January 12, 2010 4:53 PM, 15 miles WSW of Port-Au-Prince, Haiti, the ground began to shake with a 7.0 magnitude earthquake. 8 miles below the earth surface the Enriquillo-Plantain Garden fault was slipping with the Caribbean plate moving eastward against the North American plate.Unconfirmed historical earthquakes associated with this fault occurred in 1860, 1770, 1761, 1751, 1684, 1673 and 1618. A 5.9 magnitude after shock occurred at 5:00 PM followed by another 5.5 magnitude at 5:12 PM and then a 5.7 magnitude 2 minutes after midnight. Eight days later on January 20th at 6:03 AM a 6.1 magnitude struck again 35 miles WSW of Port-Au-Prince.The problem with earthquakes is the time span between them. Generations may go by before a major one hits again. People become lax, building codes relaxed and disaster strikes.The Richter scale, which records the magnitude of a quake doubles for every 0.2 increase. For example a 7.0 quake would be 32 times stronger than a 6.0 quake.
The earth’s crust is a mere 6.5 miles thick in mid ocean and an average of only 25 miles thick under the land masses. Think of the earth’s crust compared to the skin of an apple, then imagine the apple drying out and wrinkling. Well that is not quite how it happens but it looks that way.The crust is made up of large plates that are constantly on the move. The problem is that they are moving in different directions. When the plates grind against each other we have a fault and earthquakes. In other places one plate may be forced under another plate called subduction zones.The subduction zone where the Chile Ridge oceanic plate is slipping under the South American plate created the largest recorded earthquake.
The goal of earthquake prediction is to give warning of potentially damaging earthquakes early enough to allow appropriate response to the disaster, enabling people to minimize loss of life and property. The U.S. Geological Survey conducts and supports research on the likelihood of future earthquakes. This research includes field, laboratory, and theoretical investigations of earthquake mechanisms and fault zones. A primary goal of earthquake research is to increase the reliability of earthquake probability estimates. Ultimately, scientists would like to be able to specify a high probability for a specific earthquake on a particular fault within a particular year. Scientists estimate earthquake probabilities in two ways: by studying the history of large earthquakes in a specific area and the rate at which strain accumulates in the rock.Scientists study the past frequency of large earthquakes in order to determine the future likelihood of similar large shocks.
For example, if a region has experienced four magnitude 7 or larger earthquakes during 200 years of recorded history, and if these shocks occurred randomly in time, then scientists would assign a 50 percent probability (that is, just as likely to happen as not to happen) to the occurrence of another magnitude 7 or larger quake in the region during the next 50 years.But in many places, the assumption of random occurrence with time may not be true, because when strain is released along one part of the fault system, it may actually increase on another part. Four magnitude 6.8 or larger earthquakes and many magnitude 6 – 6.5 shocks occurred in the San Francisco Bay region during the 75 years between 1836 and 1911. For the next 68 years (until 1979), no earthquakes of magnitude 6 or larger occurred in the region.
Beginning with a magnitude 6.0 shock in 1979, the earthquake activity in the region increased dramatically; between 1979 and 1989, there were four magnitude 6 or greater earthquakes, including the magnitude 7.1 Loma Prieta earthquake. Both of these methods, and a wide array of monitoring techniques, are being tested along part of the San Andres fault. For the past 150 years, earthquakes of about magnitude 6 have occurred an average of every 22 years on the San Andreas fault near Parkfield, California.
The only and hence the most effective means to minimize the severe effects of earthquakes amidst the human lives is making adequate preparations for the earthquake emergencies.In the situation of an earthquake, one feels that the ground is shaking or rolling. In case the earthquake is a very sever one, that is the movements of earth’s crust are really violent, one might also hear the ground roaring or rumbling.These characteristics of an earthquake cause sheer panic among the people. Eventually this jeopardizes one’s chance of the survival. Luckily strong & devastating earthquakes do not happen that usually. Even in the locations where there is a minimal chance of earthquakes that is the places & nations that are located near the ring of fire of the earth, it is imperative to have some emergency plans to keep yourself and your family safe.Here are some tips that might help you getting prepared for the emergencies:Like it is said in the army that sweat that you put in the practice & preparations saves the blood in wars, the key for being safe in the earthquake is reacting quickly, instantly and in a practiced manner.
The moment one feels the ground shaking violently, he/she should know precisely what to do, just by their instincts. In order to have that fast reaction during earthquakes, one must regularly conduct the drills on earthquake emergency. This would keep you strong and firm on your feet in the case of emergency.The main goals of the ongoing Parkfield Earthquake Prediction Experiment are to record the geophysical signals before and after the expected earthquake; to issue a short-term prediction; and to develop effective methods of communication between earthquake scientists and community officials responsible for disaster response and mitigation.
This project has already made important contributions to both earth science and public policy.Scientific understanding of earthquakes is of vital importance to the Nation. As the population increases, expanding urban development and construction works encroach upon areas susceptible to earthquakes. With a greater understanding of the causes and effects of earthquakes, we may be able to reduce damage and loss of life from this destructive phenomenon.