Retrieving ground displacements by tightly integrating inertial instruments with GNSS

Abstract Traditional methods for calculating near-field seismic displacements using the recordings of strong-motion accelerometers require a correction procedure to remove baseline offsets, which may result from ground rotation and tilting motions. However, the baseline correction is subjective and likely to remove low-frequency components of the seismic signals. We employ a new method based on the tightly coupled integration of accelerometers, gyroscopes and GNSS, which does not require the baseline correction. To investigate how well different retrieval methods account for the effects of the rotation and tilts on the displacements, synthetic case studies are conducted using the accelerometer recordings obtained from actual earthquakes. Results showed that the method employed can provide a clear improvement over the traditional methods when the accelerometer recordings are affected by the rotation and tilting motions of the ground. Additionally, the method effectively recovers permanent displacements, partly because it incorporates GNSS measurements that enable direct observation of the ground displacements and also partly because it avoids loss of information caused by the baseline correction.