Science of Earthquakes - Term Paper Example

Abstract This paper reports a case study on the naturally occurring phenomena of earthquakes. A detailed background environmental science is presented, also covering the risk assessment of likely impacts, risk mitigation measures, and the economic, environmental, and human impacts this hazard poses. Evidence is shown that with new developments in technology, earthquakes can now be predicted, therefore reducing the risk of mitigation failure. Earthquake Background Science of Earthquakes An earthquake is a natural phenomenon that is caused by tremors below the surface of the earth. The tremors are themselves caused by the abrupt release of energy inside the earth’s crust. When this energy is released, it creates seismic waves, which then cause motion in the tectonic plates. These tectonic plates are large rocky sections which are what create the earth’s outermost crust. Earthquakes commonly occur on the fault lines which are found on the tectonic plates. This happens mostly when the plates are sliding past one another or when they come to a collision (Rose, Benadives and Chang, 2002). There are different terminologies used when describing the science of an earthquake. Focus is the origin of the quake itself. One of these words is the fault or fault line which is used to describe the surface upon which two tectonic planes slide past each other. Another term that is commonly used in earthquake science is hypocenter, the point at which an earthquake begins. The epicenter on the other hand, is the point on the surface of the earth, which is directly over the hypocenter (Rojahn, 2005). These shifting masses of underground tectonic plates normally send out some shock waves which are very powerful. The strength of the waves is enough to change the earth’s surface. This means that it can thrust up cliffs and even open up huge cracks on the ground. The waves are normally grouped into two categories: Primary waves, Secondary Waves and Surface waves (Access Science). Primary waves, or P-Waves, are very similar to sound waves. They are short wavelength, high frequency longitudinal waves. They can also pass through liquids and solids. When the shockwaves occur underneath the earth’s surface, they normally move the ground in a forward and backward direction due to the compression and decompression that they cause. However, the displacement of the ground is relatively small. P-Waves have a special characteristic that makes it possible for them to be refracted and reflected. Sometimes, they can be conditioned to change into Secondary Waves (Access Science). Secondary waves, or S-Waves, have a little less travel speed than P-Waves. These kinds of waves normally occur after P-Waves. Although they share high frequency and short wave length characteristics with P-Waves, they are not longitudinal. Instead, they are transverse. This means that they can move in any direction from where they originate from. They travel in speeds which are solely depended on the density of the crust through which they move. S-Waves cannot travel through liquids. These shockwaves normally cause the sideways displacement of fences and walls, giving them an ‘S’ shape (Berman, 2004). L-Waves are long wavelength, low frequency and transverse vibrations. They originate very close to the epicenter. Unlike P-waves and S-Waves, L-Waves can only move on the earth’s outer crust. These waves resemble sea waves. They normally cause the ground to move cyclically, in the process making it rise and fall like waves. During an earthquake occurrence, these waves normally cause the most damage (Access Science). Types of Earthquakes Tectonic Earthquakes Tectonic earthquakes normally occur when the earth’s crust is under too much strain which causes it to move. Tectonic plates found underneath the surface of the earth can move in two directions: towards each other or away from each other. When these plates slide past or collide against each other, an earthquake results. Most earthquakes occur as a result of this kind of movement (Access Science). The theory used to explain this type of earthquake is called the Elastic Rebound Theory. The San Andreas Fault found in California, US, is a good example of sliding tectonic plates. The two plates in this case are the North American Plate and the Pacific Plate which are moving towards the same direction, but one is moving at a faster speed than the other. As they move, the two plates normally slide past each other, causing small tremors every year. There are other times when the movement is large enough to cause a serious earthquake, especially around the area of San Francisco (Berman, 2004). Just before the occurrence of a major earthquake, some places normally experience a change in natural activity. For instance, there might be some minor tremors as rocks start to move. This kind of shock is known as a foreshock. When these foreshocks happen for a long time, they can cause untold damage. These small shocks also weaken some structures, which