Seismic risk is a function of hazard, vulnerability and exposure. If vulnerability and level of exposure depend on human choices and behaviour, providing the possibility to influence them, hazard (the probability of occurrence of a major earthquake) depends on natural mechanisms (mainly underground rock deformation process in conditions of high stress, temperature and pressure) that cannot be influenced by human choices and behaviour. However, it must be pointed out that some small scale earthquakes can be triggered by human activity such as mining, dam construction, drilling for oil exploitation and “fraking”, to cite just a few; this does not mean that man is able to trigger the natural causes of earthquakes, such as the relative movement of crust blocks along faults, although it is reasonable enough to imagine that high-stress human actions (see nuclear explosions, for instance) could add energy to the overall energy budget within the Earth’s crust. The earthquakes due to human activities (anthropogenic earthquakes) can be classified as “Induced earthquakes” and “Triggered earthquakes” (see Question 2).
