Developments of borehole strain observa- tion outside China     

邱泽华  石耀霖 《地震学报(英文版)》2004,17(Z1)

Introduction The Earth′s crust deforms in the regional tectonic stress field. Borehole strain observation isone important means for studies on the crustal deformation and the stress field. QIU and ZHANG(2002) have introduced the current situation of borehole strain observation in China. OutsideChina, early in September of 1968, Sacks of Carnegie Institution of Washington and Evertson ofUniversity of Texas firstly invented a borehole dilatometer in the world (Sacks, Evertson, 197…  相似文献   

Rupture process of the 1999 November 12 Düzce (Turkey) earthquake deduced from strong motion and Global Positioning System measurements     

M.-P. Bouin  M. Bouchon  H. Karabulut  M. Aktar 《Geophysical Journal International》2004,159(1):207-211

  相似文献   

Historical measurements of the Earth's magnetic field compared with remanence directions from lava flows in Italy over the last four centuries     

Roberto Lanza  Antonio Meloni 《Physics of the Earth and Planetary Interiors》2005,148(1):97-107

Direct measurements of the Earth's magnetic field in Italy since 1640 a.d. have been used to check the remanence directions derived from historically dated volcanic rocks of Etna and Vesuvius. Direct measurements consist of the records of L’Aquila and Pola geomagnetic observatories, the repeat stations of the Italian Magnetic Network and the data base of the Historical Italian Geomagnetic Data Catalogue. All have been relocated to the same reference site (Viterbo — lat. 42.45°N, long. 12.03°E) in order to draw a reference secular variation (SV) curve. The direction of the Earth's field at Viterbo has also been calculated from the historical records (2000-1600) of ref. [Jackson, A., Jonkers, A.R.T., Walker, M.R., 2000. Four centuries of geomagnetic secular variation from historical records. Phil. Trans. R. Soc. London, Ser. A 358, 957-990] database. The remanence directions from Etna show a general agreement with the trend of the SV curve, although their inclination is usually lower than that from the direct measurement. The directions from Vesuvius are more scattered. Large discrepancies occur at both volcanoes and in some cases have been ascribed in the literature to poor geographic information, making it difficult to identify the flows actually emplaced during the eruptions reported in the chronicles. Closer examination shows that the great majority of the best-defined remanence directions (semi-angle of confidence α₉₅ < 2.5°) deviate significantly from the geomagnetic direction measured at the time of the emplacement, the angle between the two directions being larger than the α₉₅ value. The value of 2.5-3.0° can thus be regarded as a conservative evaluation of the error when dealing with dating Etna and Vesuvius lava flows older than 17th century, even when the accuracy attained in remanence measurements is higher. In default of a SV curve for Italy derived from archaeological artefacts, a further error in dating is introduced when reference is made to SV curves of other countries, even if well-established, as these are from regions too far from Italy (>600 km) to confidently relocate magnetic directions.  相似文献   

Ground deformation of Nisyros Volcano (Greece) for the period 1995–2002: Results from DInSAR and DGPS observations     

E. Lagios  V. Sakkas  Is. Parcharidis  V. Dietrich 《Bulletin of Volcanology》2005,68(2):201-214

Differential GPS (DGPS) and Differential Interferometric Synthetic Aperture Radar (DInSAR) analyses were applied to the Kos-Yali-Nisyros Volcanic Field (SE Hellenic Volcanic Arc) to quantify the ground deformation of Nisyros Volcano. After intense seismic activity in 1996, a GPS network was installed in June 1997 and re-occupied annually up to 2002. A general uplift ranging from 14 to 140 mm was determined at all stations of the network. The corresponding horizontal displacements ranged from 13 to 53 mm. The displacement vectors indicate that the island is undergoing extension towards the East, West and South. A two-source “Mogi” model combined with assumed motion along the Mandraki Fault was constructed to fit the observed deformation. The best-fit model assumes sources at a depth of 5500 m NW of the centre of the island and at 6500 m offshore ESE of Yali Island. DInSAR analysis using four pairs of images taken between May 1995 and September 2000 suggests that deformation was occurring during 1995 before the start of the seismic crisis. An amplitude of at least 56 mm along the slant range appeared for the period 1996 through 1999. This deformation is consistent with the two-source model invoked in DGPS modelling. Surface evidence of ground deformation is expressed in the contemporaneous reactivation of the Mandraki Fault. In addition, a 600 m long N-S trending irregular rupture in the caldera floor was formed between 2001 and 2002. This rupture is interpreted as the release of surface stress in the consolidated epiclastic and hydrothermal sediments of the caldera floor.  相似文献   

Near-surface seismic anisotropy, attenuation and dispersion in the aftershock region of the 1999 Chi-Chi earthquake   总被引：1，自引：0，他引：1  

Yunfeng Liu  Ta-Liang Teng  Yehuda Ben-Zion 《Geophysical Journal International》2005,160(2):695-706

  相似文献   

Directional dependence of P- and S-wave propagation and polarization in foliated rocks from the Kola superdeep well: Evidence from laboratory measurements and calculations based on TOF neutron diffraction   总被引：1，自引：0，他引：1  

