Theb Great 1964 Alaska Earthquarke
Introduction
The Prince William Sound region in Alaska went down in North American books of history on March 27, 1964 for experiencing a fatal earthquake. The magnitude of the earthquake rated on various scales, but the moment magnitude rated it at 9.2mm. The epicenter was located approximately 10km to the east of college Fiord, Valdez 90km to the west of the epicenter and anchorage 120 Km to the east as fig 1.1 shows. The bearing of the epicenter was Lat. 61.04N, Long. 147.73W with an estimated depth of 25KM (American Society of Civil Engineers & Schiff 1991). At the time of its occurrence, it became the second greatest earthquake after the 1960 Chile earthquake of 9.5mm. The Alaska quake lasted for about four minutes. The earthquake produced electrifying ground motions that occasioned the ground deformations the affected regions have. The earthquake coupled up with strong local and trans-oceanic tsunamis which affected the Pacific. The tsunamis were responsible form much of the destruction that extended miles away.
Why the Alaska earthquake happened
At the time of occurrence of the earthquake, it remained scientifically unknown what could have been the cause of such a resounding earthquake that almost replicated that of Chile. It only took the investigations of a USGS scientist, George Plafker to get an interpretation of the causative factors of, not just the Alaska earthquake, but all other large earthquakes in the world. His interpretation brought a new dimension to geographical theory called the plate tectonic theory (Fisher, & Merkle 1965). It explains the earth as having several tectonic plates that are in constant motion. At the time, the plates collide and the consequence would be mountains, rifts, volcano's earthquakes among others. Based on this, an explanation was devised. The Alaska earthquake was referred to as “Megathrust” as a result of an oceanic plate having descended underneath a continental plate of Alaska. These plates slipped against each other along a plate boundary that is called subduction zone (Lallemand 2009).
Precisely, the pacific plate usually moves northwestwards at a rate of about 5 to 7cm every year that compresses the continental crust of Southern Alaska. The makes it warp depressing some areas along the coast while uplifting others inland. This movement becomes of consequence after tens or hundreds of years. This is what happened in Alaska in 1964 when the region of Montague Island having particular areas uplifted to altitudes of 4-9 meters. Conversely, some areas in the outskirts of portage subsided as deep as three meters. It also illustrated in fig 1.1.
The Great Alaska Earthquake precursors and reoccurrences
As explained, investigations and inquests into the Alaska earthquake categorized it as a megathrust. Studies indicate that for North America, Megathrusts have prior indicators that may occur several years before the actual earthquake. The foraminifera and diatom assemblages at Girdwood Flats, Alaska, indicate changes that tell of possible precursor to the earthquake. This accordingly, informs of possible previous events that were not known. It brought into consideration precursor phases as may have been contained in the marshes at Turnagain Arm and in the south Netarts bay, Oregon, which were examined for precursor related events of earthquakes (Seismology Division 1964). The foraminifera at Turnagain Arm and the camoebian were always changing from forest stages to mildly brackish phase. It happened in a period dated to be 15 years before the earthquake in 1964. Evidence of an attempted subsidence at the same place was, similarly, a precursor occurrence.
In Netarts Bay, cores were taken and by use of carbon-14 dates supplied evidence of at least four events have taken place in the past period of over 3000 years. Archeological analyses of the sites in the region noted transitions of analyzed cores from high marsh pre quake to low marsh precursor phases which on analysis were indicating tectonic activity. The studies that were done on the aftermath of the earthquake assessed the captures of Global positioning systems for any leading hints in Oregon and Alaska. Further, the Megathrust earthquake had precursor events that were spread through time and may be detected in foraminiferal zonations that are recorded (Seismology Division 1964). “Silent” earthquakes and others regarded as slow are good indicators of megathrust such as the one of 1964.
There is yet to be another earthquake as recording making as the one of 1964 either in Alaska or the entire USA. There have been recorded earthquake replicas in recent American history in such places as the Carolinas, Virginia and California. However, their magnitude has not been significantly consequential to comparative levels with the Great Alaska earthquake. Most of them have had magnitudes of below 4.5.
