Civil Engineering Reference
In-Depth Information
Table 7.1
Intensities (between VI and XII) of the MSK/EMS-98 seismic intensity scale [
13
,
14
]
Intensity
Description
VI
Minor damage to buildings (fine cracks)
VII
People leave houses; cracks and crevices develop in walls and stacks
VIII
Walls, monuments, and stacks crumble
IX
Buildings are shifted from their foundations, walls and roofs collapse, underground
pipes break, cracks develop in the ground
X
Many buildings collapse, gaps up to 1 m wide develop in the ground
XI
Many clefts are produced in the ground; landslides occur in the mountains
XII
Pronounced changes in the surface of the earth
have been recorded only since 1935. Consequently, following Medvedev-
Sponheuer-K´rnik [
1
,
5
] (MSK-64), an intensity scale of I to XII has been intro-
duced (today referred to as the European Macroseismic Scale 1998 (EMS-98)). The
intensity of an earthquake is a measure of its impact on persons, buildings and their
underground, etc. Intensities between VI and XII in Table
7.1
are listed here as an
example of this intensity scale (EMS-98) [
13
,
14
].
There are semi-empirical formulae showing the correlation between the
magnitude, M, and the different displacements and accelerations from a certain
distance [
1
,
15
]. On the other hand, relations have also been quoted between the
intensity scale and local accelerations [
16
,
17
]. In this way, it is ultimately possible
also to establish correlations between the magnitude and the intensity scale [
1
,
5
]. However, because of the rough classification of the intensity scale, these are
only rough approximations.
The earthquake with the highest intensity reported in Central Europe occurred in
Basel in 1356, causing churches, many houses, sections of the walls around the city,
and even castles in the environment of Basel to collapse. That earthquake in Basel
was assigned the intensity of IX to X [
18
-
20
] (Table
7.2
). All later earthquakes in
Central Europe are supposed not to have exceeded intensity VIII [
18
,
19
].
The mechanical loads and stresses acting on nuclear power plants in an earth-
quake are determined by the horizontal and vertical displacements and accelera-
tions, the associated frequency scales, and the duration of the earthquake.
Moreover, the qualities of the ground underneath the nuclear power plant play a
major role (Fig.
7.1
).
Taking into account many measured seismic data and theoretical considerations,
the technical safety codes define criteria for seismic design in a conservative way.
The U.S. Regulatory Guide in the United States contains definitions of so-called
response spectra for horizontal and vertical displacements and accelerations [
2
-
4
,
49
]. In Germany, KTA rule 2201 applies [
6
-
8
]. In France similar Guidelines
exist [
5
].
The German, e.g. rule contains these requirements:
• “The design basis earthquake must be defined on the basis of information about
expected maximum accelerations, duration of vibrations, response spectra, etc.
taken from seismological opinions also considering local geological conditions.”
