What Are The Impacts Of An Earthquake Environmental Sciences Essay

Tectonic earthquake is the most common form of earthquake that occurs in various parts of the world. The main cause for triggering an earthquake is due to the movement of different tectonic plates. The surface of earth is made up of a number of rigid parts called tectonic plates and is in continuous movement with each other. These plate movements are driven by forces deep within the earth. There are two types of tectonic earthquakes; they are (a) Inter plate earthquakes or Plate boundary earthquakes and (b) Intra plate earthquake or Mid Plate earthquakes [ASC India web]

Inter plate earthquakes

This type of earthquake occurs along the narrow zones that follows the boundaries of the tectonic plate. This type of earthquake is caused by the interaction of the two or more tectonic plates. There are two prominent bands of Inter-Plate boundaries in the world. One band begins from the western Mediterranean covering southern Europe, North Africa and extending through the Middle East and ending in the Himalayas. The second band is in the form of a circle around the Pacific Rim, which includes Japan, Philippines, Indonesia, Kamchatka in Russia, south pacific island nations and New Zealand in the west. The eastern part of the circle includes Alaska, California, Pacific, North-West parts of United States, Western Canada, Central America, South American countries of Colombia, Peru, Chile, and Ecuador. This circum pacific band is also known as the “Ring of Fire” [ASC India]

Intra plate earthquakes

This type of earthquake occurs far from the plate boundaries and this type of earthquakes are less frequent compare to the inter plate earthquake. This type of earthquakes are also capable of releasing the same amount of energy that is released during the inter plate earthquake and this type of earthquakes are also capable of causing destruction and damage to the society and people. The energy released from this type of earthquake contributes only 1% of the annual seismic energy released globally. This type of earthquakes occur in Indian peninsula, central Indian Ocean, Central and Eastern United States, Eastern Canada, northern Europe, Australia, Brazil, Hawaii and in the Western parts of Africa. [ASC India]

2.2.2 Volcanic Earthquake

Volcanic earthquakes are caused due to the volcanic activity which can cause threats like deformation of ground, cracking of ground and damage to buildings and other manmade structures.

2.2.3 Manmade Earthquake (Explosion, Collapse, Boring earth)

2.3 General Impacts of earthquake

2.3 Chapter Discussion and Conclusions

3 Resilience of Buildings

3.1 Introduction

3.2 Assessment of Building

3.3 Resilience to Structural Components of a Building

3.4 Improvisation in a Building

3.5 Chapter Discussions and Conclusions

4. Earthquake Hazard in India

4.1 Introduction

India is the seventh largest country in the world covering the area of about 3,287,240 Km2 (Approx.) with the population of about 1.1 billion and it has a large area of its land which are likely to be affected by wide range of probable maximum seismic intensities. In the past 100 years the country was affected by many earthquakes in different parts, which were responsible for the loss of many lives, buildings and other man-made structures. Among the number of earthquakes that affected the country, the shallow earthquake had a magnitude of M=5.0 or more on the Richter scale, and the catastrophic earthquake that has occurred in the past had a magnitude of M=8.0 or more which struck in the areas like Kutch, Andaman Island and besides the Himalayas.

This chapter discusses about damaging earthquakes that occurred in India and the main seismic regions in India. The different seismic regions are explained by illustrating the past earthquakes that occurred and its impact in the society.

4.2 Earthquake occurrences in India and the Neighborhood

In the past 100 hundred years India has suffered four great earthquakes of magnitude 8.5 or more and imposing many causalities and economic loss. The earthquake which had the largest magnitude in India was recorded as M=8.7 which had its epicenter in Shillong plateau that took place in the year 1897. The other notable earthquake to mention is earthquake that took place in Sadiya region with a magnitude of M=8.6 which was so powerful that it even changed the courses of the rivers and disturbed the ground level. The below table 1 shows the list of damaging earthquakes that has occurred in India. It gives general information about the earthquake like the affected area of the earthquake, date and time of earthquake, affected area’s location in latitude and longitude, magnitude of the earthquake and the number of deaths.