The impact of the great Alaska earthquake and its extent
Direct Consequences
Tsunami
The earthquake caused a sudden rise of the seafloor which resulted to a tsunami. The tsunami revolved and swept at a dangerous speed of 400 miles an hour. Due to the terrific speed of the tsunami and its strength spread it to as far as Hawaiian Islands. Crescent city, Oregon and California also felt the impact of the Tsunami (Oceanography and coastal engineering 1972). Enormous logs of redwood were thrown onto the streets. The tsunami also occasioned seiches in water bodies, harbors and waterways especially in Louisiana and Texas even though only minor damage was wreaked (Seismology Division 1964). Harbor waves also resulted in that ascended as far high as 100ft higher than the usual levels.
Effects on Anchorage
The soil was turned into a liquid state temporarily. This liquefaction caused rock and landslides accompanied by avalanches in Anchorage and especially Turnagain Height. Homes that numbered to 75 were destructed. The ground motion that was strong resulted in the collapse of soft clay bluffs in this location. Anchorage was treated to a great loss of property that was valued at $311 million (National Research Council 1971). Of all the affected regions, Anchorage was the worst hit in property loss. The renowned J.C. Penney Company (shown in image 1.2) was entirely destroyed while four seasons apartment building irreparably damaged. The building was made of concrete panels that broke off striking a woman driving in her car to death. Another man was also killed by the collapsing parts of the building which were being thrust on the streets. Additionally, several schools were utterly destroyed including the Government Hill elementary school in Anchorage. It was fortunate that the schools had closed up for Easter holiday and hence no casualties were reported in the schools. An air traffic controller at the Anchorage International airport died as the control tower that stood 68 ft toppled over. The destruction also resulted in the rupturing sewer, gas and water lines. Severe interruptions on telephone and electrical services ere also experienced in Anchorage.
J.C. Penney Building in Anchorage (Photo credit: NOAA/NGDC)
Valdez
This is a port which is located to the east of the anchorage with a distance of 120 miles. There was an enormous harbor wave that lifted the S.S. Chena freighter that was unloading 30 ft killing 28 people(National Research Council 1971). The waterfront of Valdez, commercial buildings and homes were destroyed. It is reported that in Valdez later in the evening, waves continued that coupled with a rising tide engulfing many areas of it. The waves went on at intervals of two hours until early morning the following day (National Research Council 1971). The residents were forced to flee and stay on to the hills of subfreezing cold in which they involuntarily spent the night.
Seward
This is an oil port that is to the south of anchorage with an approximate distance of 80 miles. Most of what happened at Valdez was replicated at Seward. However, it had an additional resultant fire catastrophe. The waves and tides caused the rupturing of oil pipes and explosion of entire oil storage tanks. This caused a sheet of fire that burned the spewed fire at the harbor that claimed twelve lives (Page 1967).
Kodiak Island
This island had not been badly destroyed by the initial quakes. However, the tides and waves caused ebb that receded water to a depth as low as 2 ft. This left the boats sitting in the mud at the bottom of the harbor as the image below shows (page 1967). A later strong wave thrust the boats and buildings that were waterfront into the town. The fishermen had earlier noticed the coming tides and neglected the boats and hence escaped death.
The foregoing indicates how far the earthquake and the tsunamis spread and the primary damage it caused to the communities at Alaska and its environs. It shows that many lives were lost in the vehemence of the destructions it caused. Buildings were destroyed; businesses stalled, and supplies of basic commodities such as water and oil and electricity were affected. Besides, the original landscape of the area was badly hurt and deformed. It also shows the extent of the earthquake as to how it spread. The tsunami that resulted had far reaching effects.
Indirect consequences
The earthquake had social impacts as scores were displaced, rendered unemployed and lost loved ones. Harbors were badly devastated; business premises closed, and some employers killed. This intertwined with economic effects of unemployment disrupted commercial activities and untold suffering and restlessness of victims. People had to come to terms with the many social, economic, and environmental problems that confronted them when all was at last calm. No schools for children, homelessness and hence the situation of internal displacement arose. Families were separated from one another by death, and mysterious disappearances and hence entire societal institutions felt the outrage of the earthquake. The cost of reconstruction was expensive as some services were supposed to be restored in a short span of time (National Research Council 1992). Besides, the reconstruction was meant to make the regions safer to forearm the regions for any recurrence of such a catastrophe. Many landmarks were also lost in the process, and it is told of people who could not trace their original place of residence or work. Besides, many data was washed away, and this might have led to the loss of important information in organizations if there were no backup systems.
