MECHANICAL BRANCH

STUDY OF EARTHQUAKE

CERTIFICATE

This is to certify that

1. Manish Belvekar(03)

2. Abhishek Bhosle(06)

3. Dinesh Kumar (13)

4. Swapnil Gurav(21)

5. Soham Koli(28)

6. Sagar Suryavanshi(66) 

Have satisfactorily completed the Group project entitled “ STUDY OF EARTHQUAKE” in semester V as laid by university of Mumbai.

Prof.Mrs. Pradnya Prof.V.J.Jog

(Project Guide) (H.O.D of Mechanical Department) 3

ACKNOWLEDGEMENT

We have great pleasure in presenting this project title “STUDY OF EARTHQUAKE”. We would like to take this opportunity to express our deepest gratitude and indebted to those who contributed their valuable time in helping us to successfully complete our project work.

We would like to express our sincere thanks to Mrs. Pradnya(our project guide) and whole staff who had distributed their valuable experience, time, knowledge and constant guidance throughout the whole project. We are extremely obliged to all of them for their guidance without them this project was not possible.

Last but not the least we would like to express our sincere thanks to all of those who directly or indirectly help us in our project.

 

INDEX

1. Summary…………………………………………………………….

2. Brief History…………………………………………………………

3. Acknowledgement…………………………………………………...

4. What are Earthquakes ?.....................................................................

5. Elastic Rebound Theory………………………………………….....

6. Focus and Epicenter of an Earthquake…………………………….

7. Occurrence of Earthquake and How often ?..................................

8. Economic and Social Impact of Earthquake……………………...

9. Seismic Waves……………………………………………………….

10. Location of Epicenter of Earthquake ……………………………..

11. Measurement of Size and Strength of Earthquake………………

12. Destructive effects of Earthquake………………………………….

13. Prediction of Earthquake……………………………………………

14. Can Earthquake be controlled ?.......................................................

15. Bibliography…………………………………………………………

SUMMARY

An earthquake (also known as a quake, tremor )is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time.

Earthquakes are measured using observations from seismometers or on local magnitude scale refer to as Richter scale At the Earth's surface, earthquakes manifest themselves by shaking and sometimes displacement of the ground. When the epicenter of a large earthquake is located offshore, the seabed may be displaced sufficiently to cause a tsunami. Earthquakes can also trigger landslides, and occasionally volcanic activity.

Earthquakes are caused mostly by rupture of geological faults, but also by other events such as volcanic activity, landslides, mine blasts, and nuclear tests. An earthquake's point of initial rupture is called its focus or hypocenter. The epicenter is the point at ground level directly above the hypocenter.

Brief History

Earthquakes have been recorded as early as 1177 B.C. in China. Of course earthquakes have been a part of myth and legend since the dawn of man. In Greek Mythology, Posseidon (Neptune in the Roman pantheon) was "God of the Sea". Yet one of his powers was thought to be that of "earth shaker". As a tsunami is often the result of an earthquake, this was an appropriate power for a sea god.

In European history, the earliest recorded earthquake occurred in 580 B.C. In North America the great earthquake of 1811-1812 occurred near New Madrid, Missouri .The magnitude of the quakes are not known, but they are estimated to have been about 8 on the Richter scale. There were actually three large quakes with aftershocks between and for months after. The quake was so wide-spread it was felt as far away as Boston .

The most destructive quake in U.S. history occurred in San Francisco in 1906, it caused the deaths of over 700 people. The great Alaskan earthquake of 1964 was twice as powerful, but less destructive due to the low population density of the area struck. The Chilean quake of 1960 was the biggest quake ever recorded. It came in at 9.5 on the Richter scale.

The study of earthquakes is called seismology. The earliest seismologists were the Chinese who worked hard to record their quakes in detail. They even developed a means to predict earthquakes by filling a ceramic jar to the brim with water and leaving it set. If the water overflowed the jar, then an earthquake was imminent. Of course, this means of prediction was unreliable and uncertain.

It is thought that some animals may feel vibrations from a quake before humans, and that even minutes before a quake dogs may howl and birds fly erratically. However, evidence for such  sensitivity by animals is purely anecdotal.

Aristotle was one of the first Europeans to create a theory about the origin of Earthquakes. He thought that they were the result of heavy winds. Not much more study was concentrated on earthquakes until the mid-1700s when London was hit by a devastating quake and a tsunami struck Lisbon, Portugal shortly after. John Mitchell in England and Elie Bertrand in Switzerland began a comprehensive study of the timing and severity of earthquakes.

Soon scientists from several countries were exchanging observations and theories on earthquakes. In the 1820's Chile became an area of interest to seismologists. After an earthquake there, it was noticed that the elevation of the coastline had changed. This was substantiated by the Captain of the H.M.S. Beagle, Robert Fitzroy. (The ship also carried Charles Darwin who was studying the flora and fauna of  the coast)

Since then, seismologists have continued to work at a furious pace, building better instruments, computer models, theories and forecast to study the causes and effects of earthquakes.

What are Earthquakes?

