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Seismic waves and tsunami - class-IX

Description: seismic waves and tsunami
Number of Questions: 62
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Tags: wave motion some natural phenomena physics structure of earth
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Assertion : An earthquake will not cause uniform damage to all building in an affected area, even if they are built with the same strength and materials.
Reason : The one with its natural frequency close to the frequency of seismic wave is likely to be damaged less.

  1. If both assertion and reason are true and reason is the correct explanation of assertion.

  2. If both assertion and reason are true and reason is not the correct explanation of assertion.

  3. If assertion is true but reason is false.

  4. If both assertion and reason are false.


Correct Option: C
Explanation:

An earth quake will not cause uniform damage to all building in an affected area because the natural frequencies of a building depend on its height and other size parameters and the nature of building materials.
The one with its natural frequency close to the frequency of seismic wave is likely to be damaged more.

An earthquake generates both transverse $(S)$ and longitudinal $(P)$ sound waves in the earth. The speed of $S$ waves is about $4 \,\,km \,\,s^{-1}$ and that of $P$ waves is about $8 \,\,km \,\,s^{-1}$. A seismograph records $P$ and $S$ waves from an earthquake.The first $P$ wave arrives $4$ min before the first $S$ wave. The epicentre of the earthquake is located at a distance of about

  1. $192 km$

  2. $384 km$

  3. $1920 km$

  4. $3840 km$


Correct Option: C
Explanation:
Let $\nu _1, \nu _2$ be speed $S$ of $S$ and $P$ waves and $t _1,t _2$ be the time taken by these waves to travel to reach the seismograph. Let the epicenter of the earthquake is located at a distance $d$ from the seismograph. Then,
$d = V _1 t _1 = V _2 t _2$          ................ .....(i)
Here, $V _1 = 4 km \,\,s^{-1}$ and $V _2 = 8 km \,\,s^{-1}$
$\therefore 4t _1 = 8t _2 \Longrightarrow t _1 = 2t _2$           ....(ii)
and  $t _1 - t _2 = 4 min = 240 s$
$\therefore 2t _2 - t _2 = 240$      ....................  [using (ii)]
or $t _2 = 240 s$
put in Eq. (ii), we get,
$t _1 = 2 \times 240 s = 480 s$
From Eq. (i), we get, $d = (4 km \,\,s^{-1}) (480 s) = 1920 km$

The weak zone around the boundaries of plates underneath the Earth, which is prone to slide and cause an earthquake is commonly known as :

  1. Fault zone

  2. Eruption zone

  3. Explosive zone

  4. Sliding zone


Correct Option: A
Explanation:

The weak zone around the boundaries of plates underneath the Earth, which  is prone to slide and cause an earthquake is known as Seismic or Fault Zones.

The correct option is A.

The natural calamity that cannot be predicted accurately in advance:

  1. Flood

  2. Cyclone

  3. Earthquake

  4. Famine


Correct Option: C

Which of the following country in the world is most prone to earthquake?

  1. India

  2. America

  3. China

  4. Japan


Correct Option: D
Explanation:

Japan is the country in the world is most prone to earthquake.

Waves produced during in earthquake are _____waves. .

  1. ultrasonic

  2. infrasonic

  3. audible

  4. both (1) and (2)


Correct Option: B

The point where the waves originate is called the _______ of the earthquake

  1. centre

  2. epicenter

  3. focus

  4. origin


Correct Option: C
Explanation:

Answer is C.

The point where the waves originate is called the focus of the earthquake.
The point within the earth along the rupturing geological fault where an earthquake originates is called the focus, or hypocenter. The point on the earth's surface directly above the focus is called the epicenter. Earthquake waves begin to radiate out from the focus and subsequently form along the fault rupture. If the focus is near the surface between 0 and 70 km (0 and 40 mi) deepshallow-focus earthquakes are produced. If it is intermediate or deep below the crust between 70 and 700 km (40 and 400 mi) deepa deep-focus earthquake will be produced. Shallow-focus earthquakes tend to be larger, and therefore more damaging, earthquakes. This is because they are closer to the surface where the rocks are stronger and build up more strain.

In which of the following states of India, earthquake is most likely to occur?

  1. Gujarat

  2. Chhattisgarh

  3. Tamil Nadu

  4. Kerala


Correct Option: A
Explanation:

In India, the seismic or fault zores lie below Kashmir, Western and Central Himalays, North-East, Runn of Kutch and Indo-gangetic plane. So, among the options provided, earthquake is most likely to occur in Gujarat.

