Earthquake - Pruthvik

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WELCOME
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Pruthvik a m

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BY
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EARTHQUAKES
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DEFINITION An earthquake (also
known as a quake, tremor ) is the result of a
sudden release of energy in the Earth's
Crust that creates Seismic Waves.
The seismicity, seismic activity of an area
refers to the frequency, type and size of
earthquakes experienced over a period of time.
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Asthenoshere

• In Greek Asthen means Weak
• Its presence was suspected as early as 1926, the
  worldwide occurrence of the Asthenosphere was
  confirmed by analyses of Earthquake waves from
  the 9.5 Great Chilean Earthquake of 22 May, 1960.
• It lies below the Lithosphere, at depths between
  80-200km.
• The thickest Asthenosphere is about 700km.
• It is generally in Solid.
• It is situated in the upper part of the Mantle.
• This includes 7 Major 21 Minor plates which
  float on Asthenosphere like a Ship in the Sea.
• The lower boundary of the Asthenosphere is
  dissolved and is not well defined.
• The thickness of the Asthenosphere depend mainly
  on the Temperature.

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EARTHQUAKE IN PHILIPPINES
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Points Of The Earthquake

• Seismos in Greek means an Earthquake.
• The depth of the focus vary from place to place.
• This depth can be even 700km in some places.
• But this depth is just 20-30km in Bihar-Nepal
  border
• There are some waves created by earthquakes. They
  are called Seismic Waves.
• These waves are recorded by an instrument called
  Seismometer with the graph called Seismograph.
• Seismographs record a zig-zag trace that shows
  the varying amplitude of ground oscillations
  beneath the instrument. 
• There are several Seismic Stations that determine
  the time, locations and magnitude of an
  Earthquake with the help of the data recorded.

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Location of Focus and Epicenter
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Seismograph
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Ancient seismograph

• The Ancient Chinese Seismograph was invented by
  Zhang Heng.

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• The Science that deals with the Seismic Waves are
  called Seismology.
• The earthquake Scientists are called
  Seismologists.
• The magnitude or intensity of an earthquake is
  measured in relation to its effects on human
  life.
• The intensity of an earthquake at a specific
  location depends on a number of factors.
• 1) the total amount of energy released,
• 2) the distance from the epicenter
• 3) the type of rocks and the degree of
  consolidation.

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Locating earthquakes

• Every year we hear at least 30,000 Earthquakes
  happening in the World.
• Earthquakes are recorded by a seismic network.
• Each seismic station in the network measures the
  movement of the ground at that site.
• In an earthquake, the slip of a block of rock
  over another releases energy that makes the
  ground vibrate.
• That vibration pushes the adjoining piece of
  ground, causing it to vibrate, and thus the
  energy travels out from the earthquake in a wave.
• As the wave passes by a seismic station, that
  piece of ground vibrates and this vibration is
  recorded.
• Therefore the Earthquake can be detected wherever
  there is measurement of the vibration.

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Richter Scale

• The magnitude or intensity of an earthquake is
  measured by Richter Scale
• This scale was invented by Charles Richter, a US
  Seismologist, in 1935.
• The most destructive earthquake ever recorded had
  a magnitude of 8.9 (Chile, 1960).

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Richter Scale

• Charles Richter

• A Graphic Representation

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Mercalli Scale

• The intensity scale commonly used in United
  Nations in the one named after an italian
  volcanologist Giuseppe Mercalli.
• The values on this scale are given from l to Xll
  in Roman Numerals.
• This values are sometimes felt by no one,
  sometimes everyone and sometimes it can be felt
  by some of the specially designed instruments for
  this purpose.

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GIUSEPPE MERCALLI
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Seismic Waves

• Seismic waves are waves of energy that travel
  through the Earth's layers, and are a result of
  an earthquake , explosion, or a volcano.
• The enormous energy released by an earthquake
  travels through the ground in the form of waves.
• Some waves can make the ground ripple up and
  down, while others can shake it from side to
  side.
• These waves travel in different speeds through
  the interior of the earth.
• These waves start their journey from center
  of the focus.
• There are mainly 3 types of seismic waves.

