Earthquakes are sudden slippages or movements in a portion of the earth's crust accompanied by a series of vibrations. Aftershocks of similar or lesser intensity can follow the main quake. Earthquakes can occur at any time of the year. An earthquake is generally considered to be the most destructive and frightening of all forces of nature. Earthquake losses, like those of other disasters, tend to cause more financial losses in industrialized countries and more injuries and deaths in undeveloped countries.
The Richter magnitude, used as an indication of the force of an earthquake, measures the magnitude and intensity or energy released by the quake. This value is calculated based on data recordings from a single observation point for events anywhere on earth, but it does not address the possible damaging effects of the earthquake. According to global observations, an average of two earthquakes of a Richter magnitude 8 or slightly more occur every year. A one digit drop in magnitude equates with a tenfold increase in frequency. Therefore, earthquakes of magnitude 7 or more generally occur 20 times in a year, while those with a magnitude 6 or more occur approximately 200 times.
Earthquakes can result in a secondary disaster, catastrophic tsunami. Tsunami, a series of waves of very great length and period, are usually generated by large earthquakes under or near the oceans, close to the edges of the tectonic plates. These waves may travel long distances, increase in height abruptly when they reach shallow water, and cause great devastation far away from the source. Submarine landslides and volcanic eruptions beneath the sea or on small islands can also be responsible for tsunami, but their effects are usually limited to smaller areas. Volcanic tsunami are usually of greater magnitude than seismic ones; waves of more than 40 meters (131.234 feet) in height have been witnessed.
Geologists have identified regions where earthquakes are likely to occur. With the increasing population worldwide and urban migration trends, higher death tolls and greater property losses are more likely in many areas prone to earthquakes. At least 70 million people face significant risk of death or injury from earthquakes because they live in the 39 states that are seismically active. In addition to the significant risks in California, the Pacific Northwest, Utah, and Idaho, six major cities with populations greater than 100,000 are located within the seismic area of the New Madrid fault. Major Third World cities in which large numbers are forced to live on earthquake-prone land in structures unable to withstand damage include Lima, Peru; Santiago, Chile; Quito, Ecuador; and Caracas, Venezuela.
Deaths and injuries from earthquakes vary according to the type of housing available, time of day of occurrence, and population density. Common injuries include cuts, broken bones, crush injuries, and dehydration from being trapped in rubble. Stress reactions are also common. Morbidity and mortality can occur during the actual quake, the delayed collapse of unsound structures, or clean-up activity.
Public health officials can intervene both in advance of and after earthquakes to prevent post-earthquake injuries. The safety of homes and the work environment can be improved by building standards that require stricter codes and use of safer materials. Measures to prevent injuries include securing appliances, securing hanging items on walls or overhead, turning off utilities, storing hazardous materials in safe, well-ventilated areas, and checking homes for hazards such as windows and glass that might shatter.
Public health workers should follow the recommendations listed previously for Cyclone.
Encourage earthquake drills to practice emergency procedures.
Recommend items for inclusion in an extensive first aid kit and a survival kit for home and automobile.
Teach basic precautions regarding safe water and safe food.
Ensure the provision of emergency medical care to those who seek acute care in the first three to five days after an earthquake.
Ensure continuity of care for those who have lost access to prescriptions, home care, and other medical necessities.
Conduct surveillance for communicable disease and injuries, including location and severity of injury, disposition of patient, and follow-up contact information.
Prepare media advisories with appropriate warnings and advice for injury prevention.
Establish environmental controls.
Facilitate use of surveillance forms by search and rescue teams to record type of building, address of site, type of collapse, amount of dust, fire or toxic hazards, location of victims, and nature and severity of injuries.
American Public Health Association © 2005 American Public Health Association
Cite this: Types of Disasters and Their Consequences - Medscape - Sep 20, 2005.