Earthquakes: Definition, Prevalence of Occurrence, Damage, and Possibility of Prediction

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Introduction

An earthquake is a dangerous tremor that is caused by sudden release of energy in the crust of the earth leading to seismic waves that cause movements of the ground thus causing deaths and damages. These movements only last for a few minutes during which many deaths and a lot of damage is caused. This damaging process begins with violent shaking of the earth after which the ground ruptures leading to permanent displacement along the earth’s fault lines.

Earthquakes have also been known to cause landslides and even damaging volcanic activity. While earthquakes can come as naturally occurring events, they are also triggered by man’s activities. Some of the human activities that can cause earthquakes include mine blasts and nuclear tests. The naturally occurring earthquakes are the most common (US Geological Survey para 2). Seismometers are the instruments used for measuring earthquakes.

Earthquakes are measured using a local magnitude scale called the Richter scale or the moment magnitude where the latter is more common in reporting earthquakes that measure higher than 5 in magnitude. The earthquakes that are below magnitude 4.5 are considered as minor earthquakes.

Those that fall below the magnitude of 3 do not cause much damage and may even not be suspected in some areas. However, those that measure magnitude 7 and above have been known to be catastrophic depending on their depth. The recent largest earthquake in the world is the one that occurred in Japan on March 2011. This particular earthquake measured magnitude 9.0.

The effect an earthquake has depends on the location where it occurs and its strength and the shallow it gets. The earthquakes that are known to be shallower lead to more damage as they destroy even the structures that are designed to handle such catastrophes.

On the other hand, an earthquake of a certain magnitude will have less impact on an area where the ground that underlies it is a solid rock than if the same earthquake occurred in an area with sediment as the underlying ground. However, the surface waves which are both shallow and of high magnitude cause great damage irrespective of where they occur. This is because they cause the ground to shake in the region that they occur and any rapid ground shaking leads to damaging of structures and buildings.

The shakes caused by these waves often buckle roads and even rail tracks (Scientific American 230). Basically, ground shaking is often viewed as the major and most common earthquake damage where it results to deaths and a lot of damage. The other damages that an earthquake can cause but not always are landslides and avalanches. These too can be equally damaging, like the one that occurred in Peru in 1970 killing about 80,000 people.

Brief history of earthquakes

Earthquakes are not new phenomena since both high rated in magnitude and those that have not made huge impacts after they have occurred have been experienced on the globe.

In the last few decades, seismologists have been keen where they have noted an increase in number of earthquakes that are of high-magnitude and those that have had great impacts. Some theorists have proposed that the energy that these earthquakes have released on a global scale in the last decade alone measures more than that which have been released in the last two or three decades before.

However, the earthquakes that occurred between 1952 and 1965 had a lot of energy just like the ones being experienced in this decade. During the period before 1950s, there was no accurate seismological equipment that would have been used to record the earthquakes that occurred during this period.

There have been large magnitude earthquakes in the world’s history ranging from 8.5 to 9.5 and causing different damages depending on where they have occurred.

For instance, in May 1960, an earthquake occurred in Valdivia, Chile killing 1665 people and injuring about 3000 others while those that were displaced amounted to more than 2 million people. This earthquake has been the highest recorded in magnitude in the world history since it was rated magnitude 9.5. The damage was so great to this nation that it caused the country around US$550 million.

The earthquake also caused a tsunami that caused deaths in Hawaii, Japan and even the Philippines with a rupture zone of more than 1000km. The earthquake also led to a volcanic eruption in Puyehue that caused steam to spread to a region of about 6km from where the eruption took place. There have been other more damaging earthquakes though rated lower than this in magnitude. The level of damage an earthquake causes depends on the location and its magnitude.

Types of earthquakes

Since earthquakes are viewed as the ground shaking, the different classifications of earthquakes depend on what causes the shaking. Basically, there are four common types of earthquakes. To begin with is a type that is known as tectonic earthquakes. The crust of the earth is composed of broken fragments of land normally referred to as tectonic plates (U.S. Department of the Interior para 4-6).