Date

(ddmmyyyy)

Area

Time in IST

Latitude in Degrees

Longitude in Degrees

Magnitude

M

Deaths

(Approximate value)

16.01.1819

Gujarat (Kutch)

Mid

Night

–

–

8.0

1500

26.08.1833

Bihar-Nepal

–

27.5

86.5

7.7

1500

12.06.1897

Assam (Shillong)

16:36

25.9

91.0

8.7

1600

08.02.1900

Kerala (Palghat)

03:11

10.7

76.7

6.0

Nil

04.04.1905

Himachal Pradesh (Kangra)

06:20

32.5

76.5

8.0

20000

03.07.1930

Assam (Dhubri)

02:33

25.8

90.2

7.1

Many

15.01.1934

Bihar-Nepal

14:13

26.6

86.8

8.3

14000

26.05.1941

Andaman

–

12.4

92.5

8

Many

23.10.1943

Assam

22:53

26.8

94.0

7.2

15-08-1950

Assam

19:39

28.7

96.6

8.6

1500

21.07.1956

Gujarat (Anjar)

21:02

23.3

70.0

7.0

115

28.10.1958

Uttar Pradesh (Kapkote)

–

30.0

80.0

6.3

Many

27.08.1960

Delhi

21:28

28.3

77.4

6.0

02.09.1963

Kashmir (Badgam)

07:04

33.9

74.7

5.5

In Hundreds

27.07.1966

Western Nepal

–

29.5

81.0

6.3

15.08.1966

Uttar Pradesh

(Moradabad)

–

28.0

79.0

5.3

02.07.1967

Nicobar

–

9.0

93.4

6.2

11.12.1967

Maharashtra (Koyna)

04:21

17.4

73.7

6.5

200

13.04.1970

Andhra Pradesh (Bhadra-chalam)

–

17.6

80.6

6.5

23.03.1970

Gujarat (Broach)

07:23

21.7

72.9

5.7

30

19.01.1975

Himachal Pradesh

–

32.5

78.4

6.5

21.08.1988

Bihar – Nepal

04:39

26.76

86.62

6.6

1003

20.10.1991

Uttar Pradesh (Uttar Kashi)

02:53

30.75

78.86

6.6

715

30.09.1993

Maharashtra (Killari)

03:55

18.07

76.62

6.3

7928

22.05.1997

Madhya Pradesh (Jabalpur)

04:23

23.1

80.1

6.0

38

29.05.1999

Uttar Pradesh (Chamoli)

00:35

30.3

79.56

6.5

63

26.01.2001

Gujarat (Kachchh or Bhuj)

08:46

23.6

69.8

7.7

13805

08.10.2005

Jammu & Kashmir (Kashmir)

09:20

34.5

73.6

7.6

India-1400

Pakistan occupied Kashmir (POK)-73726

Table 1- Some Better Known damaging Earthquakes in India [IITK, book]

4.3 Main Seismic Regions

The main seismic regions in India are divided into 7 seismic regions they are

Kashmir and Western Himalayas

Central Himalayas (including Nepal Himalayas)

Northeast India

Indo-Gangetic Basin and Rajasthan

Cambay and the Rann of Kutch

Peninsular India

Andaman and Nicobar islands.

These seismic regions are summarized below

(1) Kashmir and Western Himalayas

This region covers the states of Jammu & Kashmir, Himachal Pradesh and sub mountain parts of Punjab. This area has suffered a history of 180 earthquakes of magnitude M=5 or more. Kangra earthquake of April 4, 1905 had a maximum intensities of magnitude M=8.0, and it caused a large scale destruction in the area and resulted in loss of 20,000 lives, which are mainly due to the collapse of structures made of brick, stone and earthen materials. Other notable damaging earthquakes in this region are the Budgam earthquake of September 2, 1963, Anantnag earthquake of February 20, 1987, Dharmshala earthquake of April 26, 1986 and Kashmir earthquake of October 8, 2005. During the Kashmir earthquake more than 75,000 lives are lost due to the collapse of stone buildings.

(2) Central Himalayas

This region covers the mountain and sub mountain regions of Uttar Pradesh, sub mountain regions of Bihar and Nepal. This area has experienced more than 135 earthquakes of magnitude M=5 or more and they are mostly occurred in the eastern and western parts. The eastern side of this region has experienced a very high seismicity and the earthquake to mention in this region is Bihar-Nepal earthquake occurred on January 15, 1934 which had a magnitude of M= 8.4 and destroyed thousands of homes and 13,000 people were killed in this earthquake. The western side of this region has experienced earthquakes of magnitude from M=6 and the maximum magnitude of M=7.5 was recorded during the Dharchula earthquake in 1916. The central side of this area has not experienced any earthquakes. The most recent earthquake occurred in the central Himalaya is on August 20, 1988 with the magnitude of M=6.7 and it affected northern parts of Bihar and eastern Nepal.

