earthquakes – the result of geomorphology

WELCOME TO OUR WELCOME TO OUR PRESENTATIONPRESENTATION

ONON

EARTHQUAKES – THE RESULT OF GEOMORPHOLOGY

PRESENTED BY:

Engr. Souptik Barman Tirtha

Engr. Johana Sharmin

Thank you Sir for the opportunity and It is

really honor to present an enriched topics for the nourishment of our

knowledge

BIG BANG THEORY- ORIGIN OF THE UNIVERSE

• The Big Bang theory is basically an effort to explain what happened at the very beginning of our universe.

• According to the theory, our universe sprang into existence as singularity around 13.7 billion years ago. A singularity is a point where the predictable nature of physics breaks down. They are thought to exist at the core of black holes.


• Black holes are areas of intense gravitational pressure. The pressure is thought to be so intense that finite matter is actually squished into infinite density. These zones of infinite density are called "singularities”. This point is also called in some theories ‘the cosmic egg’.


• After the initial appearance of our universe as singularity, it apparently inflated. The violence of the explosion was so great that matter of the cosmic (space) egg was reduced to subatomic particles, which soon reassembled to form only two elements hydrogen and helium. These gases comprised the interstellar clouds, which appear often as blotches of light and dark.

FORmATION OF SOlAR SYSTEmS (SUN ANd plANETS)

• Our solar system may have begun when interstellar gas started to condense as a result of gravity and became concentrated enough to form the Sun and planets.

• The expanding cloud gradually lost its homogeneity as it was drawn into many smaller gas clouds, each held together by its own gravitational attraction.


• The collapse in smaller particles is initially slow, but it accelerates and the cloud soon becomes much denser at its center.

• The disk of dust and gas that formed the Sun and planets is known as the solar nebula.

• As these Smaller gas clouds concentrated, their central cores were gradually heated by compression.


• When a temperature of approximately 11 million degree Celsius was reached, thermonuclear fusion was spontaneously initiated, and the SUN was born.


• As the disk began to cool, different elements and compounds were able to condense depending on their distance from the Sun which impacted the compositions of the forming planets.

• Planets may have been formed by the Accretion Theory.


• Refractory elements, such as iron, comprise the terrestrial planets, which are close to the Sun. Volatile elements, such as ices and gases like hydrogen, comprise the planets further from the Sun, where it is cool.

OTHER THEORIES STATING ABOUT ORIGINATION OF THE UNIVERSE

• Geocentric Theory: by PtolemyHe assumed that the Earth was motionless and all other objects they could see were moving around the Earth.

• Heliocentric Universe: by Nicolas CopernicusThe Sun is the center of the Universe.

• The steady state theory: by Herman Bondi, Thomas Gold and Fred HoyleThe theory states that matter is being continuously created, at the rate of a few hundred atoms per year. This would allow the density of the universe to remain constant as it expands.

OTHER THEORIES STATING ABOUT ORIGINATION OF THE UNIVERSE

• Freidman's Universe: by Alexander Freidman

The Friedman universe begins with a Big Bang and continues expanding for untold billions of years (that’s the stage we’re in now.) But after a long enough period of time, the mutual gravitational attraction of all the matter slows the expansion to a stop.” The universe will eventually start to contract in a big crunch.

Theories of origin of solar system and earth

In general, theories of the origin of the solar system (and the earth) can be divided in to two groups. These are:

A. Evolutionary theories, and

B. Catastrophic theories

A.Evolutionary Theories• Evolutionary theories refer to those theories which

suggest that the planets including the earth were formed during the evolutionary formation process of the sun.

B. Catastrophic Theories• Refer to those theories which suggest that planets were

formed by some special accident or catastrophe, such as the close approach or collision of two stars.

FORmATION OF ATmOSpHERE OF plANET EARTH

• The early atmosphere of The early atmosphere of Earth would have been Earth would have been similar to the Sun--mainly similar to the Sun--mainly hydrogen and helium, but hydrogen and helium, but this atmosphere was lost this atmosphere was lost quickly:quickly:

The gravity of the modest The gravity of the modest size earth was not strong size earth was not strong enough to prevent such enough to prevent such light gases from escaping light gases from escaping to space. to space.