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1) Primary/Push/Longitudinal Waves

• The velocity of these waves are more and has more
  pressure, so called as P waves or also as
  Pressure waves.
• These waves are fastest travel at a speed of
  6km/second.
• These waves are type of elastic waves.
• The effect/affect of this type of waves is very
  small. Eg Pushing pulling of rocks, stretching
  and squeezing them, etc.
• These waves can move deep into the Earth.
• The velocity of P waves increase with depth, up
  to about 2900km (mantle) below the Surface.
• The velocity of P waves get reduced after this
  layer (mantle).

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2) Secondary/Shake/Shear Waves

• These waves are also the type of elastic waves.
• These waves are unable to pass through Liquid
  substances.
• These waves can also move deep into the Earth.
• The velocity of S waves increase with depth, up
  to about 2900km (mantle) below the Surface.
• The S waves do not pass after this layer because
  liquid is present below this layer.
• Therefore it helped to conclude that Earth
  behaves like a solid up to a depth of about
  2900km from the surface.
• A light wave is a best example of S wave.

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Movement of S P waves
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3) Surface/long wavEs

• It is a type of Mechanical Wave.
• These waves travel along the Earths
  circumference.
• These waves are the last to arrive for Earth.
• These waves cause the most destructive damage on
  the Earth.
• These waves cover longer distances than the other
  waves.
• Therefore these waves are felt at last and last
  to arrive for Earth.
• This is also the reason for these waves to be
  absent in Earths Interior.
• The particles of this wave move in a circular
  path very similar to the water waves.

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Types of waves
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Cause of earthquakes

• Earthquakes are caused by the vibrations caused
  by rocks breaking under stress.
• The underground surface along which the rock
  breaks and moves is called a fault plane.
• A magnitude 8.6 earthquake releases energy
  equivalent to about 10 000 atomic bombs of the
  type developed in World War II.
• Fortunately, smaller earthquakes occur much more
  frequently than large ones and most cause little
  or no damage.
• Earthquake magnitude was traditionally measured
  on the Richter scale.
• It is often now calculated from seismic moment.
• There are several other causes such as below.

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1) Volcanic Activity

• It is known fact that the Earthquake is followed
  by volcanoes and vice-versa.
• The reason for this is, most of the earthquakes
  are along the edges of tectonic plates. This is
  where most volcanoes are too.
• Most earthquakes directly beneath a volcano are
  caused by the movement of magma. The magma exerts
  pressure on the rocks until it cracks the rock.
  Then the magma squirts into the crack and starts
  building pressure again. These earthquakes are
  usually too weak to be felt but can be detected
  and recorded by sensitive instruments. Once the
  pipe of the volcano is open and magma is flowing
  through it, constant earthquake waves,
  called harmonic Tremor, are recorded (but not
  felt).
• The explosive gases try to escape upward by
  pushing the crustal surface from below with
  great force causing the earthquakes.
• The violent eruption of Krakatoa volcano, caused
  such a severe Earthquake, that its impact was
  felt as far away as Cape Horn(some 12,000 km).

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2) Folding Faulting

• A fault is defined as a fracture plane along
  which the rocks have been displaced. There are
  vertical as well as horizontal displacements.
  Earthquakes are caused due to sudden movements of
  rocks along faults. 
• The Earthquakes caused by faults are called
  Tectonic Earthquakes.
• The horizontal as well as vertical movements of
  rocks result from the operation of endogenetic
  forces beneath the earth's surface. It is due to
  such movements that folds and faults are created.
• The sudden dislocation of rock blocks, due to the
  forces of tension and compression, causes
  Earthquakes.
• The most destructive Californian earthquake of
  1906 was caused by the movement of rocks along
  the great San Andreas Fault. It is interesting to
  note that the visible displacements were
  traceable along the fault line for about 480 km,
  and its shock was felt over a distance of more
  than 11200 km in the direction of the fault.

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3) Hydrostatic pressure anthropogenic causes

• Most of the Earthquakes are caused by the forces
  coming from within the Earth.
• Certain human activities such as pumping of
  ground water and oil, deep underground mining,
  blasting of rocks by dynamites for the
  construction of dams/reservoirs/roads, nuclear
  explosion, storage of huge volume of water causes
  tremors.
• The intensity of an Earthquake has been
  positively co-related with the level of water in
  the Reservoir.
• These human activities causes tremors of very
  serious consequences.
• Earthquake in the region of Koyna dam is one of
  the examples.

