MAKING THE BEST OF SHAKY GROUND IN THE EMPIRE STATE: NEW PROCEDURES, CORRELATIONS, AND EQUATIONS FOR DEFINING NEW YORK STATE'S EARTHQUAKE HAZARD

In this study (1) equivalences between soils identified with New York State Department of Transportation (NYSDOT) “word pictures” and Unified Soil Classification System (USCS) group symbols; (2) blow count and soil unit-weight and void ratio correlations; and (3) shear modulus correlations were developed for soils derived from glacial and recent deposits in two eastern New York State counties. The equations are of the form G_o = Αe_o^β'_v^0.5 where G_ois the low strain (<0.0001%) shear modulus in kPa, e_o is the in-situ soil void ratio, σ'_v is the effective overburden pressure in kPa, and Α and β are constants. Shear wave velocity measurements from shallow seismic refraction sites in the study counties, along with depth to water table information from borehole logs, estimates of soil unit-weights, and void ratios obtained from the blow-count correlations, were used to derive the equations. Using the developed equations, equivalence tables, and correlations, shear-wave velocity as a function of depth were estimated using available and numerous NYSDOT highway borehole logs. Percent errors of estimate ranging from (1) -10% to 12% for cohesive soils, (2) -34% to 19% for cohesionless soils with <25% gravel content, and (3) -42% to 43% for cohesionless soils with >= 25% gravel contents were obtained for shear-wave velocity estimates using the data and equations developed in this study. This permits the classification of surficial deposits into NEHRP seismic site classifications, and can be used in the construction of county-level earthquake ground motion amplification maps for the study counties.