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Liquefaction potential of four Pleistocene beach sand deposits in the Greater Charleston area, South Carolina, is assessed. The assessment is based on a review of 51 sites of conspicuous craterlets and horizontal ground displacement that occurred in beach sand deposits during the 1886 Charleston earthquake and an analysis of 82 seismic cone penetration tests with pore-pressure measurements. Of the 51 ground failure sites, 23 are associated with the Ten Mile Hill beds; 13 with the Wando Formation; 13 with the Silver Bluff terrace and younger deposits that lie adjacent to the harbor, rivers, and creeks; and two with the Ladson Formation. Liquefaction potential is analyzed using the seismic cone data with and without correction for age-related processes (diagenesis) and then expressed in terms of the liquefaction potential index (LPI). Probability curves are developed from the LPI calculations for different earthquake ground-shaking parameters. The probability curves for the Wando Formation overpredict liquefaction potential when no corrections for diagenesis are made. When corrections for diagenesis are made, the probability curves for all four sands generally agree with the observed field behavior. [ABSTRACT FROM AUTHOR]

Abstract: In this paper an improved method for evaluation of liquefaction hazard is presented. The liquefaction potential index developed by Iwasaki and his co-workers is modified using the concept of probability. The modified liquefaction potential index is then calibrated with field observation data, which yields an empirical equation for the probability of liquefaction-induced ground failure. The method and procedure is then employed to study the ground shaking level of the 1886 Charleston, South Carolina earthquake based on an analysis of liquefaction hazard in the Charleston peninsula. The results show that the ground shaking level of the 1886 event may be represented with moment magnitude M w =6.9 and peak ground surface acceleration a max =0.2 g. Finally, the liquefaction hazard in the Charleston quadrangle is evaluated and mapped using the ground motion that corresponds to the 475-year return period. Details of this assessment, including limitation of the results, are presented. [Copyright &y& Elsevier]