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4) Plate Tectonic Theory

• The outer layer of the earth is divided into many
  sections known as plates, which are floating on
  the molten magma beneath the earths crust called
  Plates.
• These plates are the bases on which the
  continents stand.
• Most of the earthquakes occur on the edges of the
  plates where a plate is under, on or across
  another plate.
• This movement disrupts the balance and position
  of all plates, which leads to tremors, which are
  called earthquakes.
• It is believed according to the recent researches
  that all the plates are moving apart at the rate
  of 10cm per Year.
• The tectonic events are taking place at the
  borders of these plates.
• Folding, Faulting Transform faults along the
  Convergent, Divergent or conservative plate
  boundaries are the major Tectonic events
  associated with these plate boundaries.

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DISTRIBUTION OF EARTHQUAKES

• The Frequency of less destructive Earthquakes is
  more than the violent Earthquakes.
• Most Earthquakes in the world are associated with
  
• 1) The zones of Young Fold Mountains,
• 2) The zones of Faulting Folding,
• 3) The zones of Active Volcanoes,
• 4) The zones representing the junctions of
  continental and oceanic margins,
• 5) Along the different plate boundaries.
• 6) In the main Seismic Belts.

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1) circum-pacific Belt

• This belt is popularly known as the Ring of Fire.
• It is the largest seismic belt in the World.
• This belt accounts for more than 75(including
  Dormant volcanoes) of the Worlds earthquakes.
• This belt covers the Eastern Western Margins of
  the Pacific Ocean.
• Its shape is Horse-shoe and covers the area of
  about 40,000km (25,000 miles).
•  It is associated with a nearly continuous series
  of oceanic trenches, volcanic arcs, and volcanic
  belts and/or plate movements.
• The eastern section of the ring is the result of
  the Nazca Plate and the Cocos Plate being subducte
  d beneath the westward moving South American
  Plate.
• The origin of this belt is the Mt.Erebus of
  Antarctica and runs Northward through Andes of
  South America and Rockies of North America to
  reach Alaska. Then it turns Eastwards along the
  coast of Asia to include the volcanoes of
  Shakaline (Japan), Kamchatka (Philippines) and
  merges with Mid-Continental belt in Indonesia.

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• It has 4 ideal conditions for the occurrence of
  earthquakes.
• 1) The junction of Continental Oceanic Margins,
• 2) The zone of Young Fold mountains,
• 3) The zone of Active Volcanoes,
• 4) The subduction zone of Convergent plate
  boundaries.
• As this belt has very large continental extent,
  we can divide it as Western Eastern Marginal
  zones.
• Western Marginal zones - Rockies Andes
  Mountain Chains (these are also the zones of
  convergent plate boundaries).
• In Western USA lies the  Cascade Volcanic Arc.
• This Arc includes nearly 20 major volcanoes,
  among a total of over 4,000 separate volcanic
  vents including numerous strato volcanoes, shield
  volcanoes, lava domes, and cinder cones, along
  with a few isolated examples of rarer volcanic
  forms such as Tuyas.
• Eastern Marginal Zones Island Arcs of
  Kamachatka, Sakhalin, Japan and Philippines.
• The Earthquakes in this zone is caused by the
  collision of the pacific the Asiatic plates.
• Japan records for more than 1500 Earthquakes per
  Year.

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2) Mid-continental belt

• This belt includes Alpine mountains and their
  offshoots in Europe, Mediterranean Sea, Northern
  Africa, Eastern Africa,Indian Himalayas, through
  Asia minor, Caucasia, Iran, Afghanistan and
  Pakistan and further to Tibet, the Pamirs and the
  mountains of Tien Shah, etc
• About 21 of the total Seismic activities occur
  in this belt.
• The Himalayan region is in the subduction zone of
  Asiatic Indian plates and has great Intensity.
• Most of the Earthquakes in India, Nepal and Tibet
  are experienced due to the gradual rise of
  Himalayas at the rate of 5cm per year.
• The origin of this belt is from Italy and
  slightly continues in Mediterranean Sea.
• The most glaring minor Earthquake is the Koyna
  Earthquake which shook Koynanagar on September 13
  and 14, 1967.

