The Definition of Earthquake

An earthquake is a sudden shift of the soil layers below the surface of the earth. When this shift occurs, then the arising vibrations called seismic waves. This wave propagates in all directions away from the epicenter, but some can only be recorded on the seismograph,and some are up to the surface of the earth and felt by humans. Vibrations that reach theearth's surface can be damaging and very dependent on the power source of the earthquake, the depth of the soil surface and not less important is the quality of the buildingis crossed by seismic waves. If the quality is very fragile building would easily collapse and cause casualties. According to Howel (1969) earthquake is the vibration of the earth's crust that is not eternal, and then spread in all directions. These vibrations actually vibrate continuously with therelative strength is so small that can only be detected by the tool. Vibration can not beregarded as an earthquake when the nature of continuous vibration. So an earthquake must have a start time and end time that obvious. Earthquakes are one of the most mysterious of natural disasters to mankind. This can happen suddenly, at any time. In contrast to the eruption of the volcano, that is alwayspreceded by the signs that may predict, an earthquake occurs suddenly, no more than a fewseconds it happened, that large earthquake could demolish the buildings. Consequently,when an earthquake occurs that there is just panic and anxiety without knowing what to do. Prior to developing the science as now, the ancients had various ideas about the causes ofearthquakes. The Mongols, for example, they believe the earth is complete after created,God then put it in the back of a huge toad. So when the frog moves the earth shook. In contrast to this view, Aristotles states that the earthquake occurred due to air trapped in the bowels of the earth to get out. When the air it can really come out, the earth belched thatthen causes an earthquake. In Japan, people think in the earth there is a giant catfish that resides there. If this catfish wiggling / shaking it will be an earthquake, is characterized by the natural phenomenon ofcatfish sticking out of the water before the earthquake. At present, after the science develops, especially since the invention of a device fordetecting vibration of the earth that commonly called a seismograph, the occurrence of an earthquake quake seen as unusual natural phenomena. Through the seismograph from the beginning of the 20th century have analyzed the composition of the earth. The experts alsocan map pathways earthquake spread across the world and its properties. So we should be able to design buildings that match the characteristics of the earthquake in which welive. To note that the attitudes and actions of how an earthquake is very important.