An earthquake is caused by

  1. shaking of the earth

  2. strain building up in the tectonic plates

  3. plates slipping along the fault lines

  4. all of the above


Correct Option: D
Explanation:

An earthquake is caused by shaking of the earth, strain building up in the tectonic plates, plates slipping along the fault lines, etc.
Earthquake is shaking of the earth's surface caused by rapid movement of the earth's rocky outer layer. Earthquakes occur when energy stored within the earth, usually in the form of strain in rocks, suddenly releases. This energy is transmitted to the surface of the earth by earthquake waves.

Match the following and choose the correct answer.

Table A Table B
a. Earthquake        1. Prevent leakage
b. Lightning 2. Fault zone
c. Insulation 3. Detection of charges
d. Electroscope 4. Earthing
  1. a-2, b-4, c-1, d-3

  2. a-3, b-4, c-2, d-1

  3. a-4, b-3, c-2, d-1

  4. a-1, b-2, c-3, d-4


Correct Option: A
Explanation:

Fault zones are highly prone to earthquakes.

Earthing is done to save buildings from lightning.
Insulation is done on conducting wires to prevent charge leakage.
Electroscopes are used to detect the presence of charges in a body.

The amplitude of vibrations measured on the Richter's scale increase by steps of about

  1. 10

  2. 20

  3. 30

  4. 40


Correct Option: A
Explanation:

Answer is A.

The amplitude of vibrations measured on the Richter's scale increase by steps of about 10.
The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included in the magnitude formula to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. For example, a magnitude of 5.3 might be computed for a moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value.

The epicenter is the point inside the earth where the earthquake originates

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient


Correct Option: B
Explanation:

Answer is B.

The point within the earth along the rupturing geological fault where an earthquake originates is called the focus, or hypocenter. The point on the earth's surface directly above the focus is called the epicenter. Earthquake waves begin to radiate out from the focus and subsequently form along the fault rupture. 
Hence, the statement is false.

Earthquake and tsunamis are difficult to predict

  1. True

  2. False


Correct Option: A
Explanation:

Answer is A.

Earthquakes are caused by by shaking of the earth, strain building up in the tectonic plates, plates slipping along the fault lines, etc. and the Tsunamis can also be caused by volcanic eruptions, underwater detonations and even landslides.
Because we cant get deep enough into the Earth to see what happens before an earthquake or tsunami happens, therefore we cant predict when its coming.

A seismograph is a scale use for measuring the magnitudes of earthquakes

  1. True

  2. False

  3. Ambiguous

  4. Data insufficient


Correct Option: B
Explanation:

Answer is B.

Seismograph is an instrument that makes a record of seismic waves caused by an earthquake, explosion, or other Earth-shaking phenomenon. Seismographs are equipped with electromagnetic sensors that translate ground motions into electrical changes, which are processed and recorded by the instruments analog or digital circuits. A record produced by a seismograph on a display screen or paper printout is called a seismogram.
Hence, it is not a scale and the statement is false.

The term used to describe a fracture along the earth's crust is

  1. aftershock

  2. fault

  3. focus

  4. tremor


Correct Option: B
Explanation:

Answer is B.

The fracture along blocks of crust (tectonic plates) is called a fault or fault line.
A fault is a planar fracture or discontinuity in a volume of rock, across which there has been significant displacement along the fractures as a result of earth movement. Large faults within the Earth's crust result from the action of plate tectonic forces, with the largest forming the boundaries between the plates, such as subduction zones or transform faults. Energy release associated with rapid movement on active faults is the cause of most earthquakes.

Choose the correct statement.

  1. 'P' waves are slower than 'S' waves.

  2. Both 'P' and 'S' waves have same speed.

  3. 'S' waves are slower than 'P' waves.

  4. None of the above.


Correct Option: C
Explanation:
The P waves and the S waves are the waves that travel throughout the planet. The P waves are the compression waves that apply force in the direction of propagation whereas the S waves are shear waves that make the medium particle move perpendicular to their direction of motion.
The energy is less easily transmitted in the medium in the case of S waves. So, P waves travel faster.

Option $C$ is correct.

How do we record seismic waves?

  1. With the help of a seismogram.

  2. With the help of a seismograph.

  3. With the help of a seismocity.

  4. None of the above.


Correct Option: B
Explanation:

Seismograph is a device which is used to record and measure seismic waves created by earthquakes.

