Analytical study of ground motion caused by seismic wave propagation across faulted rock masses

Studying seismic wave propagation across rock masses and the induced ground motion is an important topic, which receives considerable attention in design and construction of underground cavern/tunnel constructions and mining activities. The current study investigates wave propagation across a rock mass with one fault and the induced ground motion using a recursive approach. The rocks beside the fault are assumed as viscoelastic media with seismic quality factors, Q_p and Q_s. Two kinds of interactions between stress waves and a discontinuity and between stress waves and a free surface are analyzed, respectively. As the result of the wave superposition, the mathematical expressions for induced ground vibration are deduced. The proposed approach is then compared with the existing analysis for special cases. Finally, parametric studies are carried out, which includes the influences of fault stiffness, incident angle, and frequency of incident waves on the peak particle velocities of the ground motions.     

RECENT TECTONIC DEFORMATION ANOMALY AND EARTHQUAKES IN GANSU-NINGXIA-QINGHAI AREA

1　IntroductionAccordingtogeologicalstructure ,theGansu Ningxia Qinghaiareabelongstothenortheastmar ginofQinghai Tibetblock .Thisareahasbeenpaidmuchattentionby geo specialistsinChinaandabroadbecauseofitssignificanttectonicmovement,itsintensiveseismicity ,anditsimportanceinearth quakehazardmitigation .IntheDevelopmentPro gramonNationalKeyBasicResearchesundertheProject“MechanismandPredictionofContinentalStrongEarthquakes”,themechanismsofcontinen talstrongearthquakesarestudied ,usinghypo…     

昆仑山8.1级地震前中国大陆的构造应变背景

利用“网络工程”1998～2001年累积的1181个测站的GPS重复观测资料，采用双三次样条函数模型建立中国大陆水平运动模型速度场，用大地坐标在椭球面上计算各类应变场，详细分析了2001年昆仑山8．1级地震前中国大陆水平构造应变场空间分布特征。各类构造应变场的最高值都出现在喜马拉雅构造带与昆仑山地块内(地震断裂带南侧)，鲜水河—安宁河断裂带次之。分析表明，昆仑山8．1级地震正好发生在张性面膨胀应变率的高值区，第一、第二和最大剪应变率高值区边缘的突变区和最大、最小主应变率的高值区。     

Minimal Energy and Gravitation

Quantum theory in Robertson – Walker spacetime suggests the existence of a minimal energy ε of the order of 10⁻⁴⁵ erg. Reasonable forms for ε give the expansion factor R=R(t)(t= the cosmic time) with no need of gravitational field equations.Einstein's theory should be modified in gravitational fields of strength less than ε c/ħ ∼ 10⁻⁸ cm/s² where c is the speed of light and ħ is the reduced Planck constant. The cosmological term λ is expected to decrease as the universe expands.In the Appendix, ε is derived from a big bang – big crunch Newtonian cosmology.     

Parameters of the intense X-ray and gamma-ray radiation from the solar flare of May 20, 2002, as observed from the Coronas-F spacecraft

We consider temporal, spectral, and polarization parameters of the hard X-ray and gamma-ray radiation observed during the solar flare of May 20, 2002, in the course of experiments with the SONG and SPR-N instruments onboard the Coronas-F spacecraft. This flare is one of the most intense gamma-ray events among all of the bursts of solar hard electromagnetic radiation detected since the beginning of the Coronas-F operation (since July 31, 2001) and one of the few gamma-ray events observed during solar cycle 23. A simultaneous analysis of the Coronas-F and GOES data on solar thermal X-ray radiation suggests that, apart from heating due to currents of matter in the the flare region, impulsive heating due to the injection of energetic electrons took place during the near-limb flare S21E65 of May 20, 2002. These electrons produced intense hard X-ray and gamma-ray radiation. The spectrum of this radiation extends up to energies ≥7 MeV. Intense gamma-ray lines are virtually unobservable against the background of the nonthermal continuum. The polarization of the hard X-ray (20–100 keV) radiation was estimated to be ≤15–20%. No significant increase in the flux of energetic protons from the flare under consideration was found. At the same time, according to ACE data, the fluxes of energetic electrons in interplanetary space increased shortly (～25 min) after the flare.     

Synthetic SH seismograms in a laterally varying medium by the discrete wavenumber method

Summary. We present a new method to calculate the SH wavefield produced by a seismic source in a half-space with an irregular buried interface. The diffracting interface is represented by a distribution of body forces. The Green's functions needed to solve the boundary conditions are evaluated using the discrete wavenumber method. Our approach relies on the introduction of a periodicity in the source-medium configuration and on the discretization of the interface at regular spacing. The technique developed is applicable to boundaries of arbitrary shapes and is valid at all frequencies. Some examples of calculation in simple configurations are presented showing the capabilities of the method.     

中国大陆科学钻探先导孔零偏VSP资料解释

用六级三分量检波器在中国大陆科学钻探先导孔中实施了零偏VSP测量.数据处理结果表明,中国大陆科学钻探孔区超高压变质岩石的地震波速度主要介于4500～7000m/s之间,显著高于一般的沉积岩地区,而且随深度变化不明显.声波测井速度系统地稍低于VSP层速度,可能是由于井壁处岩石的完整性受到破坏而造成的.地震波速度与岩石密度和岩性存在明确的对应关系,榴辉岩的密度和地震波速度均显著高于片麻岩类岩石;由榴辉岩退变生成的斜长角闪岩类岩石,其密度和地震波速度均呈现出较大的变化,主要与其退变质程度有关;超基性岩中的裂隙系统导致其密度和地震波速度大幅度下降.由于榴辉岩与其他岩石类型之间存在较大的波阻抗差异,因此用零偏VSP资料标定该区地震波的地质层位是有效的.关于地震波反射的原因,通过综合研究地震波(包括反射纵波、上行转换横波、井筒波)的特征、岩石速度和密度分布以及井径变化,认为主要是岩性分界面、韧性剪切带和断裂(带),但还有一些因素尚待进一步研究.     

定水头注水引起的含水层水平运动和应变

基于含水层固体颗粒与孔隙水不可压缩的假设 ,本文导出了单井注水情况下泰斯承压含水层水平运动速度与水头之间的基本关系式。然后利用注水井壁处的应力、应变边界条件 ,进一步导出了单井定水头注水引起的泰斯承压含水层水平运动速度、位移和应变解析表达式。该水平位移与应变由两部分组成 :一部分为由注水压力本身引起的经典弹性力学解项 ,它仅随半径而变化 ,与注水时间无关 ;另一部分为由地下水头变化引起的水动力学位移和应变解项。其中 ,含水层水动力学水平位移随时间加长呈指数增长特征 ,水动力学径向应变则表现为近井处拉张、远井处挤压的分区特征 ,且近井拉张区随时间加长逐渐向外扩展。单井注水含水层水动力学水平位移、应变解的导出 ,完善和发展了单孔内压经典弹性平面力学问题解