then become vulnerable during the time of a major earthquake. After a major earthquake occurs, there follows what is commonly referred to as an aftershock. This is caused by rock movements when they are positioning themselves in their new locations. Aftershocks also cause major damage to places which have recently experienced earthquakes (Rose, Benadives and Chang, 2002). Volcanic Earthquakes Volcanic earthquakes are normally caused by volcanic activities such as eruptions. Compared to tectonic earthquakes, the volcano ones are relatively rare. This is mainly due to the fact that volcanic eruptions are not very many in the world today. After a volcanic eruption, the resulting earthquake can affect an area of about 10 to 20 miles radius. Tectonic earthquakes, however, can be much more severe, affecting whole continents (Rojahn, 2005). Volcanic earthquakes only happen around the mountains or areas which produce lava that is acidic. This kind of lava cools very fast when it comes into contact with air. This fast cooling normally causes the accumulation of too much lava on the volcanic vent, making it impossible for pressure to escape from the vents. When the build up of pressure becomes too high, the result is usually a violent eruption which can have devastating effects. The earthquakes produced by these eruptions are high magnitude (Access Science). A good example of a volcanic earthquake is one which occurred in 1883 when Krakatoa in Indonesia exploded. The sound of the eruption was heard as far away as Australia, which is more than 5000 kilometers away. The shockwaves from this explosion produced earthquakes and tsunamis which killed thousands of people in Java and Sumatra (Yodmani, 2001). Earthquake magnitudes are normally measured using an instrument known as a seismometer or seismographs. The recording that is made on a seismograph is known as a seismogram. The seismograph is made up of a base that holds firmly to the ground and a free-hanging heavy weight. When there is an earthquake related tremor, the seismograph also shakes but the weight is not affected. All the shaking and other movement is normally absorbed by the spring from which the weight is hanging. What is recorded is the position difference between the motionless part and the shaking part. Each earthquake has its own unique magnitude. A small earthquake will record short lines with little wiggles while large earthquakes normally record large lines that wiggle a lot (Rose, Benadives and Chang, 2002). Seismographs can also be used to locate earthquakes. P-waves which travel faster than S-Waves, cause the ground to shake first before the S-Waves occur. By considering the amount of time that elapses between a P-Wave and an S-wave, one can determine how far from a particular location an earthquake occurred (Rojahn, 2005). To determine the exact location of an earthquake, scientists normally use the triangulation method. The name of the tracking method is derived from the use of three seismographs to locate quakes. These seismographs are normally placed in three different locations. Circles are then drawn around the seimogaphs, with the radius being the distance from the earthquake to the instrument. The point at which the three circles meet is the earthquake’s epicenter (Access Science). Earthquakes have the potential to cause untold damage to human life and infrastructure (Berman, 2004). Below is a case study of a region that frequently experiences earthquakes. I will examine the impacts of the disaster to different aspects of life. I will also examine the risk mitigation measures that are in place to deal with earthquakes in the country. Case Study: Nepal Asia is one continent where natural hazards are a common feature. In Nepal, earthquakes have caused great damage to property and human life as well. The country is at the 11th position worldwide in regards to earthquake vulnerability (Chitrakar, Piya, and Nepal, 2007). This disaster has occurred many times in the history of Nepal. Nepal is vulnerable to earthquakes due to the fact that three tectonic fault zones lie underneath its crust. Another factor that contributes to the high number of earthquakes in Nepal is the country’s unstable soil condition that is as a result of eruptions of its young mountains in the Himalayas (Pandey, Tandur and Avouac, 1999). Impact of earthquakes: economic, environmental and human impact Environmental Impact Tremors and ground rapture The earthquakes that normally occur in are high magnitude, and therefore, they cause a lot of damage to the environment. Heavy tremors and ground rapture are common in various parts of the country which are prone to earthquakes. These tremors normally lead to destruction of plants, including trees. Ground rapture normally leaves wide openings which pose a risk to humans and animals as well (Bishnu, 2007). Landslides and avalanches Many places in Nepal which experience earthquakes also experience avalanches and landslides during or after the earthquakes. These landslides normally occur