BUTSURI-TANSA(Geophysical Exploration)
Online ISSN : 1881-4824
Print ISSN : 0912-7984
ISSN-L : 0912-7984
Case Study
Exploration of S-wave velocity structures beneath Kazo lowland in central part of the Kanto plain
Hidetaka ShiraishiShoichi HachinoheKouki Sasaka
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2016 Volume 69 Issue 4 Pages 289-296

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Abstract

 We have explored S-wave velocity structures of Kazo lowland in central part of the Kanto plain through microtremor survey method. Dimensions of the exploration area are east-west about 20km by north-south about 15km. Spatial autocorrelation (SPAC) technique has been employed to estimate Rayleigh wave phase velocities. The S-wave velocity structures have been estimated through inversion analyses of observed phase velocities with genetic algorisms (GA). According to some previous knowledge, it has been predicted that the maximum depth of the basement surface reach to about three kilometers. We have therefore deployed three types of circular arrays whose radii are 600m, 300m and 100m on each observation site. Creating initial structure models for the GA inversions, we have employed velocity structure models that had been created for the earthquake disaster prevention plan.
 The result shows that many of estimated basement depth are analogous to the gravity contour of the Kazo lowland which had been examined by GSJ, AIST. However, as estimated basement depth of several sites didn't accord with the gravity contour, it suggests that the further consideration for making precise velocity models will need.

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© 2016 The Society of Exploration Geophysicists of Japan
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