Influence of near-surface shear wave velocity on seismic ground motion in Turkey Earthquake and the enlightenment on revision of seismic design response spectrum characteristic parameters in China

The February 6, 2023, M_w7.8 Turkey strong earthquake was a typical strike slip shallow source earthquake, caused large-scale surface ruptures. Unexpected strong ground motions caused a large number of buildings collapsed in the near-fault area. Based on strong motion records on both sides within 60 km from Kahramanmaras-Antakya fault, spatial distribution characteristics of peak value, frequency spectrum and duration time of strong ground motions were systematically researched, and the influence law of the average shear-wave velocity of the upper 30 m soil layers (V_S30) on strong ground motion were discussed. By comparing actual response spectrums of near-fault records with Chinese design response spectrums, the differences between characteristic parameters were analyzed. The results show that: 1) The near-fault areas of the Turkey earthquake are predominantly composed of Site Class I₁ and Site Class II. The strongest ground motions with peak ground accelerations (PGA) more than 0.40 g and amplification factors exceeds 3 are concentrated in a 30 km region of hanging wall and generally belong to pulse-type. 2) The fitting results of PGA amplification factor with V_S30 are close to the empirical relationship, whereas the variation rules of energy durations with V_S30 is not significant. 3) The characteristic period of response spectrum decreases with the increase of V_S30. The amplification factor of response spectrum increases with the increase of V_S30. There are 80% characteristic periods and 45% amplification factors of actual response spectrums are larger than the values specified in Chinese codes. 4) If this earthquake occurs in Chinese earthquake fortification intensity IX area, design response spectrum of site-class I₁ and design earthquake-1st group during 0.38~1.90 s, as well as site-class Ⅱ and design earthquake-1st group during 0.65~2.00 s, will totally fail to meet the requirements for seismic fortification. This study suggests that the height and the width of design spectrum platform should be raised to fit high intensity ground motion.