The tectonic plates loose, thus can move towards each other sometimes bumping into each other or even slide past each other (Kious and Tilling 44). A tectonic earthquake, therefore, occurs when the tectonic plates slide over each other causing great earth tremor. They are the most common types of earthquakes ranging from low to high level magnitude. Tectonic earthquakes also cause the most dangerous tremors which cause massive damage within a very short time.

Volcanic earthquakes are another type though less common than tectonic earthquakes. They are known to occur prior to or after a volcanic eruption. When classifying volcanic earthquakes by type, the first type is known as “volcanic tectonic earthquakes” while the second one is known as “long period volcanic” earthquakes.

The volcanic tectonic earthquakes usually occur after a volcanic activity where the magma that erupts leaves a space. As a result, the rocks move to cover the space causing an earthquake. In most cases the lava that an eruption causes falls on its vent thus causing blockage in pressure release. Since the blocked pressure cannot be contained for long, it erupts with a great explosion.

As a result an earthquake that occurs more often than not is of great magnitude (Simkin et al 14). The long period volcanic earthquakes occur before a volcanic eruption where the change in heat of magma below the surface of the earth forms seismic waves just before the eruption. This leads to an earthquake that may either be of high or low magnitude.

Collapse earthquakes are another type and are also referred to as mine bursts. Normally, these earthquakes are of small magnitude and often occur around underground mines. They are usually caused by the pressure that is found within the rocks leading to the collapse of the mine roof. This collapse leads to earth tremors that may cause damage in the nearby areas.

The other types of earthquakes are known as explosion earthquakes. They normally result from nuclear explosions. They are an example of earthquakes caused by human activity especially the numerous modern nuclear activities. The earthquakes of this type that have occurred in the past have been caused by testing of nuclear substances, causing tremors in the region where these activities are carried out. These tremors often cause great damage to land and the people of these regions are often affected.

General effects of earthquakes

Earthquakes do not occur in all areas but are concentrated on specific areas where tectonic plates which make up the earth’s surface meet. The people who are located in these areas are the ones who are at the greatest risk of deaths and even other effects that an earthquake causes.

These are areas which lie along the Pacific Rim, island chains and even those that are along continents’ boundaries. Some of the nations that lie on these regions include Japan and Aleutians among others. It is estimated that more than 500,000 earthquakes are reported every year where those that are of too small magnitude to cause any damage form the majority.

Of those that are susceptible by humans and are about 3000, seven to eleven of them cause destruction and loss of lives. Earthquakes cause various problems in various regions in the world. The most common problem that earthquakes are associated with is urban fires. These fires are normally caused by the ground shaking that occurs during this time (Seligson and Shoaf 903). This shaking and displacement of the ground leads to destruction of electrical and gas lines.

As a result, fire break ups are common during earthquakes. Handling this effect may be a problem as the means to respond to it like water may also be affected by the water pipes rupturing. Normally, the highest damage even to the buildings is caused by theses fires which are hard to deal with during the time of this crisis. In regions that are mountainous, earthquakes often cause landslides. These landslides are equally damaging.

Earthquakes have always been known to cause a lot of damage and destruction. Depending on where the earthquake occurs, it may cause destruction by damaging structures and buildings, fires, generation of tsunamis and even lead to loss of lives. The level of damage that an earthquake causes depends on several factors.

The region that it occurs

There are earthquakes that occur in remote regions of a country where there are few structures and are sparsely populated. The effects of such earthquakes are less damaging than those that occur in densely populated and more developed areas.

This is because in remote regions fewer lives are lost and fewer structures damaged. In addition, the time of the day when an earthquake occurs can determine the number of lives lost in an earthquake occurrence. This is where earthquakes that are known to cause the highest number of loss of lives or those that occur during weekdays especially between office hours which are 9.00 in the morning to 4.00 in the evening.

