Earthquakes occur along fault lines as a result of tectonic plate movement and built up stress being released. They can cause significant damage depending on their magnitude, proximity to populated areas, and local soil and construction practices. Major earthquake zones exist along plate boundaries where tectonic plates converge, diverge, or move past each other. The largest, most destructive quakes occur in subduction zones. To minimize earthquake risk, communities can educate citizens, construct earthquake-resistant buildings, and implement emergency planning and insurance.

1. Earthquake - A Devastating
Hazard
Md Asif Hasan

2. Introduction
Earthquakes are natural geologic events. They may be
described as the vibration in the Earth produced by shock
waves resulting from a sudden displacement along a fault.
They can be catastrophic when the population is huge or
when structures are not built to withstand an earthquake.

3. Most earthquakes occur on faults – areas of broken and
displaced rocks.
Earthquakes may develop from the movement of magma or
sudden ground subsidence.
Earthquakes occur in both oceanic and continental crust at
varying depths.
Occurrence

4. Development of an earthquake
• Built up energy, stress and
strain release on plate
boundaries and faults, via
deformed rock vibrating.
• Initial earthquake rupture
occurs on the fault at the
hypocentre (also known as
focus).
• Movement (slip) occurs
along the whole fault plane
with rapid energy release in
all directions.

5. Geographic Regions at Risk from Earthquakes
• Earthquakes are not randomly distributed
• There are well-defined zones along the boundaries of
Earth’s tectonic plates

6. • Plate Boundary Earthquakes
• Earthquakes occur along all three types of plate boundaries
• Convergent
• Divergent
• Transform
• The world’s greatest earthquakes that happen in the last 100 years have been
along megathrust subduction zones
• These are called megathrust earthquakes
• Intraplate Earthquakes
• Less common
• Can be large and extremely damaging
• They don’t happen often so people are less prepared for them

8. Earthquake Shaking
• Three important factors determine the shaking you will experience
during an earthquake
• Earthquake magnitude
• Your location in relation to the epicenter and direction of
rupture
• Local Soil and rock conditions
• Generally strong shaking may be expected from earthquakes of
moderate magnitude (M 5 – 5.9) or larger
• These types of earthquakes will cause the ground to rock and
roll damaging building and other structures

9. • Regional Changes in Land Elevation
• Includes regional uplift and subsidence of the earth’s surface
• Landslides
• Earthquakes are the most common trigger of landslides
• Can be extremely damaging and cause a large loss of life
• Fires
• Happens when surface is displaced and electrical power and
natural gas pipes break
• Liquefaction
• Shaking of water-saturated material turns clay soil to fluid
resulting in subsidence, fracturing, and horizontal sliding of
the ground surface
Linkages with Other Natural Hazards

10. Four ways the actions of people can cause earthquakes
• Over -Loading the Earth’s crust with building a dam and
reservoir
• Injecting Liquid waste deep water into the ground through
disposal wells
• Creating underground nuclear explosions
• Hydraulic Fracturing-exploring for oil and natural gas
Human Interaction with Earthquakes

11. Minimizing the Earthquake Hazard
Earthquakes cause lots of damage and loss of life. Consequently
there has been research formed with the following goals to minimize
earthquake damage
• Develop and understanding of the earthquake source
• Determine earthquake potential
• Predict effects of earthquakes
• Estimation of Seismic Risk
• Perception of the Earthquake Hazard: Because there aren’t ways
to predict or warn people of earthquakes there are problems with the
perception of and adjustment to the earthquake. Society is vulnerable to
catastrophic loss from large earthquakes due to old buildings, too big of
buildings , and many other problems

12. Community Adjustments to the Earthquake Hazard
Since we can’t avoid living in earthquake prone areas, society needs
to take steps to adjust to the earthquake hazard by doing these
following steps to avoid these hazards
• Facilities which are critical to communities need to located in
safe areas
• The need to build buildings so they don’t fall down and kill
people will make society safer if an earthquake should happen
• Education on what and how to protect yourself during an
earthquake and how to build earthquake safe, decreases the
hazards of earthquakes
• If you are in an earthquake prone area, take get earthquake
insurance,
• Make adjustments to your home to make it earthquake safe and
have a plan if an earthquake happens