Evaluating the identification methods of permanent displacement derived from strong motion records: Case studies in the 2023 Turkey-Syria earthquake

On February 6, 2023, the Republic of Turkey experienced a rare occurrence of two successive earthquakes, each with a magnitude exceeding 7.0. The Disaster and Emergency Management Agency (AFAD) swiftly shared the strong motion records, thereby enriching the global database of near-fault strong motion records. Identification of permanent displacement is essential for effectively utilizing these records. In this study, we refined the permanent displacement identification method, which combines the Hermit interpolation baseline correction with flatness determination by incorporating a low-pass filter. Following this, we compared four permanent displacement identification methods, including our improved approach. We applied these to the strong motion record of station 4404 and compared the results with the Global Positioning System coseismic displacement. At the same time, we used field investigation data to verify the effectiveness of our improved method, studying its applicability for both single-wave packet and multiwave packet records. The conclusions are the following: the improved method provides a more reasonable and effective means of identifying permanent displacement. When the peak ground acceleration (PGA) exceeds 1 g, the permanent displacement identifications from the four methods differ significantly. The discrepancy in permanent displacements identified by the four methods in the horizontal direction is larger than that in the U-D direction. For the record with the largest PGA (station 4614), our improved method yields more reasonable results compared with other techniques. Furthermore, the choice of segmentation time nodes in the velocity time history significantly affects the identification of permanent displacement. On February 6, 2023, two earthquakes with the magnitude of more than 7.0 occurred in relatively rare succession in the Republic of Turkey. The Disaster and Emergency Management Agency (AFAD) has promptly released the strong motion records, which has contributed to the global database of near-fault strong motion records. The identification of permanent displacement is essential for effectively utilizing these records. In this study, the permanent displacement identification method which combines the Hermit interpolation baseline correction with flatness determination is improved by applying the low-pass filter. Then, four permanent displacement identification methods including the improved method are compared with the Global Positioning System coseismic displacement by the application of the strong motion record of station 4404. At the same time, the field investigation data is also applied to verify the effectiveness of the improved method, and the applicability of it for both single-wave packet and multiwave packet records is studied. The conclusions are as follows: the improved method is more reasonable and effective for identifying permanent displacement; when the peak ground acceleration (PGA) exceeds 1 g, the permanent displacement identifications of the four methods differ significantly; the difference in permanent displacements identified by the four methods in the horizontal direction is larger compared with the vertical direction; for the record with the largest PGA (station 4614), the improved method can obtain more reasonable results relative to other methods; the choice of segmentation time nodes in the velocity time history significantly affects the identification of permanent displacement. image