It appears that around 30 It appears that around 30 million years after the earth’s million years after the earth’s formation, it was struck by a formation, it was struck by a large object.large object.

The result: the origin of the The result: the origin of the moon and loss of earth’s moon and loss of earth’s early H, He atmosphere.early H, He atmosphere.

FORmATION OF ATmOSpHERE OF plANET EARTH (SEcONd ATmOSpHERE)

• A new atmosphere was A new atmosphere was established by the out gassing established by the out gassing of volcanoes. The mixture of of volcanoes. The mixture of gases was probably similar to gases was probably similar to those of today’s volcanoes:those of today’s volcanoes:

HH220 vapor (roughly 80%)0 vapor (roughly 80%)

COCO22 (roughly 10%) (roughly 10%)

NN22 (few percent) (few percent)

Small amounts of CO, HCL, Small amounts of CO, HCL, HS (Hydrogen Sulfide), SOHS (Hydrogen Sulfide), SO22, , CHCH44 (Methane), Ammonia (Methane), Ammonia (NH(NH33), and other trace gases.), and other trace gases.


• Virtually no oxygen in that Virtually no oxygen in that second atmosphere.second atmosphere.

• With a huge influx of water With a huge influx of water vapor and the cooling of the vapor and the cooling of the planet, clouds and earth’s planet, clouds and earth’s oceans formed.oceans formed.

• At that time the sun was about At that time the sun was about 30% weaker than today. Why 30% weaker than today. Why didn’t the earth freeze over?didn’t the earth freeze over?

• The apparent reason: so much The apparent reason: so much COCO22 so there was a very strong so there was a very strong greenhouse effect.greenhouse effect.

FORmATION OF ATmOSpHERE OF plANET EARTH (THIRd ATmOSpHERE)

• In the first two billion In the first two billion years of the planet’s years of the planet’s evolution, the atmosphere evolution, the atmosphere acquired a small amount acquired a small amount of oxygen, probably by the of oxygen, probably by the splitting of water splitting of water molecules by solar molecules by solar radiation.radiation.

• With the rise of With the rise of photosynthetic bacteria photosynthetic bacteria and early plants, oxygen and early plants, oxygen levels began to rise levels began to rise rapidlyrapidly..

Figure depicting that, Between 2.5 Figure depicting that, Between 2.5 billion years ago to about 500 by, billion years ago to about 500 by, 0022 rose to near current levels. rose to near current levels.


• While OWhile O22 was increasing, CO was increasing, CO22 decreased due to several decreased due to several reasons:reasons: In photosynthesis COIn photosynthesis CO22 is used to produce organic matter, some is used to produce organic matter, some

of which is lost to the system (e.g., drops to the bottom of the of which is lost to the system (e.g., drops to the bottom of the ocean or is buried)ocean or is buried)

Chemical weathering, which removes COChemical weathering, which removes CO22

• More Changes:More Changes:Sulfur compounds were taken out of the atmosphere as acid rain Sulfur compounds were taken out of the atmosphere as acid rain

and were deposited on the ground as sulfates.and were deposited on the ground as sulfates.N2 gas increased slowly but progressively since it was relatively N2 gas increased slowly but progressively since it was relatively

inert.inert.


• Problems occurred due to lower of Carbon DioxideProblems occurred due to lower of Carbon Dioxide With lower CO2 levels the earth became more susceptible to ice With lower CO2 levels the earth became more susceptible to ice

ages when solar radiation decreases due to orbital variations,ages when solar radiation decreases due to orbital variations, It appears that around 750-550 million years ago the earth It appears that around 750-550 million years ago the earth

cooled down and became nearly entirely glaciated. cooled down and became nearly entirely glaciated. • How Did we get unfrozen?How Did we get unfrozen?

Much of the variability forced by changing solar radiation due Much of the variability forced by changing solar radiation due to periodic changes in the earth’s orbital characteristics and tilt to periodic changes in the earth’s orbital characteristics and tilt (Milankovitch cycles) and major volcanic eruptions putting out (Milankovitch cycles) and major volcanic eruptions putting out massive CO2 that caused greenhouse effect and the earth massive CO2 that caused greenhouse effect and the earth warmed up.warmed up.

Once warming started it would have happened very rapidly.Once warming started it would have happened very rapidly.• Current composition of the atmosphere was established Current composition of the atmosphere was established

approximately a billion years ago.approximately a billion years ago.

