十一. 地球内部物理化学性质结构与动力学
(负责人：蔡永恩 马石庄 石耀林)
Physical and Chemical Properties and
Dynamist of the Earth's Interior
(Conveners: CAI Yongen MA Shizhuang SHI Yaolin)
1． 不同围压下岩石样品中微裂纹的闭合
刘斌 王宝善 季卫国
中国科学技术大学地球和空间科学系 合肥 230026
Closure of
microcracks in rock samples under different confining pressure
Liu Bin, Wang Baoshan et al.
Topic 11:
Closure of Microcracks in Rock Samples under Different Confining Pressure
Liu Bin, Wang Baoshan, Ji Weiguo
(Department of Earth and Space Sciences, University of Science and Technology of China, Hefei, Anhui 230026)
Velocity and Q-value of P- and S-waves and linear strain had been measured in three orthogonal directions, under different confining pressures, for several rocks with marked foliation and strong lattice preferred orientation. The effective Poisson’s ratio, crack density, crack porosity and c/a value (a is the length and c is the width of the coin-shaped microcrack) of microcracks are calculated from the measured data by O'connell’s model. It is resulted that the closure of microcracks normal to the foliation plane is the fastest but the corresponding c/a value does not decrease, but increase, with the increase of confining pressure. It may be caused by the roughness and rugosity of the crack faces, which can make one crack into several smaller cracks with significantly shorter lengths but widths not markedly smaller, during the progressive closure of microcracks with increasing confining pressure. So, c/a value increases with confining pressure.
2．Stochastic
Geodetic Boundary Value Problem and its Maximum Entropy Solution
Jinshui Huang, Zhuowen Zhu
(Laboratory for Geophysical Geodesy, WTUSM, Wuhan, 430079)
(E-mail: jshuang@wtusm.edu.cn)
ABSTRACT
Traditionally, Geodetic Boundary Value Problems (GBVPs) is studied in the framework of deterministic theory. With the rapid development of observation techniques, many kinds of high accurate data of gravity elements can be obtained. The non-compatibility among different kind of data, which will be more apparent when the accuracy is higher, and the observation errors make the deterministic GBVP into a non-solution problem. In the paper, the gravity field is regarded as a stochastic process. Based on this, the Stochastic GBVP is proposed. As to the solution of the problem, a method that is grounded on the information theory is put forward, which is the maximum entropy method. As a simple example, we solve the inner Stochastic GBVP with a simple model, which takes accounts of that the density in some part of the earth is only weakly determined. The numerical solution shows that the level surfaces agree well with the theoretical level surfaces of the model in the area where the density is perfectly determined, and the two kinds level surfaces depart from each other in the area where the density is weakly determined, but it will be improved when the density is much better known. For the geoid is partly inside the earth, we must have a good density model in the area outside the geoid in order to determine the geoid precisely.
3．A Time-Continuous
Finite Element Method
For Transient Heat Conduction
Xu Hehua
(Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, 100029)
A time-continuous numerical finite element method, referred to as the Laplace Transform Galerkin(LTG) method, is applicable to problem of transient heat conduction. The method eliminates the temporal derivatives term using the Laplace transform and then solves the associated equation with finite-element technique in Laplace space. Then, numerical inversion of the Laplace-transformed nodal temperature is performed using the Crump(1976) algorithm. This method is also well suited for transient flow problems and advection-dispersion equation describing solute transport in porous media.
4． 洋岛玄武岩氦同位素特征的成因
汪 洋
(中国地质大学(北京)地球科学与资源学院，北京，100029)
THE ORIGIN OF HELIUM ISOTOPE FEATURES IN OCEANIC ISLAND BASALT
Wang Yang
(School of Earth Science and Resources, China University of Geosciences, Beijing 100083, China)
The 3He/4He in mid-ocean ridge basalt (MORB) is 7-8 RA (atmospheric 3He/4He ratio). Meanwhile, the 3He/4He in oceanic island basalt (OIB) exhibits geographic diversity. Helium isotope ratio is 5-6 RA in some OIBs, which are mainly located in Southern Hemisphere (such as St Helena, Gough and Tristan, French Polynesia and many others), and 10-35 RA in others (i.e., Iceland, Loihi, Mauna Loa, Kilauea, etc.). The two-layer steady state mantle model, which requires a volatile degassed upper mantle, and a more volatile and high viscosity lower mantle, was adopted to explain these features. However, numerical simulation (van Keken and Ballentine, 1999) shows that 3He/4He ratio in upper and lower mantle exhibits no difference over 4 Ga. evolution, and degassing is more rapid in the case of high viscosity lower mantle. This result demonstrates that lower mantle is not the reservoir of primitive volatile and causes the ‘helium paradox’.