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3) MID-atlantic BELT

• This belt mainly includes the Ridge along the
  Mid-Atlantic.
• It records Moderate Earthquakes which are caused
  due to Divergent Plates.
• The origin of this belt starts near Greenland in
  North Atlantic Ocean, travels through the
  Mid-Atlantic Ridge and ends very near to the
  Antarctica.
• The occurrence of the Earthquakes can be
  explained when it occurs in the Plate Boundaries,
  but failed to be explained when the Earthquakes
  occurs Interior to the plates.
• The Seismic activities of the Indian Shield in
  Kachchh (1819), Koyna (1967), Bhadrachalam (1969)
  and Bharuch (1970) cannot be explained due to the
  same reason.
• It has least number of Seismic activities
  happening per year.

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Effects of Earthquake

• The intensity of an Earthquake is determined by
  the damage caused and not the basis of Richter
  Scale.
• There are many effects out of which following are
  main effects.
• 1) Deformed (spoil the shape of) Ground Surface
• 2) Damage to Man-made Structures
• 3) Loss of Human and Animal Life
• 4) Devastating Fires Vibrations of Earthquake
  can catch fire
• 5) Landslides
• 6) Flash Floods Tremors in dams, etc
• 7) Tsunamis

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Earthquake belts in india

• According to Seismologists Earthquakes are very
  rare in Disastrous way.
• About Two-Thirds experiences Earthquakes in
  India.
• There are 3 Zones of Earthquake.
• 1) Himalayan Zone
• The Fold mountain regions of the Himalayan zone
  are most experienced with Earthquakes.
• It is believed that Indian Plate is moving
  towards the Asian plate at the rate of 10cm per
  year.
• 2) Indo-Gangetic Zone
• Most of the Earthquakes here are in the moderate
  way (6-6.5 Magnitude on Richter Scale).
• Sometimes at the Foothills the Intensity can be
  more.
• Here the Earthquakes are more harmful due to very
  huge Population.

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• 3) The Peninsular Zone
• Earthquakes are believed to be few in number.
• But some Earthquakes like in Koyna (1967), Latur
  (1993), Jabalpur (1997) and Bhuj (2001) make us
  feel that severe Earthquakes can take place in
  any time in this Zone.
• Based on Mercalli Scale, the Indian Standard
  Institution (ISI) has divided India into 5
  seismic zones.
• Zone 1 Intensity/Magnitude 5 or below
  (Moderate)
• Zone 2 Intensity 6 (Strong)
• Zone 3 Intensity 7 (Very Strong)
• Zone 4 Intensity 8 (Destructive)
• Zone 5 Intensity 9 above (Very Disastrous)

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10 MOST DISASTOUS EARTHQUAKES

• 1) Chile 22 May, 1960 Magnitude 9.5
• 2) Prince William Sound, Alaska 28 March, 1964
  Magnitude 9.2
• 3) Off the West Coast of Northern Sumatra 26
  December, 2004 Magnitude 9.1
• 4) Kamchatka 4 November, 1952 Magnitude 9
• 5) Africa, Peru (now part of Chile) 13 August,
  1868 Magnitude 9
• 6) North Pacific coast of America 26 January,
  1700 Magnitude 9 (estimated).
• 7) Off Bio-Bio, Chile 27 February, 2010
  Magnitude 8.8
• 8) Coast of Equador 13 January, 1906
  Magnitude 8.8
• 9) Lisbon 1 November, 1755 Magnitude 8.7
• 10) Assam Tibet 15 August, 1950 Magnitude
  8.6

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10 most disastrous Earthquakes (india)

• 1) Maldives 26 December, 2004 Magnitude 9.3
• 2) Arunachal Pradesh 15 August, 1950
  Magnitude 8.5
• 3)Gujarat 16 June, 1819 Magnitude 8.2
• 4) Andaman Islands 26 June, 1941 Magnitude
  8.1
• 5) Shillong 12 June, 1897 Magnitude 8.1
• 6) Andaman Islands 31 December, 1881
  Magnitude 7.9
• 7) Himachal Pradesh 4 April, 1905 Magnitude
  7.8
• 8) Andaman Islands 10 August, 2009 Magnitude
  7.7
• 9) Gujarat 26 January, 2001 Magnitude 7.65
• 10) Kashmir 8 October, 2005 Magnitude 7.6

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Thank you