How do you choose which bridges to retrofit now and just ahead, when so many major ones here could fail in the next big earthquake?
That question is misformulated and its answers accordingly misleading.
Retrofitting a bridge pre-disaster isn’t a chancy wager on what might or might not happen to the bridge. Retrofitting is managing latent interconnectivities between bridges and other infrastructures that become manifest during and immediately after the disaster. That inter-infrastructural connections will shift and these shifts will involve bridges is far more predictable than this or that bridge will fail, unless retrofitted.
This means attention is crucial to the track record in retrofitting bridges before and after disasters, here and elsewhere. Note the implication: Retrofitting bridges has to occur in order to have a track record to monitor and learn from.
To summarize: Since there are real material and cognitive limits on controlling inter-infrastructural connectivity at any point in time, doing more by way of managing the pre-disaster latency of interconnectivities buys you more time, if only as better response.
An interviewee with engineering and management experience told us their city water infrastructure was behind the electricity utility in the adoption of automatic shut-off valves. Bringing water systems up to power’s better practices is a way of managing latent interconnectivity in advance of disaster.