Introduction
An earthquake is a tremor in the earth’s crust that results in seismic waves as a result of the sudden energy realized from the bowels of the earth. Earthquakes are most likely to occur in regions where the earth’s crust is experiencing any form of strain. The areas which are normally prone to earthquakes are normally the Faulty areas and also along the boundaries. Earthquakes that occur in the faulty areas can result from normal faults, reverse or strike faults. Earthquakes will normally come about as a result of the tectonic displacement of the earth’s crust (Jacobs, p08). Earthquakes can also be deep or shallow depending on the depth of the epicenter. Earthquakes are not the same since the causes of each earthquake are different and the size and the frequency of each earthquake therefore differ. The earthquakes are normally recorded on the seismograph and the magnitude measured on it determines the extent of damage. Most earthquakes will result in various injuries, loss of lives and damage of property in the areas they occur. Some of the known effects include shaking and deformation of the earth, landslides, fires, floods, loss of human life among other human impacts (O’Rourke, p14). To assess the difference between earthquake occurrences, this paper compares the Loma Prieta California Earthquake of October 1989 with the December 1988 Armenia Earthquake.
Causes of the earthquakes
The 1988 Armenia earthquake which is commonly referred to as the Spitak Earthquake occurred in a region that stretches from Turkey to the Arabian Sea on 7th December at 11. 41 AM. This is a seismic region that is prone to earthquake occurrences. The nature of the earthquakes in this region is believed to be caused by movement of plates in the earth’s crust. The Eurasian plate is believed to be colliding with the Arabian landmass (Urdang, p16). The earthquake was a result of faulting and the small fault which was directly under Spitak resulted in the movement of the North East side which rode up on the side facing South West. Colliding of plates normally results from the movement of plates as they are trying to realign themselves over time. History has it that the Arabian Plate and the Eurasian plate keep colliding and as a result the region has many occurrences of similar earthquakes. The earthquakes in this region result from the pressure that is built from the interlocking of the plates. According to scientists, the earthquake occurred along a fault line that had its origins from the Kars region of Turkey and went across the Armenian city.
The following year after the Armenian Earthquake, another earthquake was experienced in San Francisco Bay Area of California on 17th October at 5.04 P.M. This was the first strong earthquake that struck America in history. The earthquake occurred at a time when the country was busy preparing to host the 1989 World Series baseball championship (Jed, p17). This games actually affected the extent to which the damage could have been caused since most people were either not at their places of work or they were busy waiting to celebrate the games at home. Movement along the streets was therefore minimal as compared to other weekdays; the earthquake which occurred in the Santa Cruz Mountains of central California had actually been predicted about two weeks in advance. An increased low frequency had been observed 7 Kilometers from the epicenter. There were magnetic disturbances within the magnetic field nearby and this was measured by an instrument called Magnetometer which was used to search radio communications by the submarines. The signals which were about 20 times higher than normal were reported on 3rd October by Professor Anthony C. Fraser Smith who worked for the Stanford University. Three hours before the occurrence of the earthquake the signals were about 60 times above the normal signals (Bokelmann, p33). The earthquake was named Lorna Prieta after a nearby peak which lay 8Km Northeast of Santa Clara County.
The magnitudes, orientation and the frequencies of the earthquakes
The Epicenter of the earthquake was located in the Forest of Nisene Marks state park in the Santa Cruz County. The area was generally unpopulated. The orientation of the epicenter is given as 37002’N 121 0 53’W (Jed, p19). This is approximately 4km North of Aptos and 16km Northeast of Santa Cruz. The earthquake had a magnitude of 7.1 on the Richter scale which was considered the largest earthquake in the region after the 1906 San Francisco earthquake. The tremor is reported to have resulted from the San Andreas faults. The earthquake mostly affected the southern side of the 1906 rupture. This covered a distance of about 40 Km. the faulting was of the strike-slip and the reverse nature. This resulted in displacement of the earth’s crust about 1.2 meters as a result of the strike-slip and 1.6 meters from the reverse slip. Geologists suggested that the motion occurred on a sub-parallel fault and not on the San Andreas Fault itself. The earthquake was felt in a very large area due to its proximity. This included 6 km, ENE 610 Santa Cruz, 22 km, WSW 2440 Morgan Hill, 34 km, S 1770 San Jose, 47 km, N50 Monterey, 71 km, S1880 Livermore, 91 km, SSE1580 Oakland, 95 km, SSE1500 San Francisco and 100 km, SSE1590 Berkeley (Bokelmann, p43).
