Retrieving Ground Displacements by Tightly Integrating Inertial Instruments with GNSS

Abstract

Traditional methods of calculating near-field seismic displacements using the recordings of strong motion accelerometers require a correction procedure to remove baseline offsets that may be caused by rotation and tilting motions of the ground. The baseline correction is, however, 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. Also the method was capable of recovering permanent displacements partly because it ingests GNSS measurements that allow direct observation of the ground displacements and also partly because it does not experience loss of information induced by the baseline correction.