From the accelerogram on the surface, we could estimate the surface tilt by measuring the static offset appearing in the surface accelerogram, which was 2.2 × 10−3 radians down to the east (Figure 3b, Table 1).
3Displacement measured by the borehole accelerogram at IWTH25.
The RC frame behaviour was classified as satisfactory for the seismic action characterized by the accelerogram BF-475, not showing significant global damage, but only small local damage.
The ground displacements were well recovered from the double numerical integration of accelerograms at KMMH16 both on the surface and at the bottom of the 252-m-deep borehole.
In these analyses the earthquake ground motion is represented (a) by the recorded correlated accelerograms and (b) by the corresponding uncorrelated accelerograms.
We investigated the near-fault displacement field using the accelerograms obtained at KMMH16, a KiK-net station, where waveforms were recorded both on the surface and at the bottom of a 252-m-deep borehole.
We first computed ground displacements on the surface as well as at the bottom of the borehole of the IWTH25 station by numerically integrating the accelerograms two times in the time domain.
The waveforms were obtained by integrating the accelerograms in the frequency domain.
However, for high frequency (σ= 2.7) Tsallis produced slightly better SNR and is more feasible in detecting the occurrence of P and S waves by smoothing the accelerograms.
These velocity waveforms were derived by integrating the accelerograms, shown in Fig. 2, by using a linear acceleration method in the time domain Fig. 4 Fourier amplitude spectra and spectral ratios.
