occurring events usually the probability of the event itself is needed; e.g. the probability that a
flood will occur or the probability of an earthquake. However, more characteristics or
indicators are needed such as to facilitate a modelling of the possible consequences of the
event. Considering earthquakes typically applied indicators are the Peak Ground Acceleration
(PGA) and the earthquake magnitude (M), see e.g. Bayraktarli et al. (2004). These indicators
are useful because knowledge about them provides the basis for assessing the potential
damages caused by earthquakes such as liquefaction of soil and damages to buildings caused
by the dynamic excitation from the earthquake.
The consequences which potentially may be caused by such different exposures are manifold
and generally depend strongly on the specific characteristics of the hazard as well as the
location where it occurs. First of all the immediate or direct consequences comprise loss of
lives, damages to societal infrastructure and life lines as well as damages to the qualities of the
environment. Follow-up or indirect consequences may include additional loss of lives caused
by the outbreak of epidemics or hunger. The indirect consequences may, however, also
include losses of livelihoods, damages to the local and/or global economy as well as
sociological effects. In risk management of systems such as societies of developing countries
and ecosystems the possible consequences may not only be related to economical losses or
losses of lives and habitants but as mentioned earlier may threaten the existence of the system
itself. For such systems it has become standard to use a characteristic of the system which is
called the resilience. This term aims to describe the ability of the considered system to re-
establish itself, e.g. to describe the survivability of the system as such. In general an
assessment of the resilience of a system is difficult as many of the factors determining the
survivability of a system are not well understood. However, for what concerns poverty, limits
have been suggested below which societies are judged to dissolve. If this happens the
concerned society seen as a system is not resilient.
Considering earthquake exposure, indicators of consequences include the characteristics of
soil, types of building and building materials, design codes applied for the design of buildings,
occupancy of buildings, the time of the earthquake as well as emergency preparedness.It may easily be realized that both exposures of events of natural hazards as well as possible
consequences due to natural hazard events depend strongly on the specific geographical
location where the event occurs. For this reason it is logical to consider the use of
Geographical Information Systems (GIS) in the context of natural hazards management. In
Figure 10.15 the structure and components of GIS based natural hazards risk management is
illustrated. As illustrated in Figure 10.15 the indicators of relevance for the characterization of
exposures and consequences may be related to the models of the real world which form the
basis for the risk assessments, i.e. the exposure, the vulnerability and the robustness/resilience
of the considered system, see also Lecture 4. Finally, the risk as assessed from the models and
related to the real world through the indicators may be managed by means of various actions
of risk reduction.