LIQUEFACTION RESULTING FROM THE 2011 CENTRAL VIRGINIA EARTHQUAKE

Liquefaction is a phenomenon that occurs when the soil skeleton of loose, saturated sandy soil collapses and there is a temporary transfer of the overburden stress from the soil skeleton to the pore fluid. The collapse of the soil skeleton can be initiated in a variety of ways, one of which is earthquake shaking. The occurrence of liquefaction often manifests itself on the ground surface in the form of sand boils. Although liquefaction is a temporary state, its effects on the built and natural environment can be catastrophic (e.g., bearing capacity failures of building foundations, lateral spreading of the ground, slope failures, and ground subsidence). The occurrence of liquefaction has been documented in every major earthquake, with the smallest magnitude event known to have triggered liquefaction being the M~4.2, 1898 Val di Noto, Italy earthquake. Following the 2011, M5.8 Central Virginia earthquake the authors, along with others, searched the epicentral region for evidence of liquefaction. In total, two definite liquefaction features, one likely feature, and one questionable feature were found. The paucity of features is in stark contrast to the widespread liquefaction that was caused by similar magnitude events recently in Christchurch, New Zealand. This dichotomy is most likely due to the differences in the liquefaction susceptibility of soils in the two regions, rather than the difference in the characteristics of the ground shaking. Also, the contrast in observed liquefaction response gives credence to the use of regional magnitude bound curves for estimating the magnitudes of paleoearthquakes, with the observations from the 2011 Central Virginia earthquake being in line with the Central-Eastern US magnitude bound curve proposed by Olson, Green, and Obermeier (2005).