Development of the 7.5-arc-second Engineering Geomorphologic Classification Database and its Application to Seismic Microzoning

概要

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In a seismic hazard assessment, local geologic and ground conditions play important roles in characterizing and estimating hazards. We developed a systematically standardized GIS-based ground-condition map containing the attributes of geomorphologic classification in grid cells of 7.5 arc-seconds latitude×11.25 arc-seconds longitude for several areas including major urban areas in Japan. This paper introduces the concept of developing the 7.5-arc-second JEGM, (Japan Engineering Geomorphologic Classification Map) and presents sample images of the JEGM. As an example of the database’s application to estimating the hazards--the average shear velocity of the ground in the upper 30m,--Vs30 is estimated and mapped for the Kanto area, and the distribution of peak ground velocities (PGV) for the Great 1923 Kanto earthquake is estimated using the Vs-0 map and empirical formulae. The computed PGV distribution agrees well with the distribution of seismic intensities evaluated from damage to wooden houses for areas located far from the earthquake fault. However, it will be necessary to calculate ground motion based on an asperity model to evaluate near-fault regions.