Causes of earthquakes - class-IX

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.

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.

A seismograph is the standard scientific instrument used to detect and record the intensity, duration, and direction of seismic waves produced by earthquakes.

While floods, cyclones, and famines often have precursors or meteorological indicators that allow for some level of prediction, earthquakes currently cannot be predicted with accuracy regarding time, location, or magnitude.

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

Earthquakes produce seismic waves that travel through the earth. These waves, particularly the primary waves, often have frequencies below the human audible range, classifying them as infrasonic.

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 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 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.

Fault zones are highly prone to earthquakes.

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.

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.

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.

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.

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.

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

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.

Seismic waves are the waves of energy caused by the sudden breaking of rock within the earth or an explosion, which travel through the earth's layers.

Seismic waves are the scientific term for waves produced by earthquakes. While shock waves describes their nature and many are infrasonic, seismic waves is the correct terminology used in seismology to describe waves that travel through Earth's layers.

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

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

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

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

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.

Earthquakes and tremors can be triggered by various geological and anthropogenic activities, including volcanic eruptions, meteorite impacts, and underground nuclear testing.

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.

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

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

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

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

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

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

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

The Richter scale is logarithmic. An earthquake of magnitude 7 or higher is considered a major or strong earthquake capable of causing significant damage.

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. 

A seismograph is the instrument used to detect and record seismic waves, confirming the statement is true.

Seismic waves are mechanical waves because they require a medium (the Earth's crust or interior) to propagate energy.

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. 

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.

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.

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

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.

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.

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.

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.

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.

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

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

The Richter scale is logarithmic, meaning each whole number increase represents a 10-fold increase in measured amplitude. A difference of 2 units (4 - 2 = 2) corresponds to an increase in amplitude by 10^2 = 100 times.

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.

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.

A seismograph is a device that measures and records the seismic waves moving through the earth post an earthquake.

Seismic waves move through the Earth as the result of earthquakes.

The layer below the Earth's crust is known as mantle. This consists of magma.

The Earth's crust is not a huge single piece rather it is in many pieces or fragments. The fragments are called plates.

Storms, cyclones, earthquakes and lightning are termed as natural calamities. These causes lot of damages to the properties and enviroments. Hence, they are destructive in nature.

Due to movement of Earth's plates, most of the earthquakes occur.

On 26th January, 2001, an earthquake occurred in Bhuj district of Gujarat at a very high frequency on Richter scale.