Magnitude scaling factors

ABSTRACT

In developing the ùSimplified procedure for evalualing liquefaction resistance, Seed and Idriss (1982) compiled a sizable database from sites where liquefaction did or did not occur during earthquake with magnitudes near 7.5. From this database, these investigators defined a conservative deterministic bound separating data indicative of liquefaction from data indicative of nonliquefaction. The workshop gained consensus that a range of MSF values should be suggested for engineering practice. Practitioners could then select MSF from within this range, depending on the degree of risk they or their clients are willing to accept for various applicactions. The lower bound for that recommended range is the MSF proposed by Idriss (Column 3, Table 1) and the upper bound for the range is the factors proposed by Andrus and Stokoe (Column 7, Table 1). for magnitudes greater than 7.5 the revised factors of Idriss should be used. These factors are smaller than the original Seed and Idriss (1982) factors, and hance lead to an increase of calculated liquefaction hazard compared to the old factors. The workshop participants agreed, however, that the original factors by Seed and Idriss (1982) may not have been adequately conservative for large magnitude earthquakes. (AU)