GEOmORpHOlOGY

• The word “geomorphology" comes from the Greek roots "geo,“ “morph,” and “logos”, meaning “earth,” “form,” and “study,” respectively. Therefore, geomorphology is literally “the study of earth forms.”

• It is science that treats the general configuration of the earth's surface in terms of the classification and description of the nature, origin, and development of landforms and their relationships to underlying structures, and the history of geologic changes.

GEOmORpHOlOGY ANd ITS THEORY dERIVEd FROm HUmAN HISTORY

• Supernatural Intervention

Throughout most of human history, natural phenomena have been interpreted through myths and legends to be the result of supernatural intervention.

– Volcanoes and earthquakes are caused by angry gods and/or devils.

– Fossils placed by the devil to confuse man.

GEOmORpHOlOGY ANd ITS THEORY dERIVEd FROm HUmAN HISTORY

• Creationism

Creationism is the theory that all earth’s features, from grains of sand to mountain ranges, were designed and created individually by God.

GeomorpholoGy and its theory derived from human history

• Catastrophism

Early ideas considered geological features, such as mountain ranges, to have been created through sudden, catastrophic, events.

• UniformitarianismUniformitarianism is the idea that the same physical, chemical, and biological processes operating on and in the earth today were also active in the past and that, therefore, all geologic phenomena can be explained as natural occurrences.

GeomorpholoGy and its theory derived from human history

• Shrinking Earth Theory

The ocean floor and continents are both ancient and are fixed in their positions. Mountain ranges formed through crustal contraction during gradual cooling of a molten planetary surface. Crustal folding and sea-level changes are due to cooling and contraction of the earth's interior.

internal structure of earth


Core• Composed mostly of iron and nickel • Divided into

Inner core –about 1,200 km thick –solid layerOuter core–about 2,100 km thick–liquid layer

• Temperature between 3,000 C ⁰and 5,000 C⁰


Mantle• Mostly solid rock (flows under high temperature and pressure)• 2,900 km thick • Divided into upper mantle and lower mantle. Upper mantle is comprised of

– a layer of solid rock + asthenosphere

•Temperature between 800 C and ⁰3,000 C ⁰


Crust• Outermost layer on which we live

•Continental Crust

– thick (10-70km)

– buoyant (less dense than oceanic crust)

•Oceanic Crust

– thin (~7 km)

– dense (sinks under continental crust)


• The outermost part of the Earth's interior is made up of two layers: above is the lithosphere, comprising the crust and the rigid uppermost part of the mantle. Below the lithosphere lies the asthenosphere. When the rocks in the lithosphere melt, hot molten rock called magma is formed.

http://en.wikipedia.org/wiki/Lithosphere

http://en.wikipedia.org/wiki/Crust_(geology)

http://en.wikipedia.org/wiki/Earth's_mantle

http://en.wikipedia.org/wiki/Asthenosphere

PLATE TECTONICS

• Plate tectonics is the process by which rock material is moved from within the earth to its surface and, in some cases, back to its interior and by which the lithosphere is broken into a series of plates that move with respect to one another.

PLATE TECTONICS

• The theory of plate tectonics tells us that the Earth's rigid outer shell (lithosphere) is broken into a mosaic of oceanic and continental plates that can slide over the plastic aesthenosphere.

• The plates are in constant motion. • There are seven major crustal plates, subdivided into a number

of smaller plates • They are about 80 kilometers thick, moving relative to one

another at rates varying from 1 to 13 centimeters per year.

• Their pattern is neither symmetrical nor simple. Several different landform features found on our planet - mountains, rift valleys, volcanoes, earthquakes, faulting - are the result of geologic processes that occur where plates interact.

WHY DO PLATE TECTONICS MOVE

.Convection currents•Convection currents are movements of heat within the mantle.

WHY DO PLATE TECTONICS MOVE

Slab-pull force•This occurs when an oceanic plate (denser) sub ducts under a less dense plate and pulls the rest of the plate along.

PLATE TECTONICS = CONTINENTAL PLATE TECTONICS = CONTINENTAL DRIFT + SEA FLOOR SPREADINGDRIFT + SEA FLOOR SPREADING

CONTINENTAL DRIFT THEORYCONTINENTAL DRIFT THEORY

• In the early 1900's Alfred Wegener proposed the idea of Continental Drift.