This is because during this time there are many people in large buildings in their offices and others in schools. Earthquakes have more effect on large structures and buildings than small homes which have no storey. The construction type also determines the damage caused. The modern buildings are designed to be less susceptible to the damage caused by earthquakes. Buildings that are well built can easily withstand ground shocks, thus limiting the damage caused.

Prediction

Another factor is earthquake prediction. This is where a prior warning is given of a potential earthquake. When a warning is given early enough, the right measures to respond to it are put in place enabling less damage to occur and fewer lives to be lost. Prediction is done by estimating that an earthquake will happen in a region during a specific year.

Scientists who possess wide knowledge on earthquakes are made to determine the location that an earthquake will occur and the magnitude that it has. This is because earthquakes mainly occur in specific geographic zones where they may even recur along a specific fault line at different times. Using this awareness, prediction can be made thus creating the appropriate awareness.

Earthquake in Japan

Japan is situated on the eastern edge of the Eurasian Plate. On Friday, March in 2011, a catastrophic earthquake hit Japan. This earthquake occurred near the Pacific coast of Japan which is about 400 km away from Tokyo. The US Geological Survey rated the earthquake to be of a magnitude of 8.9 while the USGS Japan Meteorological Agency (para 5) later updated it to magnitude 9.0 and a depth of 20 miles.

This, therefore, made this particular earthquake the fourth largest in the world history and the largest in Japan as the last one that had occurred with such a high magnitude in this nation was of 8.3 magnitude. The earthquake began near Sendai, in the north east of Japan.

Due to the risky region of Japan location, the Pacific oceanic plate sunk under the Eurasian continental plate (U.S. Department of the Interior para 7). This led to a type of plate margin that is known to be very destructive. This is because during the process of sinking friction caused the Pacific Plate to stick thus building up pressure.

During the release of this pressure, an earthquake occurred due to the massive pressure that had already accumulated. The result was that the earthquake. Though the earthquake was at a shallow depth of 20 miles under the Pacific Ocean surface, it combined with the high magnitude to lead to a tsunami. This caused a dangerous tsunami at the northeastern coast of Honshu.

The earthquake triggered aftershocks and a tsunami that measured 23-feet. Besides huge loss of lives amounting to more than 10,000 people, the economic impacts were huge especially considering that the crisis also caused the shutting down of the nuclear reactors which provided power to many industries.

Effects of the earthquake on Japan

The Japan earthquake had both short-term and long-term impacts; the immediate impacts being on how the nation was going to provide humanitarian aid to those who had been affected and do it in time to prevent increase in the number of fatalities.

The earthquake caused a lot of damage that caused billions of dollars wastage with a death toll of more than 10,000 people. The National Police Agency confirmed more than 15,000 deaths and more than 6,000 injured individuals. Among those who died, 92.5 percent died from drowning where the aged who were 60 years and above composed the largest number.

This is where they rated 65.2 percent of all the deaths with 24 percent of them being those who were 70 years and above. The earthquake hit during a weekday making it even worse especially to the school going children. About 100,000 children were displaced from their homes especially those who were away attending school. The earthquake also orphaned about 300 children and killed 378 school going children.

The earthquake caused a lot of damage too besides the high numbers of casualties. Most of the damage that occurred was caused by the tsunami. Though Japan had constructed a seawall that was 39 ft high along 40 percent of the country’s coastline to prevent the effect of a tsunami, this particular one was so strong that it went past the seawall and even washed away some parts of it.

Reports given by the police indicated that while 144,330 structures were destroyed due to the tsunami, a significant 45,700 resulted from the earthquake. Among the buildings that were damaged by this crisis included 44,000 prefectures and three hundred hospitals, some of which were destroyed completely.

The earthquake had long-term impacts on the nation of Japan. Being an industrial nation, this crisis caused massive effects especially due to its destruction of the nation’s main power supplies to these industries.

This forced some industries to slow down their production processes or close temporally in order to enable the restoration of essential economy. For instance, Japan being the largest China’s customer for earth metals and alloys, the industries that deal with the processing of these products had to reduce their imports or reduce their processing capacity.