A seismograph is also known as:

  1. seismogram

  2. seismology

  3. seismometer

  4. seismocity


Correct Option: C
Explanation:
A seismograph, which measures seismic waves, is also known as a seismometer.

'S' waves are

  1. Longitudinal

  2. Electromagnetic

  3. Ultrasonic

  4. Transverse


Correct Option: D
Explanation:

The S waves moving through the planet make the medium to move perpendicular to the direction of the propagation of the wave. Therefore. the S waves are regarded as the transverse waves.

Waves produced due to earthquakes are known as :

  1. seismic waves

  2. shock waves

  3. infrasonic waves

  4. destructive waves


Correct Option: A

Waves produced due to the earthquake are known as

  1. seismic waves

  2. shock waves

  3. infrasonic waves

  4. Tectonic waves


Correct Option: A

Fill in the blank:

Seismometers can record motions in ________ directions.

  1. one

  2. all

  3. opposite

  4. same


Correct Option: B
Explanation:

Seismometer devices are located in $3$ directions and work on principle of inertia to catch the motions in all directions.

The natural phenomenon which we are not yet able to predict accurately is:

  1. earthquake

  2. flood

  3. volcanic erruption

  4. thunderstorm


Correct Option: A
Explanation:

After knowing causes of the earthquake, it is still not possible to predict when and where the next earthquake may occur.

When did a major Tsunami occur in the Indian ocean?

  1. On $26^{th}$ December, $2004$.

  2. On $26^{th}$ July, $2004$.

  3. On $26^{th}$ December, $2001$.

  4. On $26^{th}$ July, $2001$.


Correct Option: A
Explanation:

A sudden disturbance under the Indian ocean led to Tsunami through the coastal areas of India on 26th December, 2004.

_________ and _________ towns of North Kashmir suffered from a major earthquake.
  1. Uri, Tangdhar

  2. Ladakh, Uri

  3. Tangdhar, Ladakh

  4. Bhuj, Kachchh


Correct Option: A
Explanation:

Uri and Tangdhar were the two towns of North Kashmir to have faced major earthquake with huge loss of lives and properties in 2005.

Weak zones of plates are also known as:

  1. seismic zones

  2. fault zones

  3. danger zones

  4. both A and B


Correct Option: D
Explanation:

The boundaries of the plates are the weak zones where earthquakes are more likely to occur. These are also known as seismic zones and fault zones.

Tremors on the earth can also be caused when?

  1. Valcano erupts

  2. Metero hits the earth

  3. Underground nuclear explosion

  4. All of the above


Correct Option: D
The inner most part or the centre of the Earth is known as ________.
  1. outer core

  2. inner core

  3. mantle

  4. crust


Correct Option: B
Explanation:

Earth consist of core, mantle and crust. Core is the centre of the Earth. Core, again, consists of inner core and outer core. Inner core is inner most part, or, the centre of the Earth.

The intensity of an earthquake is measure on the ______?

  1. Righter scale

  2. Richter scale

  3. Seismic scale

  4. None of the above


Correct Option: B
Explanation:

Magnitude of earthquake is measure on Richter scale really distructive earthquake have magnitude higher than $7$ on the Richter scale.

The Earth's crust plates moves brushing past each other or collide. It causes:

  1. landslides

  2. volcanic eruption

  3. earthquake

  4. none of the above


Correct Option: C
Explanation:

Any disturbance deep inside the Earth's crust leads to earthquake.

The uppermost layer of the Earth is:

  1. a huge single piece

  2. fragmented

  3. in two large pieces

  4. none of the above


Correct Option: B
Explanation:

The Earth's crust is not a huge single piece. It is fragmented into pieces.

The plates or the fragments of the Earth's crust is also known as:

  1. crust plates

  2. surface plates

  3. tectonic plates

  4. none of the above


Correct Option: C
Explanation:

Earth's crust is fragmented into pieces which are called plates. These plates are also known as tectonic plates.

The boundaries of the plates, called weak zones, are also known as:

  1. danger zones

  2. seismic zones

  3. colliding zones

  4. none of the above


Correct Option: B
Explanation:

The weak zones are also known as seismic zones. These are zones where earthquake are most likely to occur.

Which scale is used to measure the magnitude of earthquake?

  1. Kelvin

  2. Parcal

  3. Celsius

  4. Richter


Correct Option: D
Explanation:

Richter scale defines magnitude of the earthquake. Richter scale is not linear.

Seismograph is a instrument used to:

  1. Record lightning

  2. Record strength of wind

  3. Record temperature

  4. Record vibrations of earthquakes


Correct Option: D
Explanation:

The tremors produces waves on the surface of the earth. These are called seismic waves. The waves are recorded by an instrument called seismograph.

