Faults and Earthquakes - Earthquake Engineering for Structural Design - page 181

of earthquakes occur far from these boundaries and others are located in the crustal
zones or under the Earth crust.
In function of the earthquake position, there are the following main earthquake
types (Fig. 6.1):
- Crustal interplate earthquakes, are produced along the tectonic convergent
plate boundaries, where a fault exists due to previous plate movements. Along the
fault, shear friction forces between the two plates equilibrate the gigantic tectonic
plate forces and the elastic strain energy is stored. When the shear force capacity is
reached, sudden slip releases the large elastic strain energy stored in the interface
rocks. So, in case of interplate earthquakes, the slipping occurs along these tectonic
plate boundaries and their positions are well defined. Only in case of existing
parallel faults, the activated one is an unknown.
Figure 6.1 Source types: Crustal interplate and intraplate earthquake, shallow and
deep intraslab (inslab) earthquakes (modified after Stern, 2002)