(3) North East India

This region covers the entire Indian Territory to the east of north Bengal. This seismic region is comprises of the neighboring countries like Myanmar (Burma) and Bhutan. This region is one of the most severe seismic regions in the world, which has a history of experiencing 520 earthquakes of magnitude M=5, among which 24 earthquakes had magnitude of M=7 or more. The largest earthquake in this region is Assam earthquake of 1897 which had a magnitude of M=8.7 and is the largest earthquake ever recorded in this region. The other earthquake which has similar magnitude to Assam earthquake is the Sadiya earthquake of 1950 which had a magnitude of M=8.6. It is the only earthquake which has been rarely repeated in the world. As these earthquakes had a high magnitude it resulted in change of topographical levels, but the economic loss and loss of life was less as the population in 1897 was less and in 1950 the earthquake occurred in a less populated area. Other reasons for reduced damage of these earthquakes is that the type of construction in Assam was different to the present situation, construction during that period had a practice of using bamboo posts and Ekra (Wattle and Daub) walling was light and strong which remained undamaged during these earthquakes. The present type of construction is different from the traditional Assam type construction, where the construction materials are changed bamboo and Ekra to bricks and stones, non-engineered buildings have increased with the increase in population. As a result there is a possibility for more damages to life and property during future earthquakes.

(4) Indo Gangetic Basin and Rajasthan

This region covers Rajasthan, Haryana, plains of Punjab, Bihar, Uttar Pradesh and Bengal situated to north of the Vindhyas. This area has suffered from 110 earthquakes of magnitude of M=5 or greater are known to occur in this region. Most of the seismic activities have occurred on the Moradabad faults, Lucknow, Patna faults and the Sohna fault near Delhi. The maximum seismic activity occurred in this area is recorded as M=6.7, which shows that this is a moderate to minor seismic zone.

(5) Cambay and the Rann of Kutch

This region is comparatively smaller than the other regions classified here, but this region has suffered from one of the worst earthquakes in India. This region has suffered from 20 earthquakes of minimum magnitude as M=5.0 and two other earthquakes of magnitude M= 7.0 and M=8.0 this earthquake occurred in Rann of Kutch in the year 1819 by killing 2000 people and destroying the town of Bhuj. Similarly the city of Anjar was also destroyed by an earthquake in 1956. But the most destructive earthquake of this area is the recent Kachchh earthquake in January 26, 2001, which had a magnitude of M=7.7 and it resulted in the loss of 14,000 people, destroying about 230,000 buildings and damaging more than 800,000 buildings. Many reinforced concrete frame buildings were destroyed due to the impact of this earthquake. The main reason for the failure of these buildings is due to bad design and construction practice. This region is considered to be severe to moderate seismic region.

(6) Peninsular India and Lakshadweep islands

This region is more stable compared to other region as this region is a pre Cambrian shield and it does not have any adjacent plate boundaries. The type earthquakes occurred here are Intra plate earthquake. This region has experienced 32 earthquakes with average magnitude M= 5.0 and maximum magnitude of M=6.5. The maximum magnitude was recorded during the Koyna earthquake of 1967. Most destroying earthquake in this region is the Marathwada earthquake of M=6.4 occurred in the year 1993 which took the lives of 8000 people. As this region has experienced very less seismic activity, this area is considered to be less to moderate seismic region.

(7) The Andaman – Nicobar Island

This region is highly seismic and has suffered from 190 earthquakes with average magnitude of M=5.0 and the maximum magnitude of M=8.1. The giant earthquake of M=8.1 occurred in the year 1941 and caused severe damages to the main town of Port Blair by damaging the civil and military installations. This area was indirectly affected during the Sumatra earthquake on December 24, 2004 which had a magnitude of M=9.3 and was the cause for the tsunami. The use of unreinforced masonry in this area is increasing with the rise in population, from which it is evident that the risk of more damages in the future events.

4.4 The Seismic Hazard Zoning Map

The seismic zoning map of India has been standardized by the Bureau of Indian Standards which is given in the earthquake design resistant code of India (IS: 1893-Part 1, 2002, fig 2). According to this seismic zoning map, the seismic zones have been revised from its previous map which had 5 or 6 zones to 4 zones based on the records of seismic activity in India. The 4 seismic zones are classified on the expected probable intensities on 12 point Modified Mercalli intensity scale or Medvedev-Sponheuer-Karnik scale (MSK). The four seismic zones are zone 2, 3, 4 and 5. The seismic zoning map of India is given below which shows the different seismic zones in India. [Jalandhar, book]

Figure Seismic Zoning Map of India

Image Courtesy [http://www.mausam.gov.in/WEBIMD/images/zone_map.jpg]