Earthquakes in China

China has been a victim of several catastrophic earthquakes in the recent history; the most recent being the one that occurred in Sichuan on May 2008 with a 7.9 magnitude and killing about 70,000 people and leaving 18,000 others missing (The New York Times para 2).

There have been others that have been equally devastating in the history of this nation. A particular one is the one that occurred in Tangshan in 1976 killing more than 240,000 people after which China acquired a new policy that required structures to build with an ability to withstand strong earthquakes.

The central point where the earthquake began is said to be the county of Wenchuan, making the earthquake be labeled as the Sichuan earthquake. The earthquake had a depth of 19 kilometers making it endanger as far as Beijing and Shaghai which are 1500 and 1700 kilometers away respectively. The earthquake became the worst to hit China since the Tangshan one. Approximately 15 million individuals were victims of the earthquake in one way or the other.

The earthquake triggered very strong aftershocks which were above magnitude 6 and these aftershocks progressed one month after the main earthquake leading to more deaths and damage. It is reported that a movement in the northeast with an impact on Sichuan Basin which is located in the northwestern region occurred. Tectonic pressure that accumulated during these events culminated into the earthquake.

Effects of the Earthquake on China

The Sichuan earthquake caused a lot of damage due to both the high number of casualties and the damage of property and other structures. The number of those who died was about 70,000 people while those who were injured were about 375,000.

Other damages included destruction of buildings including schools, hospitals and factories among others. Since this earthquake occurred in an area that had not developed like the other urban centers, the damage was even more massive on its structures due to poor constructions that had not followed the policy placed for the strength to withstand earthquakes.

Most of these buildings were old and were built without being passed by the appropriate earthquake and seismic regulations bodies. As a result, the collapse of schools alone killed around 5,500 students while around 600 were left disabled. The parents who lost their only children in this earthquake had to reverse their sterilization with the assistance from the government medical teams who advised them and gave them fertility medication in order to get more children.

The earthquake also damaged a lot of property where it left more than 5 million individuals without housing. In addition, massive agricultural products and livestock were destroyed leading to more losses. The total economic loss that the earthquake caused was estimated to be more than US$75 billion dollars. This meant that this was the most costly earthquake that the country experienced in its history.

Earthquake in US

The United States has not been spared by the phenomenon of earthquakes either. A particular one is the one that occurred in San Francisco on April 18, 1906. The earthquake was estimated to have measured magnitude 7.9 but others have given a value of magnitude 8.25. The earthquake caused a rupture of 477 kilometers of the San Andreas Fault which stretched from northwest of San Juan Bautista to Cape Mendocino.

A strong aftershock which was so strong that it was felt in the whole of San Francisco Bay occurred after which the earthquake with an epicenter near San Francisco hit. Violent shocks and very strong ground shakings that lasted a minute or less were felt. One unique feature of this earthquake is the numerous fires that it triggered making it one of the worst natural disasters in the country’s history. The total death toll that the earthquake caused was about 3,000 people in addition to the huge economic impact it had on this nation.

Effects of the Earthquake on US

The earthquake caused deaths that were estimated to be 3,000 people though the government only reported a few deaths of about 400 people with an aim of preventing negative impacts on the rebuilding efforts. Most deaths were experienced in San Francisco but deaths also occurred in other neighboring cities like Santa Rosa (US Geological Survey, para 4-7).

The earthquake also left about 300,000 people homeless since at the time of its occurrence, San Francisco was the largest city on the West Coast. The effect was so massive that it destroyed 80 percent of this city where most of the damage was caused by the fires.

his is because more than 30 fires from ruptured gas mains led to destruction of more than 25,000 buildings and around 500 city blocks where they burned four days continuously. About USD 9.5 billion was the cost incurred as damage. San Francisco lost some important treasures like the Palace hotel which was the city’s landmark. In addition, scientific libraries and their rich discoveries were also destroyed by the fire. The monumental “Bear Flag Revolt” was also destroyed thus denying California its original flag.

