Optimized baseline correction method for the near-fault observation strong motion records

Deriving velocity and displacement time histories from near-fault observation strong motion records and recovering the permanent displacement information is the first obstacle need to be solved while studying the near-field strong ground motion characteristics. Most near-fault observation strong motion records are plagued by baseline drifts aroused by background noise or tilt of instruments due to strong motion triggering. Thus, there is an urgent need to develop an intuitive and effective baseline correction method. Iwan proposed an adjustment procedure for removing baseline drifts from accelerograms in 1985, the further modification to Iwan et al.' s original method is termed by Boore (2001), the v0 correction method. Our discussion is based on v0 correction method. At first, we introduced consecutive slope ratios, standard deviations of fitted velocity segment and mean square error of adjusted displacement segment. With the aid of these three parameters, we proposed an improved baseline correction optimization method and specific steps. Observation strong motion records of Wenchuan Ms8.0 earthquake are used to verify this method. Permanent displacement information obtained from records are in good agreement with GPS measurements. Compared with v0 baseline correction method, proposed optimized method can determine fitted range of final segment of velocity with linear trend. To some extent, it could reduce baseline correction uncertainty which comes from determining fitted range subjectively.