This slide is prepared by me under guidance of my teacher Nirmal Kafle for general understanding about Earthquake and Seismicity. I am very thankful to my teacher and friends. I hope this slide may help you to understand about to understand something about Earthquake.

1. PREPARED BY:
Binod Gurung (071BCE09)
(Under guidance of Sir Nirmal Kafle)
Khwopa College of Engineering 1

2.  Shaking of the earth
crust due to the rapid
movement of the outer
layer of the earth.
 Occur when rocks are
stressed beyond their
elastic limits and fail
in the brittle fashion.
2
Tangshan Earthquake

3. Earthquake types distance of focus from
earth surface
1) Shallow earthquake o-70 km
2) Deep earthquake 70-700 km
TYPES OF EARTHQUAKE
3

4.  HYPOCENTER: The location
at which the first breaks
in the rock occurred.
 EPICENTER: The location of
the earth surface directly
above the focus of an earthquake.
 FOCUS: It is the point where
earthquake originates
4

5.  MERCALLI INTENSITY SCALE: Describes the intensity
of an earthquake based on its observed effects.
5
Giuseppe Mercalli
Harry O. Wood Frank Neumann

6. Mercalli intensity Characteristics effects Appxro. Ritcher scale
I-Instrumental Not felt 1
II-Just perceptible Felt by a few person 1.5
III-Slight Felt quite in upper floor 2
IV-Perceptible Indoor more, outdoor few 3
V-Rather strong Felt by nearly everyone 4
VI-Strong Felt by all 5
VII-Very strong Damage may occur in poor
structures.
5.5
VIII-Destructive Damage in ordinary
buildings
6
IX-Ruinous Damage in special design
structures
6.5
X-Disastrous Most structures damaged. 7
XI-Very disastrous Bridges destroyed. 7.5
XII-Catastrophic Total damage 8
6

7.  RITCHER MAGNITUDE SCALE: Describes the
magnitude of the earthquake by measuring seismic
waves.
7
Charles Ritcher

8. Ritcher magnitude scale Release energy (kJ)
1 < 10 to the power 5
2 < 10 to the power 5
3 10 to the power 6
4 10 to the power 7
5 10 to the power 8
6 10 to the power 9
7 10 to the power 11
8 10 to the power 12
Greater than8 10 to the power 13
8

9. 9

10.  INTENSITY: It describes the degree of shaking caused
by the earthquake at a given place and decreases with
increase in distance.
 MAGNITUDE: It is measure of earthquake size and
decreases with increases in distance.
 Increase in one magnitude= 10 times increase in
measured amplitude.
 Increase in one magnitude= 31 times increase in
energy released.
10

11.  Local magnitude (ML):
 Good for earthquake less than 1000 km from the instrument
measuring the earthquake.
 Valid for earthquake less than 6 units of magnitude.
 Body wave magnitude(Mb):
 Based on the amplitude of the P body waves generated by the
earthquake.
 Appropriate for earthquake about 1300 km
 Valid for magnitude less than 6.5 units.
11

12.  Surface wave magnitude(MS):
 Suitable for about 8 magnitude
 Appropriate between 555-19980 km.
 Moment magnitude(Mw):
 Based on actual physical area of moving fault.
 Area(S)=amount of slip(d)*Constant depend on the
rigidity properties of the rocks that slip(u)
Thus, Seismic moment(Mo)=u*S*<d>
 Suitable for any units of magnitude.
12

13. 13
INTENSITY VS MAGNITUDE
MERCALLI INTENSITY RITCHER MAGNITUDE
1) It has a linear scale
prepared by Giuseppe
Mercalli.
1) It has a logarithmic scale
prepared by Charles Ritcher.
2) It is based on the observed
effects .
2) It is based on strength of
the earthquake or seismic
waves.
3)It is expressed in roman
numbers from I to XII.
3) It is expressed in the
decimal numbers from 0 to 10.
4) It is only useful for
measuring earthquake in
inhabited areas.
4) It is useful to measure the
strength of the earthquake at
different times and location.

14. 14
 AMPLITUDE: It is the size of the wiggles on an
earthquake recording.
 SRENGTH: It describes the amount of energy released
at the earthquake focus. Defined by both intensity and
magnitude.
 SEISMIC WAVES: Waves of the energy propagating
through the Earth’s layers, and are the result of the
earthquake, volcano etc.

