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本文选取了云南和四川地区62个数字地震台站记录到的Rayleigh面波资料,使用相匹配滤波技术从记录中提取基阶面波信号.利用与震源处于同一大圆弧上的两台记录的基阶振型计算出台间Rayleigh面波衰减系数,其周期为10.40～80.64s,反演出两台之间0～200km深度范围内的S波品质因子.结果表明,云南地区地壳Q值在20～140之间,整体呈现出低Q背景,但其横向变化较为显著.大致以红河断裂为界,其西侧的大部分地区,地壳Q仅20左右,并延伸到120km深处,地壳Q这一分布特征与滇西大范围出露新生代火山岩、侵入岩分布相一致,暗示滇西地区地壳与上地幔正处于热活动的状态;小江断裂东侧的滇东块体,南部地区地壳Q为140,北部地壳Q仅为20,并延伸到深度120km.另外,滇中块体上的渡口-楚雄一带,地壳上地幔Q值为60～100,呈现出高Q特征,表明地壳物质是坚硬的,这是由于印度板块-欧亚板块的缝合,使该区由裂谷期的拉伸反转为造山期的挤压,导致地壳裂隙闭合,随着时间的流逝,孔隙流体逐渐消失,于是形成了地壳高速层和地表低热流值.云南地区地壳Q值在低背景下呈现出了明显的块体分布特征,这一分布特征与地表热流值分布相一致.红河断裂、小江断裂既是构造分界线,同时也是地壳高、低Q的分界线,产生低Q值的原因可能是大震破裂造成介质破碎,热物质沿深大断裂带上涌的结果.
In this paper, Rayleigh surface wave data recorded by 62 digital seismic stations in Yunnan and Sichuan regions are selected, and the matched surface acoustic wave (PSF) signals are extracted from the recorded data by using the matched filtering technique.With two records on the same arc Based on the fundamental order mode, the attenuation coefficient of Rayleigh surface wave was calculated and its period was from 10.40 to 80.64s, and the S-wave quality factor in the depth range from 0 to 200km was inverted.The results show that the Q value of the crust in Yunnan is between 20 ~ 140, showing a low Q background as a whole, but its lateral variation is more obvious.With the Honghe fault as a boundary, in most of its western part, the crust Q is only about 20 and extends to a depth of 120 km. The crust Q The distribution features are consistent with the Cenozoic volcanic rocks and the intrusive rocks distributed in a large area in western Yunnan, suggesting that the crust and upper mantle in the western Yunnan are in a state of thermal activity. The crust Q in the eastern Yunnan block and the southern part of the Xiaojiang fault are 140 , The northern crust Q only 20, and extends to a depth of 120km. In addition, the block on the central Yunnan-Chuxiong area, the Q value of the crust and upper mantle from 60 to 100, showing a high Q characteristics, indicating that crustal material is hard, This is due to the Indian plate - the Eurasian plate Sutured to make the area reverse from rifting period to extrusion during orogenic period, leading to the closure of the crustal cracks. With the passage of time, the pore fluid gradually disappeared, thus forming the crustal high-velocity layer and the surface low heat flow value. The Q value of the crust shows obvious block distribution characteristics under the low background, which is consistent with the distribution of the surface heat flow value.The Honghe fault and the Xiaojiang fault are not only the tectonic demarcation line but also the boundary line between high and low crustal crust The reason for the low Q value may be the result of the crushing of the medium caused by the earthquake and the upwelling of the thermal material along the deep fault.