Inversion of multimode surface wave data: evidence for sub-lithospheric anisotropy

Summary. Multiparameter inversions of multimode dispersion data are performed for two large regions: the Pacific Ocean and North America. Anisotropy is taken into account by considering transversely isotropic structures with a vertical axis of symmetry. Two fundamental questions are studied in detail: (1) how to make the inverted models consistent when using different sets of parameters, (2) what is the significance of transversely isotropic inversion for the actual Earth's structure? It is proved that full consistency of the inverted models can be achieved by properly taking into account some a priori informations on the model and it is shown that the use of transversely isotropic models with vertical axis of symmetry does not cause severe limitations when interpreting the data. The models we have obtained are discussed in the light of these investigations. Considering an olivine-rich upper mantle, we make a tentative interpretation of these models in terms of preferred orientation of the a -axis of the crystals in one fixed horizontal direction.     

大陆岩石圈对扩张机制的响应—辽蒙地质走廊中—新生代火山活动的时空分布

选择辽西为中心,以近东西向延伸800km的辽蒙地质走廊为研究区,通过年代学研究,确认130Ma以来的中、新生代火山活动对称分布的时空格局,具有“中间老、两侧新”的特点,而且随着时间的推移,软流圈来源的岩浆向东西两侧侧向流动,岩浆来源不断加深。在此基础上提出“软流圈底辟体上涌和水平侧向流动”的模式。     

Post-seismic relaxation following the great 2004 Sumatra-Andaman earthquake on a compressible self-gravitating Earth

The   M _w γ 9.0  2004 December 26 Sumatra-Andaman and   M _w = 8.7  2005 March 28 Nias earthquakes, which collectively ruptured approximately 1800 km of the Andaman and Sunda subduction zones, are expected to be followed by vigorous viscoelastic relaxation involving both the upper and lower mantle. Because of these large spatial dimensions it is desirable to fully account for gravitational coupling effects in the relaxation process. We present a stable method of computing relaxation of a spherically-stratified, compressible and self-gravitating viscoelastic Earth following an impulsive moment release event. The solution is cast in terms of a spherical harmonic expansion of viscoelastic normal modes. For simple layered viscoelastic models, which include a low-viscosity oceanic asthenosphere, we predict substantial post-seismic effects over a region several 100s of km wide surrounding the eastern Indian Ocean. We compare observed GPS time-series from ten regional sites (mostly in Thailand and Indonesia), beginning in 2004 December, with synthetic time-series that include the coseismic and post-seismic effects of the 2004 December 26 and 2005 March 28 earthquakes. A viscosity structure involving a biviscous (Burgers body) rheology in the asthenosphere explains the pattern and amplitude of post-seismic offsets remarkably well.     

华北板内深部构造

华北板块的形成经历了早前寒武纪、燕山期及喜马拉雅期3个主要构造发展期，由于华北板块自身运动及所受应力场的作用，加之上地幔岩石圈的不均一性等因素，在中、新生代形成许多特殊的板内构造块。综合应用地质、地球物理和地球化学的成果，对华北板内深部结构进行了研究。从深部构造角度划分出6个金及金金属成矿带、4个金刚石成矿带，并对华北地区的地震及地热资源与新生事大陆裂谷的关系进行了探讨。     

软流层、中地壳与盆-山系

虽然大量的地学断面研究为我们提供了及其丰富的有关中地壳的信息，但极少有人将中地壳的与盆地、断隆山的形成和演化相联系．大陆层控构造理论认为，上地壳正断层上盘在下降过程中，挤压下伏中地壳塑性层，中地壳塑性层物质在该压力作用下从下降幅度最大、垂向压强最大的箕状盆地翘降端压出，主要流向垂向压力较小、紧邻断层面应变空间的下盘，促使该盘向上倾斜，形成断隆山，组成盆—山系．现今中国东部阴山、秦岭、太行山和燕山等断隆山脉，无不与同时代深沉降的断陷盆地毗邻．松辽盆地和西侧大兴安岭以嫩江断裂为界，断陷盆地和断隆山由晚侏罗世到早白垩世同时开始形成到新生代，伴随松辽盆地大幅度沉降，大兴安岭大幅度隆升．在重力均衡作用下，盆—山系形成引起莫霍面隆起和上地幔软流层隆升，在沉积盆地和断隆上形成大量金属、非金属和油气矿产．中生代以后，软流层大规模发育．软流层隆升对大型含油气区形成具有决定性意义。     

地壳运动驱动力的探讨——核能与地球演化

本文综合核物理、天文和地质学的最新研究成果,推导出在45亿年前太阳系的全部原始类地行星及其某些卫星(包括地球及月球)上,发生过大规模的、持续的铀、钚链式核裂变,释出了巨大的热能,熔化了整个原始星球。新星球的物质发生了重力分异作用、形成了按密度划分的圈层结构。地球中心是内地核,在高压下压成了固态。铀、钚下沉到内地核顶部停留,继续发生链式核裂变,但改变不了内地核的固态性质。从此处产生的核裂变能,主要以热对流的形式外导。直到前45亿年以后,铀的链式核裂变停止了,只剩下钚的链式核裂变,生成的热能减少了,地球开始冷凝。当熔浆表面温度下降到700~800℃时,较轻的花岗岩质岩浆首先凝固成薄层。它很脆弱、经不起大风浪和潮汐力的冲击,破碎成小块,随着下面对流的玄武岩质熔浆汇集起来,形成大片飘浮物,后来就成为大陸;小片的便成为岛屿。温度逐渐下降,地幔冷凝成固体。温度下降至100℃以下,大气中的水蒸气冷凝成水,下落汇集在地表低凹处,便有了海洋和湖泊。所以海洋底主要分布着玄武岩。从内地核顶部不断产生的核能以"地幔柱"的形式穿过固体地幔,上升至地壳。受坚硬地壳的隔挡、便集中在地壳下构成软流层。当地壳岩石受热软化和可以流动之后,便开始向压力小的方向流动。又受日、月引力和地球自身自转力的作用,软流层的动能又有了增强。这种巨大的能量支配了地壳的升降、褶曲、断裂、变质、岩浆、火山和地震等活动。地球是天体之一,无时不受自然界各种作用力的影响,但支配它演化的主要作用力是核能。本文还简述了核能、核素与太阳系星体演化的关系。     

再论纬向正常密度假说与内波假说的比较

本文对“纬向正常密度假说”和“内波假说”再次进行了讨论,进一步比较了二者的联系和区别.根据岩石圈板块概念和地幔对流假说的基本观点、以及“纬向正常密度假说”和“板块运动重力机制”的基本观点,提出了“软流圈板块”概念.