Earthquake Resistant Building Construction Civil Engineering Final Year.

 →Definitions of Earthquake: - 

Earthquake is defined as the shaking of earth’s surface due to any reason which, result in 

release of large amount of energy.

For example-: The energy released in during 2001 Bhuj Earthquake (Gujrat, india) was 

about 200 times that of energy released by Atom bomb dropped on Hiroshima 

(Japan) In the year of 1945.

 Or

* The ground vibrations, both feeble and strong, produced on the surface of earth due to any 

reason what so ever are described as earthquake.

* Define Earthquake Engineering/Seismology-:

The branch of science which deals with the study of earthquakes.

It includes causes and types of earthquake, Study of origin, Propagation, Recording and 

analyzing seismic waves that occur inside the earth along with the source that produce them 

is known as Earthquake Engineering or Seismology.

* Important Terminology related with Earthquake Engineering 

Seismology-:

1. Hypocenter or focus or seismic center-: The exact point or place inside the surface of 

earth at which an earthquake originates is termed as focus or seismic centre. It is also 

known as Hypocenter. Most of the damaging earthquakes have shallow focus with 

focal depth less than 70 K.M its position is determine with the help of seismograph 

records.

2. Epicenter-: The point on the earth's surface vertically above the focus of an earthquake

known as Epicenter or Epicentral line.

3. Focal depth-: The depth of focus from the Epicenter is called as focal depth. Or the

vertical distance between Epicenter and Hypocenter/focus.

4. Epicenter distance or depth-: The horizontal distance from epicenter to any place or 

discussion is known as epicentral distance. As the Epicentral Distance is increased, the 

effect of earthquake becomes less.

5. Anti center-: The point on the surface of earth diametrically opposite to the epicenter is 

called as anti center.

6. Seismic waves: - The wave transmitted in all the directions due to large strain energy 

released from the focus during an earthquake are known as seismic waves. These are two 

types Body waves and Surface waves.

7. Seismograph-: An instrument which is used to record ground vibration or surface 

displacements known as seismograph.

Seismographs are used only to record weak motion. For recording higher intensities, special 

strong motion instrument called accelerographs are used.

8. Isoseismal-: An imaginary line on the surface of the earth along which the intensity of 

measured seismic shock is equal at every point is termed as Isoseismal. It is just like a 

contour line which joins points of same elevation.

9. Isoseismal Map-: A map showing different Isoseismal for a particular earthquake is 

termed as isoseismal map. Such a maps is quiet helpful to scientists and engineers in the 

development of seismic zones.

10. Seismic Zone & Seismic Belt-: The region of earth’s crust where earthquake occur 

frequently and repeatedly are known as seismic zone & seismic Belt. Depending upon the 

intensity of seismic activity, these zone are further divided into Highly Seismic, Moderately 

Seismic, and Poorly Seismic zone.

11. Fault-: A fracture or a crack along which blocks of earth’s mass move relatively on either 

side parallel to the fracture is termed as a fault. This sliding of earth’s mass takes place in 

pieces called “tectonic Plates”

12. Tsunamis-: Tsunami is a series of large sea waves caused by earthquake or seismic 

activity near the coastal regions or at the ocean floor.

Necessity of Earthquake engineering:-

1. To carry out advance research and development for effective earthquake management.

2. for earthquake preparedness that is to learn how to prepare facing earthquake.

3. for seismic evaluation and retro fitting.

 Causes of Earthquakes: -The important causes of the earthquake are-: 

A. Natural Causes of Earthquake.

B. Artificial Causes of Earthquake.

C. Superficial Causes

A. Natural Causes of Earthquake:-

1. Tectonic Movement: This particularly happens when the continental plate collides 

against the oceanic plate. The oceanic plate is overridden by the continental plate. By a 

process called subduction jerky movements are caused along the inclined surface. Tectonic 

earthquakes have occurred in Assam in 1950.

2 Volcanic Activity: Earthquakes may also be caused by the movement of lava beneath the 

surface of the earth during volcanic activity. The earthquakes due to Krakatoa volcanic 

eruption in 1883 is a good example of volcanic eruption.

3. Dislocation of the Earth’s crust: Earthquakes may be caused by the dislocation of the 

crust beneath the surface of the Earth.

4. Adjustment in inner Rock Beds: Earthquakes are also caused where is an adjustment 

between Sima [i.e., beneath the ocean is formed by Silica and Magnesium = Si + ma =

Sima] and Sial (i.e., Continent is formed by Silica and Aluminum = Si + al = Sial) in the 

interior of the Earth’s Crust. This Earthquake may be called as a Plutonic Earthquake.