Zone 2

This zone has the least amount of seismic activity experienced in India and this zone is classified as the Low Damage Risk Zone. This zone is expected to have probable occurrence of MSK VI or less. The horizontal ground acceleration in this zone is 0.1 g, and this factor is considered by the Engineers in the structural designing of earthquake resistant structures. Zone 2 seismic area in India is less compared to other zones. [Jalandhar, relief, seismo, book]

Zone 3

This zone has moderate amount of seismicity and this zone is classified as Moderate Damage Risk Zone. This zone is expected to have probable occurrence of MSK VII. The horizontal ground acceleration in this zone is 0.16 g or 10-20 % of gravitational acceleration. This zone covers the cities like Ahmedabad, Vadodara, Rajkot, Bhavnagar, Surat, Mumbai, Agra, Bhiwandi, Nasik, Kanpur Pune, Bhubaneswar, Cuttack, Asansol, Kochi Kolkata, Varanasi, Bareilly, Lucknow, Indore, Jabalpur, Vijayawada, Dhanbad, Chennai, Coimbatore, Mangalore, Kozhikode, Trivandrum, and Andaman Nicobar islands. [Jalandhar, relief, seismo, book]

Zone 4

This zone has high seismicity and this zone is classified as High Damage Risk Zone. This zone is expected to have probable occurrence of MSK VIII. The horizontal ground acceleration in this zone is 0.24 g or 20-30% of gravitational acceleration. This zone This zone covers the cities like Dehradun, New Delhi, Yamuna Nagar, Patna, Meerut, Jammu, Amritsar, and Jalandhar. [Jalandhar, relief, seismo, book]

Zone 5

This zone has highest seismicity in India and this zone is classified as Very High Damage Risk Zone. This zone is expected to have probable occurrence of MSK IX or more. In this zone the area which has trap or basaltic rock are more prone to earthquakes. The horizontal ground acceleration in this zone is 0.36 or 30-40 % of gravitational acceleration and this is the peak value of gravity that is experienced during a Maximum Credible Earthquake (MCE). This covers cities like Guwahati and Srinagar. Punjab, Kashmir, western Himalayas, central Himalayas, Northeast India and Rann of Kutch also fall in this zone. [Jalandhar, relief, seismo, book]

Seismicity Map of India

Seismicity map gives the relative frequency and distribution of earthquakes in a given zone. Below is the seismicity map of India, it clear shows the distribution of earthquakes in India and the neighborhood countries. The green stars represents the areas which has suffered from earthquakes of magnitude M=5.0 to 5.9, blue stars represent the areas which has suffered from earthquakes of magnitude of M=6.0 to 6.9, pink stars represent the areas which has suffered from earthquakes of magnitude M= 7.0 to 7.9, red stars represent the areas which had suffered from earthquakes of magnitude M= 8.0 to 8.9., and yellow stars represent the areas suffered from earthquakes of magnitude M= 9.0 or above.

C:UsersSalahudeenDesktopseismicity_map.jpg

Figure Seismicity Map of India [http://www.mausam.gov.in/WEBIMD/images/seismicity_map.jpg]

4.5 Damaging Effects of Earthquake

Earthquakes can cause damage to the society and indirectly affect the economy of the country. Earthquakes are the greatest destroyers of man-made structures like buildings, power plants, bridges, dams etc… Generally when a person thinks about the effects of an earthquake, ground shaking comes to a person’s mind, but ground shaking is not the only effects of an earthquake; there are possibilities for other natural hazards like landslides, liquefaction, and tsunamis. These hazards are directly related to earthquake, as they are caused due to direct impact of an earthquake. Other possible hazards are cracking of dam walls which can cause leakage of water and causing flood, falling of electricity poles can cause live wires to be exposed and can trigger a fire, damage of underground gas pipelines and can trigger a fire, damage of underground water pipelines – this could be difficult in case of controlling fire. [UWIE seismic]

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Some of the possible damaging effects of an earthquake are shown in the flowchart below (fig 3). An earthquake can cause two events like surface rupture or seismic waves. The surface of the earth ruptures during an earthquake, which shifts the surface and causes the building to collapse, resulting in personal injury or loss of life and loss of properties. If the surface rupture takes place in the ocean it produces a sea wave/tsunami and can cause flooding in the nearby coastal areas. Seismic waves created as a result of earthquake causes the surface of earth to shift. Surface shifts can lead to dynamic settlement of rock wedge or soil liquefaction and cause damages to manmade structures. Surface shifts can cause slope movements on the path of river and creating a barrier to form a natural dam and cause flooding in the nearby area. Surface shifts can directly affect the buildings and structures and cause fire or flood. It is clear that earthquake does not kill people, other events which are triggered due to earthquake only kills, so measures should be taken to withstand or overcome the following events of an earthquake. [Book]

