AN EMPIRICAL-METHOD TO ESTIMATE SHEAR-WAVE VELOCITY OF SOILS IN THE NEW-MADRID SEISMIC ZONE

In this study, a set of charts are developed to estimate shear wave ve locity of soils in the New Madrid seismic zone (NMSZ), using the stand ard penetration test (SPT) N values and soil depths. Laboratory dynami c test results of soil samples collected from the NMSZ showed that the shear wave velocity of soils is related to the void ratio and the eff ective confining pressure applied to the soils. The void ratio of soil s can be estimated from the SPT N values and the effective confining p ressure depends on the depth of soils. Therefore, the shear wave veloc ity of soils can be estimated from the SPT N value and the soil depth. To make the methodology practical, two corrections should be made. On e is that held SPT N values of soils must be adjusted to an unified SP T N' value to account the effects of overburden pressure and equipment . The second is that the effect of water table to effective overburden pressure of soils must be considered. To verify the methodology, shea r wave velocities of five sites in the NMSZ are estimated and compared with those obtained from held measurements. The comparison shows that our approach and the field tests are consistent with an error of less than of 15%. Thus, the method developed in this study is useful for d ynamic study and practical designs in the NMSZ region. Copyright (C) 1 996 Elsevier Science Limited