Q1: Define Seismic.
Ans:A phenomenon which occurs due to vibrations causing shaking of the earth’s surface is known as seismic or earthquake.
Q2: Write some causes of earthquakes.
Ans:Earthquakes are mainly caused by the movement of Tectonic plates.
Q3: Write some effects of seismic.
Ans:
Some of the effects of earthquake are as follows:- ➔ Damage to buildings
- ➔ Trees are uprooted
- ➔ Electric/telephone poles are likely to get disrupted
- ➔ Landsliding
- ➔ Cracks may appear in the ground
- ➔ Rivers are likely to become flooded and may also change their course
- ➔ Drainage system and water supply system are likely to get disturbed
Q4: Define Seismology.
Ans:The science which deals with all the aspects of earthquakes is known as seismology.
Q5: Define Seismograph.
Ans:The instrument which records the pattern of seismic waves causing earthquake shocks is called seismograph.
Q6: Define Seismogram.
Ans:The pattern of seismic waves recorded by a seismograph are known as seismograms.
Q7: Name the types of Seismographs.
Ans:
Following are the types of Seismographs:- ➔ North-South
- ➔ East-West
- ➔ Vertical
- ➔ Pen-Plotter
- ➔ Digital
Q8: Define Seismic Center.
Ans:The place origin of an earthquake within the earth’s crust is termed as the seismic center or focus. Its depth may vary from 10 to 300 km. In most cases, it lies up to 50 km below the earth’s surface.
Q9: Define Focus.
Ans:The focus (or hypocenter) is the point underground where the earthquake originates.
Q10: Define Focal Depth.
Ans:Focal depth is the depth below the Earth's surface where an earthquake originates. It is the distance between the earthquake’s focus (hypocenter) and the Earth’s surface.
Q11: Define Epicenter.
Ans:The point on the Earth’s surface directly above the point or origin of an earthquake; only two measurements, latitude and longitude, are needed to locate it.
Q12: Define Fault.
Ans:earthquakes occur on faults. A fault is a thin zone of crushed rock separating blocks of the earth's crust. When an earthquake occurs on one of these faults, the rock on one side slips with respect to the other.
Q13: Define Anti-center.
Ans:The point opposite to the epicenter, below the earth’s crust is called the anti-center.
Q14: Define Richter Scale.
Ans:The Richter scale is a numerical scale used to measure the magnitude (strength) of an earthquake.
Q15: Define Continental Crust.
Ans:The outermost layer of the earth is 35 km deep and is known as Continental crust.
Q16: Define Oceanic Crust.
Ans:Out of the continental crust, 7 km depth consists of water and it is known as oceanic crust.
Q17: Define Tsunami.
Ans:A tsunami is a series of ocean waves caused by large-scale disturbances, such as underwater earthquakes or volcanic eruptions.
Q18: Define Tectonic Plates.
Ans:The Continental Crust is divided into various parts known as tectonic plates. Tectonic Plates remain continuously in motion having an average annual velocity of 50mm (2 inch). When two tectonic plates compress each other, a stress is induced. This stress, when exceeds the capacity of the plates, causes a depression that ultimately results in vibrations, called earthquake.
Q19: Write the classification of seismic on the basis of depth.
Ans:
Seismic is classified as follows:- ➔ Shallow Seismic.
- ➔ Intermediate Seismic.
- ➔ Deep seated seismic.
Q20: Define Shallow seismic.
Ans:The seismic having depth of their focus within 60 km from the surface of earth are known as Shallow Seismic.
Q21: Define Deep seismic.
Ans:The seismic with depth of their focus more than 300 km from the surface of earth are known as deep seated seismic. Such earthquakes are very rare and at the same time, very disastrous.
Q22: Write the classification of seismic on the basis of cause.
Ans:
Seismic is classified as follows:- ➔ Tectonic Seismic.
- ➔ Non-tectonic Seismic.
Q23: Define Tectonic Seismic.
Ans:The seismic occurring due to the movement of crustal blocks along faults is known as tectonic seismic.
Q24: Define Non-tectonic seismic.
Ans:The seismic occurring due to volcanic eruptions, subsidence or landslides are called non-tectonic seismic.
Q25: Define Seismic Waves.
Ans:The waves originating at the center of disturbance and causing horizontal and vertical ground movement are known as seismic waves. earthquake waves are elastic waves.
Q26: Define Primary Waves.
Ans:The seismic wave that moves vertically downward into the earth with greater velocity are known as primary waves or P-waves.
Q27: Define Secondary Waves.
Ans:The seismic waves which move vertically downward into the earth with lesser velocity are called secondary waves or S-waves.
Q28: Define Rayleigh Waves.
Ans:These waves are the most common surface wave. They are similar to water waves except they have a backwards rotation and cause horizontal and vertical movement. These are slower than Long waves.
Q29: Define Seismic Zones.
Ans:The earth is divided into different parts based on the amount and intensity of earthquakes and such parts are known as Seismic Zones. The world is divided into 7 seismic zones.
Q30: How many Seismic zones of Pakistan?
Ans:
Pakistan is divided into 5 zones namely:- ➔ Zone 1
- ➔ Zone 2A
- ➔ Zone 2B
- ➔ Zone 3
- ➔ Zone 4
Q31: What is the seismic zone of Lahore?
Ans:The seismic zone of Lahore is 2A.
Q32: What is the seismic zone of Islamabad?
Ans:The seismic zone of Islamabad is 3.
Q33: What is the seismic zone of Quetta?
Ans:The seismic zone of Quetta is 4.
Q34: What is the seismic zone of Gilgit?
Ans:The seismic zone of Gilgit is 4.
Q35: What is the seismic zone of Karachi?
Ans:The seismic zone of Karachi is 2B.
Q36: What is the seismic zone of Peshawar?
Ans:The seismic zone of Peshawar is 2B.
Q37: Write the classification of seismic zones.
Ans:
Seismic zones are classified as follows:- ➔ Highly Seismic Zones.
- ➔ Moderately Seismic Zones.
- ➔ Poorly Seismic Zones.
Q38: Define a Highly Seismic Zone.
Ans:The areas having the greatest intensity of earthquake are known as highly seismic zones.
Q39: Define a Poorly Seismic Zone.
Ans:The areas having the lowest intensity of earthquake are known as poorly seismic zones.
Q40: Define Damping in earthquakes.
Ans:Damping is a process that slows down the shaking of buildings during an earthquake to reduce damage and increase safety.
Q41: Explain the process of Damping in earthquakes.
Ans:Damping reduces earthquake vibrations by absorbing and dissipating seismic energy through special materials or devices, helping to control building movement and prevent damage.
Q42: Define Seismic Retrofitting.
Ans:It is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes.
Q43: When is Seismic Retrofitting needed?
Ans:
The two circumstances are:- ➔ earthquake damaged buildings
- ➔ earthquake-vulnerable buildings (with no exposure to severe earthquakes)
Q44: What building guidelines should be adopted in seismic zones?
Ans:
Following are the guidelines:- ➔ Use earthquake-resistant design and materials.
- ➔ Keep structures light and symmetrical.
- ➔ Provide proper foundation and soil analysis.
- ➔ Ensure strong connections between structural elements.
Q45: What is base Isolation and how does it work?
Ans:Base isolation involves separating the building's foundation from the ground using special devices that absorb earthquake energy, reducing the forces transmitted to the structure.
Q46: Why are flexible materials like steel preferred in earthquake resistant buildings?
Ans:Steel can bend and deform under stress, allowing the building to sway and absorb energy without fracturing, unlike brittle materials like concrete.
Q47: What is the biggest cause of earthquake?
Ans: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.
