Earthquake risk management of civil infrastructure: integrating soft and hard risks - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 231

temic. The word epistemic means 'pertaining to knowledge or the condi-
tions for acquiring it'. Again it is unclear why such a term is useful since at
a philosophical level all uncertainties are due to limitations in what we
know or the conditions for acquiring or understanding. In this sense all
uncertainty is knowledge-based. For example, random uncertainty is epis-
temic since randomness is the lack of pattern or specifi c order in data and
must therefore depend on our understanding and consequent models of
what we mean by order. Some (but not all) of the epistemic uncertainties
seem to arise from assumptions made in the modelling of a system, the
methods of analysis and limitations of data. They may be reduced by using
more resources to perform more detailed analysis and obtaining more data
but there will always be a residual uncertainty because we can never have
certainty - there is always a gap between what we think we know and what
we do, resulting in the possibility of unintended and unwanted conse-
quences. It is this residual uncertainty which is the real challenge to risk
managers since it can sometimes lead to unintended, unforeseen, and
unwanted disastrous consequences, such as 9/11, Chernobyl, the near col-
lapse of the world's banking system in 2008 and the damage to nuclear
reactors by the tsunami after the 2011 earthquake in Japan. Social scientists,
such as Turner and Pidgeon (1998), have argued that the preconditions to
major disasters can incubate or develop in a way so that it may be possible
in some instances to identify before a fi nal disastrous event. They argue that
we need to develop methods for identifying those preconditions with suf-
fi cient dependability to make such politically diffi cult and potentially
expensive decisions to avoid the even greater costs and consequences of a
disaster. This is a point to which we will return later.

9.4 Seismic vulnerability

Before we continue to unpack the sources of uncertainty in managing
seismic risks and how we might develop a general theory to deal with them,
let us look at another technical approach to the problem of evaluating
the vulnerability of our urban heritage to earthquakes. Vulnerability is
'susceptibility to harm' and, like risk, is an idea central to the planning of
retrofi ts (Bernardini and Lagomarsino, 2008). The focus of vulnerability
analysis is the extent to which the form of a structure increases the risk of
damage when exposed to a hazard - something only partially considered
in reliability theory (Agarwal, 2013; Agarwal et al. , 2001, 2003; Nafday,
2010). A hazard is defi ned as a 'state of affairs' with a potential for harm
and the dominant one, as far as we are concerned in this chapter, is an
earthquake.
Monumental buildings, such as churches and cathedrals in Italy,
are embedded in a complex of classical urban environment of traditional