Earthquakes and Ground Motions - Earthquake Engineering for Structural Design - page 232

Figure 7.12 Site classifications in function of the distance from the epicenter
(Gioncu and Mazzolani, 2002)
- Epicentral site , including the area around the epicenter, generally with a
radius equal to the source depth;
- Near-source site (near-field site), including an area within a distance of
25-30 km from the epicenter;
- Intermediate-source site (intermediate-field site), including an area within
a distance of about 150 km from the epicenter;
- Far-source site (far-field site), including an area with distance more than
150 km.
In the following, the main effects of the path traveling are presented.
Traveled soil types. The path effects on ground motions depend on the
percentage of the path travel through rock or through soft sediments (see Figure
7.1). Deviations from uniform horizontally layered crust model occur along the
path of wave propagation from the fault to site. These deviations are produced due
to the topography of basement rock, the path being a collection of sedimentary
basins with alluviums, separated by irregular basement rock, forming mountains
and geological and topographical irregularities. Using a map showing these
distributions of rock, soft rock and alluvium, it is possible to characterize the
transmission path for the fault site (Trifunac and Novikova, 1995a). The simplest
procedure is proposed by Erdik (1995), who suggest to consider the propagation-
path effects as a sum of different soil conditions depending on the source distance
and to multiply the corresponding value by an amplification coefficient. The