摘要
菲律宾群岛受到欧亚板块、菲律宾海板块和印度—澳大利亚板块的碰撞作用,地质环境复杂,构造因素多样.尽管近几年来已经有了少数关于该区域层析成像的研究,但这些研究的区域主要集中在马尼拉海沟、吕宋岛及中菲律宾地区,而关于群岛周围其他海沟和南菲律宾地区的讨论相对较少.到目前为止,还没有同时获得过关于菲律宾群岛深部纵、横波速度结构的研究,本次研究通过反演155779条P波震相和59642条S波震相,同时获得了菲律宾群岛从地表至150km深度的纵、横波速度结构.地震层析成像结果表明该地区的壳幔速度结构具有较强的不均一性,地壳内部存在着广泛的低速异常,而表征俯冲板块的高速异常则沿着群岛周边的海沟展布.南海块体在马尼拉海沟中段的俯冲角度和俯冲活动性比南段小;菲律宾海板块在东吕宋海槽南段微弱的俯冲作用很有可能同本哈姆海台的碰撞有关.菲律宾群岛大部分M_W>6.0的强震沿着各个板块的边界发生,体现出菲律宾海板块同欧亚板块之间的强耦合作用,群岛西侧的南海块体在马尼拉海沟16°N—20°N之间呈现出的弱耦合状态可能跟北吕宋地区的拉张应力环境有关,南海块体在16°N以南的地区同上覆块体之间的耦合作用较强;群岛东侧的菲律宾海板块在14°N以北的地区没有强震发生,它与菲律宾群岛之间的耦合程度从北向南逐渐增强,在12°N以南的地区要强于12°N以北的地区;此外苏禄海盆和菲律宾构造带之间也存在着强耦合关系.
The complicated geological settings and tectonics of the Philippine Archipelago is mainly caused by the convergence of the Eurasian,the Philippine Sea and the Indian-Austrian plates.Although a few seismic tomographic studies have been conducted in the Philippine Archipelago,most of them focused on the Manila Trench,Luzon Island arc and the middle Philippine.So far fewP-and S-wave tomographic studies in the crust and upper mantle of the Philippine Archipelago and its surrounding regions have been carried out.We obtained VP and VS velocity structures of Philippine Archipelago for the first time by inverting 155779 P-wave rays and 59642 S-wave rays simultaneously.Our seismic tomography shows strong heterogeneities seated in the crust and upper mantle beneath Philippine Archipelago.Widely spread low velocity anomalies emerge in the crust which may be caused by dehydration of oceanic crusts and sediments whereas high velocity anomalies extend along trenches around Philippines.Smaller dip angle and weaker subduction activity in the middle part of South China Sea Plate than the south part are shown.Little subduction can be seen in the south terminal of East Luzon Trough and northern part of Philippine Trench,which could be ascribed to the subduction of Benham Rise.We therefore suggest that strong coupling between Philippine Sea Plate and Eurasia Plate is revealed by the occurrence of M_W>6.0 earthquakes along plate boundaries,weak coupling between 16°N to 20°N in South China Sea slab along Manila Trench might be caused by the extensional stress in north Luzon,on the contrary,strong coupling are shown south of 16°N.On the east side of Philippine Archipelago,no big earthquake occurred north of 14°N in the Philippine Sea Plate,interpolate coupling becomes stronger from north to south,coupling extent is much bigger to the south of 12°N than to the north.Besides,strong coupling exists between Sulu Sea basin and Philippine Mobile Belt too.
引文
Aurelio M A.2000.Shear partitioning in the philippines:Constraints from philippine fault and global positioning system data.Island Arc,9(4):584-597.
Bautista B C,Bautista M L P,Oike K,et al.2001.A new insight on the geometry of subducting slabs in northern Luzon,Philippines.Tectonophysics,339(3-4):279-310.
Besana G M,Negishi H,Ando M.1997.The three-dimensional attenuation structures beneath the Philippine archipelago based on seismic intensity data inversion.Earth and Planetary Science Letters,151(1-2):1-11.
Chen A H,Xu H H.2014.Phase transformation and study of earthquakes formation mechanism of Manila trench.Chinese Journal of Geology(in Chinese),49(3):924-934.
Chen Z H,Li J B,Wu Z Y,et al.2009.Tectonic evolution implication of geometry shape characteristics for manila trench.Marine Geology&Quaternary Geology(in Chinese),29(2):63-69.
Espurt N,Funiciello F,Martinod J,et al.2008.Flat subduction dynamics and deformation of the South American plate:Insights from analog modeling.Tectonics,27(3):TC3011,doi:10.1029/2007TC002175.
Fan J K,Wu S G,Spence G.2014.Tomographic evidence for a slab tear induced by fossil ridge subduction at Manila Trench,South China Sea.International Geology Review,57(5-8):998-1013.
Fan J K,Wu S G.2014.P-wave seismic tomography of the Manila subduction zone.Chinese Journal of Geophysics(in Chinese),57(7):2127-2137,doi:10.6038/cjg20140709.
Fan J K,Zhao D P,Dong D D.2016.Subduction of a buoyant plateau at the Manila Trench:Tomographic evidence and geodynamic implications.Geochemistry,Geophysics,Geosystems,17(2):571-586.
Fan J K,Zhao D P,Dong D D,et al.2017.P-wave tomography of subduction zones around the central Philippines and its geodynamic implications.Journal of Asian Earth Sciences,146:76-89.
Gripp A E,Gordon R G.1990.Current plate velocities relative to the hotspots incorporating the NUVEL-1global plate motion model.Geophysical Research Letters,17(8):1109-1112.