T.I. Ivankina  H.M. Kern  A.N. Nikitin 《Tectonophysics》2005,407(1-2):25-42

We have measured P- and S-wave velocities on two amphibolite and two gneiss samples from the Kola superdeep borehole as a function of pressure (up to 600 MPa) and temperature (up to 600 °C). The velocity measurements include compressional (Vp) and shear wave velocities (Vs1, Vs2) propagating in three orthogonal directions which were in general not parallel to inherent rock symmetry axes or planes. The measurements are accompanied by 3D-velocities calculations based on lattice preferred orientation (LPO) obtained by TOF (Time Of Flight) neutron diffraction analysis which allows the investigation of bulk volumes up to several cubic centimetres due to the high penetration depth of neutrons. The LPO-based numerical velocity calculations give important information on the different contribution of the various rock-forming minerals to bulk elastic anisotropy and on the relations of seismic anisotropy, shear wave splitting, and shear wave polarization to the structural reference frame (foliation and lineation). Comparison with measured velocities obtained for the three propagation directions that were not in accordance with the structural frame of the rocks (foliation and lineation) demonstrate that for shear waves propagating through anisotropic rocks the vibration directions are as important as the propagation directions. The study demonstrates that proper measurement of shear wave splitting by means of two orthogonal polarized sending and receiving shear wave transducers is only possible when their propagation and polarization directions are parallel and normal to foliation and lineation, respectively.  相似文献   

临震前地壳变形不动点现象与机制研究     

牛安福  张凌空  章静  李媛  赵静  闫伟  岳冲  苑争一 《大地测量与地球动力学》2020,40(1):1-6

在综合分析国内外地形变前兆研究现状的基础上,结合汶川8.0级地震前GPS、应变、重力等研究结果,提出临震前震源区域可能出现变形不动点现象。地壳变形过程中的不动点现象是临震前区域应力场进入临界状态的重要标志,是地震潜在危险区域划定的重要依据。借助不动点理论,给出汶川地震前变形不动点集合的演化,结合大区域地震活动空区与远场显著形变异常分布,探讨变形不动点现象发生的动力学背景,验证了汶川地震前地壳变形的不动点现象是大区域应力场有序运动的结果。  相似文献   

Borehole failure analysis in a sandstone under anisotropic stresses     

Euripides Papamichos 《国际地质力学数值与分析法杂志》2010,34(6):581-603

Borehole failure under anisotropic stresses in a sandstone is analyze numerically for various borehole sizes using a nonlinear elastic–plastic constitutive model for a Cosserat continuum. Borehole failure is identified as macroscopic failure of the borehole through the development of shear bands and breakouts. The results compare well both qualitatively and quantitatively with experimental results from polyaxial tests on Red Wildmoor sandstone. They show that the hole size effect of the borehole failure strength is independent of the far‐field stress anisotropy and follows a ? power law of the hole size. A similar scale effect equation with a ? power law is proposed for the scale effect of the maximum plastic shear strain at failure. This equation can be useful for better predicting hole‐size‐dependent failure with standard codes based on classical continua. The effect of stress anisotropy on the borehole failure stress is found to be independent of the hole size. The failure stress decreases linearly to 40% as the stress anisotropy increases. However, the maximum plastic shear strain at failure is stress anisotropy independent and therefore the critical plastic shear strain for failure is only hole‐size dependent. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

某双向混凝土立交桥顶推法施工控制测量     

马勇  李仲勤  梅泽 《测绘与空间地理信息》2016,(11):213-215

文中所选立交桥为双向三车道桥梁,单幅为3跨105 m的箱型连续梁,重量3 400 t,横跨铁路线。对于跨铁路的桥梁建设,顶推法施工可最大限度地减少对交通的影响。桥梁重量大,所须牵引力约280 t,施工过程中对桥墩及其他建筑物产生的变形较大,施工前模拟施工状态,设计控制测量监控的基本方案,利用控制测量方法,对施工状态实时监测,预测变形及偏位、纠偏,使施工状态最大限度地接近理想状态。顶推到位后,轴向偏位满足1 cm的限差,桥墩变形基本满足施工规范的要求,最终顺利完成顶推过程。  相似文献   

松辽盆地大陆科钻二开段大井眼钻井液技术     

郑文龙 《地质与勘探》2016,52(5):931-936

CCSD-SK2井是一口钻穿松辽盆地白垩纪陆相沉积地层的中国大陆科学钻探井。二开段先以216mm口径钻至2806.20m,然后进行444.5mm口径扩孔。泥页岩地层大井眼钻进过程中粘土矿物含量高且易造浆,砂砾岩层渗透性强易粘卡,井壁稳定控制与钻屑携带难度大。选用了钾铵聚合物钻井液体系和聚磺钻井液体系,通过正交实验确定了钻井液配方。将钻井液控制在合适的密度、较低的失水量以及较强的封堵性,有效实现了井壁稳定;保持适当的环空返速、较高的动塑比以及定期打稠塞举砂等措施,有效实现了井眼净化。1086.45m~1147.56m与1182.74m~1256.01m井段累计收获岩心130.90m,取心率达到97.41%,平均机械钻速为0.84m/h;最终顺利钻至2806.20m。  相似文献