Natural disaster seismic waves. At the Earth's surface, earthquakes manifest themselves by vibration, shaking, and sometimes displacement of the ground. Earthquakes are caused by slippage within geological faults. The underground point of origin of the earthquake is called the "seismic focus". The point directly above the focus on the surface is called the "epicenter". Earthquakes by themselves rarely kill people or wildlife. It is usually the secondary events that they trigger such as building collapse, fires, tsunamis (seismic sea waves) and volcanoes. Many of these could possibly be avoided by better construction, safety systems, early warning and planning. When natural erosion, human
Tunnel effect Tunnel effect In experimental psychology, the tunnel effect is the perception as a single object moving beyond an occluding object and then reappearing after a suitable amount of time on the other side of it. This phenomenon has been studied by Burke (1952), who discovered that the optimal amount of time for giving the impression of a single object is shorter than what is actually needed to cross the occlusion at that speed. The "tunnel effect", when talking about long stretches of road, refers to the environment surrounding the driver that begins to merge towards the central point of the