• His ideas centered around continents moving across the face of the earth.

• Pangea was the supercontinent that existed 250 million years ago during the Paleozoic and Mesozoic eras.

CONTINENTAL DRIFT THEORYCONTINENTAL DRIFT THEORY

EVIDENCE FOR CONTINENTAL DRIFTEVIDENCE FOR CONTINENTAL DRIFT

PUZZLE-LIKE FIT THE CONTINENTSPUZZLE-LIKE FIT THE CONTINENTS

SOUTH AMERICA

AFRICA

COAST LINE FIT

COAST LINE FIT

FOSSIL CLUESFOSSIL CLUES

CLIMATE CLUESCLIMATE CLUES

ANCIENT GLACIATIONS

PRESENT GLACIATIONS

ROCK CLUESROCK CLUES

ANCIENT MOUNTAINS PRESENT MOUNTAINS

SEA FLOOR SPREADINGSEA FLOOR SPREADING

Atlantic 65 m.y. ago Present Day Atlantic

NAME OF TECTONIC PLATESNAME OF TECTONIC PLATES

Intermediate Plates: Caribbean, Cocos, Nazca, Arabian, Phillippine, Juan de Fuca and Scotia

PLATE BOUNDARIES - TYPESPLATE BOUNDARIES - TYPES

• Divergent boundaries or constructive plate margin-- where new crust is generated as the plates pull away from each other.

• Convergent boundaries or destructive plate margin-- where crust is destroyed as one plate dives under another.

• Transform boundaries or conservative plate margin -- where crust is neither produced nor destroyed as the plates slide horizontally past each other.

PLATE BOUNDARIES - TYPESPLATE BOUNDARIES - TYPES

PLATE BOUNDARIES – TYPESPLATE BOUNDARIES – TYPES

Types of movement

Types of plates Landforms Examples

Divergent - plates move away from each other

Oceanic-oceanic plate divergence Oceanic ridges Mid-Atlantic Ridge

Continental-continental plate divergence Rift valley, volcanoes

The Great Rift Valley, Cascade

Range

Convergent - plates move

towards each other

Oceanic–oceanic plate convergence

Oceanic trenches, volcanoes, island arc

Mariana Trench, Mount Etna, Mariana

Islands

Continental–oceanic plate convergence

Ocean trenches, mountain ranges

Sunda Trench, Barisan Mountains

Continental–continental plate convergence

Mountain ranges Himalayas

Transform - plates move past each

other

Continental-continental plates sliding past each other

NoneSt Andreas Fault,

North Anatolian Fault

PLATE BOUNDARIES – DIVERGENTPLATE BOUNDARIES – DIVERGENT

Boundary between two plates that are moving apart or rifting

Oceanic – Oceanic Plate Divergence• Magma rises from the mantle to fill the gap between the plates

as they diverge. • New sea floor is formed when the magma cools and solidifies.

This process is called sea-floor spreading. • Magma rises at the zone of divergence zone to form a ridge of

new ocean floor called mid-oceanic ridge.

• E.g. the Mid-Atlantic Ridge is found in the middle of the Atlantic Ocean cutting across Iceland.


WORLD DISTRIBUTION OF MID-OCEANIC RIDGESWORLD DISTRIBUTION OF MID-OCEANIC RIDGES


MID-ATLANTIC RIDGEMID-ATLANTIC RIDGE

• Map showing the Mid-Atlantic Ridge splitting Iceland and separating the North American and Eurasian Plates.

• The section of the ridge that includes the island of Iceland is also known as the Reykjanes Ridge. The average spreading rate for the ridge is about 2.5 cm per year.


Continental–Continental plate divergence• Can result in the breakup of continents • E.g. Great Rift Valley (East Africa)

– formed by Somalian boundary of the African Plate moving away from the Nubia plate boundary of the African Plate

– Can result in the formation of linear sea

– E.g. Red Sea and Gulf of Aden near the Great Rift Valley

PLATE BOUNDARIES – CONVERGENTPLATE BOUNDARIES – CONVERGENT

• destructive plate boundary is an actively deforming region where two or more tectonic plates or fragments of the lithosphere move toward one another and collide.

