Surface ruptures induced by the Wenchuan earthquake: Their influence widths and safety distances for construction sites

Surface ruptures studied in this paper refer to those induced by the 2008 Wenchuan earthquake. They mostly appear as two prominent surface rupture zones: one is about 240 km long, distributed along the Central Fault; and another about 70 km long, along the Front Mountain Fault. The influence width of a surface rupture is an important factor to determine the safety distance for construction sites to keep away from it. In measuring the influence width, the shortening amount or rate must be paid enough attention to. The statistical analysis of 85 sets of practically measured data of surface ruptures shows that the influence widths are concentrated in the scope of 15 m and 60 m, and that there is a linear relationship between the vertical displacements (H) and influence widths (D) of surface ruptures, which can be approximately expressed as: D = 11H + 14. The influence scopes on both sides of a surface rupture are asymmetric and their proportion between the hanging side and the down side is generally from 3:1 to 2:1.