青藏高原东北缘超壳断裂的地震学证据
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摘要
使用天水流动台阵资料,通过远震接收函数偏移成像研究了位于青藏高原东北缘的天水强震区下方地壳速度结构。结果表明位于该区域的略阳-迭部和西秦岭北缘断裂为超壳断裂。即断裂达到地壳底部且穿过了莫霍面,导致莫霍面上下两侧速度跃变降低。结果还表明,该区域中强地震常集中发生于地壳内部速度变化显著区域,该区域历史上的巨大地震可能发生在断裂与20 km深度附近康拉德界面相互作用的部位。
The crustal structure beneath the temporary seismic array is imaged with teleseismic receiver functions in Tianshui earthquake-prone area in the northeast margin of Qinghai-Tibet Plateau.The results indicate that the Lueyang-Diebu fault and the north margin of West Qinling Mountains fault are ultra-crust faults which penetrate the Moho and lead to the weakness of impendence-contrast of Moho.The earthquakes in this area often nucleate in the margin region with sharp variety of the velocity,and the huge earthquakes in history might occurred near the asperity resulting from the interaction between faults and Conrad discontinuity at the depth of about 20 km.
The crustal structure beneath the temporary seismic array is imaged with teleseismic receiver functions in Tianshui earthquake-prone area in the northeast margin of Qinghai-Tibet Plateau.The results indicate that the Lueyang-Diebu fault and the north margin of West Qinling Mountains fault are ultra-crust faults which penetrate the Moho and lead to the weakness of impendence-contrast of Moho.The earthquakes in this area often nucleate in the margin region with sharp variety of the velocity,and the huge earthquakes in history might occurred near the asperity resulting from the interaction between faults and Conrad discontinuity at the depth of about 20 km.
引文
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[2]李清河,郭建康,周民都,等.成县—西吉剖面地壳速度结构[J].西北地震学报,1991,13(增刊1):37–43.(LIQing-he,GUO Jian-kang,ZHOU Min-du,et al.The crustalvelocity structure inferred from Chengxian-Xiji deep seismicsounding profile[J].Northwestern Seismological Journal,1991,13(S1):37–43.(in Chinese))
[3]李清河,郭建康,周民都,等.天水地震区深部构造与地震关系初步探讨[J].西北地震学报,1991,13(增刊1):68–70.(LI Qing-he,GUO Jian-kang,ZhOU Min-du,et al.Apreliminary study on the relationship between deep tectonicsand earthquakes in Tianshui earthquake area[J].NorthwesternSeismological Journal,1991,13(S1):68–70.(in Chinese))
[4]林长佑,武玉霞,杨长福.天水地区莫霍面附近的高导层及壳幔过渡带[J].地震学报,1995,8(2):281–288.(LINChang-you,WU Yu-xia,YANG Chang-fu.On the highconductive layer near the moho and the transitional zonebetween the crust and mantle in Tianshui region[J].ActaSeismologica Sinica,1995,8(2):281–288.(in Chinese))
[5]郭守年,徐敬文,孟万辉,等.天水地区重力剖面测量结果与地壳结构[J].西北地震学报,1995,17(1):36–42.(GUOShou-nian,XU Jing-wen,MENG Wan-hui,et al.Surveyingresults of gravity profiles and crustal structures in theTianshui area,Gansu[J].Northwestern Seismological Journal(in Chinese with English abstract),1995,17(1):36–42.(inChinese))
[6]郭守年,董治平,蒋梅,等.天水地震区综合地球物理剖面的建立与壳幔结构[J].西北地震学报,1997,19(3):49–51.(GUO Shou-nian,DONG Zhi-ping,JIANG Mei.Establishment of comprehensive geophysical section andcrust mantle structure in Tianshui earthquake gerion[J].Northwestern Seismological Journal,1997,19(3):49–51.(in Chinese))
[7]LANGSTON C.Structure under Mount Rainier,Washington,inferred from teleseismic body waves[J].J Geophys Res,1979,84(4):4749–4762.
[8]AMMON C,RANDALL G,ZANDT G.On the nonuniquenessof receiver function inversions[J].J Geophys Res,1990,95(B10):15303–15318.
[9]LIGORRIA J,AMMON C.Iterative deconvolution andreceiver-function estimation[J].Bull.Seismol.Soc.Am,1999,89:1395–1400.
[10]KENNETT B L N,ENGDAHL R E.Travel times for globalearthquake location and phase identification[J].Geophys J Int,1991,105:429–465.
[11]YUAN X,NI J,KIND R,et al.Lithospheric and upper mantlestructure of southern Tibet from a seismological passivesource experiment[J].J Geophys Res,1997,102(B12):27491–27500.
[12]SHEN X Z,ZHOU H L,KAWAKATSU H.Mapping theupper mantle discontinuities beneath China with teleseismicreceiver functions[J].Earth Planets Space,2008,60(7):713–719.
[13]ZHU L,KANAMORI H.Moho depth variation in southernCalifornia from teleseismic receiver functions[J].J GeophysRes,2000,105(B2):2969–2980.
[14]HUANG Z,SU W,PENG Y,et al.Rayleigh wavetomography of China and adjacent regions[J].J Geophys Res,2003,108(2):2073.
[15]SCHIMMEL M,PAULSSEN H.Noise reduction anddetection of weak,coherent signals through phase weightedstacks[J].Geophys J Int,1997,130:497–505.
[16]沈旭章,周蕙兰.接收函数CCP-PWS偏移方法探测中国东北地区620km深处低速层[J].科学通报,2009,54(2):215–223.(SHEN Xu-zhang,ZHOU Hui-lan.Thelow-velocity layer at the depth of 620 km beneath NortheastChina.Chinese Sci.Bul.l,2009,54(17):3067–3075.(inChinese))
[17]AN M J,SHI Y L.Lithospheric thickness of the Chinesecontinent[J].Phys Earth Planet Ints,2006,159:257–266.
[18]刘百箎,曹娟娟,袁道阳,等.青藏高原北部活动地块内部的活断层定量资料[J].地震地质,2008,30(1):161–175.(LIU Bai-chi,CAO Juan-juan,YUAN Dao-yang,et al.Quantitative data of active faults within the active tectonicblock in north Qinghai-xizang plateau[J].Seismology andGeology,2008,30(1):161–175.(in Chinese))
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