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 the Envelope Inversion of Acceleration Seismograms and Synthesis of Near-Field Accelerograms

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30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（〉1Hz）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60~90km区域、北川和南坝东北侧30km处;（3）断层破裂停止的东北端约30km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 （〉1 Hz） wave radiation areas on the Wenchnan 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 90 krn northeast of epicen ter, and areas 30 km northeast of Beichuan and Nanba; （3） the area within 30 km 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.