单选题
Earthquake
Every year throughout the world approximately 6000 earthquakes are detected. The vast majority of these are either too small or too far from populated areas to be felt. Several hundred, however, are felt and the majority of these, while frightening, are relatively harmless. A small number of earthquakes, however, are severe enough to cause serious damage to property, as well as injuries and even deaths. Earthquakes are a serious concern in major cities such as Tokyo, Mexico City, Los Angeles and San Francisco, which lie on or near earthquake faults.
Earthquakes are a result of the earth"s continuous friction movements along fault lines. Tectonic plates grind past or along side each other without interruption in areas that are prone to earthquakes. These sliding moves are only traced by seismologists in their labs, and are not evident for people going about their day to day lives. However, when the moving tectonic plates do not glide smoothly by one another, the resulting collision gives rise to tremors and shudders. Stronger impacts result in earthquakes.
Major earthquakes, while uncommon, rank among the deadliest of natural
catastrophes
. In the 20th Century, an average of 15,000 people has died every year due to earthquakes. Many deaths are caused by collapsed buildings, houses, bridges and other structures. Much damage—both in terms of material and human lives—however, is the result of side effects produced by earthquakes, such as tidal waves, landslides, avalanches, fires and the collapse of dams. Additionally, serious earthquakes may devastate a city"s infrastructure, resulting in contaminated drinking water, impassable roads, and disruptions in the supply of power and phone service. If damage to a city"s sanitation system and disruption of food and water supplies lasts for a longer time, earthquakes can cause significant injury and death long after the shaking of the earthquake itself has
subsided
.
Because earthquakes are
inevitable
, a program of hazard reduction is the only way to combat the severe damage earthquakes can inflict on life and property. Seismologists still cannot accurately predict the timing of earthquakes, but they can identify areas which are subject to seismic risk. Education of the population about the dangers of earthquakes and what to do in the event one occurs is important in limiting damage.
A number of nations, particularly the U.S. and Japan, have implemented stringent building codes which take into account the possibility of earthquakes in the design of buildings. The other way to limit the damage caused by earthquakes is the implementation of programs of emergency procedures in the event of an earthquake. These include evacuation plans, backup power sources and communication systems designed to keep citizens informed in the event of an earthquake.
For several years now, the Pacific Northwest has been in a vast state of preparedness in the event of an earthquake. Seismologists have long warned against the imminent danger of a major earthquake striking the Seattle—Portland metropolitan area. Such warnings come on the heel of recently tracked tremors along the Juan de Fuca fault line that borders the northwestern U.S. states. No major earthquake has hit the area in more than a few decades, and
a huge one
is bound to occur anytime soon.
Glossary
fault:
a crack in the earth"s crust resulting from the displacement of one side with respect to the other
infrastructure:
the stock of basic facilities and capital equipment needed for the functioning of a country or area
property:
any tangible or intangible possession that is owned by someone
seismologist:
a scientist who studies earthquakes