Natural and Man-induced Destructive Earthquakes in Stable Continental Regions

Despite the real societal challenge posed by their important potential of destruction, the infrequent moderate and large earthquakes in tectonically-stable continental regions (SCR) have causes that are not well understood yet. Nevertheless, recent studies suggest that large earthquakes in SCR can be explained by transient disturbances of local crustal stress or fault strength because the tectonic loading on faults is very slow. In this paper, we assert that this new hypothesis is well supported by the observation that many moderate MW 5.5-6.0 SCR earthquakes are shallower than similar events in active regions. Moreover, by using the basic principles of frictional fault reactivation, we explain why these temporary stresses play a more fundamental role in the initiation of large earthquakes in SCR than at plate boundaries. As these disturbances in stresses can be related to natural environmental phenomena, but also to human activities, we also debate about the potential role of man-made earthquakes in SCR seismicity and seismic hazard. This discussion highlights the need to better understand the contribution of man-made earthquakes in the
observed seismicity.