Tidal Waves or Tsunami

Figure 3 Flow chart of damaging effects of an earthquake [book]

Impact on Man/Society

Personal injury

Loss of belongings

Psychological effects

Sociological effects

Overall earthquake effects

Floods

Non – Structural Damage

Collapse of structural components / fire/ flood (e.g. by dam break)

Damage to building & structures

Natural river Damming

Damage to building & structures

Slope Movement

Primary effects

Near Surface Shift

Near Surface Shift

Dynamic Settlement, Soil Liquefaction

Coastal Floods

Damage to building & structures

Near Surface Shift

Near Surface Shift

Near Surface Shift

Seismic Waves

Surface Rupture

Earthquake of Magnitude M = 5- 8.7

Geologic effects of Ground Shaking

During an earthquake a person can observe the shaking of the ground, the shaking duration depends on the size of the earthquake i.e. its magnitude, distance from epicenter, amplitude, location and its regional geology. Shaking of ground can cause the structure to collapse, shaking of ground also depends on the type of soil, if the soil is soft and loose the shaking will be more, (see fig.4) if the soil is tight and compactly packed the shaking will be less. It is important to make sure that the structures are built on hard ground or on the hard rock. If there is a need to build structure on the soft surface, it has to be compacted before constructing. The epicenter of an earthquake also depends on the duration of shaking, nearer the epicenter more the duration of shaking. Ground shaking also depends on the amplitude; amplitude will be high with increase in the size of the earthquake. [Geology]

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Figure Regional Geology of Shaking [geology]

Figure [Landslides]Landslides and liquefactionC:UsersSalahudeenDesktoplandslide.JPG

Landslides are defined as the mass movement of rock, debris or earth down a slope due to gravity, they can occur on any terrain with suitable conditions of soil, moisture, and the angle of slope. Landslides can be triggered by rains, floods, earthquakes, volcanoes, and other man made causes like grading, terrain cutting and filling etc… Manmade structures are not the only affected due to stress of the seismic waves, natural structures like mountain slopes and hillsides also fail due to the stress of the seismic waves. In India the most vulnerable regions for landslides are Himalayas and Western Ghats. [Landslides 1, 2]

In the below fig.5 is a graph showing the cumulative number of fatalities since September 2002 in India and China. The number of deaths caused due to the earthquake induced landslides is clearly shown which approximates 40,000 fatalities during both the Kashmir earthquake and Wenchuan earthquake. [Landslides]

Tsunamis

Figure Tsunami InitiationTsunami is a Japanese term that means “harbor wave”, they are generally confused with tidal waves but they both are different. Tsunamis are caused by a sudden vertical offset in the ocean floor triggered by underwater earthquakes, undersea landslides and undersea volcanic deformation. The sudden offset of the ocean floor changes the elevation of the ocean and initiates a water wave that travels outward from the region of sea-floor disruption which is shown in fig 6.C:UsersSalahudeenDesktoptsu 3.png

In 26 December, 2004, a tsunami wave hit the countries situated around the Bay of Bengal. The tsunami wave was triggered by an earthquake of magnitude M=8.9 which had its epicenter in the west coast of Sumatra in Indonesia. The damage of this tsunami in India almost affected 876 villages in south India with an area of 4000 hectares and it affected population of 3.5 million. [Tsunami]

It is clear that the number of people died as a result of an earthquake is less when compared to the deaths caused by the triggering events following an earthquake.

4.6 Earthquake Prediction

4.7 Earthquake Hazard risk to Urban Areas

4.8 Chapter Discussions and Conclusions

5. Earthquake Resistant Structure

5.1 Introduction

5.2 Classification of Seismic Designs

5.3 Comparison of Seismic practices in India and Abroad

5.4 Chapter Discussion and Conclusion

6. Case Study Bhuj Earthquake

6.1 Introduction and Methodology

6.1.1Case Study as Research Methodology

6.1.2 Case Study Design

6.2 Damage Assessment

6.3 Factors influenced the earthquake damage

6.3.1 Type of Building Construction

6.3.2Quality of materials

6.3.3 Liquefaction

6.4 Chapter Discussion and Conclusion

7. Discussions

8. Conclusion