The shaking or trembling caused by the sudden release of energy is called an Earthquake . It is usually associated with faulting or breaking of rocks . Continuing adjustment of position results in aftershocks. Earthquakes are the Earth's natural means of releasing stress. When the Earth's plates move against each other, stress is put on the lithosphere. When this stress is great enough, the lithosphere breaks or shifts. Imagine holding a pencil horizontally. If you were to apply a force to both ends of the pencil by pushing down on them, you would see the pencil bend. After enough force was applied, the pencil would break in the middle, releasing the stress you have put on it. The Earth's crust acts in the same way. As the plates move they put forces on themselves and each other. When the force is large enough, the crust is forced to break. When the break occurs, the stress is released as energy which moves through the Earth in the form of waves, which we feel and call an earthquake.

how energy is stored in rocks. ?

Rocks bend until the strength of the rock is exceeded

Rupture occurs and the rocks quickly rebound to an unreformed shape

Energy is released in waves that radiate outward from the fault

What is the Elastic Rebound Theory?

The point within Earth where faulting begins is the focus, or hypocenter.

The point directly above the focus on the surface is the epicenter.

The Focus and Epicenter of an Earthquake

Seismographs record earthquake events

At convergent boundaries, focal depth increases along a dipping seismic zone called a

Benioff zone

Where Do Earthquakes Occur and How Often?

80% of all earthquakes occur in the circum-Pacific belt most of these result from convergent margin activity 15% occur in the Mediterranean-Asiatic belt remaining 5% occur in the interiors of plates and on spreading ridge centers more than 150,000 quakes strong enough to be felt are recorded each year

The Economics and Social Impacts of EQs

Damage in Oakland, CA, 1989 Building collapse Fire Tsunami Ground failure Homelessness Disease Widespread Hunger

What are Seismic Waves?

Seismic waves are  waves of energy that travel through the earth

Seismic wave fields are measured by a  seismograph , geophone , accelerometer.

Earthquakes create various types of waves with different velocities; when reaching seismic observatories, their different travel time enables the scientists to locate the Epicenter .

The propagation velocity of the waves depends on density and elasticity of the medium. Velocity tends to increase with depth, and ranges from approximately 2 to 8 km/s in the Earth's crust up to 13 km/s in the deep  mantle.

Two types:

Body waves

P and S

Surface waves

R and L

Body Waves: P and S waves

P or primary waves

fastest waves

travel through solids, liquids, or gases

Compression wave, material movement is in the same direction as wave moves

S or secondary waves

slower than P waves

travel through solids only

shear waves - move material perpendicular to wave movement

Surface Waves: R and L waves

R or Rayleigh wave

Travel as ripples with motions that are similar to those of waves on the surface of water

They are slower than body waves, roughly 90% of the velocity of S waves for typical homogeneous elastic media

L or love wave

Love waves are surface waves that cause circular shearing of the ground

They usually travel slightly faster than Rayleigh waves, about 90% of the S wave velocity, and have the largest amplitude.

How is an Earthquake’s Epicenter Located?

Seismic wave behavior

P waves arrive first, then S waves, then L and R

Average speeds for all these waves is known

After an earthquake, the difference in arrival times at a seismograph station can be used to calculate the distance from the seismograph to the epicenter.

How is an Earthquake’s Epicenter Located?

Time-distance graph

showing the average travel

times for P- and S-waves.

The farther away a

seismograph is from the

focus of an earthquake, the

longer the interval between

the arrivals of the P- and S-

waves

How is an Earthquake’s Epicenter Located?

Three seismograph stations are needed to locate the epicenter of an earthquake

A circle where the radius equals the distance to the epicenter is drawn

The intersection of the circles locates the epicenter

How are the Size and Strength of an Earthquake Measured?

Intensity

• subjective measure of the kind of damage done and people’s reactions to it.

• Iso-seismal lines identify areas of equal intensity.

How are the Size and Strength of an Earthquake Measured ?

Magnitude

Richter scale measures total amount of energy released by an earthquake; independent of intensity.

Amplitude of the largest wave produced by an event is corrected for distance and assigned a value on an open-ended logarithmic scale.

Modified Mercalli Intensity Map1994 Northridge, CA earthquake, magnitude 6.7

What are the Destructive Effects of Earthquakes?

Ground Shaking

• Amplitude, duration, and damage increases in poorly consolidated rocks

Landslides and avalanches

• Landslides are a major geologic hazard because they can happen at any place in the world, much like earthquakes. Severe storms, earthquakes, volcanic activity, coastal wave attack, and wildfires can all produce slope instability.

Can Earthquakes be Predicted?

Earthquake Precursors

changes in elevation or tilting of land surface, fluctuations in groundwater levels, magnetic field, electrical resistance of the ground

seismic dilatancy model

seismic gaps

Can Earthquakes be Predicted?

Earthquake Prediction Program

include laboratory and field studies of rocks before, during, and after earthquakes

monitor activity along major faults

produce risk assessments

Can Earthquakes be Controlled?

Graph showing the relationship between the amount of waste injected into wells per month and the average number of Denver earthquakes per month

Some have suggested that pumping fluids into seismic gaps will cause small earthquakes while preventing large ones

Bibliography

Donald Hyndman, David Hyndman- Natural Hazards and Disasters (2nd edition).

www.wikipedia .com

www.earthquake info.org

Kanamori Hiroo- "The Energy Release in Great Earthquakes". Journal of Geophysical Research.

"Earthquakes" by Edward J. Tarbuck, Frederick K. Lutgens, and Dennis Tasa.