in areas which are near hills and the avalanches are common in areas surrounding mountains. The landslides cause more damage to plant life and human life as well (Lave and Avouac, 2000). Fires Soil Liquefaction Earthquakes also normally cause soil liquefaction, making it unsuitable for farming. This liquefaction also causes the soil to be weak. Therefore, a slight tremor can upset the soil and this may bring untold damage to property (Bishnu, 2007). Tsunamis and Floods The earthquakes in Nepal are normally accompanied by more environmental disasters such as tsunamis and floods. The floods can wreck havoc over a whole town, leaving people with nothing to eat or drink for a long time. Lives are also lost in the ensuing tsunamis (Rose, Benadives and Chang, 2002). The environmental impact of earthquakes in Nepal normally leads to poor productivity and instability of the economy. It is also quite challenging to sustain the social and cultural lives of people who are used to being affected by devastating earthquakes (Pandey, Tandur and Avouac, 1999). Economic Impacts Nepal has experienced great losses due to past earthquake experiences.  The 1934 earthquake that occurred in Nepal left approximately 20,000 people dead (Lave and Avouac, 2000)..  Later, in 1988 another quake killed about 720 people causing damage to about 15,000 classrooms and over 65,000 houses. The country has lost several buildings and constructions to earthquakes as traditional measures to counter earthquakes have been thrown to the wind. Instead, people mostly use modern building materials and building techniques (Chitrakar, Piya, and Nepal, 2007). The country’s three main cities of Lalitpur, Kathmandu, and Biratnagar are known to be earthquake prone areas. This means that whenever earthquakes occur, a lot of infrastructure and property are damaged making transport and communication difficult. The earthquakes normally disrupt business and mostly render government activities futile (Chitrakar, Piya, and Nepal, 2007). Apart from disrupting learning and business activities, the government loses much in its rescue and recovery efforts. Furthermore, the cash-trapped government spends a significant amount in trying to institute measures that are aimed at countering future earthquakes. The government for example has to train its people on earthquake resistant construction (Lave and Avouac, 2000). Human Impact Nepal has for a long time been the location of hundreds of earthquakes. The human impact of these earthquakes is serious, although the situation is getting better as more mitigation measures are implemented. Death is the most serious impact of earthquakes in this Asian country. Many people have perished inside buildings after the occurrence of serious earthquakes. In addition, many more die due to lack of basic needs such as food and clean water. Earthquakes in Nepal normally cause floods, which can destroy all the crops in the fields. Those people who rely on their fields for food are normally forced to go for many days without anything to eat (Lave and Avouac, 2000). Things are made even worse by poor and earthquake-destroyed infrastructure, which makes it almost impossible to get food and water to those affected by the disaster. Earthquakes are not only destructive to the environment; they also cause destruction to various aspects of human life (Chitrakar, Piya, and Nepal, 2007). In Nepal, earthquakes have been known to cause the lack of basic needs and necessities such as food and clean water. This has led to disease outbreaks, loss of life and high rates of insurance premiums (Rose, Benadives and Chang, 2002). Risk Mitigation Measures Administrative Arrangements: Strategic Response to earthquakes The Tenth Plan was a national policy that was created in 2003 and lasted until 2008. The policy framework identifies some forms of natural disaster management as a major need for sustainability and long term economic well being of the country. The plan also adopted some risk reduction measures to reduce the impact of earthquakes on human life and in infrastructure. The plan included several preparedness activities that were related to disaster management at the community and national levels (Bishnu, 2007). This plan integrated different objectives to help in mitigation of earthquake-related risks. One of these objectives was to develop and build structures that were reliable, effective and sustainable (Chitrakar, Piya, and Nepal, 2007). Another objective was to create the appropriate programs and strategies for disaster mitigation and human life security. To this end, the policy presented provisions for help to NGOs, local bodies, the private sector as well as to community organizations including relief and rescue during natural disasters (Pandey, Tandur and Avouac, 1999). The key strategies that were adopted by the Tenth Plan included the adoption of relevant technologies in a bid to bring to minimal level environmental and human impacts of natural disasters. Another strategy was to make rescue and relief