; and $500,000 damage to the west coast of the United States.

17. Most Destructive Known Earthquakes on Record in the World Date Location Deaths Magnitude Comments May 31, 1970 Peru 66,000 7.9 $530,000,000 damage, great rock slide, floods. July 27, 1976 China,  Tangshan 255,000 (official) 7.5 Estimated death toll as high as 655,000. Sept 19, 1985 Mexico Michoacan 9500 (official) 8.0   Estimated death toll as high as 30,000 Old lake bed magnified shock waves by 500% 2001 Jan 26 India 20,023 7.7 166,836 injured, 600,000 homeless . 2004 Dec 26 Sumatra 283,106 9.0 Deaths from earthquake and tsunami

18. Location and size of earthquakes in the United States According to thr U.S.Geological servey, earthquake pose a significant risk to 75 million people in 39 states. Most of the large earthquakes occur in the western states. Quakes in California, Utah, Idaho, Montana, Washington and other western states are related to known faults and usually involve surface rupture of the ground.

19. Cont.... Earthquake east of the Rocky Mountain rarer and generally smaller and deeper than earthquakes in the western United States. Although large quakes are extremly rare in the central and eastern United States, when they do occur they can be very destructive and widely felt, b/c earth crust is older, cooler and more brittle in the east then in the west and seismic wave travel more efficiently