Monday, May 23, 2016

Earthquake Risk and US Highway Infrastructure

Thanks to our friends at the Federation of American Scientists (FAS) a recent Congressional Research Service report entitled Earthquake Risk and U.S. Highway Infrastructure: Frequently Asked Questions was posted.  This 11-page report is an excellent overview of the current state of natural and man-made (read - "Fracking") earthquake impact on the US highway system.



Two figures in the report are very telling as to the concentration of earthquakes and implications on "Shaking expected for Tall Structures Like Bridges" (below)...


as well as a graphic showing the chance of human-induced and natural earthquakes.  (Look at the concentration around Oklahoma presumably due to Fracking.)


Key Comments in the Report

The report approaches these issues in a FAQ approach...so, here are some quick highlights:

Q:  What Are the Components of Seismic Risk?

A:  Seismic risk to a highway system is determined by three factors:

  • Likelihood of seismic events of varying magnitudes, and related physical events, often referred to as the hazard;
  • Vulnerability of highway structures to damage from such events; and
  • Potential consequences of that vulnerability (e.g., lives lost, economic disruption, etc.)
Q: How Vulnerable Is the U.S. Highway System?

A:  "No national database exists on the seismic design and retrofit status of highway system components; thus, a perspective on vulnerability at the national level is unavailable.  However, many states with large seismic hazards have compiled data on the vulnerability of highway components within their borders..."

Q:  How Vulnerable are Highway Bridges?

A: Basically many of the most vulnerable older bridges -- particularly in the West Coast States -- have been retrofitted to improve seismic resilience; however, many older bridges (around 13,000) in the New Madrid seismic zone (AR, IL, IN, KY, MO, MS, TN) have not been retrofitted.

Q: How Costly is Retrofitting Highway Infrastructure?

A:  Because no national data exist on the status of retrofitting existing highway bridges or other infrastructure (e.g.,tunnels, highway systems), no national estimates exist.  


Conclusion

If you are involved in transportation policy or a student of infrastructure, this is a useful starting point to give you a sense of the daunting task of improving the resilience of highway structures against earthquakes.


1 comment:

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