摘要:
北京时间2025年1月7日，西藏定日县发生6.8级地震, 造成严重人员伤亡和建筑结构损坏。本文基于D0004、D0007和DS002等3个台站的强震动记录，结合现场震害调查，分析了地震的震动特征、场地效应及其方向性特征。通过对77条主余震记录的标准数据处理，并对比烈度计与强震仪的数据，发现DS002台站因选址严格、噪声较低，其可用周期范围优于其他台站。主震记录显示，D0007台站因距离断层最小(11.7 km)，峰值地面加速度(PGA)最大(NS向395.3 cm/s²)，导致周围建筑受损显著。场地效应分析表明，D0004和D0007台站在低频时(0.66和0.44 Hz)放大效应显著(7.85和8.09倍)，而DS002台站在高频段(3.2 Hz)放大4.48倍，且其场地放大方向性特征与地形相关，垂直山脉方向的场地放大卓越频率明显小于平行方向。本研究可为西藏地区的地震动参数区划、抗震设计和震害评估提供参考。
Abstract:
On January 7, 2025, a Mw 6.8 earthquake struck Dingri County, Tibet, causing severe casualties and structural damage. This study analyzes the ground motion characteristics, site effects, and rupture directivity effects of the earthquake based on strong-motion records from three stations (D0004, D0007, and DS002) combined with on-site damage investigations. Standard data processing was applied to 77 mainshock and aftershock records, and a comparison between intensity meter and strong-motion seismometer data revealed that DS002, due to its strict site selection and lower noise levels, exhibited a more reliable effective period range than the other stations. The mainshock record showed that D0007, located closest to the fault (11.7 km), recorded the highest peak ground acceleration (PGA) (395.3 cm/s² in the NS direction), leading to significant damage to nearby structures. Site effect analysis indicated that D0004 and D0007 exhibited significant amplification in the low-frequency range (0.44 and 0.66 Hz) with amplification factors of 7.85 and 8.09, while DS002 showed a 4.48-fold amplification at 3.2 Hz in the high-frequency range. Moreover, the site amplification directivity effect at DS002 was terrain-dependent, with the predominant frequency of amplification in the direction perpendicular to the mountain range being notably lower than that in the parallel direction. This study provides crucial insights for ground motion parameter zoning, seismic design, and disaster assessment in the Tibet region.
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