| Strong motion records are important indicators for assessing the earthquake destructive power and disaster risk at the location of the recorded station.Due to instrument errors and noise interference,the original records often cannot reflect the real characteristics of earthquake motion.Therefore,accurate processing and analysis of these data is crucial.It is very important,especially the permanent displacement is of great significance for the seismic design of long-span engineering structures.This paper aims to discuss the method and technology of near-fault strong motion data processing,and mainly discusses the calculation method of post-earthquake permanent displacement of near-fault strong motion data.This paper first introduces the acquisition method and processing steps of strong motion data,including data preprocessing,filtering,baseline correction,outlier identification and processing,etc.These steps are important for reducing noise and errors,and improving data quality and accuracy.Then,according to the characteristics of the strong motion data near the fault,on the basis of the Iwan（1995）and Boore（2001）methods,a method for automatically calculating the permanent displacement of the strong motion data near the fault based on the arrival of P waves and S waves is proposed,and by processing and solving the Chichi earthquake data of Taiwan,China on September 21,1999,the Nurdagi earthquake data of Turkey on February 6.2023.and the central Italy earthquake data of August 24,2016,the feasibility and effectiveness of the proposed method are verified.The main research work and conclusions of this paper are as follows:（1）Summarized the various parts of the strong motion data processing flow,including the introduction of data preprocessing,detrending,filtering and other steps,and focused on discussing some problems in strong motion data processing,such as P wave and S wave arrival time solution,solution,baseline drift,outlier and filter cut-off frequency selection,each step and its details will be explained with examples,and the most applicable suggestions will be given,and each part of the strong motion data processing process will be summarized..（2）Based on Iwan’s（1995）two-stage method and Boore’s（2001）VO correction method,a new method for calculating permanent displacement of near-fault strong motion data based on P-wave arrival time and S-wave arrival time is introduced.By calculating the P-wave arrival time and S-wave arrival time,set the small-scale correction parameters,and then iterate in combination with the flatness to determine the time point tj of the permanent offset at the beginning of the strong earthquake segment and the time point t2 of the permanent offset at the end segment.Then determine the parameter reference slope according to the influence of the offset constant of each segment of the original velocity time history of the ground motion,and then determine the fitting offset of each segment based on the t1 and t2 points to determine the correction method to perform single-stage or two-stage formula correction,as far as possible to automatically solve the permanent displacement of the strong motion data near the fault.（3）Based on the strong motion data recorded by the stations near the fault of the Chichi earthquake in Taiwan,China on September 21,1999,62 stations within 100km of the epicentral distance were selected,and the permanent displacement was automatically calculated using the new method,and compared with the adjacent GPS station,compared with the station data and the permanent displacement results calculated by other methods,the reliability of the new method is verified.The results show that the new method can solve the permanent displacement with higher accuracy than other existing methods,simplify the complex iterative method,and make it easier to realize automatic calculation.Moreover,the calculated permanent displacement distribution is in good agreement with the vector distribution of the adjacent GPS stations,and the arrangement and the displayed earthquake mechanism and characteristics are relatively consistent,which can reflect the local disaster situation of the earthquake and various practical features reveal that the focal mechanism of this earthquake is a typical low-angle thrust fault,regardless of horizontal displacement or vertical permanent displacement,which shows that the value of the fault hanging wall is greater than that of the foot wall.Moreover,the overall permanent displacement calculated by the stations distributed along the Chelungpu fault presents the characteristic of extrusion towards the fault.（4）Based on the strong motion data recorded by the station on the Nurdaji earthquake fault in Turkey on February 6,2023,and according to the characteristics of the data recorded by the strong motion,the calculation of the starting offset point t1 of the strong motion segment is adjusted accordingly,using the new method to automatically calculate the permanent displacement,the calculated horizontal permanent displacement distribution and vertical permanent displacement distribution are in line with the focal mechanism solution,that is,the overall performance is a left-dipping strike-slip fault rupture along the East Anatolia fault,and again the rationality and applicability of the method in this paper are verified.（5）Based on the strong motion data recorded by the station near the fault of the central Italy earthquake on August 24,2016,the method in this paper is used to automatically calculate the permanent displacement,and compared with the data of the adjacent GPS station,it is found that the horizontal space of the two types of data,the distribution range has good consistency,including its overall direction and the magnitude of the different components.And further compared with the focal mechanism solution,it is found that the permanent displacement obtained by the solution shows a four-quadrant symmetrical distribution with the fault line as the critical point,and the permanent displacement direction is opposite,and the deviation from the fault line shows a tension distribution,which is consistent with the normal fault-based focal mechanism,the solution verifies the applicability and feasibility of the method in this paper for such data. |
