Abstract

Prior to construction, structures in active tectonic regions can be protected from surface fault rupture by establishing a no-build zone (NBZ). The width of the NBZ is important. Surveys of cultural features demonstrate that potentially damaging brittle and non-brittle off-fault deformation (OFD) can extend tens to hundreds of meters beyond the principal slip zone (Lawson, 1908; Haeussler et al., 2004). NBZs designed to also mitigate OFD are likely to be very wide for M ≥ 7 earthquakes, indicating the need to incorporate design solutions to safely accommodate potentially large strains (Bray, 2009; Treiman, 2010). OFD was surveyed following the 2002 rupture of the Denali fault at the Trans-Alaskan Pipeline System (TAPS) crossing. Fortunately, the pipeline did not fail. The performance of TAPS was the result of excellent geologic studies and engineering design and because the fault could not be located below the proposed pipeline route. The approximate location of the fault was interpolated between two known locations (Haeussler et al., 2004); 579 m of TAPS was designed to accommodate fault slip. If the fault had been located, the zone designed to accommodate fault slip would have been reduced 87 percent (Honegger et al., 2004), potentially exposing TAPS to OFD that was approximately 78 percent of the 5.8 m of total deformation. The motivation for this empirical analysis of nine strike-slip earthquakes was to simplify the estimate of OFD and the width of the zones where brittle and non-brittle deformation occurs, thereby allowing for the implementation of design buffers (Treiman, 2010).

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