西安建筑科技大学学报(自然科学版)

2021年云南漾濞地震序列包括4次MS≥5.0中强地震(MS5.6前震、MS6.4主震、MS5.0和MS5.2余震),这四次中强地震中强震动台站和地震烈度速报台共获得强震动记录近千组,尤其近场记录,这些记录为分析强震动特征提供了良好契机.本文选取550组高质量的强震动记录,经过严格的记录数据处理后,采用插值方法给出了MS6.4主震峰值地面加速度(PGA)和峰值地面速度(PGV)的空间分布,空间分布受震源破裂方向性和局部场地效应的影响,利用破裂方向性系数Cd表示震源破裂方向性相关的强震动峰值参数的方位角相关性,反演给出了四次地震的震源破裂方向性特征,其中MS6.4主震为沿NNW-SSE走向的双向非对称破裂事件,优势破裂方向为SSE,在优势破裂方向上的破裂约占整个破裂长度的85%.将四次地震PGA、5%阻尼比拟加速度反应谱(PSA)与ASK14预测模型的预测中位值进行对比,事件间残差均为负值,表明四次漾濞中强地震中地震动的震源效应相对较弱,短周期地震动的震源效应可能与地震类型相关,震源效应MS5.6前震>MS6.4主震>MS5.2余震,事件间残差随距离增大呈上升趋势,表明漾濞地震发震区及附近区域的非弹性衰减相对较弱.

The 2021 Ynagbi, Yunnan earthquake sequence consists of four moderate-to-large earthquakes with MS≥ 5.0, i.e., the MS5.6 foreshock, MS6.4 mainshock, MS5.0 and MS5.2 aftershock.In the four events, the strong-motion and seismic intensity stations totally obtained about 1000 free-field three-component strong-motion recordings, which provided excellent chance for investigating strong-motion characteristics.In this paper, 550 sets of high quality strong motion records are selected.After rigorous processing of the recorded data,the spatial distribution of peak ground acceleration(PGA )and peak ground velocity(PGV )of MS6.4 main shock are given by interpolation method.The spatial distribution is affected by the rupture directivity and local site effect.The source rupture directivity coefficient Cd is utilized to represent the dependency of strong-motion peak parameters on the azimuth, and the parameters of source rupture directivity are estimated for the four Yangbi events.The MS6.4 mainshock is a bidirectional asymmetric rupture event along the NNW-SSE direction.The dominant rupture direction is SSE, and the rupture in the dominant rupture direction accounts for about 85% of the total rupture length.Comparing the predicted median values of the four earthquakes PGA, 5% damping psedu-acceleration response spectrum(PSA )and the ASK14 prediction model, the residuals between events are negative, indicating that the source effect of ground motion in the four Yangbi moderate-strong earthquakes is relatively weak.The source effects on short-period ground motions approximately show the dependence on earthquake type, i.e., MS5.6 foreshock >MS6.4 mainshock>MS5.2 aftershock.The increasing trend of inter-event residuals with the increasing distance indicates the weaker anelastic attenuations in the study region than those described by the ASK14 model.

引言
1 强震动观测数据
2 破裂方向性识别
3 与NGA衰减模型对比
4 结论

图1 2021年漾濞地震序列MS≥3.0地震震中和MS6.4主震中震中距200 km以内获取记录的强震动台、地震烈度速报台<br/>Fig.1 Strong motion stations and seismic intensity quick report stations recorded within 200 km from the epicenter of the 2021 Yangbi earthquake sequence MS≥ 3.0 earthquakes and MS6.4 main shock

图1 2021年漾濞地震序列MS≥3.0地震震中和MS6.4主震中震中距200 km以内获取记录的强震动台、地震烈度速报台
Fig.1 Strong motion stations and seismic intensity quick report stations recorded within 200 km from the epicenter of the 2021 Yangbi earthquake sequence MS≥ 3.0 earthquakes and MS6.4 main shock

图2 漾濞MS6.4主震中震中附近区域的PGA、PGV空间分布<br/>Fig.2 Spatial distributionof the horizontal and vertical peak amplitudes(PGAs and PGVs)in the MS6.4 mainshock

图2 漾濞MS6.4主震中震中附近区域的PGA、PGV空间分布
Fig.2 Spatial distributionof the horizontal and vertical peak amplitudes(PGAs and PGVs)in the MS6.4 mainshock

图3 四次漾濞地震的PGA残差随方位角变化及最佳拟合的破裂方向性系数<br/>Fig.3 Path-corrected residuals for PGAs against azimuths for the four Yangbi earthquakes and the best-fitted rupture directivity coefficient

