海南岛及邻区地壳三维P波速度结构
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摘要
利用海南岛及邻区1999—2005年9个地震数字化台站记录到的3500余条区域初至波到时资料,确定了海南岛及邻区地壳三维P波速度结构.结果表明,该区域浅部上地壳的波速异常与地表地质构造有一定的相关性,即王五—文教断裂带以北地区波速较低,而以南地区为相对高的波速异常区.这与琼北地区为凹陷、并伴有多期火山活动和较高的地热背景,而琼中南地区为较稳定的隆起等构造特征相一致.在其中下地壳,琼东地区相对琼西地区波速较低,可能暗示了地幔热物质上涌等动力学过程.波速异常分布模式还暗示出北西向断裂带(如铺前—清澜断裂带)较浅,而近东西向的王五—文教断裂带较深,有可能延伸至莫霍面或更深.
Using over 3500 first P arrival times recorded by 9 digital seismic stations of the Hainan Digital Seismic Network during 1999—2005, a 3-D P-wave velocity model of the crust beneath Hainan Island and adjacent regions was determined. Our result shows that in shallow upper crust the spatial distribution of velocity anomalies is somewhat associated with surface geological structure in the region. A relatively low velocity anomaly appears north of Wangwu--Wenjiao fault, while a relatively high anomaly is found south of that fault. This spatial velocity variation is consistent with the following regional tectonic feature: northern Hainan Island is a depressional region with many active volcanoes and high geothermal activity, while central-southern Hainan is an uplifted and stable region. In middle and lower crust the velocity is lower in eastern Hainan than that in western region, possibly suggesting the existence of hot materials upwelling from the mantle in eastern Hainan. The pattern of velocity anomaly also indicates that the NW--SE trending faults, e.g., the Puqian--Qinglan fault, may be shallow, while the W--E trending Wangwu--Wenjiao fault may be deep, perhaps extending down to the Moho discontinuity.
Using over 3500 first P arrival times recorded by 9 digital seismic stations of the Hainan Digital Seismic Network during 1999—2005, a 3-D P-wave velocity model of the crust beneath Hainan Island and adjacent regions was determined. Our result shows that in shallow upper crust the spatial distribution of velocity anomalies is somewhat associated with surface geological structure in the region. A relatively low velocity anomaly appears north of Wangwu--Wenjiao fault, while a relatively high anomaly is found south of that fault. This spatial velocity variation is consistent with the following regional tectonic feature: northern Hainan Island is a depressional region with many active volcanoes and high geothermal activity, while central-southern Hainan is an uplifted and stable region. In middle and lower crust the velocity is lower in eastern Hainan than that in western region, possibly suggesting the existence of hot materials upwelling from the mantle in eastern Hainan. The pattern of velocity anomaly also indicates that the NW--SE trending faults, e.g., the Puqian--Qinglan fault, may be shallow, while the W--E trending Wangwu--Wenjiao fault may be deep, perhaps extending down to the Moho discontinuity.
引文
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Lei J,Zhao D.2007a.Teleseismic evidence for a break-off subducting slab under Eastern Turkey[J].Earth Planet SciLett,257:14--28.
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Qiu X,Priestley K,Mckenzie D.2002.Teleseismic P-waveformreceiver function analysis and its application to qiong-zhong station(QIZ)of Hainan Island,NWsouth Chian sea[J].J Geosci China,4(1):1--8.
Sleep N.1990.Hotspots and mantle plumes:Some phenomenology[J].J Geophys Res,95:6715--6736.
Waldhauser F,Ellsworth WL.2000.Adouble-difference earthquake location algorithm:Method and application to theNorthern Hayward Fault,California[J].Bull Seism Soc Amer,90(6):1353--1368.
Wessel P,Smith W.1995.New version of the Generic Mapping Tools(GMT)version3.0released[J].EOS TransAGU,76:329--329.
Zhao D,Hasegawa A,Horiuchi S.1992.Tomographic i maging of P and S wave velocity structure beneath northeasternJapan[J].J Geophys Res,97:19909--19928.
Zhao D.2001.Seismic structure and origin of hotspots and mantle plumes[J].Earth Planet Sci Lett,192:251--265.
Zhao D,Lei J.2004.Seismic ray path variations in a3-D global velocity model[J].Phys Earth Planet Interi,141:153--166.
陈运平,席道瑛,樊星.2002.用分形理论研究海南岛的活动断裂[J].地震研究,25(4):351--355.