• As a result of pressure, friction, and plate material melting in the mantle, earthquakes and volcanoes are common near convergent boundaries.

• When two plates move towards one another, they form either a subduction zone or a continental collision.

• When the rate of plate convergence is high, a trench is formed at the boundary between plates. Earthquakes are generated at the interface between the subducting and overriding plates.


1. Oceanic-Continental

Oceanic plate sub ducts due higher density

2. Oceanic-Oceanic

they typically create an island arc, deep oceanic trench

3. Continental-Continental

Himalayas


Oceanic – Oceanic Plate Convergence• When two oceanic plates converge, one subducts under the other,

creating a deep oceanic trench.• The subduction of the oceanic plate causes the solid mantle

material to melt and magma is formed.• The magma rises through the mantle and ocean floor to emerge as

volcanoes.• Eventually a chain or arc of islands called island arc is formed.


FORMATION OF MARIANA TRENCH• The Pacific plate is subducted beneath the Mariana Plate, creating

the Mariana trench, and (further on) the arc of the Mariana islands, as water trapped in the plate is released and explodes upward to form island volcanoes.


Continental –Continental Plate Convergence• Plates made largely of continental crust may collide with other

plates made largely of continental crust. • Instead, the plates break, slide along fractures in the crust and fold,

forming fold mountains.

• E.g. the Himalayas - convergence of the Indian Plate and the Eurasian Plate.


FORMATION OF HIMALAYA• About 225 million years ago,

India was a large island still situated off the Australian coast, and a vast ocean (called Tethys Sea) separated India from the Asian continent.

• When Pangaea broke apart about 200 million years ago, India began to forge northward.

• About 80 million years ago, India was located roughly 6,400 km south of the Asian continent, moving northward at a rate of about 9 m a century.


FORMATION OF HIMALAYA• When two large landmasses,

India and Eurasia, driven by plate movement, collided.

• Because both these continental landmasses have about the same rock density, one plate could not be subducted under the other.

• The pressure of the impinging plates could only be relieved by thrusting skyward, contorting the collision zone, and forming the jagged Himalayan peaks.


Continental –Oceanic Plate Convergence• The magma rises through the mantle and crust to emerge as

volcanoes on land.• The edge of thick continental plate buckles to form fold

mountains.


FORMING SUNDA TRENCHThe Australian Plate subducting under a section of the Eurasian Plate near Sumatra formed the Sunda Trench.

PLATE BOUNDARIES – TRANSFORMPLATE BOUNDARIES – TRANSFORM

• These faults neither create nor destroy lithosphere

• Most transform faults are hidden in the deep oceans where they form a series of short zigzags accommodating seafloor spreading

• As they do so, tremendous stress builds up.

• This stress is eventually released, often as a violent earthquake.

• E.g. San Andreas Fault, United States of America & North Anatolian Fault, Turkey

PLATE BOUNDARIES – TRANSFORMPLATE BOUNDARIES – TRANSFORM

FORMING OF SAN ANDREAS FAULT, UNITED STATES OF AMERICA

• In 1906, an earthquake occurred in San Francisco between the Pacific Plate and the North American Plate.

• This caused several hundred kilometers of North American Plate to move an average of 2.5 m and at one point almost 7 m all in less than 1 minute.

RING OF FIRE – CIRCUM PACIFIC BELTRING OF FIRE – CIRCUM PACIFIC BELT

• The Ring of Fire is an area in the basin of the Pacific Ocean where a large number of earthquakes and volcanic eruptions occur. About 90% of the world's earthquakes and 81% of the world's largest earthquakes occur along the Ring of Fire.

RING OF FIRE – CIRCUM PACIFIC BELTRING OF FIRE – CIRCUM PACIFIC BELT

FORMING OF RING OF FIRE• The Ring of Fire is a direct result of plate tectonics and the

movement and convergent collisions of lithospheric plates. • The eastern section of the ring is the result of the Nazca

Plate and the Cocos Plate being subducted beneath the westward moving South American Plate.

• A portion of the Pacific Plate along with the small Juan de Fuca Plate are being subducted beneath the North American Plate.

• Farther west, the Pacific plate is being subducted along the Kamchatka Peninsula arcs on south past Japan.

