According to plate tectonics, the global distribution of epicentres is related to boundaries between lithospheric plates. Earthquakes at plate boundaries are called interplate earthquakes. Less commonly, earthquakes also take place in plate interiors and these are called intraplate earthquakes. The most active region in the world corresponds to the margins of the Pacific Ocean. Earthquakes with large magnitudes take place along this zone in the Americas from the Aleutian Islands to southern Chile and from the Kamchatka peninsula in Asia to New Zealand. Besides shallow earthquakes, throughout most of this long region, intermediate and deep shocks take place along the margin of Central and South America and on the other side of the Pacific along the systems of island arcs (Aleutians, the Kuriles, Japan the Philippines)
Another large seismically active region is known as the Mediterranean-Alpine-Himalayas region and extends from West to East from the Azores to the eastern coast of Asia. This region is related to the boundary between the plates of Eurasia to the North and Africa, Arabia, and India--Australia to the South. Its seismicity involves shallow, intermediate, and deep earthquakes. A third seismic region is formed by earthquakes located on ocean ridges that form the boundaries of oceanic plates, such as the Mid-Atlantic Ridge, East Pacific Rise, etc. In these regions earthquakes of shallow depths are concentrated in relatively narrow bands following the trend of the oceanic ridges. In general, boundaries between oceanic plates and between oceanic and continental plates have simpler distributions of seismicity than do boundaries between continental plates.
The most well known method of measuring the intensity of an earthquake is the Richter scale. The Richter scale is named after an American seismologist named Charles Francis Richter, and measures the amount of energy released at the focus of a quake. It uses a logarithmic scale that runs from "1" to "9." Because this scale is logarithmic, each number is actually an increase of ten times than the number which precedes it. Thus, a 7.0 earthquake is ten times more powerful than a 6.0 and 100 times more powerful than a 5.0. To allow a greater degree of precision, a decimal equivalent was provided. At one time it was believed that an earthquake with a magnitude of 8.5 was the most powerful possible but new seismic measuring techniques have revealed that it is possible to reach 9.5. This is reliable source as to how destructive an earthquake can be, although it does not specifically relate to how much damage will be caused, for example a less economically developed area which has a high population density will suffer greater loss than a more economically developed area which has better education, more stable buildings and emergency plans as well as sufficient communication.