日本北海道胆振东部M_(W)6.6地震近断层地震动的上盘效应  

The Hanging-wall Effect of the Near-fault Strong Ground Motions during the Hokkaido Eastern Iburi M_(W)6.6 Earthquake

作　　者：赵晓芬 谢俊举[1] 温增平[1] 李志恒 Zhao Xiaofen;Xie Junju;Wen Zengping;Li Zhiheng(Institute of Geophysics,China Earthquake Administration,Beijing 100081,China;Shandong Earthquake Agency,Jinan 250014,China)

机构地区：[1]中国地震局地球物理研究所,北京100081 [2]山东省地震局,济南250014

出　　处：《震灾防御技术》2023年第3期432-449,共18页Technology for Earthquake Disaster Prevention

基　　金：国家重点研发计划(2022YFC3003503);中国地震局地球物理研究所基本科研业务专项(DQJB22B27)。

摘　　要：上盘效应是近断层地震动的主要特性之一,而目前就上盘效应的定量研究较少。本文利用日本K-NET和KiK-net强震动台网获取的近场强震动加速度记录,定量研究了北海道M_(W)6.6地震的上盘效应对地震动PGA、PGV和不同周期的加速度反应谱值空间分布和衰减特征的影响,探讨地震动上盘效应的特征及其影响范围,并将上、下盘观测结果与地震动预测经验模型进行对比。研究结果表明:(1)在断层距小于45 km时,此次北海道地震具有显著的上盘效应特征,断层上盘记录的PGA、PGV和加速度反应谱值明显大于下盘和中间区域的地震动观测值,且高于本次地震的平均值。上盘效应影响范围与震源破裂过程反演得到的断层尺度相吻合。(2)断层上盘的PGA观测值高于此次地震平均水平的对数偏差为0.61±0.16,这与1994年北岭地震和1999年集集地震等逆冲型地震的影响水平接近。上盘记录的PGV高于平均水平的对数偏差为0.39±0.12,即高于平均水平约35%。上盘观测地震动在周期T为0.2、0.5、1.0、2.0、3.0、5.0 s时的加速度反应谱值高于平均水平的对数偏差分别为0.33±0.19、0.54±0.23、0.53±0.20、0.26±0.21、0.24±0.19、0.16±0.16,随着周期的逐渐增大,上盘效应引起的偏差不断减小。此次地震上盘效应对地震动的影响主要以PGA和短周期(T≤1.0 s)地震动为主。(3)从实际观测结果与地震动预测经验模型的对比来看,对于PGA和小于1.0 s的短周期地震动,BSSA2014和CB2014的2个模型对此次地震上盘效应的预测效果更好,但对1.0 s以上的长周期,ASK2014、CB2014、CY2014模型的预测效果更好,BSSA2014模型则可能会高估地震动。The hanging-wall effect is one of the main characteristics of near-fault strong ground motion.However,there are few quant-itative studies on the hanging-wall effect.Here,based on the near-fault strong ground motion recordings obtained by K-NET and KiK-net during the M_(W)6.6 Hokkaido Eastern Iburi earthquake,we investigated the hanging-wall effect of the near-fault and its influence on spatial distribution and attenuation features of horizontal peak ground acceleration(PGA),peak ground velocity(PGV)and accelera-tion spectra(Sa)of different periods.The characteristics and the influence range of the hanging-wall effect were investigated.And the observation of hanging-wall and footwall was compared with NGA-West2 prediction models.The results show the following:(1)The Hokkadio earthquake has a distinct hanging-wall effect.Within about 45 km from the fault,the observation of PGAs,PGVs and Sa are larger on the hanging-wall sites than on the footwall sites and the netural sites,and above the regressed median curve.The region of in-fluence of the hanging-wall effect is consistent with the fault scale given by the rupture process.(2)The PGA mean residual of the hanging-wall sites is 0.61±0.16.This value is similar to the mean residual from 1994 Northridge earthquake,1999 Chi-Chi earthquake and other dipping fault earthquakes.The PGV mean residual of the hanging-wall sites is 0.39±0.12,that is,the observed PGV is 35%larger than the fitted mean.The mean residual for the spectra acceleration at periods of 0.2 s to 5.0 s are 0.33±0.19、0.54±0.23、0.53±0.20、0.26±0.21、0.24±0.19 and 0.16±0.16.With the increase of the period,the mean residual of acceleration spectra on the hanging-wall tends to gradually decrease.The analysis results show that the PGA and the short-period ground motion are systematic-ally affected by the hanging-wall effect.(3)Based on the comparison between the observation and the prediction results,for the PGA and the short period ground motions less than 1.0 s,observation shows a coincidence wit

关 键 词：近断层 上盘效应 地震动预测模型 

分 类 号：P315[天文地球—地震学] TU352.11[天文地球—固体地球物理学]