Introduction
Earthquakes are not a new phenomenon in the U.S.: numerous parts of the country experience them. They are cause stress accumulation in the underground rocks. The accumulation of this stress is a clear indication of the slow but constant movement of the earth’s outermost rocky layers.
These are large sections of which move about earth as tectonic plates. The collision or grinding of adjacent plates leads to stressing of rocks. This stress is then released to the earth’s surface in the form of sudden shifts. Consequently, plate boundaries are the primary breeding ground for earthquakes.
Earthquakes have many effects. They can cause deaths, injuries, and damages to buildings and other structures. They may lead to a wide range of long term economic or social impacts. As such, they should be addressed with a proportionate measure of seriousness and concern. Governments should use the past as a lesson on addressing any future occurrences of these disasters. This report examines the scope of the earthquake phenomenon in New Madrid and Fulton city, Missouri.
Earthquakes in New Madrid: When did it all begin?
The winter of 1811-12 was not an average humdrum winter to the residents of New Madrid. If anyone had been keen to record the events of that season, the manuscript would probably have been rejected as being just too fanciful for compelling fiction.
Indeed, seismologists call it the greatest release of seismic energy is so short a time ever witnessed and recorded by human beings. A few individual earthquakes have been bigger. In a few instances perhaps they have been more numerous within a short span. However, never so many were so big in so short a time (Braile et al., 1982).
The drastic events that took place on December 16, 1816 indicate that catastrophic earthquakes do not occur in the western [parts of the United States alone. In the last two and half decades, seismologists have come to learn that strong earth quakes that occur in the central Mississippi Valley are not mere events but have occurred repeatedly throughout the geologic past. This area has come to be known as the New Madrid Seismic Zone (NMSZ) (Pratt, 2009). The zone occupies the southeastern part of Missouri and the southern part of Illinois. The NMSZ consists of a number of thrust faults stretching from Marked Tree in Arkansas, to Cairo in Illinois.
Earthquakes that occur in the eastern or central parts of the United States are worse than those of similar magnitude in the western parts. For instance, an earth quake that occurred in San Francisco, California in 1906 had some magnitude of 7.8 measured on the Richter scale. It was experienced some 350 miles away in the center of Nevada.
However, an earthquake of almost a similar magnitude that occurred in New Madrid on December of 1811 went to the extent of ringing bells in Boston, a city that is 1000 miles away from the epicenter. Such geographical disparities in the east and west are caused by the Rocky Mountains.
The large earthquakes, which occur in the region notably, affect the New Madrid Seismic Zone. The closest areas that are also affected by the zone earthquakes are Arkansas, Tennessee, Kentucky, and Illinois (Weznger 213). The southwestern parts of Indiana and the northwestern Mississippi have also declared to receive extraordinary shaking from the region’s strong earthquakes. The latest New Madrid fault system covers an area of 120 miles, cutting across the Mississippi River, as well as Ohio River (Braile et al., 1982).
Geology of New Madrid Seismic Zone
The New Madrid Seismic Zone is found in the northern region of Mississippi embayment. The latter is a broad trough full of marine sedimentary rocks that are dated 50-100 million years ago. The top 30 meters of sediment that is in the embayment comprise of sand, silt, and clay. They were deposited by Rivers Mississippi, White, Ohio, and St. Francis. The NMSZ is composed of faults that were experienced when the area currently referred to as North America broke up. This occurrence occurred approximately 750 million years ago (Penick, 2001).
The main cracks formed resulted to the present faults that are found in the zone. The magma that was pushed from inside the rocks came at the surface and formed themselves into igneous rocks. The rift that was formed when the earth was splitting off remained as a region of weakness underneath the earth surface. Later, yet another unsuccessful rifting trial left the area weaker than before, hence, creating more faults.
The second occurrence of unsuccessful rifting occurred approximately 200 million years ago (Pratt, 2009). The reel foot rift was realized because of geological structures that emerged after every rifting attempt. The large rocks that are found underneath the earths surface in New Madrid are feared to be mechanically weaker than most of other parts of North America, due to the past fault that were created.