丁原章,李坪,时振梁,林季曾,朱振宇.1988.海南岛北部地震研究文集[M].北京:地震出版社:1--299.
丁志峰,李卫平,吴庆举,胡久长,何正勤,张炼.2004.琼北火山区的地震观测与壳幔结构的研究[G]∥张中杰,高锐,吕庆田,刘振宽主编.中国大陆地球深部结构与动力学研究:庆贺滕吉文院士从事地球物理研究50周年.北京:科学出版社:846--857.
胡久常,陈金燕,黄妙影.1997.1995年海南东方近海5.2级地震特征分析[J].华南地震,17(1):39--45.
嘉世旭,李志雄,徐朝繁,沈繁銮,赵文俊,杨卓欣,杨键,雷宛.2006.雷琼拗陷地壳结构特征[J].地球物理学报,49(5):1385--1394.
姜效典,李巍然.1994.海南岛潜在震源区的研究[J].自然灾害学报,3(1):104--109.
雷建设,周蕙兰.2002.中国西南及邻区上地幔三维速度结构研究[J].地震学报,15(2):134--142.
李建生.1991.海南岛地区断裂构造体系与区域稳定性[J].海洋科学,(3):19--21.
李志雄,赵文俊,刘光夏.2006.1605年琼州大地震深部构造和应力状态[J].华南地震,26(1):28--36.
孙建忠,樊祺诚,陈文寄.1988.琼北地区第四纪火山活动的研究[G]∥丁原章,李坪,时振梁,林季曾,朱振宇编.海南岛北部地震研究文集.北京:地震出版社:26--33.
Courtillot V,Davaille A,Besse J,Stock J.2003.Three distinct types of hotspotsinthe Earth's mantle[J].Earth PlanetSci Lett,205:295--308.
Davies G.1988.Ocean bathymetry and mantle convection1:Large-scale flow and hotspot[J].J Geophys Res,93:10467--10480.
Lebedev S,Chevrot S,Nolet G,van der Hilst R.2000.Newseismic evidence for a deep mantle origin of the S.China ba-salts(the Hainan plume?)and other observations in SE Asia[J].EOS Trans AGU,81:48.
Lei J,Zhao D.2005.P-wave tomography and origin of the Changbai intraplate volcano in Northeast Asia[J].Tectono-physics,397:281--295.
Lei J,Zhao D.2006.Global P-wave tomography:Onthe effect of various mantle and core phases[J].Phys Earth PlanetInteri,154:44--69.
Lei J,Zhao D.2007a.Teleseismic evidence for a break-off subducting slab under Eastern Turkey[J].Earth Planet SciLett,257:14--28.
Lei J,Zhao D.2007b.Teleseismic P-wave tomography and the upper mantle structure of the central Tien Shan orogenicbelt[J].Phys Earth Planet Interi,162:165--185.
Liang C,Song X,Hunag J.2004.Tomogaphic inversion of Pn travel ti mes in China[J].J Geophys Res,109,doi:10.1029/2003JB002789.
Paige C C,Saunders MA.1982.LSQR:An algorithmfor sparelinear equations and spareleast squares[J].ACMTransMath Soft ware,8:43--71.
Qiu X,Priestley K,Mckenzie D.2002.Teleseismic P-waveformreceiver function analysis and its application to qiong-zhong station(QIZ)of Hainan Island,NWsouth Chian sea[J].J Geosci China,4(1):1--8.
Sleep N.1990.Hotspots and mantle plumes:Some phenomenology[J].J Geophys Res,95:6715--6736.
Waldhauser F,Ellsworth WL.2000.Adouble-difference earthquake location algorithm:Method and application to theNorthern Hayward Fault,California[J].Bull Seism Soc Amer,90(6):1353--1368.
Wessel P,Smith W.1995.New version of the Generic Mapping Tools(GMT)version3.0released[J].EOS TransAGU,76:329--329.
Zhao D,Hasegawa A,Horiuchi S.1992.Tomographic i maging of P and S wave velocity structure beneath northeasternJapan[J].J Geophys Res,97:19909--19928.
Zhao D.2001.Seismic structure and origin of hotspots and mantle plumes[J].Earth Planet Sci Lett,192:251--265.
Zhao D,Lei J.2004.Seismic ray path variations in a3-D global velocity model[J].Phys Earth Planet Interi,141:153--166.
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