we began to hear a rumbling noise, like that of carriages, which increased to such a degree as to equal the noise of the loudest cannon; and immediately we felt the first shock, which was succeeded by a second and a third; on which, as on the forth, I saw several light flames of fire issuing from the sides of the mountains, resembling that which may be observed on the kindling of coal- This eyewitness account of an earthquake in Libson dates as far back as 1756, describing in intricate detail what one might encounter during a major earthquake (Gold 1).
The adjective "major- is a lay man's term used to refer to the earthquake's seismic magnitude, or the amplitude of ground shaking that occurs. Although in the last half a century, millions of people have been killed by earthquakes worldwide just like the one described, very few people actually have a broad knowledge of this destructive natural phenomena. .
For instance, many people may be interested to learn that there is more than one type of earthquake that takes place. There are tectonic earthquakes, which are caused by sudden releases of stored energy within the rocks along faults, as well as volcanic earthquakes which are strikingly similar to tectonic but occur near active volcanoes. The majority of earthquakes however are tectonic, and of the millions that take place each year, only a few (about 15) are actually violent enough to inflict serious damage (Beiser& Krauskoff 480). .
Most scientists, who study earthquakes, or seismologists, attribute these quakes to the theory of plate tectonics. This theory states that the outer shell of the earth is made up of thin, rigid plates that move relative to each other. It was first formulated during the early 1960s, and it revolutionized the field of geology. In addition, the Elastic Rebound Theory, which was devised by Harry Fielding Reid in 1911 after observing the 1906 quake in California, addresses the specific path which most earthquakes embark on.