The underneath weaknesses, together with the effects of stronger rocks, allow the east west condensed forces to reinforce the old faults. Although there are several rifts that are experienced in most parts of North America, not all of them are associated with the modern types of earthquakes that occur in the area.
For instance, the mid-continent rift system that starts from Minnesota and ends in Kansas may not be associated with any earthquake, as other processes may add to mechanical stress on the already existing faults (Braile et al., 1982). Some of the local processes that are suspected to cause earthquakes are downward pulling from underneath rocks that are below the fault. Other incidences include bending of the lithosphere because of continental glaciers melting.
The earthquake experiences: a ground for further investigations
Several suggestions are made concerning the heating that happen in the lithosphere, may result in making the big rocks inside more plastic. This heating may cause the concentration of compression force in the shallow underneath regions, where the faulting happens.
There is also a model that describes local stress to happen because of a change in the passage of the mantle below the New Madrid Seismic Zone, due to sinking Carillon Plate. There are three types of trends realized when epicenters of modern earthquakes are presented in the form of a map.
The first system of a trend is referred to as general northeast southwest. This trend is parallel to the drift of the Reel foot Rift in part of Arkansas. The second system of the trend is called southeast to northwest. This drift is experienced at the southwest part of New Madrid. The third system of a trend is known as northeast to northwestern. It extends to the farthest end of the Reel foot Fault (Penick, 2001).
The New Madrid Seismic Zone recorded four of the largest earthquakes that have happened in North America. They were big earthquakes believed to be as large as 8.0. The largest earthquakes that were first experienced in this zone occurred between 1811 and 1812. The New Madrid Sequence is the overall effect of all the earthquakes that happened during that period. It has been always a challenge to measure the effect of one earthquake. The magnitude approximates and epicenters are based on the results of historical records, and this may vary from one period to the other.
Earthquakes in the past or the recent ones that have happened for the last 10000 years have been caused by faults, which are not always micro seismically active. According to some of the researches done, it is evident that quiet faults are at times dangerous than the active ones.
High built up stress blocks both sides of the fault, hence hindering the occurrence of micro seismic earthquakes. This process happens before the major rupture of the fault happens; investigations are still ongoing to define whether such types of faults do happen in New Madrid Seismic Zone (Weznger, 2010). Further investigations are required to proof, as it would be hard to locate such incidences. For the last 10000 years, people in this zone felt more than two thousand quakes. Crude seismograph instruments were used to detect these quakes, and most journalists managed to record these events in personal journals (Pratt, 2009).
In the central United States, rocks that are found there are hard, cold, and dry. The presence of such rocks makes earthquake in this region to be strong than the earthquakes that happen in California as well as in other areas. The earthquakes, which happen within the New Madrid Seismic Zone, cause damages, which are approximately 20 times larger than in other areas (Penick, 2001).
The measurement challenge
For many years, it has been a great challenge to estimate the recurrence of earthquake. With approximate locations, time and dates, and the size, it would be capable to provide a rough estimate of recurrence interval (Nixon, 2009)). Currently, some pale seismologists have provided people with information that two or more earthquakes of seven or more magnitude were experienced in the last 2000 years.
They used some information to come up with a recurrence interval estimate of 3000 to 1000 years. It was estimated that, after 100 years, the New Madrid Seismic Zone would experience an earthquake of magnitude more than 6. These 100 hundred years were to be calculated since 1812, but this time has already elapsed. The estimates are not always accurate, and that is one of the major issues, which require further investigations.
Effects of the 1811-1812 New Madrid earthquakes
The 1811-1812 earthquakes in the New Madrid Seismic Zone had many effects. The most obvious of these include sandy blows. These were due to the upsurge of water and sand to the ground surface. This phenomenon is known as earthquake-induced liquefaction (see chart below). This is the process by which a saturated soil substantially loses its power and strength due to a stress that is applied to it by an earthquake shaking. This makes the soil to act like a liquid. Soil liquefaction leads to a number of cascading hazards such as floods, landslides, and river debris (Tuttle & Associates, 2011).
