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Rayleigh面波衰减特性与汶川地震关系研究

发表时间:2013-11-15  浏览量:1104  下载量:315
全部作者: 程先琼
作者单位: 成都理工大学地球物理学院
摘 要: 搜集中国大陆72个数字地震台站7 321个长周期波形记录,从中挑选出符合条件的489对经过中国大陆的双台路径记录,采用相匹配滤波和频率域维纳滤波相结合的方法,计算出双台之间的混合路径衰减系数,再通过网格化反演得到中国大陆每个网格单元的纯路径衰减系数。结果显示:短周期(深度约20~50 km)四川盆地Rayleigh面波衰减较小,松潘—甘孜地块Rayleigh面波衰减较大,反映在该深度四川盆地已进入上地幔,松潘—甘孜地块仍处于下地壳;地震波衰减特性与强震分布关系密切,汶川地震及余震平面分布在四川盆地低衰减区与青藏高原东缘高衰减区的过渡地带,并且有着略偏向低衰减一侧的趋势。汶川地震序列纵向主要发生在壳内高衰减区上方的上地壳深度范围内;松潘—甘孜地块内,存在壳内的由西向东逐渐减薄的楔状高衰减区,该高衰减区在下地壳延伸到扬子地块之下。不存在四川盆地向龙门山以西的俯冲现象,松潘—甘孜地块的上地壳与上地壳内高衰减区滑脱解耦,形成铲形逆冲推覆,是形成汶川地震的主要构造原因。
关 键 词: 固体地球物理学;Rayleigh面波;衰减系数;龙门山;汶川地震;双台法
Title: Relationship between distribution of attenuation for Rayleigh surface wave and reason of Wenchuan earthquake
Author: CHENG Xianqiong
Organization: Geophyics School, Chengdu University of Technology
Abstract: This paper selected 489 pairs of Rayleigh wave from 7 321 wavefoms recorded by 72 stations in continental China. The pure-path attenuation coefficients of the Rayleigh wave for each cell in China were attained by inversting each cell after getting mix-path attenuation coefficients by the phase-matched method and the frequency-domain Wiener filter. It is concluded that the attenuation of Rayleigh wave was lower in Sichuan basin than Songpan-Garze fold belt at short period,that was 20~50 km, which showed this depth was upper mantle in east China and crust in west China. Furthermore, there was a close connection between the distribution of seismic wave attenuation and large earthquke. Wenchuan earthquake and it�s aftershocks occurred in the transitional zone of high attenuation in Sichuan and low attenuation in eastern Qinghai-Tibet plateau and closed to low attenuation area and occurred in the crust above high attenuation zone. There was a wedge high attenuation in crust in Songpan-Garze fold belt, which extended to Yangzi block. At the same time, we found Sichuan basin didn�t dive to Longmen mountain, and the main reason of Wenchuan earthquake was that upper crust decouple from high attenuation in Songpan-Garze fold belt forming Spade thrust-nappe structure.
Key words: solid earth geophysics; Rayleigh surface wave; attenuation coefficient; Longmen mountain; Wenchuan earthquake; two-station method
发表期数: 2013年11月第21期
引用格式: 程先琼. Rayleigh面波衰减特性与汶川地震关系研究[J]. 中国科技论文在线精品论文,2013,6(21):2110-2117.
 
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