The Armenian earthquake is considered to be the fourth strongest earthquake in the region. This clearly indicates that the region is more prone to strong earthquakes as compared to the California region which experienced its first strongest earthquake. Other strong earthquakes that had hit the region had magnitudes of 7.3. This specific earthquake had a magnitude of 6.9 (Urdang, p21). The region experienced 14 other similar earthquakes in Asia in 1988. Its epicenter was located in the mountainous region of Lesser Caucasus. This was 25miles/ 40Km towards the north of Armenia. This epicenter region is prone to volcanic actions and it is comprised of various volcanic rocks and faults that lie beneath the rocks (Hovanesian, p41). The rupture of this earthquake had several branches. Two of these services reached the surface with the first rupture beginning at Alavar. The branch started at N1400 and it stretched a distance of 11km and finally 4Km towards the South East of Spitak. This branch also had strike-slip faults with a length of 50cm. The second branch was the major one starting 8 Km between Gekhasar and Spitak. Its orientation was N1200 and its faults were of the reverse nature. The earthquake was then followed by aftershocks of a magnitude of 5.8 (Jacobs, p13). Other land deformations were also observed in Gekhasar which included some normal faults resulting in uplifting of rocks and also some folds along the north-western side. Both the earthquakes had their epicenters in the mountainous regions giving an indication that these regions are subject to volcanic actions and thus possibility of occurrence of earthquakes.
Injuries, damages and the destruction caused by both earthquakes
Both of these earthquakes resulted in a lot of destruction, injuries and loss of lives. The extent of the damages however differed in that the structural buildings in both regions are not the same. The magnitudes were also not the same and the Lorna Prieta earthquake covered a wider region than the Armenian earthquake. The Armenian earthquake destroyed the whole city of Spitak and minor damages were also reported in the nearby cities of Gyumri and Vanadzor. Damages were also observed in the surrounding villages. The nuclear power plant at Metsamor was actually closed following the damages that followed (Urdang, p35). The earthquake killed a lot of people most of which were school children. The statistics indicate that a total number of 25,000 people perished in the earthquake (Jacobs, p19). The local structures which were affected mostly included the hospitals and the schools. The geologists have however blamed the massive destruction on the poorly constructed buildings. Reports indicate that if the earthquake could have occurred five minutes later most school children would have left the buildings and the number of deaths reported would have been lower.
The disaster management of that time was not adequately prepared for a disaster of this magnitude and this meant they could not adequately handle the situation. This necessitated the invitation of foreign relief efforts to help in the recovery process (Jacobs, p23). This was actually the first time that the foreign workers were allowed to work in the sovereign union region. Efforts to rebuild the city and the houses were received from all over the world. An Architecture monument was erected in Washington D.C in 1990 to reflect the appreciation of the Armenian people for the help they received from the U.S. The earthquake however left many school children with a lot of trauma after experiencing death of their friends and relatives in the school buildings. Other aftermath effects included the distortion of the time of the day, very low winter temperatures and poor soils.
The Lorna Prieta Earthquake resulted in sixty-three deaths six of which were as a result of direct effects of the earthquake. Other 3,757 injuries were reported (Bokelmann, p56). This was a minor number as compared to the deaths that resulted from the Armenian earthquake. Major injuries resulted from the collapse of Cypress Street Viaduct. In this area, a double-decker portion of the Nimitz freeway collapsed leading to massive crushing of cars on the lower side. The Oakland Bay Bridge experienced a 50-foot collapse which caused two cars to fall on the lower deck. These bridges are reported to have been there for a long period but no one had taken the initiative to strengthen them. The injuries that resulted from this earthquake could have been higher could this have been a normal day. Many people had left their places of work early while others stayed late to participate in other activities. As a result the normal heavy traffic was not experienced on this day and this minimized the number of deaths that would have occurred.