15. TYPES OF THE SEIMIC WAVES
1) Body wave: Travel through the interior of the body.
a)P-wave: Fastest wave, can move through both rock ad
fluid. Also called compression wave.
15

16. b) S-wave: Slower wave, can pass through solid rock.
16

17. P wave S wave
1. It has compression and dilatation
motion.
1. It has shearing motion.
2. It makes the rock vibrate parallel to
the direction of motion.
2. It makes the rock vibrate
perpendicular to the direction of path.
3. It is very fast travel at a rate of 4-7
km/sec.
3. It travels slower than P wave at about
2-5 km/sec.
4. It can travel through both solid and
fluid.
4. It can passes through solid only.
5. P waves cause less effects. 5. It wave cause more effects.
17

18. 2) Surface wave: Travelling through the crust, lower
frequency than body wave.
a) Love wave: Named after Augustus Edward Hough
Love(British mathematician ), fastest surface wave.
18
A.E.H LOVE

19. b) Rayleigh wave: Named after Lord Rayleigh, rolling
motion
19

20. 20

21. Rayleigh wave Love wave
1. It has rolling motion. 1. It has shearing plus side to side
motion.
2. It is slower than the love wave. 2. It is faster than the Rayleigh wave.
3. It has high intensity. 3. It cause intensity less than Rayleigh
wave.
4. It can propagate through both solid
and water .
4. It can propagate through solid only.
5. It is proposed by lord Rayleigh. 5. It is proposed by A.E.H Love.
21

22.  Seiches: Small Tsunami like. It is the waves sloshing
in the lake as a result of earthquake ground shaking. It
is observed in lake, reservoir etc.
 Seismic hazard: The potential for damaging effects
caused by earthquakes.
 Seismic risk: The chance of injury, damage, or loss
resulting from seismic hazards.
 Surface Faulting: propagation of an earthquake
generating fault rupture.
22

23.  Tectonic subsidence: Down dropping and tilting of
the basin floor on the down dropped side.
23

24.  Caused by sudden slip along the geologic faults.
 Elastic rebound theory(Tectonic cause)
 Proposed by American seismologist Harry
Fielding Reid .
 Explain how energy is spread during earthquake.
 Sudden fault slip due to plate tectonic movement.
 States that rocks under strain suddenly break,
creating the fracture along the fault. Thus fault
slips causing the vibration on the crustal rocks
and releasing seismic waves.
 Describes mechanism of earthquake.
24
Harry Fielding Reid

25. 25
Elastic rebound theory

26.  Non tectonic activities
 Working of heavy machinery in industries.
 Blasting.
 Collapsing of mines.
26

27. 27
 Fire
Great San Francisco

28.  Tsunami/Harbor wave
28
Miyako city street, Japan

29. 29
•Property Damage
China

30. Landslide
30Nepal

31. Volcanic eruption
31

32. GLOF
32

33.  Other Secondary Effects
 Diseases/Pestilences
 Lack of cleaning drinking water
 Lack of food/Famine
Economic loss
33

34.  Public awareness about earthquake.
 Earthquake resisting structures .
 Early warning system.
 Seismic microzonation, Seismic risk assessment and
Seismic hazard analysis.
34

35. Earthquake magnitude Recurrence interval
(years)
5-6 2
6-7 5
7-7.5 8
7.5-8 40
>8 81
35

36.  Seismic gap identification
 Foreshocks
 Dilatancy theory: Dilate through fracture.
 Animal behavior
36

37.  Recurrence interval: Stress uniform so earthquake at
regular interval of time.
Earthquake history of Nepal above 6 or nearly 7
magnitude
Years are 1954, 1962, 1965, 1966, 1980, 1988
Mean of difference of yrs.=X
X= (1962-1954)+(1965-1962)+(1966-1965)+(1980-1966)+(1988-1980)
6
Thus X= 5.67 nearly 6 yrs
S.D.=1.98 nearly 2yrs
Hence, Predicted year=(1988+6) 2 yrs
37


38. 38
Method 1 : Plotting of isoseismal lines

39. 39

40. 40

41. 41
sp
ps
p
VV
VV
t


.
)t(d s
For typical crustal rocks
Vp = 6.5 km/s
Vs = 3.7 km/s
Method 2: Determining Epicentral
distance

42.  PHASE A) INTERSEISMIC
 The time between large earthquake .
 PHASE B) PRESEISMIC
 The time just before an earthquake.
when an anomalous things happen.
 PHASE C) COSEISMIC
 The time during an earthquake.
 PHASE D) POSTSEISMIC
 The time after earthquake when an anomalous things happen.
42

43.  What is earthquake hazard map?
Map showing distribution of earthquake shaking
levels at different area.
 Why it is prepared?
Prepared to provide detail information possible to
assist engineers in designing structures and to update
building codes.
 How it is prepared?
It is prepared with the help of latest technology such
as GIS, remote sensing and photogrammetry.
43

44. ANY QUESTIONS?
44

45. THANKS FOR WATCHING
45
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