Earthquake 1.Interior of earth 2.Convection currents cause the movement of plates 3.Tectonic Plate 4.Why do earthquakes occur? 5.Where do earthquakes occur. 6.Definitions 7.Seismic waves: forms 8.Measuring earthquakes 9.Classification of earthquake 10.Locating the shaking 11.Earthquake risk and prediction 12.Short-term predictions 13.Impacts of Earthquake Prediction

1. Earthquake
Prepared by,
Sujith Velloor S
Lecturer
Civil Department
Engineering College
Tuwa

2. Outline
1. Interior of earth
2. Convection currents cause the movement of plates
3. Tectonic Plate
4. Why do earthquakes occur?
5. Where do earthquakes occur.
6. Definitions
7. Seismic waves: forms
8. Measuring earthquakes
9. Classification of earthquake
10. Locating the shaking
11. Earthquake risk and prediction
12. Short-term predictions
13. Impacts of Earthquake Prediction

3. Interior of earth
 1. Crust
 2.Mantle
 3. Core

4. Crust
 It is lithosphere thinnest outer solid shell about(5-
40km)
 There are 2 different type of crust
1.thin oceanic crust that underlines the ocean
basin
2.Thicker Continental crust that underline
continents
There are 2 different type of crust are made up of
different type of rock
Oceanic crust Basalt(3-4 mile)
Continental crust Granite (20-30 mile)

5. Mantle
 It is Asthenosphere about
a thickness of 2900km
 Mantle contain hot dense,
ultra basic igneous rocks in
plastic state
 It has the property to flow
 It has different
temperature at different
depths

6. Core
 It is Barosphere Central part of earth
 There are 2 different type
Inner Core(1290km)
Outer Core(2200km)
Temperature at the core is about 2500 degree
Celsius

7. Convection currents cause
the movement of plates
 Convection Current Occur in mantle
because of high temperature & pressure
Gradient Between Core and Crust
 It occur result in a circulation of earth mass,
Hot molten lava comes out & cold Rocks
goes into earth where it melt & become a
part of mantle
 Potential Energy (PE) builds up
 PE may be released as KE and the plates
move abruptly apart
 This sudden release of energy is an
earthquake

8. Convection current of mantle causes
slide mantle on core This sliding of earth
mass is called Tectonic Plate
Tectonic Plate

9. Tectonic Plate

10. Why do earthquakes
occur?
 Fractures, faults
 Energy released
and propagates in all
directions as seismic
waves causing
earthquakes
focus
epicenter

11. The shaking of ground or Vibration
caused by slip or volcanic or magmatic
activity or sudden stress changes in
earth are called Earthquake

12. Where do earthquakes
occur:
1) Most earthquakes occur
along the edge of the
oceanic and continental
plate
2) Along faults: normal, reverse,
transform
3) Between the Tectonic plate
4) Focus is the location for
earthquake origin

13. Definitions
 Earthquake = Vibration of the Earth
produced by the rapid release of
energy
 Seismic waves = Energy moving
outward from the focus of an
earthquake
 Focus= location of initial slip on the
fault; where the earthquake origins
 Epicenter= spot on Earth’s surface
directly above the focus

14. Seismic waves: forms
 P-waves: (primary or first)
 called compressional, or push-pull waves
 Propagate parallel to the direction in which the wave is moving
 Move through solids, liquids
 Fastest moving – reach seismic station first
 S-waves: (secondary)
 Called shear waves
 Propagate the movement perpendicular to the direction in which the
wave is moving
 Reach seismic station second

15. Longitudinal wave
P-waves
Sound waves
Transverse wave
S-waves
Light waves

16. Surface waves (Love waves & Rayleigh
Waves).
1. Love Waves
- Moves in Horizontal and
transverse plane
- They are fastest waves than
Rayleigh waves
-They Create Breaking
Rupture
2. Rayleigh Waves
-Moves as oscillation
-Waves are produced as when rock
thrown in pond
-Waves are produced by intersection
of p and s waves

17. •b
•a
Which diagram shows a transverse wave and a longitudinal
wave?
an s-wave and a p-wave?

18. Measuring earthquakes
 Seismometers:
instruments that
detect seismic
waves
 Seismographs
Record intensity, height
and amplitude of seismic
waves

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

22. Locating the shaking

24. Earthquake size: two ways
to measure
1) Magnitude: Richter Scale
• Measures the energy released by fault movement
• related to the maximum amplitude of the S wave
measured from the seismogram
• Logarithmic-scale; quantitative measure
• For each whole number there is a 31.5 times
increase in energy
 eg. an increase from 5 to 7 on the Richter scale = an
increase in energy of 992 times!!

25. 2) Intensity: Mercalli Scale:
 What did you feel?
 Assigns an intensity or rating to measure an
earthquake at a particular location (qualitative)
 I (not felt) to XII (buildings nearly destroyed)
 Measures the destructive effect
 Intensity is a function of:
 Energy released by fault
 Geology of the location
 Surface substrate: can magnify shock waves e.g. Mexico City (1985)
and San Francisco (1989)

26. Classification of
earthquake
 Classification based on Location
1. Interplate earthquake:-boundary
layer(99%)
2. Intraplate earthquake:- Away from
boundary layer(1%)
Classification based on Focal Depth
1. Shallow earthquake:- <70km
2. Medium earthquake:- 70km-300km
3. Deep earthquake:- >300km

27. Classification based on Magnitude
1. Great-8 or above
2. Major-7-7.9
3.Strong-6-6.9
4. Moderate-5-5.9
5. Light-4-4.9
6. Minor-3-3.9
7.Very Minor-<3
Classification based on Epicentral
distance
1.Local Earthquake:- <1degree
2.Regional Earthquake:-1 to 10 degree
3.TeleSeimic Earthquake:- >10 degree

28. 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.

30. Earthquake damage
 Ground Failure - constructions collapse
 Fires - from broken gas and electrical lines
 Landslides - EQ's triggered; occur in hilly/mountainous areas.
 Liquefaction - water-saturated, unconsolidated materials flow
 Tsunami (seismic sea waves; "tidal" waves) - can grow up to 65
m

31. Earthquake risk and prediction
 Long-term methods
1) seismic hazard maps
2) probability analysis
based on:
- historical EQ records
- geologic EQ records
- slip-rate on active faults
- frequency and
magnitude of recent EQ's
Real-time 24 Hour
Forecast

32. Short-term predictions
Precursor phenomena (<1 year to days)
1. Foreshocks: usually increase in magnitude
2. Ground deformation
3. Fluctuations in water well levels
4. Changes in local radio wave characteristics
5. Anomalous animal behavior???

33. Impacts of Earthquake Prediction

34. THANKING YOU