• Earthquakes and Structures
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• v.18 no.3
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• pp.297-312
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• 2020

The KiK-net by NIED is a vertical array measurement system. In the database of KiK-net, singular pulse waves were observed in the seismic record at the borehole of TTRH02 during the mainshock (the magnitude of Japan Meteorological Agency (M_J) 7.3, M_W 6.8) and aftershock (M_j 4.2) of Tottori-ken Seibu earthquake in 2000. Singular pulse waves were also detected in the seismic records at the borehole of IWTH25 during the Iwate-Miyagi Nairiku earthquake in 2008 (M_J 7.2, M_W 6.9). These pulse waves are investigated by using the wave shape analysis methods, e.g., the non-stationary Fourier spectra and the double integrated displacement profiles. Two types of vibration modes are discriminated as the occurrence mechanism of the singular pulse waves. One corresponds to the reversal points in the displacement profile with the amplitude from 10^-4 m to 10^-1 m, which is mainly related to the fault activity and the amplification pass including the mechanical amplification (collision) of the seismograph in the casing pipe. The other is the cyclic pulse waves in the interval of reversal points, which is estimated as the backlash of the seismograph itself with the amplitude from 10^-5 m to 10^-4 m.

• Journal of the Korean Society for Railway
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• v.13 no.2
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• pp.208-213
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• 2010

This paper describes the instruments used, and the test procedures adopted, and the findings obtained from a research project aiming to investigate, via full-scale field tests, the ground borne vibration caused by underground railway tunnel constructed in hard rock. The ground borne vibration induced by high-speed trains (i.e. the Korea Train eXpress (KTX) services) with a speed of approximately 200km/hr was measured inside the borehole constructed in the close proximity to the KTX tunnel using 3-component borehole seismographs in order to investigate the wave propagation of ground borne vibration. This paper also discusses the limitation associated with the current practice of measuring ground borne vibration using conventional borehole seismograph.