Seismic risk analysis using Bayesian belief networks - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 186

7.4.1 Example of BBN for regional seismic
risk assessment

Regional damage estimation requires aggregation of different non-
commensurable input parameters. Different aggregation techniques are
reported in the literature, e.g. minimum, maximum, average, weighted arith-
metic mean (WAM). Aggregation of multiple inputs into a single output
can also be viewed that a whole is synthesis of the parts (Ross 2004). In
aggregating through a hierarchical structure, there is a potential for loss of
information due to exaggeration and eclipsing (Tesfamariam and Sadiq
2008). Exaggeration occurs when all input parameters are of relatively low
importance, yet the aggregated score comes out unacceptably high. Eclips-
ing is the opposite phenomenon, where one or more of the input parameters
are of relatively high importance, yet the aggregated score comes out as
unacceptably low.
The EDRI quantifi es earthquake risk by aggregating hazard (ground
shaking and collateral hazards), exposure and vulnerability (physical infra-
structure, population, economy, social-political system), external context
(economy, transportation, politics, culture), and emergency response and
recovery capability (planning, resources, mobility and access) (Fig. 7.8). This
method gives the general risk assessment of a city or country, and facilitates
decision for resource allocation and further detailed analysis. The key per-
formance indicators used to quantify the hazard, exposure, vulnerability,
external context, and emergency and recovery planning are provided in
Table 7.6.

Data transformation

Input parameters of the EDRI are furnished in non-commensurable units,
e.g., number of hospitals, population size, and seismic hazard. Since units of
the performance modifi ers are non-commensurable, as a result, transforma-

EDRI

Damage/loss Consequence of failure

Hazard Exposure Vulnerability External

context

Emergency response and
recovery planning

7.8 Framework for earthquake disaster risk index.