5. Pressure of gases in the interior: The expansion and contraction of gases in the interior 

of the Earth sometimes cause a sudden shake on the Earth’s surface.

B. Artificial Causes of Earthquake:-

Man-made Earthquakes:-

1. The impounding of large quantities of water behind dams disturbs the crustal balance. 

This causes earthquakes such as the Koyna earthquake in Maharashtra.

2. The shock waves through rocks set up by the underground testing of Atom bombs or 

Hydrogen bombs may be severe to cause earthquake.

C. Superficial Causes:-

1. Landslides and avalanches,

2. Denudation of the Landmasses and depositions of materials,

3. Faulting and folding in the rock beds are responsible for causing minor earthquakes.

4. Mining blasts in mining areas.

* Effects of Earthquake-

A. Destructive Effects:-

1. Earthquake causes dismantling of buildings, bridge and other structures at or near 

epicenter. Many men and animals are killed or buried under collapsed houses.

2. Rails are folded, underground wires broken. Fire breaks out inevitably in large towns.

3. Earthquakes originate sea waves called Tsunamis.

4. Earthquakes result in the formation of cracks and fissures on the ground formation.

5. The earthquakes cause landslides and disturb the isostatic equilibrium.

6. Landslide due to earthquake may block valleys to form lakes.

7. Earthquake causes damage to the building, bridges and dams.

8. Earthquake in many cases can cause great loss of life.

9. Earthquake can also cause floods and landslides. Landslides, triggered by earthquake, 

often cause more destruction than the earthquake themselves.

10.If the earthquake happens to be beneath the ocean floor, they can lead to a tsunami.

B. Constructive Effects:-

1. Sometimes the earthquakes cause formation of hot springs which are very useful to 

people.

2. The earthquakes sometimes cause submergence in coastal land, and result in formation 

of inlets, bays and gulfs which help to develop of fishing and shipping etc.

3. Sometimes, the earthquakes cause emergence of costs and bring fertile shore out of 

water to give chance to develop crop production.

 Seismic waves: - 

The wave transmitted in all the direction due to large strain energy released from the focus 

during an earthquake is known as seismic waves. These are two types Body waves and 

Surface waves.

* There are two type of seismic wave:

1. Body Waves: - 1.1 Primary waves or p waves, 1.2 Secondary waves or s waves 

2. Surface Waves: - 2.1 Rayleigh waves (LR-waves), 2.2 Love wave (LL- wave).

1. Body waves: - The wave which travels through the earth layer in all directions and are 

not restricted to any depth is known as body wave.

Body wave are of two types: - 1.1 Primary waves or p waves

 1.2 Secondary waves or s waves

1.1 Primary waves or p waves: The waves in which material particles vibrate in the 

direction of propagation of the wave with a push and pull effect are known as primary wave.

These are also called as longitudinal wave or compressional waves. 

Due to effect of "P" wave the particle undergo extensional strain (Pull effect) and 

compression strain (push effect)

 Characteristics of primary waves/ p-waves: - P wave have the following important 

characteristics.

1. These wave are fastest to travel (hence are first to be recorded). At the recording station.

2. In granite rock P waves have the velocity of 5 km/sec.

3. These wave are capable of passing through the solid as well as liquid.

4. These waves are responsible for preliminary shocks upon the earth surface.

5. These are longitudinal and compressional in nature like sound waves.

6. These waves cause volumetric change in the material through which they pass.

Secondary waves/S-waves:- The wave in which material partial vibrate at right 

angle to the direction of propagation i.e. secondary wave. These are also called as 

shear waves shake waves.

 Characteristic of Secondary waves/ S-waves:-

1. These wave slower to p wave slower at the recording station in same material.

2. In granite rock velocity of S wave is approximate 3 km/sec.

3. These waves are capable of passing through the solid but are unable to propagate 

through fluid as they do not have any shear strength.

4. These wave are transverse in nature like light waves.

5. These wave unlike P wave don't change the volume of the material through which they 

pass.

6. Vertically polarized S waves are known as SV waves on other hand

Horizontally polarized s waves are called as SH waves.

2. Surface waves or Long waves: - The wave which travels along the surface 

of the earth in a circumferential path is known as surface wave or long wave. These 

waves do not propagate deal inside of the surface of the earth.

