Tectonic Plates and Faults - Earthquake Engineering for Structural Design - page 155

boundaries is presented in Figure 5.11. One can see a very significant similitude
between these continental transform boundaries. Similar continental transform
boundaries occur in New Zealand, being known as the Alpine Fault .

5.3 DIFFUSE ZONES AND FAULT TYPES

5.3.1 Zones with Diffuse Faults

An important category of seismic zones, extending through the very densely
inhabited areas, is the one occurring in the large areas along the plate boundaries or
in areas between boundaries of tectonic plates. The occurrence of earthquakes
violates the plate tectonic model, which considers that the earthquakes are
concentrate on the narrow bands of plate boundaries.
The characteristics of faults in diffuse zones are very complex due to the
multitude of fault types. Looking to the world map of seismic zones (see Fig. 2.2),
one can see that there are zones where the model of tectonic plates is not accurate.
Nevertheless, this spreading is mainly due to (Fig. 5.12):
-

Extension of seismic zones under subducted plates;

- Collision between two continental plates;

- Fracture of weak crustal plates between the boundaries.

Extension of
subduction

Collision

Fracture of
crustal plate

Stable areas

(a)
Figure 5. 12 (continues)