EarthquakesWhat are earthquakes? An earthquake is what happens when two pieces of earth suddenly slide past each other. The surface on which they slide is called a fault or fault plane. The place below the earth's surface where the earthquake begins is called the hypocenter, and the place directly above the earth's surface is called the epicenter, or focus. Sometimes, but not always, an earthquake results in foreshocks. These are smaller earthquakes that occur before the larger earthquake, or mainshock, in the same location. Scientists cannot say that an earthquake is a shock until the mainshock occurs. Main shocks always have aftershocks that follow. These are smaller earthquakes that then occur in the same location as the mainshock. Depending on the magnitude of the mainshock, aftershocks can continue for weeks, months, or even years after the mainshock. The bigger the mainshock, the bigger the aftershocks will be. What causes earthquakes and where do they occur? The Earth has four main layers: the inner core, the outer core, the mantle and the crust. The crust and the top of the mantle constitute a thin skin on the surface of our planet. This skin is not entirely in one piece. It is made up of several pieces covering the surface of the earth, like a puzzle. These puzzle pieces continue to move slowly, sliding past each other and colliding. We call these puzzle pieces tectonic plates. The edges of tectonic plates are called plate boundaries. Plate boundaries are made up of many faults, and most of the world's earthquakes occur on these faults. The edges of the plates are rough and get stuck while the rest of the plate continues to move. Eventually, the edges of a fault's plates peel away and cause an earthquake....... middle of paper ...... or higher, the stronger and potentially more dangerous an earthquake. Besides magnitude, intensity is also observed. Intensity is the measure of force often associated with shaking caused by an earthquake. The intensity varies depending on where you are during the earthquake. Unexpected Consequences of Earthquakes Earthquakes generally have unexpected consequences depending on the environment in which they occur. The consequences can be tsunamis, building collapses, structural deformation, landslides and liquefaction. and Patrick J. Kiger. “How Earthquakes Work.” How things work. HowStuffWorks, Inc., January 16, 2001. Web. April 21, 2014. “The Science of Earthquakes.” USGS. July 24, 2012. the web. April 21. 2014. .