Shota IWASAKI
Study on the Relation Between the House Damage and the Microtremors Takamachi-Danchi
Yasuyuki MIYAKI
Takamachi-Danchi, a residential land developed by mounted earth or cut earth, suffered big damage by the Chu'etsu Earthquake on Novemver 23, 2005.The microtremors in Takamachi-Danchi was mesured by three-directional mesuring device.
I search for the correlation of the collapse and non-collapse in an earthquake by the difference in the microtremorses and consider dangerous degree judgment.
The mesurement points were 60 points, 30 points in the area damaged by the earthquake(A Group) and 30 points in the area without damage(B Group).
The microtremors waves were Fourier-transformed and the H/V power spectrum was obtained.H spectrum is in the horizontal direction and V is in the vertical.The predominant period was defined by the period of the maximum value in the H/V spectrum.The seismic wave spectrum in the microtremors mesurement point was estimated by the Chu'etsu Eartuquake wave and the H/V spectrum, the seismic wave was obtaindbu the inverse Fourier transformation and evaluated by RMS(g)(Root Mean Square)
The displacement response of the house was estimatedby the seismic wave and the assumed natural period(0.2~0.6sec.), snd was evaluated by RMS(h).
The predominant period found out that the correlation of non-collapse isn't judged as a collapse with RMS (g). It was also analyzed in the other ones, but the correlation was hardly seen. I decided to presume displacement response in a house more than a foundation acceleration corrugation and check a relation with easiness of shaking which is the house which can be put in a measurement spot. Because the proper period of the house is concentrating for 0.2~0.4 seconds, 0.2~0.4 sec RMS (h) is calculated on weighted by their probabilities. This RMS will be called RMS (h) from now on.
It was analyzed using a separation function to separate the collapse and non-disintegrating. It was to determine the collapse and the non-collapse by linear discriminant function. I found out that it's related in RMS (h) and H/V.
I think that the RMS(h) and the maximun value of the H/V power spectrum may distinguish between A Group and B Group.The hitting rate 36/60 was obtained by the discriminant analysis using Maharanobisu' Distance, and the hitting rate 40/60 was obtained by the discriminant analysis using linear discriminant function.A relation wasn't judged from an analysis using RMS (g).It was possible to separate non-collapse from a collapse for the most part in an analysis using RMS (h) and H/V.I can think it's possible to improve the accuracy by also measuring a microtremors in Takamachi housing complex from now on and increasing the number of data. Therefore it's important to be increasing data steadily.
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