Hyndman R D,Yamano M,Oleskevich D A.1997.The seismogenic zone of subduction thrust faults.Island Arc,6(3):244-260.
Lin J Y,Lo C L.2013.Earthquake-induced crustal gravitational potential energy change in the Philippine area.Journal of Asian Earth Sciences,66:215-223.
Liu Z F,Zhan W H,Zhang Z Q.2007.Tectonic implications of the double island arc between Taiwan and Luzon.Geotectonica et Metallogenia(in Chinese),31(2):145-150.
Martinod J,Funiciello F,Faccenna C,et al.2005.Dynamical effects of subducting ridges:Insights from 3-D laboratory models.Geophysical Journal International,163(3):1137-1150.
Martinod J,Guillaume B,Espurt N,et al.2013.Effect of aseismic ridge subduction on slab geometry and overriding plate deformation:Insights from analogue modeling.Tectonophysics,588:39-55.
Martinod J,Regard V,Letourmy Y,et al.2016.How do subduction processes contribute to forearc Andean uplift?Insights from numerical models.Journal of Geodynamics,96:6-18.
Mason W G,Moresi L,Betts P G,et al.2010.Three-dimensional numerical models of the influence of a buoyant oceanic plateau on subduction zones.Tectonophysics,483(1-2):71-79.
Qu C,Zhou H L,Zhao D P.2007.Deep structure beneath the west margin of Philippine Sea plate and South China Sea from P and Swave travel time tomography.Chinese Journal of Geophysics(in Chinese),50(6):1757-1768.
Rosenbaum G,Mo W.2011.Tectonic and magmatic responses to the subduction of high bathymetric relief.Gondwana Research,19(3):571-582.
Schmidt M W,Poli S.1998.Experimentally based water budgets for dehydrating slabs and consequences for arc magma generation.Earth and Planetary Science Letters,163(1-4):361-379.
Sun J L,Xu H L,Cao J H.2011.Crustal movement and its dynamic mechanism of the Taiwan-Luzon convergent zone.Chinese Journal of Geophysics,54(12):3016-3025,doi:10.3969/j.issn.0001-5733.2011.12.004.
Wang Z,Zhao D P.2005.Seismic imaging of the entire arc of Tohoku and Hokkaido in Japan using P-wave,S-wave and sPdepth-phase data.Physics of the Earth and Planetary Interiors,152(3):144-162.
Xu Y,Li Z W,Hao T Y,et al.2007.Pn wave velocity and anisotropy in the northeastern South China Sea and adjacent region.Chinese Journal of Geophysics(in Chinese),50(5):1473-1479.
Yang T F,Lee T,Chen C H,et al.1996.A double island arc between Taiwan and Luzon:Consequence of ridge subduction.Tectonophysics,258(1-4):85-101.
Yumul G P Jr,Dimalanta C B,Tamayo R A Jr,et al.2003.Collision,subduction and accretion events in the Philippines:Asynthesis.Island Arc,12(2):77-91.
Yumul G P Jr,Dimalanta C B,Maglambayan V B,et al.2008.Tectonic setting of a composite terrane:A review of the Philippine island arc system.Geosciences Journal,12(1):7-17.
Yumul G P Jr,Dimalanta C B,Marquez E J,et al.2009.Onland signatures of the Palawan microcontinental block and Philippine mobile belt collision and crustal growth process:A review.Journal of Asian Earth Sciences,34(5):610-623.
Zhang K L,Wei D P.2011.On the influence factors of double seismic zones.Chinese Journal of Geophysics(in Chinese),54(11):2838-2850,doi:10.3969/j.issn.0001-5733.2011.11.014.
Zhao D P,Hasegawa A,Horiuchi S.1992.Tomographic imaging of P wave and S wave velocity structure beneath Northeastern Japan.Journal of Geophysical Research:Solid Earth,97(B13):19909-19928.
Zhao D P,Hasegawa A,Kanamori H.1994.Deep structure of Japan subduction zone as derived from local,regional,and teleseismic events.Journal of Geophysical Research:SolidEarth,99(B11):22313-22329.
Zheng Y F,Chen R X,Xu Z,et al.2016.The transport of water in subduction zones.Science China Earth Sciences,59(4):651-682.
陈爱华,许鹤华.2014.马尼拉俯冲带相变与地震成因机制研究.地质科学,49(3):924-934.
陈志豪,李家彪,吴自银等.2009.马尼拉海沟几何形态特征的构造演化意义.海洋地质与第四纪地质,29(2):63-69.
范建柯,吴时国.2014.马尼拉俯冲带的地震层析成像研究.地球物理学报,57(7):2127-2137,doi:10.6038/cjg20140709.
刘再峰,詹文欢,张志强.2007.台湾-吕宋岛双火山弧的构造意义.大地构造与成矿学,31(2):145-150.
瞿辰,周蕙兰,赵大鹏.2007.使用纵波和横波走时层析成像研究菲律宾海板块西边缘带和南海地区的深部结构.地球物理学报,50(6):1757-1768.
孙金龙,徐辉龙,曹敬贺.2011.台湾-吕宋会聚带的地壳运动特征及其动力学机制.地球物理学报,54(12):3016-3025,doi:10.3969/j.issn.0001-5733.2011.12.004.
胥颐,李志伟,郝天珧等.2007.南海东北部及其邻近地区的Pn波速度结构与各向异性.地球物理学报,50(5):1473-1479.
张克亮,魏东平.2011.双地震带的影响因素探讨.地球物理学报,54(11):2838-2850,doi:10.3969/j.issn.0001-5733.2011.11.014.
郑永飞,陈仁旭,徐峥等.2016.俯冲带中的水迁移.中国科学:地球科学,46(3):253-286.
