Baseline correction for near-fault ground motion recordings of the 2008 Wenchuan Ms8.0 earthquake

Abstract

In this study, both records of a digital accelerometer and a seismograph at a far-field station for the 2008 Ms8.0 Wenchuan earthquake were analyzed, and a pulsive noise model for acceleration record was found. By comparing with the result of a rotary-table tilt test, we concluded that the noises in the acceleration records were caused by ground tilt as a result of rotational ground motion. We analyzed the key noises that may cause baseline offset, and proposed a baseline-correction scheme for preserving the long-period ground motion in accordance with specific pulse positions. We then applied this correction method to some near-field strong-motion acceleration records. The result shows that this method can obtain near-field ground displacements, including permanent displacements, in agreement with GPS data, and that this method is more stable than other methods.

Keywords

• strong ground motion
• baseline correction
• permanent displacement
• rotational motion
• tilt