Seismic risk management for water pipeline networks - Seismic Risk Analysis and Management of Civil Infrastructure Systems - page 635

Table 23.5 Defi nitions of seismic performance and failure modes

Performance
damage
mode

Component
damage
mode

Seismic
performance Defi nition

1 The system performance can be

maintained without any
disruption for the Level 1
earthquake ground motion
(EQ 1 ), if the system is slightly
damaged or undamaged.

Minor
D E Q nor

Minor
Z E Q nor

2 The system performance can be

restored after quick repair for
the Level 2 earthquake ground
motion (EQ 2 ), if the system is
not signifi cantly damaged.

Moderate
D E Q 2 derate

Moderate
Z E Q 2 derate

3 The system performance can be

restored after recovering from
disruption for the Level 2
earthquake ground motion
(EQ 2 ), if the system is not
completely damaged.

Major
D EQ ajor

Major
Z EQ ajor

Source: Imai and Koike (2009).

23.3.2 Seismic hazard surrounding the lifeline system

Generally the lifeline system is surrounded by many potential earthquakes
which might be triggered by a large active fault located far from the system,
or by a comparatively short active fault located in the vicinity of the system.
There are two extreme approaches for seismic risk assessment with the
hazard conditions of these various faults. One approach is that the most
signifi cant earthquake should be selected, and the others neglected. The
second approach is that all the active faults should be collected for the
seismic assessment. If there are very many active faults around the system,
the second approach is not practical. The fi rst approach, on the other hand,
cannot erase the seismic risk due to the neglected faults (denoted by the
residual risk).
When the most signifi cant earthquake is selected as a seismic design load,
a scenario earthquake approach may be adopted to assess whether the
designed system survives without signifi cant disruption and damage under
the considered scenario. In this design procedure, the residual risk, which
might not be accounted for when adopting one particular situation/case as
the scenario earthquake, has to be taken into consideration. One solution
to this diffi culty is to adopt several scenario earthquakes as possible future
earthquakes. If there are insuffi cient historical earthquake data in the