more effective and reliable. The strategies also included creating hazard maps for vulnerable areas and enhancing the capabilities of different earthquake measurement stations (Lave and Avouac, 2000). Public awareness activities and programs were also part of the strategies fir this policy. This awareness creation also included training individuals at the community level on disaster management (Pandey, Tandur and Avouac, 1999). As a result of the implementation of the Tenth Plan, the natural Calamities Relief Act was amended to define disaster to help reduce risk. The act covers many types of disasters, including earthquakes. A new building code and measures for construction measures were created. Awareness programs at the national and local community level have also been jumpstarted (Pandey, Tandur and Avouac, 1999). However, despite the seeming efforts being put for earthquake risk mitigation, there are a number of challenges that have affected the full implementation of the Tenth Plan. For instance, poor planning and leadership has made it difficult to offer rescue and relief aid to the affected regions. It is also quite hard to create firm and proper mitigation measures that will reduce the impact of earthquakes in the country (Bishnu, 2007). Economic Implications due to Lack of Mitigation Until a few decades ago, Nepal’s there was almost no mitigation effort on the part of the government or even the public sector. This led to many problems for the country, including being economically impotent (Lave and Avouac, 2000). Due to the nature of the earthquakes that frequently occurred in the country, a lot of destruction on property and loss of human life was commonplace. Businesses crumpled and people could not carry out o\any economically meaningful activities due to this destruction. Unemployment and illiteracy was at high levels since the earthquakes destroyed many learning institutions (Pandey, Tandur and Avouac, 1999). However, the situation began to change slowly after the government took some steps in mitigating the risks of some of the common disasters in the country, including earthquakes (Bishnu, 2007). Although Nepal is far much better economically than it was some decades, ago, a lot needs to be done to ensure that disaster management programs are strong enough to deal with vulnerability that occurs after earthquakes and other natural disasters (Pandey, Tandur and Avouac, 1999). Conclusion Earthquakes are some of the common natural disasters that occur in different parts of the world. Earthquakes normally start from deep within the crust of the earth; therefore it is impossible to control them. These disasters have seen many people perish and property worth lots of money destroyed. Although it is impossible to control earthquakes, there is need to create proper mitigation measures in areas that are prone to such disasters. Risk mitigation measures are useful in reducing the impact of earthquakes wherever they happen. References Access Science, n.d., Designing for and mitigating earthquakes, Encyclopedia of Science and Technology Online, McGraw Hill. Berman, D., 2004, Examining the Blakely Earthquake and its Aftershocks, Federal Sentencing Reporter, Vol 16., No. 5, pp. 307-311 Bilham, R. and Feidl, N., 2006, Great Himanalyan earthquakes and the Tibetan Plateau, Nature, Vol. 444, pp. 165-170 Bishnu, C.K., 2007, Cheap Easy Trick for Rural Nepal Against Earthquakes, Accessed 30, Nov.: http://www.scidev.net/en/news/cheap-easy-trick-for-rural-nepal-against-earthqua.html Brunious, C. and Warner, A., 1998, Earthquakes and Society, accessed 30th Nov. from: http://www.umich.edu/~gs265/society/earthquakes.htm Chitrakar,G., Piya, B., and Nepal D, 2007, some Notable Disasters In Nepal and their Mitigation, Journal of Nepal Geological Society, Vol. 36 Lave, J. and Avouac, J., 2000, Active folding of fluvial terraces across the Siwaliks Hills, Himalayas of central Nepal, Journal of Geophysical Research, Vol. 105, No. b3, pp. 5735-5770 Pandey, M., Tandur, R. and Avouac, J., 1999, Seismotectonics of the Nepal Himalaya from a Local Seismic network, Journal of Asian Earth Sciences, Volume 17, Issues 5-6, October-December 1999, Pages 703-712 Rojahn, C. 2005, Translating Earthquake Hazard Mitigation Measures from one Country to Another: A Case Study, Washington, DC: OECD. Rose, A., Benavides, J., Chang, S. and Szczesniak, P., 2002, The Regional Economic Impact of an Earthquake: Direct and Indirect Effects of Electricity Lifeline Disruptions, Journal of Regional Science, Vol. 37, no. 3, pp. 247-458 Stein, s. and Wysession, M., 2003, An introduction to seismology, earthquakes, and earth structure, Hoboken, NJ: Wiley-Blackwell Tarbuck, J and Lutgens, K. 1996, Earth: An Introduction to Physical Geology. Prentice Hall: New Jersey (Tarbuck and Lutgens, 1996) Yodmani, S. (2001). Disaster Risk Management and Vulnerability Reduction: Protecting the Poor. Paper Presented at the Social protection Workshop 6: Protecting Communities – Social funds and Disaster Management, Manila. Read More