 Characteristics of surface or long wave :-

1. These waves are the slowest to travel and therefore last to be recorded at the recording 

station.

2. These waves are also transverse in nature.

3. Behaviour of surface wave is similar to that of sea waves.

4. These waves are most destructive in nature.

5. Surface wave or long waves are responsible for all the damage on the surface on the 

earth during earthquakes.

Types of surface wave or long waves:-

1. Rayleigh waves (LR-waves)

2. Love wave (LL- waves)

1. Rayleigh waves/ (LR-waves):-These waves are first discovered by Lord Rayleigh in 

the year 1885 the major axis is along vertical direction and minor axis is in the direction of 

wave propagation. Thus resulting elliptical particle motion can be described as a 

combination of P and SV motion. Rayleigh wave is the part of surface wave in which 

material particle vibrate in an elliptical path in the vertical plane i.e. Rayleigh wave.

 Characteristics of Rayleigh waves :-

1. The shacking produced by Rayleigh waves causes both vertical and horizontal

movement.

 2. They advance in a backward rotative elliptical motion 

2. Love waves/ (LL- waves):-

It is the part of surface wave in which practical motion is in the horizontal plane and 

vibrates in right angle and to the direction of propagation i.e. love wave.

Love wave is similar to that of sec. Wave but with no vertical component.

History: - 

These waves are first described as seismologist AEH in the year 1911 in which the 

particle motion can be described as Sh vibration.

 Characteristics of love waves:-

1. Love wave cause surface motion. Similar to secondary waves, but with no vertical 

component.

2. Love wave motion is from side to side in a horizontal plan roughly ||el to the earth 

surface.

3. Love waves travel faster than Rayleigh eave.

4. Love wave do not move through liquid or air.

5. Love wave along with secondary wave cause max. Damage to the structures.

Earthquake size: -

Earthquake size is measured of the quantitative and qualitative effects of the vibration 

produced by the earthquake.

It is defined as in terms of two things:-

1. Earthquake Magnitude. 2. Earthquake Intensity.

1. Earthquake magnitude: - 

Earthquake magnitude is a quantitative estimate of the earthquake size.

It is measures of amount of energy release during the earthquake.

The magnitude of an earthquake is generally measured on Richter scale.

 Explanation:-

Richter magnitude scale is the most globally accepted scale which is used to define 

size of an earthquake according to Richter scale magnitude can be defined as 

logarithm (base 10) of the maximum amplitude A (in micron = 1/1000 mm) of the 

ground motion on a standard Seismograph at a distance of 100 km from the epicenter.

Richter gave a relationship between strain energy released by an earthquake and its 

magnitude.

It is given by ( log10E

= 11.4 + 1.5 M )

M = magnitude of an earthquake

E = energy in earg.

For Example: - 

As per table energy release in magnitude 7 earthquake is 80×1020 and energy released in 

a magnitude 8 earthquake is 2500×1020 ergs which is approximately 31 time of M 7.0 

earthquake. or it should be note that M less than 5 on Richter scale is of no Engineering 

Significance.

2. Earthquake intensity:-

Intensity of an earthquake may be defined as qualitative measures of actual vibration set 

up on the earth’s surface due to seismic shock.

 OR

It may also be state as measures of the degree of destruction caused by an earthquake.

Intensity of an earthquake decrease with distance from the epicenter.

Question:-What factors earthquake intensity depends: -

1. Earthquake magnitude

2. Distance from hypocenter and epicenter

3. Type of foundation material

4. Buildings style

5. Duration of shaking

 Compression b/w magnitude and intensity :-



MAGNITUDE INTENSITY

1. Magnitude is a quantitative estimate of 

Earthquake.

Intensity is a qualitative estimate of 

Earthquake

2. Measured on Richter scale. Intensity scale

3. Magnitude of an earthquake is 

measured of its size in the form of amount 

of strain energy released by the fault 

rupture.

Intensity is an indicator of the severity of 

the earthquake caused due to shacking of 

ground at the given location.

4. Magnitude on an earthquake is a single 

value.

--------------–--------

Intensity is different at different Location, 

thus many value.

 Based on the above factors two scales are commonly used:-

1. MSK Intensity Scale.

2. Modified Mercalli Intensity (MMI) Scale.

Both Scale is quite similar and range from I (least Severity) to XII (Most Sever).

 The intensity scale are developed keeping in view the following 

things:-

1. The experience of people.

2. Performance of Building.

3. Changes in natural Surroundings.