SEISMIC MICROZONING ON SOIL LIQUEFACTION POTENTIAL BASED ON GEOMORPHOLOGICAL LAND CLASSIFICATION

抄録

A simplified procedure without using boring data is proposed for the seismic microzoning on soil liquefaction potential. The geomorphological land classification is adopted as the index for liquefaction susceptibility, because the classification data are easily available for an area of interest. For each geomorphological unit, the critical peak ground velocity which separates liquefiable from non-liquefiable conditions is investigated based on case histories at about 250 sites during 19 Japanese earthquakes. The critical peak ground velocities at the sites with the same geomorphological unit are almost the same. These critical velocities vary depending on the geomorphological unit. For reclaimed land, drained land, natural levee, river channel, sand dune and lowland between sand dunes, the velocity is 15 kines (cm/s). For back marsh, valley plain and delta, the velocity is 25 kines. And, for sand bar and alluvial fan, the velocity is 35 kines. Combining the land classification map and the isoseismal map of an earthquake which represents the distribution of peak ground velocity, the seismic microzoning on liquefaction potential during an earthquake can be readily made.