An earthquake of magnitude $7$ or more in Richter scale is a _____ one?

  1. Stronger

  2. Weaker

  3. Medium

  4. None of the above


Correct Option: A

Magnitude of earthquake is measured by

  1. electroscope

  2. Richter scale

  3. seismograph

  4. coulomb


Correct Option: B
Explanation:

Magnitude of earthquake is measured by Richter scale. A electroscope is an early scientific instrument that is used to detect the presence and magnitude of electric charge on a body.  A seismograph is used to record of seismic waves caused by an earthquake, explosion, or other Earth-shaking phenomenon. Coulomb is the unit of electrical charge. 

State whether true or false:
Seismic waves recorded by an instrument is called seismograph.

  1. True

  2. False


Correct Option: A

What types of waves are seismic waves?

  1. Non-mechanical waves

  2. Elastic waves

  3. Mechanical waves

  4. Electromagnetic waves


Correct Option: C

The movement of Earth's plates causes

  1. Lightening

  2. Cyclons

  3. Earthquake

  4. Thunderstorms


Correct Option: C
Explanation:

The movement of Earth's plates causes Earthquake. Earth's crust is broken up into large pieces called tectonic plates. Tectonic plates are giant pieces of the Earth's crust that fit together and move around on the Earth's surface. Tectonic plates are constantly moving slowly, but sometimes friction between them causes them to lock together and become unable to move. The rest of the plates carry on moving, which leads to increased pressure on the locked section. Eventually, the locked section succumbs to the pressure, and the plates move past each other rapidly. This movement causes a tectonic earthquake. The waves of released energy move through the Earth's crust and cause the shaking we feel at an earthquake site. 

Which of the following is not a after-effect of earthquake?

  1. Destruction of livelihood

  2. Death and injuries

  3. Water waves and tsunamis

  4. Rainfall


Correct Option: D
Explanation:

An earthquake is a sudden shaking movement of the surface of the earth. The primary effects of earthquakes are ground shaking, ground rupture, landslides, tsunamis, liquefaction, destruction of livelihood. death and injuries. Rainfall is not an after-effect of earthquake.

Earthquake can cause

  1. Tsunami

  2. Floods

  3. Landslide

  4. All of the above


Correct Option: D
Explanation:

The primary effects of earthquakes are ground shaking, ground rupture, landslides, tsunamis, flood and liquefaction. Fires are probably the single most important secondary effect of earthquakes.

State whether the given statement is True or False :

Tremors on the Earth can also be caused by the eruption of a volcano. 

  1. True

  2. False


Correct Option: A
Explanation:
Tremors on the Earth can be caused when a volcano erupts, or a meteor hits the Earth, or an underground nuclear explosion is carried out. However, most earthquakes are caused by the movement of Earth’s plates.

State whether the given statement is True or False :

Earthquakes occur all the time all over the world. 

  1. True

  2. False


Correct Option: A
Explanation:
The statement is true. Earthquake in less magnitude are not even noticed. 

Seismic waves that vibrate perpendicular to the direction of their path.

  1. Spread on the surface of the earth

  2. Travel through the solid as well as other parts of the earth

  3. Travel through the solid parts of the earth only

  4. None of the above


Correct Option: C
Explanation:

Seismic waves that vibrate perpendicular to the direction of motion travel through the solid parts of earth only.

Earthquake is also known as :

  1. nektons

  2. blusters

  3. temblors

  4. flickers


Correct Option: C
Explanation:

An earthquake also known as a temblor, quake, tremor is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves.

Which of the following is/are true regarding Earthquake ?

  1. It refers to shaking of the Earth.

  2. It occurs due to release of energy.

  3. It generates waves that travel in all direction.

  4. All of the above.


Correct Option: D
Explanation:

Earth's crust is broken up into large pieces called tectonic plates. Tectonic plates are giant pieces of the Earth's crust that fit together and move around on the Earth's surface. Tectonic plates are constantly moving slowly, but sometimes friction between them causes them lock together and become unable to move. The rest of the plates carry on moving, which leads to increased pressure on the locked section. Eventually, the locked section succumbs to the pressure, and the plates move past each other rapidly. This movement causes a tectonic earthquake. The waves of released energy move through the Earth's crust in all direction and cause the shaking we feel at an earthquake site.

Which of the following Earth's plates is responsible for causing an earthquake?

