2. •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. The devastation of cities and
towns is one of the effects of earthquake.
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3. •What is 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
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4. •Focus(Hypocenter):
•Focus is the point on the fault
where rupture occurs and the
location from which seismic
waves are released.
•Epicenter:
•Epicenter is the point on the
earth’s surface that is directly
above the focus ,the point where
an earthquake or underground
explosion originates.
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5. The primary cause of an earthquake is faults on
the crust of the earth.
•“A Fault is a break or fracture b/w two blocks of rocks in
response to stress.”
❑This movement may occur rapidly, in the form of an
earthquake or may occur slowly, in the form of creep.
❑Elastic Rebound theory
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6. Some major causes of earthquakes on basic of its causes are:
Surface causes (hydrostatic pressure &
Anthropogenic causes)
Volcanic causes
Tectonic causes
•Surface cause:
• Great explosions, landslides, slips on steep coasts, dashing
of sea waves , avalanches , railway trains, heavy trucks, some
large engineering projects cause minor tremors. some of them are
man made, other are natural.
• Hydrostatic pressure ( construction of dams and reservoirs)
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7. •Volcanic cause (Vulcanicity):
• Volcanic eruptions produce earthquakes. Earthquakes may
precede, accompany and frequently follow volcanic eruptions.
• They are caused by sudden displacements of lava within
or beneath the earth crust.
•ELASTIC REBOUND THEORY
•There are two general
categories of earthquakes that
can occur at a volcano:
•
volcano-tectonic
earthquakes
long period earthquakes.
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8. •Tectonic cause:
•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.
•Convergent plate boundaries
•Divergent plate boundaries
•Transform plate boundaries
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9. Primary Waves (P-waves) Secondary Waves(S-wave)
High frequency High frequency
Short Wavelength Short Wavelength
Longitudinal waves Transverse waves
Pass trough both solids and
liquids
Can not move through liquids
Move forwards and
backwards as it compressed
and decompressed
Move in all direction from
their source
P-wave is faster S-wave is more slower than P-
wave
First P-wave arrive After P-wave,S-wave is arrive
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10. • VOLCANIC EARTHQUAKES
– Either accompanying or preceding the volcanic activity
– Deep explosion of gases, emitted form magma
– Hydraulic shocks of magma
•DENUDATION EARTHQUAKES
– Due to collapse
– Collapsing of considerable masses of rocks (mountain
region)
– Sinking of underground cavities (karst caves and large
landslides)
•TECTONIC EARTHQUAKES
– Short relaxations of mechanical stresses
– Reciprocal displacement of individual blocks
(instantaneous displacement)
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11. •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 kilometres from
the earthquake epicentre.”
• 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.
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14. ➢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.
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18. DISTRIBUTION OF EARTHQUAKES
• Circum-pacific belts
– Ring of fire
– Correspond to 68% of all earthquakes
– Majority of them are deep focus variety
– Western coast of N & S America, the Aleutians, Kamchatka, the
Kurills, Japan, the Philippines and strip through the East Indies to
NZ.
• Mid-continental belts or The Mediterranean or
Alpine and Trans Asiatic belt
– Accounts for 21% of all earthquakes
– Extends along the Alpine Mn system of Europe and N Africa,
through Asia Minor and the Caucasus, Iran and Pakistan to the
Himalayan system including Tibbet, the Pamir & China
– Characterized by larger earthquakes but shallow or some
intermediate in origin
– Deep focus earthquakes almost absent
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19. DISTRIBUTION OF EARTHQUAKES
• Mid-Atlantic Ridge Belt
– Shallow variety
– Run from N to S through middle of Atlantic Ocean,
– Along major fracture zone along divergent plate boundaries
• Other belts
– As some distance away from above referred main belts
– Number of mountain structures
– In Mongolia and China,
– the Baikal regions,
– Indian Ocean to the coast of Arabia,
– Eastern parts of Africa and
– South of Malagasy
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23. Date Place Scale Damage
Sept 2,
1993
Latur
(maharashtra)
6.3 Large areas of Maharashtra
rocked. 10,000 people lost
lives.
May 22,
1997
Jabalpur
(Maharashtra)
6.0 40 person killed and over
100 injured.
March 29,
1999
Nandprayag 6.8 widespread destruction in
chamoli , rudraprayag and
other areas. Massive loss of
human life.
Jan. 26,
2001
Bhuj (gujrat) 7.8 Tremors left by India and its
neighboring countries. Over
1 lakh people killed. Huge
loss to property and
infrastructure.
Oct. 8,
2005
Muzzaffarabad
in Pakistan
occupied
Kashmir
7.4 Heavy damage to life and
property.
Death toll about one lakh in
Pakistan and nearly 2000 in
India.
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24. Largest earthquake in the world
Chile : 1960 May 22
19:11:14 UTC
Magnitude 8.9
•More than 2,000 killed, 3,000 injured,
2,000,000 homeless, and $550 million
damage in southern Chile
• tsunami caused 61 deaths
•$75 million damage in Hawaii;
• 138 deaths and $50 million damage in
Japan;
•32 dead and missing in the Philippines;
and $500,000 damage to the west coast of
the United States.
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25. • Date: 26th January ,2001
• Origin line: 08 hrs.46 min. 42.9 sec. IST
• Epicenter: Latitude 23.40° N Longitude 70.28°E
• Magnitude: 7.7
• Focal Depth: 25 kms.
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27. Most Destructive Known Earthquakes on Record in the World
Date Location Deaths Magnitude Comments
May 31, 1970 Peru 66,000 7.9 $530,000,000
damage, great rock
slide, floods.
July 27, 1976 China,
Tangshan
255,000
(official)
7.5 Estimated death toll as
high as 655,000.
Sept 19, 1985 Mexico
Michoacan
9500
(official)
8.0 Estimated death toll as
high as 30,000
Old lake bed magnified
shock waves by 500%
2001 Jan 26 India 20,023 7.7 166,836 injured,
600,000 homeless
.
2004 Dec 26 Sumatra 283,106 9.0 Deaths from earthquake
and tsunami
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28. Landslides: May 30, 1970 Peru disaster
Magnitude: 7.9
•A large mass of ice and rock slid from a
vertical face on Nevado Huascaran, the
highest peak in Peru
•Debris reached a velocity of 280 km/hr
•traveled 11 km horizontally in about 4
minutes at a mean velocity of 165 km/hr.
•Buried the towns of Yungay and
Ranrahirca, The death toll in both
villages was 20,000.
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29. Jun 23, 2001 S.Peru earthquake
Arequipa
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