In here I propose a new model to solve the paradox. In my model, the low 3He/4He OIB (5-6 RA) has a lithosphile-rich reservoir, in which enriched U, Th product more radiogenic 4He and lead isotopes than MORB reservoir. The enriched reservoir of these OIBs results from contamination by pelagic sedimentation; and its spatial distribution is controlled by subduction slabs under Pangea. However, the reservoir of high 3He/4He OIB is related to the blob that is mixed by U and Th much depleted recycle oceanic crust or lower continental crust and the undegassed mantle blob. After long period (e.g., 1-2 Ga.) evolution, the reservoir will have much less radiogenic 4He and higher 3He/4He ratio than that of MORB. It should be noted that the mixing blob is relative refractory, and this means that the reservoir of high 3He/4He OIB is more stable than MORB reservoir. The melt interaction between the degassed MORB and the high 3He/4He plume can satisfactorily explain the isotope features of high 3He/4He OIB, such as Nd, Pb as well as He. The melting of high 3He/4He reservoir is related to the increasing of mantle temperature, which results from superplume upwelling or avalanche of 670-km boundary. The diverse geographic distributions of high and low 3He/4He OIBs infer the complex hemispheric asymmetry patterns of mantle circulation.
5．地壳岩石脆延性\脆塑性转化
周永胜 何昌荣
（中国地震局地质研究所，中国地震局构造物理开放实验室，北京，100029）
The Brittle-Ductile \Brittle-Plastic Transition in Crustal Rocks
Zhou Yongsheng He Changrong
(Institute of Geology & Labotary of Tectonophysics, CSB, Beijing, 100029)
Abstract
It is a different concept
from brittle-ductile and brittle-plastic transition in rocks. The
brittle-ductile transition generally refers to a change from localized failure
(by macroscopic fracture or faulting) to macroscopic homogeneous flow. This
change often is associated with macroscopic texture and mechanical
behavior. The brittle-plastic
transition means the change from brittle (including fracture or faulting,
cataclasis and fraction) to crystal-plastic deformation. This change is assoiated
with mechanical behavior and micro-mechanism. Such transitions are important in
understanding earthquake source mechanics, the strength of the lithosphere, and
the style of deformation. The brittle-ductile\plastic transition of the main crust
have been introduced.
6．青藏高原及其邻区地壳应变的地震矩张量和GPS反演分析，
许才军 刘经南 李志才 董立祥， 武汉测绘科技大学，武汉，430079
Analyze characteristic of deformations in
Qinghai-Tibet and its margins by inverting seismic moment tensors and GPS velocities Caijun Xu Jingnan Liu et. al.
Analyze characteristic of deformations in
Qinghai-Tibet and its margins
by
inverting seismic moment tensors and GPS velocities
Caijun Xu Jingnan Liu Zhicai Li and Lixiang Dong (School of Geo-science and
Surveying Engineering, Wuhan Technical University of Surveying and Mapping, 129
Luoyu Road, Wuhan, 430079, E-mail: cjxu@wtusm.edu.cn)
Abstract: We determine
approximate average rates of deformation in the Qinghai-Tibet plateau and its
margins. These rates are based on the GPS in last 10 years and the moment
tensors from earthquakes between 1900 and 1999. We determine the strain rate
(seismic strain rate) associated with the seismic deformation using 254 
earthquakes, and
estimate the shortening and extension rates for every block in above area. We
also estimate the strain rate (geodetic strain rate) by 80 GPS sites’ velocity
vectors; we analyze characteristic of kinematics by two kinds of strain rates
in the area, and discuss earthquake potential in the area. As a result, The deformation rates from
seismic moment tensors and from GPS velocities are basically agree with each
other. It is viable for analyzing earthquake
potential by comparing with geodetic strain rate and
seismic strain rate. There is no strong earthquake potential (>M7) in
the Qinghai-Tibet plateau and its margins, but there is earthquake potential
(>M5) in middle Tibet in few years.