  1. The crust of the earth

  2. The mantle of the earth

  3. The inner core of the earth

  4. The outer core of the earth


Correct Option: A
Explanation:

Most earthquakes are tectonic earthquakes, which happen when the large, thin plates of the Earth's crust called tectonic plates become stuck as they move past one another. They lock together, and pressure builds up. When they finally release, earthquakes occur.

Earthquake at two places A and B were measured by a seismograph which recorded the magnitude as 2 and 4. The magnitude of tremors and its destructive energy at A and B can be compared as:

  1. Tremor at B are two times that at place A

  2. Tremor at B are four times that at place A

  3. Tremor at B are 100 times that at place A

  4. Tremor at B are 1000 times that at place A


Correct Option: C
Explanation:

As the magnitude records by seismograph at a place is more by 1, the magnitude of tremors will be 10 times more. Hence, the magnitude of tremors at 'B' are 100 times than at place 'A' since they differ by 2 in magnitude.

Name the scale on which the destructive energy of an earthquake is measured.

  1. Temperature scale

  2. Vector scale

  3. Richter scale

  4. Energy scale


Correct Option: C
Explanation:

The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes. The magnitude of an earthquake is determined from the logarithm of the amplitude of waves recorded by seismographs. Adjustments are included in the magnitude formula to compensate for the variation in the distance between the various seismographs and the epicenter of the earthquakes. On the Richter Scale, magnitude is expressed in whole numbers and decimal fractions. For example, a magnitude of 5.3 might be computed for a moderate earthquake, and a strong earthquake might be rated as magnitude 6.3. Because of the logarithmic basis of the scale, each whole number increase in magnitude represents a tenfold increase in measured amplitude; as an estimate of energy, each whole number step in the magnitude scale corresponds to the release of about 31 times more energy than the amount associated with the preceding whole number value.
The Richter scale has the readings from 1 to 10. The reading of magnitude 3 on the Richter scale would be recorded by a seismograph. If the Richter scale gives a reading of magnitude 3, then the earthquake is not likely to cause much damage. Generally, earthquake of magnitudes higher than 7 is considered destructive in nature.

Earthquake at two places A and B were measured by a seismograph which recorded the magnitude as 2 and 4. The magnitude of tremors and its destructive energy at A and B can be compared as under:

  1. Tremor at B is 2 times to that at place A

  2. Tremor at B is 4 times to that at place A

  3. Tremor at B is 100 times to that at place A

  4. Tremor at B is 1000 times to that at place A


Correct Option: C
Explanation:

Richter scale is not a linear scale. It is a logarithmic scale. A difference in magnitude of $2$ implies a multiplication factor of $10^2 = 100$.

The first seismograph was invented in

  1. Germany by Albert Einstein.

  2. China by zhang Heng.

  3. Germany by Emmy Noether.

  4. none of the above.


Correct Option: B
Explanation:

A Chinese mathematician, named Zhang Heng, inverted and constructed the first seismograph in A.D. 132.

Earthquake at two places A and B were measured by a seismograph which recorded the magnitude as 2 and 4. The magnitude of tremors and its destructive energy at A and B can be compared as under

  1. tremor at B are two times that at place 'A'

  2. tremor at B are four times that at place 'A'

  3. tremor at B are 100 times that at place 'A'

  4. tremor at B are 1000 times that at place 'A'


Correct Option: C

The earth shakes when _________ occurs. 

  1. Tsunami

  2. Flood

  3. Earthquake

  4. Drought


Correct Option: C
Explanation:

Earthquakes are usually caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake.

State whether the given statement is True or False :

The plates of the outermost layer of the Earth are always in continuous motion. 

  1. True

  2. False


Correct Option: A
Explanation:

The outermost layer of the Earth is called as crust. It is not in one piece but fragmented. Each fragment is called as a plate. Such 7-8 major plates are present. Also, there are many minor plates. These plates are in continuous motion. When these plates brush past one another or a plate goes under another, it causes collision. This causes earthquake on the surface of the Earth. Earthquakes occur all the time around the world. But they are too small to be noticed. Major earthquakes are less frequent. Hence, given statement is true.

What happened on $26^{th}\ December\ 2004$ on the coastal areas of india?

  1. Earthquake

  2. Lightning

  3. Cyclone

  4. Tsunami


Correct Option: D
Explanation:

Earthquakes can causes floods, landslides and tsunamis, Earthquakes occurs all the time, all over the earth but at very less magnitude & earth's plates are in continual motion.

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