Thomas chinnappan geologist keeranur, pudukkottai, tamilnadu, india.

1. ENVIRONMENTAL
GEOLOGY
EARTHQUAKE
BY:
THOMAS CHINNAPPAN . A ,
M.SC.APPLIED GEOLOGY,
PERIYAR UNIVERSITY,
SALEM.

2. SYNOPSIS
• Introduction
• Earthquake
• Intensity and magnitude of earthquake
• Seismometers- The measures of earthquake
• Seismic waves
• Plate boundary related Earthquakes
• Tectonic causes of Earthquake
• Effects of Earthquake
• Earthquake Prediction
• Earthquake warming system

3. INTRODUCTION
• Earthquakes constitute one of the worst natural hazards which often
turn into disaster causing widespread destruction and loss to human
life.
• The effects of earthquake vary upon the magnitude and intensity.
Earthquakes occur every now and then all round the world, except in
some places where earthquakes occur rarely.

4. EARTHQUAKE
• An Earthquake is the result of a sudden release of energy in the
earth’s crust that creates seismic waves. The seismic activity of an
area refers to the frequency, type and size of earthquakes
experienced over a period of time.

5. Intensity and magnitude of earthquake
• The intensity and strength of an earthquake is measured on Richter
scale, the scale invented by Charles Richter California ,USA in
1935.which categories earthquake on the basis of energy released.
• Definition: “The logarithm to base ten of the maximum seismic-wave
amplitude recorded on a standard seismograph at a distance of 100
kilometers from the earthquake epicenter.”
Scientists measure the strength of earthquakes using machines known
as seismographs. Seismology is the scientific study of earthquakes and
the propagation of elastic waves through the Earth.

6. Seismometers- The measures of
earthquake
• Seismometers are instruments that measure motions of the ground,
including those of seismic waves generated by earthquakes, volcanic
eruptions, and other seismic sources. Seismometers may be deployed
at Earth's surface, in shallow vaults, in boreholes, or underwater.

8. Seismic waves
• Seismic waves produced due to earthquake are basically divided into two
major types:
• Body waves and
• Surface waves
• Body waves are Primary and secondary waves.
• Primary waves travel faster, move in a push-pull pattern, travel through
solids, liquids and gases, and cause less damage due to their smaller size.
• Secondary waves travel slower, move in an up-and-down pattern, travel
only through solids, and cause more damage due to their greater size.
• A surface wave is a seismic wave that is trapped near the surface of the
earth. A seismic wave that travels across the surface of the Earth as
opposed to through it.

9. Plate boundary related Earthquakes
• Earthquakes occur along fault lines, cracks in Earth's crust where
tectonic plates meet. They occur where plates are subducting,
spreading, slipping, or colliding. As the plates grind together, they get
stuck and pressure builds up. Finally, the pressure between the plates
is so great that they break loose.

10. Tectonic causes of Earthquake
• Structural disturbances resulting in the parts of the lithosphere is the
main cause of this type of earthquake. Most of the disastrous
earthquakes belong to this category and occur in areas of great faults
and fractures. Sudden yielding to strain produced on the rocks of
accumulating stress causes displacements especially along old fault
zones known as great transform faults.

11. Earthquake caused by human activities
• Both the Construction process and water disposal have been shown
to trigger earthquakes. These aren't the only human activities that
can trigger earthquakes, though.
• Scientists point out that earthquakes can also be triggered by other
human activities, such as construction of mega Dams, skyscrapers and
nuclear explosions.

12. Effects of Earthquake
• Loss of life and property
• Damage to transport system i.e. roads, railways, highways, airports,
marine
• Damage to infrastructure.
• Chances of Floods – Develop cracks in Dams
• Chances of fire short-circuit.
• Communications such as telephone wires are damaged. Water
pipes, sewers are disrupted
• Economic activities like agriculture, industry, trade and transport are
severely affected.

13. Ground shaking is the vibration of the ground during an
earthquake.
The primary earthquake hazard is surface rupture. It can be
caused by vertical or horizontal movement on either side of a
ruptured fault.
.

14. Earthquakes can trigger landslides and mudslides, especially
in areas with water-soaked soils. Landslides may result in
falling rocks and debris that collide with people, trees, animals,
buildings and vehicles.
.

15. An earthquake generated within the Pacific Ocean floor will
generate a Tsunami, which is actually a series of very long
waves. Large tsunamis which travel to the ocean floor to the
surface are dangerous to human health, property, and
infrastructure.
• .

16. Earthquake damage facts show fires caused by
earthquakes are the second most common hazard.
Earthquake fires start when electrical and gas lines
are dislodged due to the earth’s shaking.

17. Earthquake Prediction
• Earthquake prediction is usually defined as the specification of the
time , location , and magnitude of a future earthquake within stated
limits.
But some evidence of upcoming Earthquake are following:
• Unusual animal behavior
• Water level in wells
• Large scale of fluctuation of oil flow from oil wells
• Foreshocks or minor shocks before major earthquake
• Temperature change
• Uplifting of earth surface
• Change in seismic wave velocity

18. Earthquake warming system
• Earthquake warming system otherwise known an earthquake early
warning (EEW) system that detects significant earthquakes so quickly
that alerts can reach many people before shaking arrives.
• Earthquake advance warning systems detect the nondestructive
primary waves (P waves) that travel quickly through the earth's crust,
in advance of the destructive secondary waves (S waves). The delay
between the arrival of P waves and S waves controls the amount of
advance warning.

19. Earthquake warming system