7． Magnetic Petrology of Xenoliths and Terrains of Granulite-Facies
in the Hannuoba Region, China
Liu Qingsheng1 , Hu
Xiangyun1 , Gao Shan2 , Liu Yongsheng2
1. Department of Geophysics, China University of Geosciences, Wuhan
430074, China,
2. Faculty of Earth Science, China University of Geosciences,
Wuhan 430074, China
Magnetic
parameters with mineralogical and geochemical compositions of granulite facies
terrains and xenoliths from the Hannuoba region, North China Craton show that
granulite facies terrains have generally strong magnetism and obvious Hopkinson
Effect and high magnetic stability versus temperature varing. Both of xenoliths
and terrains do not contain magnetic carriers which Curie point (Tc)
are higher than those of magnetite (580 ℃).
Terrains are favourable to preserve magnetism relatively to xenoliths under
crustal background. Average susceptibility of terrains is 3464×10-6 SI and corresponds with those
of calculated by regional aeromagnetic anomalies. So, we propose that
continental lower crust in the Hannuoba area with low heat flow consists
predominanly of granulite facies terrains rock exposed on surface. It’s source
of regional aeromagnetic anomalies with moderate-low intensity. Magnetic bottom
of the continental crust was situated probably on the crust-mantle boundary in
this region.
8．西太平洋俯冲带流变结构的研究*
臧绍先 宁杰远 景志成
北京大学地球物理系，北京100871
Rheology structure of the subduction
zones at west Pacific
Shao-Xian Zang Jieyuan Ning
Zhicheng Jing
(Geophysics Department of Peking University, Beijing 100871)
Subducted oceanic lithosphere is a great tectonic unit, which has great importance in geodynamics. The rheology structure of which is the focus of geodynamic research on subduction zones, because interaction of slabs with the surrounding mantle, mechanism of deep focus earthquakes, and the deformation of subduction zone are all related with it. Based on analyses of different rheological model, calculated thermal parameters of different temperature and pressure based on the newly published laboratory data, calculated thermal structures of subduction zones at west Pacific, and calculated phase structures of subduction zones at west Pacific, we carried out rheological structures of subduction zones at west Pacific region.
9．亚稳态橄榄石的存在与深源地震的发生*
景志成 宁杰远 臧绍先
（北京大学地球物理学系，北京 100871）
Existence of Metastable Olivine and Deep Focus Earthquakes
Zhicheng Jing Jieyuan Ning Shao-Xian Zang
Geophysics Department of Peking University, Beijing 100871
In Wadati-Benioff (W-B) zones, earthquakes occur along inclined planes that extend down into the Earth’s mantle from below ocean trenches to depths approaching 700 km.. The frequency of earthquakes in subduction zones decreases exponentially with depth down to about 300 km, then increases again between 400 and 600 km before dropping off abruptly between 600 and 680 km .
The anticrack theory of faulting as originally put forth by Green and Burnley（1989）and many laboratory experiments were carried out. The results of the experiments showed that deep focus earthquakes that the depths are deeper than 400 km could be explained very well by the anticrack theory (Green and Houston, 1995). Nevertheless, this mechanism needs further examination, especially needs supports from the results of stress simulation for subduction zones and from evidences that there could exist metastable olivine in depths between 400km and 680km in subduction zones.
We calculated thermal structure and phase structure in subduction zones of west Pacific. It seems that subduction zones with high frequency of deep focus earthquakes has relation with existence of metastable olivine.
10．亚洲大陆下的地幔流动及其对亚洲地壳作用的应力
孙荀英1) 张 怀2)
梁国平2)
1〕 北京大学地球物理系,地球动力学中心, 100871
2〕 中国科学院数学所, 100080
The Mantle Flow Under The Asia and The
Stresses act Under the crust of The Asia
Xunying Sun1) Huai Zhang2) et al.
