Spatial distribution of water supply reliability and critical links of water supply to crucial water consumers under an earthquake

Observations from past earthquakes, such as the 1906 San Francisco earthquake, the 1994 Northridge earthquake, and the 1995 Hyogoken-Nanbu (Kobe) earthquake, have clearly demonstrated that compromising water supply systems after an earthquake not only impairs fire fighting capacity, but also disrupts residential, commercial, and industrial activities, and threatens the economic well-being, security, and social fabric of the communities they serve. In the event of a major earthquake, crucial water consumers, such as acute care facilities, must remain operational to rein in the losses, and this calls for the need for seismic mitigation of water supply to these crucial water consumers. A key step in the seismic mitigation is to identify critical links of the water supply that significantly affect these crucial water consumers. This paper presents a method for identifying critical links of water supply to crucial water consumers under an earthquake. Two conditional probability quantities are proposed that describe the effects of damage to each individual pipe on the crucial water consumers under an earthquake. With the aid of Monte Carlo simulations, the concept of efficient frontier is employed to identify the critical links. As an illustration, the critical links for a crucial water consumer are identified in a hypothetical water supply system using the proposed method.