学会誌「自然災害科学」

盛岡市域における震度推定式作成の試み －ボーリング資料に基づく解析－

Derivation of Empirical Seismic Intensity Equations for Morioka Area
- Analysis Based on Borehole Data -

山本 英和*・濱田 泰治**・斎藤 徳美*

Hidekazu YAMAMOTO*, Taiji HAMADA**, and Tokumi SAITO*

Abstract

In seismic micro-zoning, it is necessary to know ground vibration characteristics in each local area. Empirical equations proposal of seismic intensity in Morioka area was based on borehole data using multi-variable regression analysis. In boring model, the equation was derived by N-value and water level obtained from borehole data. In ground information model, S-wave velocity and S-wave amplification were used in the equation in addition to the parameters used in the first model. Two data sets were sampled using a 250m square mesh and sampling at a point where both questionnaire seismic intensity and borehole were examined. The former method is called mesh model and the latter close-point model.

The results were as follows:
(1) Close-point model shows higher correlation coefficient than mesh model. This suggests that vibration characteristics vary in area smaller than 250m x 250m mesh.
(2) Ground information model gives higher correlation coefficient than boring model. However, the model has only three principal components, suggesting that the equation has too many predictor variables.
(3) Four variables namely: ground water level, averaged S-wave velocity between 0 and 5 m in depth, S-wave amplification and its pre-dominant frequency are selected in derivation of the equation of seismic intensity using AIC test.

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