Tectonic Plates and Faults - Earthquake Engineering for Structural Design - page 152

152 Earthquake Engineering for Structural Design

(b)

Figure 5.8 Convergent continental-continental boundaries: (a) Collision between
two continental plates; (b) India-Eurasia Plates collision (USGS, nd)

Similar collisions were produced between European and Asian plates forming the
Ural Mountains, and Adrian and European plates forming the Alps.

5.2.5 Transform Boundaries

Transform boundaries are locations where two plates slide along each other. There
are two transform boundary types, one oceanic and one continental.
Most transform boundaries are found on the ocean floor , where they often
offset spreading ridges to form a zigzag plate boundary (Fig. 5.9a), being
transversal to the divergent oceanic boundaries, such as the Mid-Atlantic, Nazca
or Antarctic ridges (Fig. 5.9b). The name of transform boundaries is proposed to
underline that they transverse the mid-oceanic ridges. Generally, this boundary
type is not interesting for Engineering Seismology, due to the fact that usually it
does not affect inhabited areas, belonging to oceanic plates.
Few transform boundaries occur on land. For the continental zone , one of the
most famous examples of these transform boundaries occurs along the boundary of
North America and Pacific plates and it is known as the San Andreas Fault (Fig.
5.10). It is interesting to notice that the sliding of the San Andreas Fault occurs in
some part at depth, without surface traces, but in some others part its movements
are marked at the surface by valleys and lakes. Another very important case is the
NorthAnatolianFault (see Fig. 3.4). A comparison between these two transform