Evidence of Liquefaction-Induced Gradual Ground Tilt Settlement at Strong-Motion Stations

Abstract We analyzed strong-motion recordings, which were reportedly related to potential development of soil liquefaction during the 2011 Mw 9.0 Tohoku earthquake and the 2011 Mw 6.2 Christchurch earthquake. Besides visual inspection of recorded accelerograms, their Stockwell spectrograms, and their integrated velocities, the corrected ground displacements, obtained using the baseline correction method with physics-based correction patterns, were carefully analyzed. We found that soil liquefaction could be one possible cause of the nonlinearly drifted integrated velocities by triggering gradual ground tilt settlement of the concrete instrument pad that holds an accelerometer. Tilt settlement may be less pronounced for strong-motion stations with larger instrument pads. With such an explanation, the baseline correction method proposed for linearly detrended accelerograms was applied to calculate ground displacements using recorded accelerograms from the 2023 Mw 7.8 Kahramanmaraş earthquake. The calculated coseismic displacements are generally consistent with geodetic measurements.