During the 1811-12 earthquakes, sand blows formed over an extremely large area measuring about 10, 400 square kilometers. The effects of these were experienced 200km away in the northeastern part of the NMSZ. Even today, sand blows are visible in the New Madrid region. They appear as sandy patches that have a light color in cultivated fields.
Recent earthquakes of medium magnitude have led to loss of lives and destruction of property worth billions of dollars. For instance, in Northridge, California, an earth quake of magnitude 6.7 led to the death of 33 residents, and destruction of property worth $20 billion.
In the following year, an earthquake of magnitude 6.9 occurred in Kobe, Japan killing 5, 500 people and destroying property valued at $100 billion (Penick, 2001). These statistics indicate that there is a need for the inhabitants of New Madrid Seismic Zone to be prepared in case an earthquake of such medium magnitude happens in the future. This is because earthquakes of medium magnitude are likely to occur than those of great magnitude. In deed, seismologists approximate the likelihood of the occurrence of an earthquake that is of magnitude 6.0 or greater within the next 50 years ranges from 25% to 40% (Weznger, 2010).
If such a disaster happens, it is bound to affect more people than the incident that occurred on December 1811. This is because the population of the central Mississippi Valley was smaller compared to the current one consisting of millions of people. In addition, the calamity is likely to be dangerous because many structures in the area were not designed to withstand earthquakes as is the case in areas that are more seismic active such as California (Pratt, 2009).
Earthquakes in Fulton, Missouri
Fulton is the largest city in the Kingdom of Callaway County. As of 2009, it population stood at 12, 814. According to the 2000 census, the average household income is $32, 625. Callaway water district provides a lot of employment opportunities for the residents of Fulton City.
Other institutions that are of economic value to the city include Fulton State Hospital and Missouri School for the Deaf. According to the 2000 census, the average household income is $32, 625 (City of Fulton, MO., 2011).
Geology of Fulton.
The city is situated on a low-lying land. Missouri River is the defining physical feature in Mid-Missouri, and it surrounds the southwester border of Callaway County. There are three dominant soil types in the Callaway County. These are alluvium, sandy clay, and clay loam till soils (Chalfant, 2008). Just like the rest of Missouri County, the weather patterns in Missouri are not constant.
There are both extremes of temperature. The county has experienced a number of natural hazards in the history of its existence. These include floods, severe weather conditions, tornadoes, and hail. In the recent past, the most memorial natural hazard that took occurred in this county is the Flood of 1993. This flood affected a large portion of Missouri State causing a lot of damage on commercial properties, public facilities, transportation, as well as agriculture.
The geology of Fulton is similar to that of the central region of the U.S. It consists of cold, dry and less fractured rocks. Although the probability of an earthquake is not high as in the case of New Madrid, any occurrence of the same will be more hazardous than it would have been the case in other regions such as California.
In the recent past, a number of earthquakes have been recorded in the area. On July 31, 2005, an earthquake of magnitude 3.3 was experienced 43 miles from the city center. On March 30, 2001, an earthquake of magnitude 3.1 was felt 98 miles from Fulton City center (Citi-Data.com, 2011).
The above statistics indicate that the risk of, although the magnitude of earthquakes occurring in the city may be small and do mot occur in the city centre, there is a high probability of such occurrences in the future. Nevertheless, the occurrence of earthquakes in Fulton is way below that of the entire Missouri state.
However, this does not imply that the phenomenon is not an issue of concern to the city. Although earthquakes in this area have not been very destructive in the past as compared to that in New Madrid, any occurrence of earthquakes in this region can destroy the Callaway Nuclear Facility, hence cutting off the livelihoods of many residents who work in it (American Services, 2011).
