芦山级地震近断层地震动的方向性|近断层_断裂构造

芦山7.0级地震近断层地震动的方向性

中国地震局地球物理研究所, 北京 100081

中国地震风险与保险实验室, 北京 100081

北京工业大学建筑工程学院, 北京 100124

中国地震局工程力学研究所, 哈尔滨 150080

国家自然科学基金项目（51578513，51639006，51738001）和中央级公益性科研院所基本科研业务专项（DQJB17C02）资助

中图分类号:P315

Institute of Geophysics, China Earthquake Administration, Beijing 100081, China

China Earthquake Risk and Insurance Laboratory, Beijing 100081, China

College of Architecture and Civil Engineering, Beijing University of Technology, Beijing 100124, China

Institute of Engineering Mechanics, China Earthquake Administration, Harbin 150080, China

基于芦山7.0级地震中断层距小于100 km自由场台站的强震动记录观测数据，研究此次地震近断层地震动的方向性特性，并探讨方向性特性与震源破裂机制、断层距离和空间方位的关系.研究结果表明：（1）与距断层较远记录不同，近断层地震动在不同的观测方向上表现出显著的强度差异，存在明显的极大和极小作用方向.在不同的方向上，最大加速度反应可达最小值的4倍以上；（2）这种方向性差异在T=1.0 s以上的长周期段更为明显，在T=0.1 s以下的短周期段，地震动随方向变化的差异较小.地震动强度随方向变化的差异随周期增大而增大，不同方向上的加速度反应谱值的最大值与最小值之比从周期T=0.01 s时的约1.7增大到周期T=10 s时的约2.4；（3）在距离断层约35 km以内，地震动具有明显方向性，地震动卓越方向具有垂直断层走向的特征，随断层距的增大，这种方向性不明显.从不同方向上地震动强度的差异来看，随断层距增大，地震动强度在不同方向上的差异在减小，表现为各个周期的最大值/中值和最大值/最小值比值均随断层距离增大缓慢减小；（4）近断层地震动的方向性特性主要受断层上、下盘的相对运动所控制，其在长周期的卓越方向与水平同震位移方向一致，且该卓越方向上的地震动强度绝对大小与地震破裂造成的静态位移明显相关，表现为地震动强度随水平同震位移的增大而增大.

图 1选取的断层距小于100 km近场强震动台站的分布

选取的断层距小于100 km近场强震动台站的分布

Figure 1.Locations of near-field strong motion stations within 100 km from the causative fault

Locations of near-field strong motion stations within 100 km from the causative fault

图 2芦山地震51BXD台地震动(EW和NS向)作用下周期T=1.0 s自由振子在水平面内的加速度响应轨迹(a)和计算得到的反应谱值随旋转角度的变化(b)

芦山地震51BXD台地震动(EW和NS向)作用下周期T=1.0 s自由振子在水平面内的加速度响应轨迹(a)和计算得到的反应谱值随旋转角度的变化(b)

Figure 2.Example of acceleration response trace of a 2 degree-of-freedom oscillator with T=1.0 s subjected to the 51BXD record during the Lushan earthquake

Example of acceleration response trace of a 2 degree-of-freedom oscillator with T=1.0 s subjected to the 51BXD record during the Lushan earthquake

图 3近断层51BXD (a)、51BXM (b)、51BXY (c)和51BXZ (d)台地震动记录作用下T=1.0 s振子的加速度反应

近断层51BXD (a)、51BXM (b)、51BXY (c)和51BXZ (d)台地震动记录作用下T=1.0 s振子的加速度反应

Figure 3.Acceleration response trace of a 2 degree-of-freedom oscillator with T=1.0 s subjected to the near-fault recordings of 51BXD (a), 51BXM (b), 51BXY (c) and 51BXZ (d) during Lushan earthquake

Acceleration response trace of a 2 degree-of-freedom oscillator with T=1.0 s subjected to the near-fault recordings of 51BXD (a), 51BXM (b), 51BXY (c) and 51BXZ (d) during Lushan earthquake

图 4近断层51BXD (a)、51BXM (b)、51BXY (c)和51BXZ (d)台记录作用下T=3.0 s振子的加速度反应

近断层51BXD (a)、51BXM (b)、51BXY (c)和51BXZ (d)台记录作用下T=3.0 s振子的加速度反应

Figure 4.Acceleration response trace of a 2 degree-of-freedom oscillator with T=3.0 s subjected to the near-fault recordings of 51BXD (a), 51BXM (b), 51BXY (c) and 51BXZ (d) during Lushan earthquake

