Earthquake hazard and risk mitigation

Earthquake risk is the combination of three factors: the earthquake hazard, the loss potential and the vulnerability. To examine the risk it is first necessary to consider the global distribution of earthquakes, their size and their frequency of occurrence. Migratory trends and temporal patterns of activity are sought as a means of defining the locations of future seismic hazard. It is important also to appreciate the kind of damage that is brought about by an earthquake, including the social and economic effects that can follow. Where loss potential is high, in areas of high population density, and where there is a known hazard from earthquakes, it is vital to mitigate the risk by reducing the vulnerability so far as possible. This can best be achieved through earthquake-resistant construction of buildings and other structures, but there are limits to what can be achieved. Consequently earthquake prediction may prove an alternative, complementary approach that could at least save lives. A range of possible precursory phenomena have been discovered, a number of which can be related empirically to the size and time ahead of an impending earthquake, but since the physical mechanism of earthquakes is still poorly known, these phenomena have only a weak scientific basis. At present none are established as definite precursors, and although a few successful predictions have been claimed, there are too many failures to predict, and too many false alarms, for Predictions to be reliable or credible. For the time being, as research progresses, the uncertainty of predictions will pose problems for scientists and government authorities alike.