1) Department of Geophysics, Peking University, 100871
2) The Reseach Institute of Mathmatics, The
Chinese Academy of Sciences, 100080
The Mantle Flow Under The Asia and The
Stresses act Under the crust of The Asia
Xunying Sun , Huai
Zhang et al.
This Paper computed the
Navier-Stokes equations and the
heat conduction equation for the lithosphere and the mantle of the Earth. The
velocities, the temperatures and the stress fields of the lithosphere and the
mantle including the Asia continental and its mantle, and they changes with
time were obtained by means of the Laglanginal Multiplier Domain Disconnect Method (LMDDM) and the Laglanginal Multiplier Discontinuous Deformation Analysis
(LMDDA) for the 3-dimension finite element method (FEM) which were applied
to the problems of the
nonstability heat convection for the incompressure
viscous fluid in a thick spherical shell. According to the plate tectonic
theory, the Earth surface was break up 16 areas. Each area represents one plate except the Eurasia plate which
was divided two areas. The east one is the Asia , and the weat one is the
European . The temperatures, the velocities and the stresses of the crust and
the mantle of each area except the boundary were computed at one accessary node
(CPU) and the inter-area information were computed at the main node. After the
multipliers of inter-area were obtained and sent to the corresponding accessary
nodes, the temperatures, the velocities and the stresses of each area and its
mantle could be calculated at one's own accessary node.
11．饱和岩石的各向异性和应变率效应
席道瑛 刘斌 白石羽 张程远 刘小燕 田象燕 陈运平
（中国科学技术大学地球及空间科学系 合肥 230026）
Anisotropy and strain rate effect
of saturated rocks
Xi Daoying,Liu Bin,Bai Shiyu,Zhang Chengyuan,
Liu Xiaoyan,Tian Xiangyan,Chen Yunping
(Dept. of Earth and Space Sci,Univ. of Sci. and Tech. of China,Hefei,230026)
The uniaxial failure test of sandstone and marble is conducted on MTS to study anisotropy and strain rate effect of rocks. It is concluded that sandstone’s anisotropy is obvious while marble’s is weak, and both of these saturated rocks show distinct strain rate effect, which can be enhanced by saturation liquids.
12．Structure of
660km discontinuity beneath north-eastern part of China and its interaction
with subdution
Zang Shaoxian and Zhou Yuanze
Department of Geophysics, Peking University, 100871
The subducting slab of Pacific lithosphere subducted beneath the north-eastern part of China. The structure of 660km discontinuity beneath this area was studied both using rectilinear polarized filter of P-SV converted wave from the discontinuity and the slant stack of the waveform of P-SV wave. The result shows that the structure of discontinuity near 660km beneath MDJ station is more complicated and consist of several layers from 660km to 710km depth and the structure beneath HIA is simple and very clear. The structure beneath the stations located between MDJ and HIA graduately changes from the MDJ type to HIA type, it may be caused by the subducted slab of Pacific plate from Japan trench.
13．菲律宾海板块欧拉参数的确定及板内变形
陈起永 臧绍先
（北京大学地球物理系 北京 100871）
The Determination of the Euler Parameters of the Philippine Sea Plate
and the Internal Deformation of the Plate
Qiyong Chen and Shaoxian Zang
(Department of Geophysics, Peking University, Beijing 100871)
67 slip vectors around the boundary of Philippine Sea plate and the velocities relative to the Eursia plate of 4 GPS stations are selected. Then, by using a global inversion method, the Euler Vectors of 13 plates are gotten(Pacific fixed) using the data above, together with those used in Nuvel_1 model. The predicted results of our Euler Vector of Philippine Sea plate are consistent with those slip vectors used and the observed results of GPS stations, especially at the station Okino Torishima. By adjusting the Euler Vector of CR-PH which was proposed by Weissel and Anderson(1978), together with our PA-PH Euler Vector, a PA-CR Euler Vector that can satisfy the PA-CR conditions is obtained. The relative motions of Philippine Sea plate relative to the adjacent plates and the internal deformation of the Philippine Sea plate are discussed and then are compared to other researchs' results.