DEVICE FOR DETECTING CHARACTERISTICS OF SURFACE LAYER GROUND

摘要

PURPOSE:To improve the estimation accuracy of dominant frequency of a surface layer ground and to attain estimation at an optional time band by finding out the vector ratio of a horizontal direction component to that of a vertical direction component of a microtremors wave measured on a ground surface. CONSTITUTION:A waveform is read out from the electric signal of a vertical direction component of ground motion based upon a recorder or a sensor by a 1st waveform detecting part 2 and the amplitude spectrum of the horizontal direction component waveform is calculated by a spectrum operation part 5. A waveform is similarly read out from the electric signal of the vertical direction component of the ground motion by 1 2nd waveform detecting part 3 and the amplitude spectrum of the vertical direction component waveform is calculated by a spectrum operation part 6. Then, the ratio of the amplitude spectrum of the horizontal direction component to the vertical direction is calculated by a spectrum ratio operating part 8 to find out the dominant frequency highly accurately as frequency applying the largest peak value of the spectrum ratios. Since artificial vibration is smaller than the dominant frequency in the horizontal direction of the surface layer ground, the restriction of a time band for measuring the microtremors of the ground surface is loosened.