地震研究

利用滇西北地震亚失稳观测实验区43个密集观测台站记录的2018年4月5日—12月30日远震三分量波形数据,计算并分析滇西北地区的地壳厚度和泊松比变化情况。结果表明:①研究区的地壳厚度总体呈现北深南浅的变化特征,且形成以云龙、蝴蝶泉—阳和、岩曲—羊窝棚—哨横为中心的3个莫霍面隆起区,在26°N附近形成一个向南的舌状突出,呈现两隆两凹状的莫霍面结构; ②研究区泊松比为0.209～0.328,整体被2条对角线分隔呈四象限分布,北、南两区是高泊松比(σ>0.28)地区,推测地壳物质富含铁镁质成分,西、东区为低泊松比(σ<0.26)区域,地壳物质可能富集长英质成分; ③云龙、蝴蝶泉—阳和以及南涧—红土坡地区的高泊松比(σ>0.3)可能是上地幔物质底侵致使下地壳物质部分熔融引起; 维西—乔后—巍山断裂北段的通甸—建基村,其与龙蟠—乔后断裂交汇的丰乐—禾头,以及维西—乔后—巍山断裂中段的脉地—紫阳村—瓦窑—太邑—岔河,是泊松比高梯度带,具备发生中强以上地震的孕震环境。

Using teleseismic waveform data recorded by 43 stations in meta-instability observation experiment area of northwestern Yunnan from April 5 to December 30,2018,we calculated and analyzed the changes of crustal thickness and Poisson's ratio in northwestern Yunnan.The results showed:the crustal thicknesses in this area are generally the variation characteristics of deeper in north and shallower in south; the three areas of Yunlong,Hudiequan-Yanghe,and Yanqu-Yangwopeng-Shaoheng are mantle uplifting sites,and the Moho surface is characterized as a tongue shape protruding southward and basically featuring two uplifts and two depressions near 26°N.The Poisson's ratio ranges from 0.209 to 0.328 in the study area,which is divided into four quadrants by two diagonal lines,the north and south regions are high Poisson's ratios(σ>0.28),the crust maybe enriched with iron and magnesium; the west and east regions are low Poisson's ratios(σ<0.26),the crust maybe rich in felsic.Very high Poisson's ratios(σ>0.3)are found in Yunlong,Hudiequan-Yanghe,and Nanjian-Hongtupo areas maybe the partial melting of lower crustal material caused by the bottom intrusion of upper mantle material.The Tongdian-Jianji,Fengle-Hetou,and Maidi-Ziyangcun-Wayao-Taiyi-Chahe areas are high gradient zones of Poisson's ratio and are seismogenic environments with moderate to strong earthquakes.

引言
1 资料选取
2 计算方法
3 结果分析
4 结论

图1 研究区主要断裂和地震台站分布<br/>Fig.1 Distribution of main faults and seismicstations in the study area

图1 研究区主要断裂和地震台站分布
Fig.1 Distribution of main faults and seismicstations in the study area

图2 远震分布情况<br/>Fig.2 Distribution of teleseismic events

图2 远震分布情况
Fig.2 Distribution of teleseismic events

图3 近水平均匀介质中P波传播路径(a)及相应的接收函数(b)<br/>Fig.3 P-wave propagation path in horizontal homo-geneous media(a)and receiver function(b)

图3 近水平均匀介质中P波传播路径(a)及相应的接收函数(b)
Fig.3 P-wave propagation path in horizontal homo-geneous media(a)and receiver function(b)

图4 岔河台接收函数<br/>Fig.4 Receiver function of the Chahe station

图4 岔河台接收函数
Fig.4 Receiver function of the Chahe station

表1 接收函数分析结果<br/>Tab.1 Analysis results of receiver function

表1 接收函数分析结果
Tab.1 Analysis results of receiver function

图5 本文得到的地壳厚度(a)和泊松比(b)分布情况(断裂同图 1)<br/>Fig.5 Distribution of crustal thickness(a)and Poisson's ratio(b)in this study(faults are the same as Fig.1)

图5 本文得到的地壳厚度(a)和泊松比(b)分布情况(断裂同图 1)
Fig.5 Distribution of crustal thickness(a)and Poisson's ratio(b)in this study(faults are the same as Fig.1)

图6 增补前人研究结果后地壳厚度(a)和泊松比(b)分布情况(断裂同图 1)<br/>Fig.6 Distribution of crustal thickness(a)and Poisson's ratio(b) after adding stations(faults are the same as Fig.1)

图6 增补前人研究结果后地壳厚度(a)和泊松比(b)分布情况(断裂同图 1)
Fig.6 Distribution of crustal thickness(a)and Poisson's ratio(b) after adding stations(faults are the same as Fig.1)

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备注

引言

1 资料选取

2 计算方法

3 结果分析

4 结论

期刊信息