• The southern portion is more complex, with a number of smaller tectonic plates in collision with the Pacific plate from the Mariana Islands, the Philippines, Bougainville, Tonga, and New Zealand; this portion excludes Australia, since it lies in the center of its tectonic plate.

ALPIDE BELTALPIDE BELT

• The Alpide belt or Alpine-Himalayan orogenic belt is a seismic belt and orogenic belt that includes an array of mountain ranges extending along the southern margin of Eurasia, stretching from Java to Sumatra through the Himalayas, the Mediterranean, and out into the Atlantic.

• It is the second most seismically active region (5-6%) in the world, after the circum-Pacific belt (the Ring of Fire), with 17% of the world's largest earthquakes.

TECTONIC HARZARD - EARTHQUAKESTECTONIC HARZARD - EARTHQUAKES

• Sometimes the movements have caused the rock to deform so much that they fracture. These fractures are called faults.

• An earthquake is caused by a sudden slip on a fault. The tectonic plates are always slowly moving, but they get stuck at their edges due to friction. When the stress on the edge overcomes the friction, there is an earthquake that releases energy in waves that travel through the earth's crust and cause the shaking that we feel.


REASONS OF EARTHQUAKE:ELASTIC REBOUND THEORY• Following the great 1906 San

Francisco earthquake, Henry Feilding Reid examined the displacement of the ground surface around the San Andreas Fault.

• From his observations he concluded that the earthquake must have been the result of the elastic rebound of previously stored elastic strain energy in the rocks on either side of the fault.

TECTONIC HARZARD - EARTHQUAKESTECTONIC HARZARD - EARTHQUAKES• Elastic rebound theory states that as

tectonic plates move relative to each other, elastic strain energy builds up along their edges in the rocks along fault planes.

• Since fault planes are not usually very smooth, great amounts of energy can be stored along the fault.

• When the shearing stresses induced in the rocks on the fault planes exceed the shear strength of the rock, rupture occurs.

• At that time, a sudden movement occurs along the fault, releasing the accumulated energy, and the rocks snap back to their original undeformed shape.


• At the boundaries between plates, friction causes them to stick together. When built up energy causes them to break, earthquakes occur.


The distribution of the earth’s major earthquakes

BANGLADESH – THE POSITIONS OF FAULT LINESBANGLADESH – THE POSITIONS OF FAULT LINES

BANGLADESH – THE FAULT ZONES AND THE BANGLADESH – THE FAULT ZONES AND THE ESTIMATED MAXIMUM MAGNITUDEESTIMATED MAXIMUM MAGNITUDE

NAMEMAXIMUM MAGNITUDE

(ESTIMAED)

BOGRA FAULT ZONE 7.0

TRIPURA FAULT ZONE 7.0

SUB DAUKI FAULT ZONE 7.0

ASSAM FAULT ZONE 8.5

SHUILONG PLATEAU 7.0

MODHUPUR FAULT ZONE 7.5

RECENT SIGNIFICANT EARTHQUAKES – ALL RECENT SIGNIFICANT EARTHQUAKES – ALL ARE ALONG TECTONIC PLATESARE ALONG TECTONIC PLATES

NEPAL EARTHQUAKE – 25NEPAL EARTHQUAKE – 25thth APRIL, 2015 APRIL, 2015• On April 25, 2015, A magnitude

7.8 earthquake in Nepal killed more than 8,000 people, injured at least 19,000, and displaced hundreds of thousands in cities and villages near the Himalayas.

• The quake destroyed infrastructure and homes, both modern and historic, while triggering landslides on Mount Everest, near the village of Langtang, and in several other locations around Kathmandu.

• The Gorkha earthquake has been called the worst natural disaster in Nepal since a magnitude 8.0 earthquake in 1934.

NEPAL EARTHQUAKE - SCENARIONEPAL EARTHQUAKE - SCENARIO• The Gorkha earthquake changed

the shape of the Earth—literally—by raising up and dropping landscapes by several meters. Along a 90 by 30 kilometer (55 by 20 mile) swath of land in Nepal, a fault along the edges of the Indian and Eurasian tectonic plates slipped as much as 6 meters (20 feet). The release of stress in Earth’s crust had devastating effects felt in Nepal, India, China, and Bangladesh.