Earthquakes prediction

There has been need for the prediction of earthquakes in the recent past due to the damaging effect that this phenomenon has been causing. Although studies have indicated the areas that are at risk, predicting the specific time that any earthquake may occur is still a challenge. However, using past statistics, geologists have been able to identify that most large earthquakes normally occur on far stretching fault zones especially around Pacific Ocean margin.

This has been caused by the consistent enlargement of the Indian Ocean while on the other hand the Pacific Ocean is shrinking. This shrinking effect pushes the ocean floor under the Pacific Rim making it vulnerable to earthquakes. In addition, the Pacific is characterized by long fault zones that cause geologic irregularities that lead to minor fault segments that crack separately (Ludwin para 2).

During such situations, the magnitude and timing of the earthquake is determined by the size of this fault, the stress that has accumulated below the surface and the type of rock of underneath. In the areas where the fault line and the movement of the earth plate have been established, there is a high possibility of an earthquake occurrence. This is particularly if these areas have had a history of breaking in history. However, this can only be possible when the fault zone is well established.

Earthquake prevention

There are various ways that earthquakes can be prevented in order to prevent their damaging effects. This is possible especially with those that are caused by human activities. Scientists have been trying to come up with ways of reducing the friction that is caused by colliding plates during the occurrence of an earthquake. This is through pouring water on areas where the two plates glide acting as a lubricant to the fault.

This releases one plate making it reduce the effect caused by the earthquake. The other solution that has been suggested is preventing the tidal waves. This is where sea tides are discontinued by obstructing the sea passage that is around the South Pole. This can be done in the area that borders Antarctica and South America. Matter can be brought closer to the earth using material from Andes Mountains thus help to come up with a long term solution to the problem of earthquakes (Earthquakes para 1-3).

Conclusion

Earthquakes are phenomena that will continue having their impacts on the human population especially having in mind that each earthquake is unique. This is besides there being new technological innovations which enable individuals to come up with new building designs and other structures that are complex in nature.

Since most earthquakes are a natural phenomenon, there is therefore the need for individual nations to come up with methods that are efficient to enable the processes of prevention and handling of these crises possible (Winchester 126). This will require the field of epidemiology to invent new methods of doing this. This will enable the nations to be better prepared when earthquakes happen in order to reduce the damage that they cause and reduce the deaths that these catastrophic events cause.

In order to effectively reduce this loss, there also need to be an increased efficiency in the way information is collected and distributed across agencies both in the local and international levels. This is where epidemiologists, seismologists and even designs engineers need to diversify their information sharing through linking their information databases with an aim of reducing the impacts of these crises.

This is because the information from these fields will provide timely details concerning the occurrence of an earthquake, thus enabling people and the whole nation to remain alert and well prepared. In addition, the population will be enlightened on the measures to take to prevent greater impacts through improving their construction methods and also remain informed on how to react when such a crisis occurs.

Disaster managers will also need to have easy access to important information after the research methods are improved in order to come up with better prevention methods and also better ways of handling the occurrence of an earthquake.

Through comparisons of various earthquakes that have occurred and their impacts on the human population, important lessons can be learnt where the nations will avoid repeating mistakes that were done in the past. In addition, new methods of carrying out the rescue processes can be invented. This is through coming up with better methods of delivering medical services and evacuating the individuals who are injured during such occurrences.

Works Cited

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Scientific American. Continents adrift and continents aground – Reading from Scientific American. San Francisco, CA: W.H. Freeman and Co., 1976. Print.

Seligson, Hope A and Shoaf, Kimberley I. “Human impacts of earthquakes”, Chapter. 28. In Chen WF, Scawthorn C, eds. Earthquake engineering handbook. Boca Raton, FL: CRC Press LLC, 2003. Print.

Simkin, Tom, Unger John D. and Tilling Robert I. et al. The dynamic planet: world map of volcanoes, earthquakes, impact craters, and plate tectonics. Denver, CO: US Geological Survey. Web.

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Winchester, Simon. A crack in the edge of the world: America and the Great California earthquake of 1906. New York, NY: HarperCollins Publishers, 2005. Print.

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