云南盈江地区地震波非弹性衰减Q值、场地响应及震源参数研究

Research on Inelastic Attenuation Q-value,Site Response and Source Parameters in Yunnan Yingjiang Region

利用云南盈江地区19个固定和流动台站记录到的2014—2016年数字地震波形资料,分别使用Atkinson方法和Moya方法反演得到了盈江地区的非弹性衰减系数和台站场地响应,并在精确扣除余震区地震波衰减与台站场地响应的基础上,联合反演了2014年盈江MS5. 6和MS6. 1地震序列共1 524次ML≥2. 0地震的震源参数。结果显示:(1)盈江地区Q值和频率的关系为:Q(f)=201. 1f0. 445 4。(2)台站场地响应总体上呈现出明显的低频放大、高频衰减的现象。(3)盈江地震序列的地震矩的变化范围为3. 16×1011～1. 50×1015N·m,与震级呈现较好的线性关系;震源破裂尺度的变化范围为87～790 m,与地震矩具有一定的正相关关系;拐角频率的变化范围为1. 6～15 Hz,与地震矩呈负相关关系;应力降的变化范围为0. 01～5. 16 MPa,有随震级增大而增大的趋势,但无明显的线性统计关系。(4)通过分析ML3. 0～3. 5地震的应力降时空演化过程,发现MS5. 6与MS6. 1地震序列的应力降的空间分布表现出明显的差异性,可能主要受到各自发震断层的控制; MS5. 6地震序列的应力降均值高于MS6. 1地震序列的应力降均值,MS6. 1地震序列余震密集区的应力降小于后期余震的应力降; MS5. 6地震序列的应力降时空演化特征对MS6. 1地震的发生具有一定的指示作用; MS6. 1地震序列中多次较大余震发生在应力降值下降后的缓慢上升过程中,其震中位置多位于应力降高值分布区域。

Based on the digital seismic waveform data recorded by 19 fixed and temporary stations around the Yunnan Yingjiang region,we calculated the inelastic attenuation coefficients and site responses by the Atkinson method and Moya method.And through accurate deduction of seismic attenuation and site response in aftershock area,we calculated source parameters of 1 524 M L≥2.0 earthquakes of the Yingjiang M S5.6 and M S6.1 earthquake sequence.The results show that:(1)The relationship between Q-value and frequency is Q(f)=201.1f 0.4454;(2)The site responses of 19 stations obtained by genetic algorithm show the characteristic of obvious low frequency amplification and high frequency attenuation;(3)There is a good linear relation between seismic moments M 0(3.16×10 11~1.50×10 15 N·m)and local magnitude M L.The source rupture radius range between 87 m and 790 m,which have a certain positive correlation with M 0;The corner frequency ranges between 1.7 Hz and 15 Hz,which is negatively correlated with M 0.The stress drop ranges between 0.01 MPa and 5.16 MPa,and increases with M L,but there is no obvious linear statistical relationship between them;(4)The temporal and spatial evolution process of stress drops of M L3.0~3.5 earthquakes shows that the spatial distribution of the stress drops of M S5.6 and M S6.1 earthquake sequence show obvious difference,which was mainly controlled by their own seismogenic fault.The mean stress drop of M S5.6 earthquake sequence is higher than that of the M S6.1 earthquake sequence,and the stress drop of M S6.1 earthquake sequence in the aftershock concentration zone is lower than that of the later aftershock.The temporal and spatial evolution process of stress drops of M S5.6 earthquake sequence have a certain directive effect on the the M S6.1 earthquake.The most aftershocks of M S6.1 earthquake sequence occurred in the process of stress drop decreasing and slowly turning up,whose epicentres located in the high stress drop area.