Perhaps Mother Nature offers no greater force than that of theearthquake. Across the span of time, earthquakes have been recorded for theirincredibledestructive forces, and their abilities to awe mankind with theirunparalleledforce.
Earthquakes can often strike without any notice, leveling largecitiesand killing scores of innocent people. Not only can earthquakes bring harmtosociety through these methods of destruction, but they can also causemillionsof dollars worth of damage to the areas they destroy, causing economicchaos. An earthquake is a natural phenomenon, occurring throughout the history oftheworld. Descriptions as old as recorded history show the significanteffectsearthquakes have had on people’s lives. Long before there were scientifictheories for the cause of earthquakes, people around the world createdfolkloreto explain them.
Until recent times, science has not had a completeunderstanding of how earthquakes are caused, and what can be done topredictwhen they will strike. This essay will discuss how earthquakes are formedandoccur, how scientists can more accurately predict the arrival ofearthquakes. Before contemplating how earthquakes might possibly be prevented, itisessential that the process and formation of and earthquake be understood. Earthquakes are caused when the earth’s crustal plates move, rub, or pushagainst each other. The earth’s crust (the outer layer of the earth) ismade upof seven major plates and approximately thirteen smaller ones.
The nameplateis used to describe these portions of the earth’s crust because they areliterally “plates” or sections, composed of dirt and rock. These platesfloaton molten lava, called magma. Since the plates are floating on magma, theycanslowly move. The place where friction occurs between plates is called afault. A fault is a crack in a plate or a place where two or more plates meet.
Anexample of a fault where two plates meet is the San Andrea’s fault inCalifornia,where the Pacific and North American plates meet. The plates are about30miles thick under land and can be one to five miles thick beneath theocean. The plates move because of convection currents. Magma has currents liketheocean does, that move in a circular motion beneath the plates. When twoplatesare pushing against each other, they are constantly building up tension onthefault.
When two plates finally slip, they release a great amount of energyinthe form of shock waves. These shock waves cause vibrations, which in turncause the ground around the fault line to move and shake. This phenomenonisknow as an earthquake. Because of the incredible destructive capabilities of earthquakes,scientists are constantly trying to devise ways to ensure their earlydetection. Earth scientists have begun to forecast damaging earthquakes in California.
Although quake forecasting is still maturing, it is now reliable enough tomakeofficial earthquake warnings possible. These warnings help government,industry,and private citizens prepare for large earthquakes and conduct rescue andrecovery efforts in the aftermath of destructive shocks. In recent years,earthquake forecasting has advanced from a research frontier to an emergingscience. This science is now being applied in quake-plagued California,whereshocks are closely monitored and have been studied for many years. Earthquakeforecasts declare that a temblor has a certain probability of occurringwithin agiven time, not that one will definitely strike. In this way they aresimilarto weather forecasts.
Scientists are able to make earthquake forecastsbecausequakes tend to occur in clusters that strike the same area within a limitedtimeperiod. The largest quake in a cluster is called the mainshock, thosebefore itare called foreshocks, and those after it are called aftershocks. In any cluster, most quakes are aftershocks. Most aftershocks aretoosmall to cause damage, but following a large mainshock one or more maybepowerful. Such strong aftershocks can cause additional damage andcasualties inareas already devastated by a mainshock, and also threaten the lives ofrescuerssearching for the injured. In the first few weeks after the 1994 magnitude6.
7Northridge, California, earthquake, more than 3,000 aftershocks occurred. Onemagnitude 5. 2 aftershock caused $7 million in damage just in electricutilityequipment in the Los Angeles area alone. The U. S.
Geological Survey(USGS)first began forecasting aftershocks following the 1989 magnitude 7. 1 LomaPrieta,California, earthquake. By studying previous earthquakes, scientists haddetected patterns in the way aftershocks decrease in number and magnitudewithtime. With such knowledge, scientists can estimate the daily odds for theoccurrence of damaging aftershocks following large California temblors.Theseforecasts are relayed directly to the California Office of EmergencyServices(OES) as well as to the public.Some of the more larger earthquakes are preceded by foreshocks.Knowledge of past earthquake patterns allows scientists to estimate theoddsthat