西藏定日6.8级地震地面运动特征空间分布分析

Spatial distribution characteristics of ground motions from the Dingri M6.8 earthquake in Xizang

摘要:

北京时间2025年1月7日9时5分,西藏自治区日喀则市定日县发生6.8级强烈地震,造成大量人员伤亡和财产损失。针对中国地震局工程力学研究所强震动观测中心提供的35组地震动记录,首先对原始数据进行基线校正与滤波处理,绘制水平和竖向加速度反应谱;随后开展峰值加速度(PGA)和周期0.2 s谱加速度[S_a(0.2 s)]空间分布,累积绝对速度(CAV)和Arias强度(I_A)等广义强度参数分布，以及显著持时(DS)分布的系统分析,最终完成三向地震动脉冲特征识别。研究结果表明:(1)本次地震事件对自振周期0.2~0.7 s的建筑结构破坏效应显著,其中拉孜县台站XZ.D0007记录的南北向加速度反应谱峰值超出8度极罕遇地震设计谱限值;(2)CAV和I_A参数在水平向和竖向呈现相似空间分布特征;(3)定结县台站XZ.D0004和拉孜县台站XZ.D0007处的CAV值超过相关规定阈值,拉孜县台站XZ.D0007处的I_A值超过相关规定阈值;(4)地震动呈现典型上/下盘效应,上盘区域S_a(0.2 s)与PGA较高而持时较短,下盘区域呈现相反特征;(5)基于Baker脉冲辨识准则,确认本次地震动均不是脉冲地震动。研究结果将为揭示地震动的强度分布特征提供科学依据,为西藏地区日后工程结构的抗震设防提供参考。

Abstract:

At 09:05 Beijing Time on January 7, 2025, an M6.8 earthquake struck Dingri County, Shigatse, Xizang Autonomous Region, causing casualties and property damage. In this study, 35 sets of ground motion records of this event were obtained from the Strong Motion Observation Center of the Institute of Engineering Mechanics, China Earthquake Administration, and horizontal and vertical acceleration response spectra were drawn after baseline correction and filtering of the raw data. A systematic analysis was then conducted encompassing the spatial distributions of the peak ground acceleration (PGA) and spectral acceleration at 0.2 s \[S_a (0.2 s)\] as well as generalized intensity parameters including the cumulative absolute velocity (CAV), Arias intensity (I_A), and significant duration (D_S). The results were used to identify the pulse characteristics in three-component ground motions. The earthquake was found to induce significant damage to structures with natural periods of 0.2—0.7 s; the north-south acceleration response spectrum recorded at station XZ.D0007 (Lhazê County) exceeded the design spectrum threshold for extremely rare earthquakes (intensity 8). CAV and I_A exhibited similar spatial distribution patterns in the horizontal and vertical directions. CAV values at station XZ.D0004 (Dingjie County) and XZ.D0007 (Lhazê County), along with the I_A value at station XZ.D0007, exceeded regulatory thresholds. Ground motions displayed typical hanging-wall/footwall effects where S_a (0.2 s) and PGA were higher but had shorter durations on hanging walls. No pulse-like ground motions were identified based on Baker’s pulse characterization criterion. This study provides a scientific basis for revealing the intensity distribution characteristics of ground motions and is expected to serve as a reference for future aseismic fortification of engineering structures in Xizang.