Acceleration response trace of a 2 degree-of-freedom oscillator with T=3.0 s subjected to the near-fault recordings of 51BXD (a), 51BXM (b), 51BXY (c) and 51BXZ (d) during Lushan earthquake

图 5近断层51BXM台记录(a)与距断层较远的51HYQ台记录(b)作用下周期T=1.0 s的加速度反应

近断层51BXM台记录(a)与距断层较远的51HYQ台记录(b)作用下周期T=1.0 s的加速度反应

Figure 5.Comparison of acceleration traces of a 2 degree-of-freedom oscillator with T=1.0 s when subjected to the near-fault and far-fault recordings of 51BXM (a) and 51HYQ (b) during Lushan earthquake

Comparison of acceleration traces of a 2 degree-of-freedom oscillator with T=1.0 s when subjected to the near-fault and far-fault recordings of 51BXM (a) and 51HYQ (b) during Lushan earthquake

图 6计算得到不同方向上的反应谱最大值SaRotD100与中值SaRotD50的比值随周期的变化

计算得到不同方向上的反应谱最大值SaRotD100与中值SaRotD50的比值随周期的变化

Figure 6.Ratio of SaRotD100 (maximum) to SaRotD50 (median) for near-fault recordings observed as a function of vibration periods

Ratio of SaRotD100 (maximum) to SaRotD50 (median) for near-fault recordings observed as a function of vibration periods

图 7计算得到不同方向上的反应谱最大值SaRotD100与最小值SaRotD00的比值随周期的变化

计算得到不同方向上的反应谱最大值SaRotD100与最小值SaRotD00的比值随周期的变化

Figure 7.Ratio of SaRotD100 (maximum) to SaRotD00 (minimum) for near-fault recordings observed as a function of vibration period

Ratio of SaRotD100 (maximum) to SaRotD00 (minimum) for near-fault recordings observed as a function of vibration period

图 8长周期(T≥1.0 s)地震动的最大方向随断层距离变化的分布

长周期(T≥1.0 s)地震动的最大方向随断层距离变化的分布

Figure 8.Variation in maximum direction orientation with source-to-site distance for the long-period (T≥1.0 s)

Variation in maximum direction orientation with source-to-site distance for the long-period (T≥1.0 s)

图 9SaRotD100/SaRotD50 比值随震源距Dhyp的变化

SaRotD100/SaRotD50 比值随震源距Dhyp的变化

Figure 9.Variation of ratio of SaRotD100 to SaRotD50 with source-to-site distance Dhyp

Variation of ratio of SaRotD100 to SaRotD50 with source-to-site distance Dhyp

图 10最大与最小加速度反应比(SaRotD100/SaRotD00)随震源距离Dhyp的变化

最大与最小加速度反应比(SaRotD100/SaRotD00)随震源距离Dhyp的变化

Figure 10.Variation of maximum to minimum acceleration response ratio (SaRotD100/SaRotD00) with source to site distance Rrup.

Variation of maximum to minimum acceleration response ratio (SaRotD100/SaRotD00) with source to site distance Rrup.

图 11芦山地震中观测近断层地震动在周期T=0.2 s (a)、0.5 s (b)、1.0 s (c)和3.0 s (d)的最大强度方向

芦山地震中观测近断层地震动在周期T=0.2 s (a)、0.5 s (b)、1.0 s (c)和3.0 s (d)的最大强度方向

Figure 11.Maximum response direction of near-fault strong motions during Lushan earthquake at period T=0.2 s (a), 0.5 s (b), 1.0 s (c) and 3.0 s (d)

Maximum response direction of near-fault strong motions during Lushan earthquake at period T=0.2 s (a), 0.5 s (b), 1.0 s (c) and 3.0 s (d)

图 12不同周期的地震动卓越方向与水平同震位移方向的关系以及随周期的变化

不同周期的地震动卓越方向与水平同震位移方向的关系以及随周期的变化

Figure 12.Variation of maximum response direction with period for near-fault strong motion during Lushan earthquake

Variation of maximum response direction with period for near-fault strong motion during Lushan earthquake

图 13卓越方向的地震动强度与水平同震位移的相关性

Figure 13.Correlation of maximum IMs at various periods with co-seismic displacement

Correlation of maximum IMs at various periods with co-seismic displacement

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