There are also other positive sides of the earthquake. After the earthquake, much archaeological information was uncovered which was dated and informed much about historical happening underneath the earth surface. Besides, reconstruction of the affected regions; roads, bridges, hospitals, schools, electricity lines, sewers among other important infrastructural facilities and structures provided employment opportunities (American Society of Civil Engineers., & Schiff 1991). Many improvements were realized from the aid that was poured in the region for reconstruction purposes. For instance, Valdez was moved to a different site that was more stable, provision of better facilities at the ports among other ripple effect improvements.
There was a major contribution of the earthquake to the geological discipline. It motivated more focused inquest that fully developed the plate tectonic theory that has become established as a one of the frameworks of explaining such events. A study of the soil characteristics, rocks, among other scientific tests were of great value to the knowledge base of catastrophe resolutions in the future.
Alaska Today
After the earthquake, it is fifty years down the memory lane. A description of the quake-struck Alaska has been turned into a region with much environmental prowess. The region has been bewares of the catastrophe possibility. The region is well planned. Skyscrapers are no longer constructed on plains and low latitude areas and hence plateaus are beautifully left to present good scenery of medium and short buildings. The earthquake must have served as a wake call on the government to institute more decisive regulatory factors as it regards constructions and other human activities that may pose a danger (Madden 2005). The government immediately established the national Tsunami Warning center which installed technologies that will warn of anyone that is impending and sounds an alarm in regard to its direction. This influence planning of Alaska avoiding congestion that could predispose the region to more damage as was the case in 1964.Alaska is better equipped with survey kept continuous to ensure there are no surprise strikes. Commercial activities in all the affected areas seem to go o as usual regardless of what happened over 50 years ago. The landscape still has evidence of the earthquake as some regions were sunk as other were lifted up (Madden 2005). However, local people take that as a heritage and an epitome of their history. The region ever since remains a tourist destination as the earthquake left some intriguing landmarks.
Conclusion
The great Alaska earthquake was phenomenal for it occasioned many changes environmentally, socially and economically. The devastation caused still lives vivid in the memory of many local communities. The damage assessment of the earthquake, however, points to it as having caused fewer fatalities compared to its outrage. This is because of its time and day which was Good Friday. However, buildings collapsed, industries brought to the ground and homes badly destructed. Its magnitude of 9.2mm was the fiercest in North American History and the second the world over. However, the research findings of the aftermath have helped America and the affected regions move forward in disaster preparedness with many technologies fixed that constantly monitor tectonic activity. These detect any precursor events for early alerts for communities to beware.
There has not yet occurred another similar earthquake. The tsunamis were responsible for most of the destruction caused that was valued at over $ 300 million. Families were displaced; employment destructed and business activities badly devastated. Disaster management agencies were instituted by the government in America to help in forewarning and geological studies enhanced that have yielded vital research information. The “megathrust” led to the strengthening of the Tectonic Plates theory that remains the most reliable framework of explaining large earthquakes.
Reference
Oceanography and coastal engineering. (1972). Washington: National Academy of sciences.
National Research Council (U.S.). (1971). The great Alaska earthquake of 1964. Washington, D.C: National Academy of Science.
Seismology Division. (1964). Prince William Sound, Alaskan earthquakes, March-April 1964: Preliminary Report. Washington, D.C: U.S. Department of Commerce, Coast and Geodetic Survey.
Page, R. A. (1967). Aftershocks and microaftershocks of the great Alaska earthquake of 1964. New York.
American Society of Civil Engineers., & Schiff, A. J. (1991). Guide to post-earthquake investigation of lifelines. New York, N.Y: American Society of Civil Engineers.
National Research Council (U.S.). (1992). The Economic consequences of a catastrophic earthquake: Proceedings of a forum, August 1 and 2, 1990. Washington, D.C: National Academy Press.
Lallemand, S. (2009). Subduction zone geodynamics. Berlin: Springer.
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Fisher, W. E., Merkle, D. H., & AIR FORCE WEAPONS LAB KIRTLAND AFB N MEX. (1965). THE GREAT ALASKA EARTHQUAKE, VOLUME I. Ft. Belvoir: Defense Technical Information Center.