Summary of main findings
Earthquakes are always occurring, with some being too small to be felt while others are large enough to cause irreparable damages. On average, major earthquakes happen once in a year. This will depend on the location of a place on the planet. However, more seismic active areas like the New Madrid Seismic Zone have high risks of experiencing hazardous earthquakes than other areas in the state of Missouri. This high probability is of great concern to Fulton city as it predisposes the latter to this risk.
The duration of earthquakes is generally short compared to other hazards such as floods. It could be minutes, or even seconds. The main earthquake event lasts for a short duration. The foreshocks and aftershocks linked with a single geological shift can be detected weeks before or months later. This was the case with the December 1811-12 earthquakes that span for a period of three months until March the following year.
The amount of destruction that results from an earthquake depends on several factors, one of them is strength. Earthquakes vary remarkably in their power. Some can be barely felt while others can knock one off their feet or buildings off their foundation.
There are two principal methods of measuring earthquakes. These are the Richter scale and Mercalli Scale. The Richter scale is more famous than the Mercalli scale. It was formulated in 1935 by Charles F. Richter, a seismologist. The scale indicates ground motion in an earthquake. Its values range from 0 to 9 (see appendix). However, theoretically, the range can be higher. The numbers are logarithmic, implying that each whole number is ten times greater than the preceding whole number. For instance, the New Madrid earthquakes of 1811-12 were of magnitude (Heatwole, 2011).
The second scale, the Mercalli scale, was developed in 1902 by Giuseppe Mercalli. The scale measures the intensity or violence of an earthquake in terms of damage caused to human-built structures. It is expressed by a series of Roman numerals ranging from I to XII (see appendix). An increase in the scale implies an incr4ease in intensity of the violence caused by the earthquake. Going by this scale, the New Madrid earthquakes of 1811-12 were so intense such that the Mississippi River changed its course, and an island in the river disappeared (Feldman, 2005).
In addition, new land arose, forests were cleared, and the ground rolled in visible waves that swept houses away, gardens, and fields. Nevertheless, few people perished during the incident due to the fact the area was sparsely populated then (Missouri Department of Natural Resources, 2011).
Mitigating the risks of earthquakes: Prevention is better than cure
The decision for mitigation of lifelines against seismic hazard is a quite complex issue as different institutions such as government, local authorities, lifeline companies, or the insurance industry are involved. In addition, the decision is further complicated since it is based on the results of the seismic risk assessment of lifelines which include various uncertainties owing to seismic hazard, vulnerability, performance, and loss estimation.
Considering that earthquakes are a natural phenomenon little can be done to adjust the natural events system. As such, any mitigation efforts should be directed to human use systems (Balassanian, 2000). A number of practices can be handy in the mitigation of earth quakes. These include regulation of land use, education of the population about possible extreme events, as well as outfitting infrastructure tom meet local building codes. The readability of structures to withstand stress caused by earthquakes can be. Soil liquefaction caused by earthquakes can be mitigated through the installation of drains or use of deep, resistant pillars in construction (Keith & Petely, 2009).
Conclusion
This report has explored the earthquake in Fulton and New Madrid. It is evident that these two are at a great risk of experiencing an earthquake in the near future. However, the frequency of another big earthquake in New Madrid or Fulton areas of Missouri is debatable.
Nevertheless, the undeniable reality is that the region has a high seismic action. There is a need for education programs to enlighten the residents on the precaution measures that are highly required in the event of an earthquake. In addition, buildings in these two areas should take into account the vulnerability of the regions.
As such, they should be enhanced by use of smart designs along with appropriate materials such as steel and reinforced-concrete. If history is anything to go by, residents of these areas should not throw caution to the wind as far as earthquake mitigation is concerned.
They should take the appropriate measure to avoid a repeat of the events December 1811-12. Although an earthquake is a purely natural phenomenon, prevention is of prominence in these earthquake-prone areas. As they say, prevention is better than cure, or even, to be for-warned is to be for-armed.
References
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