What is a Fault Investigation?
Surface fault rupture during an earthquake can be a serious and dangerous hazard to people and structures, especially if built over a fault. Surface fault rupture has been observed to create differential offsets of up to several tens of meters. As it is not possible to design structures to accommodate the differential ground movements associated with fault rupture, it is imperative to identify the precise locations of potential fault rupture surfaces to properly site new structures away from faults and to evaluate the potential hazards to existing structures that may be located over the fault traces.

​The most direct method of identifying surface fault rupture hazard is to excavate trenches across the general trend of the suspected fault trace and visually identify stratigraphic discontinuities that may indicate a seismogenic origin. In an urban built environment, there may not be sufficient space to excavate trenches to allow for direct observation. Where trenching is not possible, geologists are now using a large array of different subsurface exploration techniques. These techniques include using combinations of high-resolution geophysical surveys, closely spaced continuous core borings, large-diameter borings allowing downhole logging by a geologist, and cone penetration test soundings.