The earthquake resulted in major damages especially in San Francisco and Oakland. Other regions such as San Mateo, Santa Clara, Santa Cruz, San Benito County, Monterey Counties and Alameda experienced a lot of damage. Majority of the property destroyed was 95 Km away from the epicenter which mostly affected the Marina District. The extensive damage in this district resulted from the liquefaction of soil that was used to fill the waterfront property. The district was mostly affected because it was built on filled land. The filling was mostly sand and other materials included dirt and ripple. When an earthquake occurs in such a region the sand becomes water-like and the buildings built on it cannot stand on it anymore (O’Rourke, p19). The areas comprised of many story buildings which collapsed on the earth’s tremor.
At the junction of the Divisadero Street and the San Francisco’s Beach a gas rupture occurred which resulted in a major fire destruction. Other aftermath effects that resulted from the earthquake were landslides, ruptures and also sand volcanoes. About 25,753 business premises and 18,306 homes were destroyed by the earthquake. Forty buildings collapsed in San Cruz killing six people. The historic Pacific Garden Mall suffered great damage that resulted in several deaths. The Capitola Village also experienced significant structural damage. Many of the wooden structures in Watson Ville had their foundations demolished resulting in loss of lives. Other structures and buildings were also destroyed in the other cities (Jed, p25). The earthquake caused a great effect on the transportation sector of the affected regions for about one month as they awaited the repair of the affected means of transport. Other people lost their homes while others lost their jobs and sustained serious injuries.
The extent of the damage caused by the earthquake was actually not expected since the epicenter was very far from the regions that were worst hit by the earthquake. Geologists however concluded that the damage was extensive due to the seismic waves that went as deep as 24 km in the earth’s surface. The property that was destroyed was estimated to have a value of between $6 Billion and $ 13 Billion (O’Rourke, p21). This marked the most expensive natural disaster in the history of the United States. Most citizens were involved in the rescue mission of the trapped victims in the buildings. The police and the fire rescue teams were also greatly involved. The US also received a lot of donations that were used to assist in the recovery of the damage caused by the earthquake. President George Bush assigned $3.45 billion as a relief package towards the earthquake recovery. The Armenian earthquake though it had a smaller magnitude than the Lorna Prieta Earthquake, it resulted in many deaths and structural destruction. The latter earthquake did not have many deaths although many people sustained serious injuries. The earthquake mostly had massive destruction of property as compared to the Armenian earthquake.
Conclusions
In conclusion, both of these regions are faulty areas that are prone to earthquakes. The Armenian region however is observed to be more at risk due to movement of the Eurasian and the Arabian plate. This makes it experience more earthquakes than the California region. Despite the knowledge of the risks that are deemed to occur in this area, the authorities seemed to be not well prepared for such disasters. Even though the magnitude of the earthquake was unexpected, history had it that there were other earthquakes of greater magnitudes that had occurred in the region. The damages that may result from one earthquake may not be the same as the other and this makes it very important for the governments in such regions to be prepared for any magnitude of destruction from such tremors. The Lorna Prieta earthquake was well handled by the authorities and the general public even though the magnitude and the location of the epicenter were not expected to cause such damage. The government also responded well in recovering the damages done. The experiences in both of these disasters indicate the importance of investing in more stable structures such that in periods of such tragedy, the kind of structural damage experienced would be minimal. This is because the statistics in both earthquakes indicate that majority of the buildings that collapsed were either not stable or were built on filled-up lands. The bridges that collapsed in the Lorna Prieta earthquake were also not strong enough to escape the damage (O’Rourke, p37). Regions prone to earthquakes should always check and reinforce the buildings after a period of time. The government should also be involved in training more disaster management teams who can help during such periods. The general public should also be equipped with more awareness on how to handle themselves during periods of natural disasters such as lying flat on the ground under a table, switching off any gas, keeping first aid kits among others.
Works cited
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Melkonian A, Noji EK and Hovanesian. Deaths and injuries due to the earthquake in Armenia. International Journal of Epidemiology, 1997. 12-68
Nigg and O’Rourke. Lessons Learned from the Loma Prieta Earthquake in California. Prentice Hall.1989 12-54
S Baisch and GHR Bokelmann. Seismic waveform attributes before and after the Loma Prieta earthquake. Journal of Geophysical Research, 2001.112-120
11Schiff and A. Jed. The Loma Prieta, California, Earthquake, 1989. U.S Geological Survey Professional Paper, 1998. 17-78