NEPAL EARTHQUAKE – REASONS NEPAL EARTHQUAKE – REASONS • As we have already discussed

about Plate tectonics movement, we know that the Indian plate continues to move northwards, at a rate of a couple of inches a year, carried along by currents deep in the semi-molten mantle. Because both Asia and India are made of solid rock, the movement causes immense stresses, which are released in periodic shudders – such as Nepal’s earthquake.

NEPAL EARTHQUAKE – REASONS NEPAL EARTHQUAKE – REASONS


• SHINGLING EFFECTS occur when tectonic plates collide and create thrust faults. The movement of Indian plate has created an unstable fissure in the planet's crust, known as the Himalayan frontal thrust fault. This boundary zone, continues to release enormous earthquakes.

• Faults of a second type are found near the crest of the Himalaya, dipping northward below the Tibetan Plateau. Constituting what is known as the South Tibetan fault system, these faults share geometric similarities with the thrust faults, but rocks slip along this system in the opposite direction. New evidence suggests that northward slip along the South Tibetan fault system and simultaneous southward slip along the southern faults permit the southward extrusion of this channel toward the Himalayan range front.


• Geologically, the Nepal Himalayas are sub-divided into five tectonic zones from north to south and, east to west and almost parallel to sub-parallel. These five distinct morpho-geotectonic zones are: (1) Terai Plain, (2) Sub Himalaya (Sivalik Range), (3) Lesser Himalaya (Mahabharat Range and mid valleys), (4) Higher Himalaya, and (5) Inner Himalaya (Tibetan Tethys)

RESULTS OF INDIAN PLATE MOVEMENTRESULTS OF INDIAN PLATE MOVEMENT

EFFECTS IN BANGLADESHEFFECTS IN BANGLADESH

• Bangladesh is close to the meeting point of the Indian, Eurasian and Myanmar plates. The movement of Indian and Eurasian plate has been locked the foot of the Himalayas for many years, storing strain energy. From Nepal Earthquake, we have understood that the lock has released and it is letting out strain energy causing major earthquakes which is affecting Bangladesh. Because of the plate movements, the Bihar-Nepal earthquake (1934), the Assam earthquake (1950), the Mandelay earthquake (1858) and the Nepal earthquake (2015) has affected Bangladesh already. Among eight fault zones, it has been observed that Dauki fault zone, Shahibazar fault zone and Tripura to Assam fault zone are very active and have been generating energy for a quite long time.

THE MOST ACTIVE FAULT ZONE IN THE MOST ACTIVE FAULT ZONE IN BANGLADESH - DAUKI FAULTBANGLADESH - DAUKI FAULT

• The Dauki fault lies in the Dauki town of Shillong Plateau. According to Evans (1964), it is a tear fault (strike- slip) that trends transverse to the strike of the deformed rocks of the Shillong Mikir Hills Plateaus. Murthy (1969) contradicted this proposition and said that Dauki fault has a vertical uplift to the North, causing the Shillong-Mikir Hills Plateaus as an uplifted region with Northward tilting. But occurrences of seismic activities, and the presence of two different tectonic regimes, i.e., thrust dominated on north and fold dominated on south suggest that the nature of the Dauki fault, can be similar to a Compartmental Fault (one kind of Transform Fault).

GEOLOGICAL FORMATION OF DAUKI GEOLOGICAL FORMATION OF DAUKI FAULTSFAULTS

POSITION OF DAUKI FAULT IN POSITION OF DAUKI FAULT IN BANGLADESH MAPBANGLADESH MAP

TAIWAN EARTHQUAKE - REASONS TAIWAN EARTHQUAKE - REASONS

• Taiwan is active geologically, formed on a complex convergent boundary between the Yangtze Subplate of Eurasian Plate to the west and north with a convergence rate of ~ 80 mm/yr., the Okinawa Plate on the north-east, the Philippine Plate on the east and south, and the Sunda Plate to the southwest. This plate boundary is rather complex since it comprises two subduction zones of reverse polarities. Plate interaction is marked mainly by the collision of the Luzon volcanic arc and the Asiatic continental margin.

TAIWAN EARTHQUAKE - REASONS TAIWAN EARTHQUAKE - REASONS

earthquakes – the result of geomorphology

Engineering