云南地区中小地震震源机制及构造应力场研究
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摘要
利用云南数字地震台网记录的区域波形资料 ,通过波形反演确定了发生在云南地区的33次中小地震的震源机制 .结果表明 ,在川滇菱形块体内部及边界附近的地震以走滑为主 ,由震源机制得到的主压应力方向从北到南由北北西 南南东方向转向近南北向 ,张应力轴方向则主要表现为北东东 南西西或北东 南西向 ;在青藏高原东部地区 ,主压应力方向从青藏高原内部向外成放射状展布 ,张应力方向大多与该地区的弧形构造平行 .在 2 8°N附近地区 ,主压应力轴和张应力轴方向都存在较大的变化 ,其分界线似与龙门山断裂向西南方向的延长线相对应 .川滇菱形块体之外的地震的主压应力轴和张应力轴方向与块体内部的方向存在一定的差异 .通过与哈佛大学中强地震震源机制结果的对比发现 ,云南地区中小地震震源机制的反演结果与强震震源机制的结果有较好的一致性 ,表明中小地震的震源机制可用于该地区区域构造应力场的研究 .
In this paper, source mechanisms of 33 small-to-moderate earthquakes occurred in Yunnan are determined by modeling of regional waveforms from Yunnan digital seismic network. The result shows that most earthquakes occurred within or near the boundary of the Sichuan-Yunnan rhombic block have strike-slip mechanisms. The orientations of maximum compressional stresses obtained from source mechanisms are mainly in NNW-SSE in north of the block, and turns to NS in the south. The tensile stresses are mainly in ENE-WSW or NE-SW. In the eastern Tibetan Plateau, the orientations of P axes radiate toward outside from the plateau, and the T axes mostly parallel to arc structures. Near in 28°N, the orientations of both P and T axes changed greatly, and the boundary seems related to the southwest extension line of Longmen Shan fault. Outside of the Sichuan-Yunnan rhombic block, the orientations of P and T axes are some different from those within the block. The comparison shows that the source mechanism of small-to-moderate events presented in this paper is consistence with that of strong earthquakes determined by Harvard University, which means the source mechanism of small-to-moderate events can be used to study the tectonic stress field in this region.
In this paper, source mechanisms of 33 small-to-moderate earthquakes occurred in Yunnan are determined by modeling of regional waveforms from Yunnan digital seismic network. The result shows that most earthquakes occurred within or near the boundary of the Sichuan-Yunnan rhombic block have strike-slip mechanisms. The orientations of maximum compressional stresses obtained from source mechanisms are mainly in NNW-SSE in north of the block, and turns to NS in the south. The tensile stresses are mainly in ENE-WSW or NE-SW. In the eastern Tibetan Plateau, the orientations of P axes radiate toward outside from the plateau, and the T axes mostly parallel to arc structures. Near in 28°N, the orientations of both P and T axes changed greatly, and the boundary seems related to the southwest extension line of Longmen Shan fault. Outside of the Sichuan-Yunnan rhombic block, the orientations of P and T axes are some different from those within the block. The comparison shows that the source mechanism of small-to-moderate events presented in this paper is consistence with that of strong earthquakes determined by Harvard University, which means the source mechanism of small-to-moderate events can be used to study the tectonic stress field in this region.
引文
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梁尚鸿,束沛镒,李幼铭,等.1986.攀西地区地震分布和构造应力场特征[J].地球物理学报,29(6):557～566
林中洋,胡鸿翔,张文斌,等.1993.滇西地区地壳上地幔速度结构特征的研究[J].地震学报,15(4):427～440
明跃红,吴建平,楼海.2003.用地震波波形拟合方法研究中小地震的震源机制[J].地震地磁观测与研究,24(3):20～26
王椿镛,楼海,吴建平,等.2002a.腾冲火山地热区地壳结构的地震学研究[J].地震学报,24(3):231～242
王椿镛,MooneyWD ,王溪莉,等.2002b.川滇地区地壳上地幔三维速度结构研究[J].地震学报,24(1):1～16
许忠淮,汪素云,黄雨蕊,等.1987.由多个小震推断的青甘和川滇地区地壳应力场的方向特征[J].地球物理学报,30(5):476～486
姚振兴,郑天愉,温联星.1994.用P波波形资料测定中强地震震源过程的地震距张量反演方法[J].地球物理学报,37(1):36～44
张培震,王琪.2001.中国大陆现今地壳运动和构造变形[A].马宗晋,汪一鹏,张燕平主编.青藏高原岩石圈现今变形与动力学[C].北京:地震出版社,21～35
HelmbergerDV ,EngenGR .1980.Modelinglong periodbodywavesfromshallowearthquakesatregionaldistances[J].BullSeismSocAmer,70:1699～1714
HerrmannRB ,WangCY .1985.Acomparisonofsyntheticseismograms[J].BullSeismSocAmer,75:41～56
WangCY ,HerrmannRB .1980.AnumericalstudyofP ,SV ,andSH wavegenerationinaplanelayeredmedium[J].BullSeismSocAmer,70:1015～1036
ZhaoLianshe,HelmbergerDV .1994.Sourceestimationfrombroadbandregionalseismograms[J].BullSeismSocAmer,84:91～104
ZhuLupei,HelmbergerDV .1996.Advancementinsourceestimationtechniquesusingbroadbandregionalseismograms[J].BullSeismSocAmer,86:1634～1641
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