图3 四次漾濞地震的PGA残差随方位角变化及最佳拟合的破裂方向性系数
Fig.3 Path-corrected residuals for PGAs against azimuths for the four Yangbi earthquakes and the best-fitted rupture directivity coefficient

图4 PGA和部分周期PSA观测值与ASK14模型预测中位值的残差<br/>Fig.4 Residuals between the observed values and the predicted medians by the ASK14 model for the four Yangbi earthquakes

图4 PGA和部分周期PSA观测值与ASK14模型预测中位值的残差
Fig.4 Residuals between the observed values and the predicted medians by the ASK14 model for the four Yangbi earthquakes

图5 基于ASK14模型的四次漾濞中强地震事件间残差和事件内残差<br/>Fig.5 Inter-events and intra-event residuals for the four Yangbi earthquakes according to the ASK14 model

图5 基于ASK14模型的四次漾濞中强地震事件间残差和事件内残差
Fig.5 Inter-events and intra-event residuals for the four Yangbi earthquakes according to the ASK14 model

[1] 徐锡伟,闻学泽,郑荣章,等.川滇地区活动块体最新构造变动样式及其动力来源[J].中国科学(D辑), 2003, 33(S1): 151-162.
[2]常祖峰,常昊,臧阳,等.维西—乔后断裂新活动特征及其与红河断裂的关系[J].地质力学学报,2016,22(3):517-530.
[3]龙锋,祁玉萍,易桂喜,等.2021年5月21日云南漾濞MS6.4地震序列重新定位与发震构造分析[J].地球物理学报,2021,64(8):2631-2646.

_S

[4]段梦乔,赵翠萍,周连庆,等.2021年5月21日云南漾濞MS6.4地震序列发震构造[J].地球物理学报,2021,64(9):3111-3125.

_S

[5]WANG Hongwei,WEN Ruizhi.Attenuation and basin amplification revealed by thedense ground motions of the 12 July 2020 MS5.1 Tangshan, China, Earthquake[J].Seismological Research Letters, 2021,92(4), 2109-2121.
[6]ABRAHAMSON N A,SILVA W J.Empirical response spectral attenuationrelations for shallow crustal earthquakes[J].Seismological Research Letters, 1997,68(1):94-127.
[7]SMITH WH F, WESSEL P.Gridding with continuous curvature splines intension[J].Geophysics, 1990,55(3): 293-305.
[8]WEN Ruizhi, WANG Hongwei, REN Yefei.Rupture directivity from strong-motion recordings of the 2013 Lushan aftershocks[J].Bulletin of the Seismological Society of America, 2015,105(6): 3068-3082.
[9]俞言祥, 李山有, 肖亮.为新区划图编制所建立的地震动衰减关系[J].震灾防御技术, 2013, 8(1): 24-33.
[10]李小军.地震动参数区划图场地条件影响调整[J].岩土工程学报, 2013, 35(S2): 21-29.
[11]吕红山,赵凤新.适用于中国场地分类的地震动反应谱放大系数[J].地震学报, 2007, 29(1): 67-76.
[12]HEATH D, WALD D J, WORDEN C B, et al.A global hybrid VS30 map with a topographic slope-based default and regional map insets[J].Earthquake Spectra, 2020, 36(3): 1570-1584.
[13]ABRAHAMSON N A, SILVA W J, KAMAI R.Summary of the ASK14 ground motion relation for active crustal region[J].Earthquake Spectra, 2014, 30(3): 1025-1055.
[14]杨九元, 温扬茂, 许才军.2021年5月21日云南漾濞MS6.4地震:一次破裂在隐伏断层上的浅源走滑事件[J].地球物理学报, 2021, 64(9): 3101-3110.

_S

[15]AL Atik L, ABRAHAMSON N, BOMMER J J, et al.The variability of ground-motion prediction models and its components[J].Seismological Research Letters, 2010, 81(5): 794-801.
[16]BALTAY A S, HANKS T C, ABRAHAMSON N A.Earthquake stress drop and Arias intensity[J].Journal of Geophysical Research: Solid Earth,2019, 124(4): 3838-3852.
[17]MOYER P A, BOETTCHER M S, MCGUIRE J J, et al.Spatial and temporal variations in earthquake stress drop on gofar transform fault, east pacific rise: implications for fault strength[J].Journal of Geophysical Research: Solid Earth,2018, 123(9): 7722-7740.
[18]WANG Hongwei, WEN Ruizhi.Earthquake source characteristics and S-wave propagation attenuation in the junction of the northwest tarim basin and kepingtage fold-and-thrust zone[J].Frontiers in Earth Science, 2020, 8: 567939.

备注

引言

1 强震动观测数据

2 破裂方向性识别

3 与NGA衰减模型对比

4 结论

期刊信息