基于包络的汶川大地震高频地震波辐射区域反演及近场加速度合成
Estimation of HighFrequency Wave Radiation Areas of Wenchuan Earthquake by

合理地估计汶川破坏区域的地震动有助于地震灾害的研究.通过利用芦山地震记录建立的加速度包络衰减关系和汶川地震近场3 0个台站的加速度包络,基于线源模型,采用差分进化方法反演了汶川地震断层面上高频(>1H z)辐射区域分布.结果表明:断层面上高频辐射分布很不均匀,辐射较强的区域主要位于:(1)产生较大地表破裂的映秀、北川和南坝区域;(2)映秀和北川等凹凸体的周边区域,包括震中东北侧6 0~9 0km 区域、北川和南坝东北侧3 0km处;(3)断层破裂停止的东北端约3 0km长的区域.其中,破裂贯穿到地表的映秀、北川和南坝是低频和高频辐射都很强的区域.对于无观测记录场点,选择其临近且场地条件类似的台站加速度提取平稳随机过程,结合高频辐射分布和衰减关系得到的包络,合成了加速度时程,可为汶川地震结构震害分析提供地震动输入.
It's helpful for studying earthquake disaster by estimating seismic oscillation reasonably in Wenchuan area. Based on the line source model, the highfrequency (＞1Hz) wave radiation areas on the Wenchuan earthquake fault plane are inversed by the differential evolution method, using the acceleration envelopes attenuation relationship of Lushan earthquake and envelopes of 30 nearfield stations acceleration seismograms in Wenchuan earthquake. The results indicate that the highfrequency wave radiation areas are very nonuniform, with most of the High-frequency waves radiated in: (1) the surface rupture areas, including Yingxiu, Beichuan and Nanba areas; (2) the areas close to the boundaries of the asperities, including that with epicentral distance from 60 to 90km northeast of epicenter, and areas 30km northeast of Beichuan and Nanba; (3) the area within 30km length near the fault northeastern tip. Both high and low frequency wave radiation were much higher in areas with large surface rupture. Utilizing the inversed high-frequency wave radiation areas and the acceleration envelopes attenuation relationship, near-field accelerations are synthesized. The accelerations in areas with no seismic records are synthesized by the synthetic envelopes and a stationary stochastic process extracted from its near station with similar site conditions. The results could be used as the earthquake input for analyzing seismic damage of structures in Wenchuan earthquake