Earthquake Research Project


__Charles Richter developed the Richter scale in 1934. In this scale, the magnitude of an earthquake is calculated from the amplitude of the largest seismic wave recorded, no matter which type was, in fact, the strongest. The increase of one in magnitude corresponds to a ten-fold increase in the amplitude of shaking. This scale could not be used universally because he only used a certain type of seismograph and he measured merely shallow earthquakes in southern California.
__In 1902, Giuseppe Mercalli invented the Mercalli scale. Unlike the Richter, this scale used the observations of the people who experienced the earthquake to measure it’s intensity. This scale, of course, is not considered as scientific or thorough as the Richter. This is because people’s reactions to things tend to sway from person to person. One might exaggerate what he or she might have seen in such a tragedy and visa versa. Also, the amount of damage caused by the earthquake may not accurately show how strong it was.
__When a sudden break or shift happens in the earth’s crust, the earth radiates out as seismic waves. There are three types of these seismic waves. The first type of wave is the ‘P’ wave, or the compressional wave. These waves travel from one to five miles per second, which is greater than the speed of other waves. They are able to travel through solids, liquids and gas, and therefor are the first to arrive at any surface location. Next are the ‘S’ waves, or shear waves, which travel just behind the ‘P’ waves. These waves can only travel through solid material, which keeps them from going straight through the earth. When ‘P’ and ‘S’ waves reach the surface of the earth, they form ‘L’ waves. These are the slowest of all of the seismic waves, which is why the most damaging shaking comes at the end of the earthquake. The most intense ‘L’ waves radiate out from the epicenter.
__In San Francisco, California on April 18th, 1906, one of the highest ranking, most significant earthquakes ever recorded took place. The violent, horrendous shocks lasted forty-five to sixty seconds. The shaking was felt from southern Oregon to south of Los Angeles and as far as central Nevada. This massive quake brought deadly fires as well as devastating shaking damage. Over 3,000 lives were lost in the earthquake, as well as 28,000 buildings destroyed. The San Francisco quake was an 8-9 on the Mercalli intensity scale and had a magnitude of 7.7.
__There are a long list of procedures that should be taken before, during and after an earthquake to ensure safety. Before the shaking begins, make sure you know the safe spots in your area. Places like inside walls and study tables or supported doorways are prime examples. Next, know where the danger areas are. Stay away from windows, mirrors, hanging objects, and tall furniture or fixtures. And lastly, know where your emergency telephone numbers are kept. During the shaking, if you are indoors, stay there. Get under a desk or stand in a doorway until it is safe. If you happen to be outdoors at the time of the shaking, retreat to an open area away from trees, buildings or power lines. Do not use elevators and if you are in a crowded place, do not run for the doors. Move away from shelves with things on them that may fall. Finally, after the shaking is over, check around you for injuries, contact an emergency authority–if it has not been done yet– and be prepared for the aftershocks.