Development of dynamic slip model for a shear crack

<正>The objective of this paper is to develop a dynamic slip model for a shear crack under constant stress drop.This crack problem is formulated by a traction boundary integral equation(BIE) in the frequency domain and then solved by the hyper-singular boundary element method as well as the regularization technique proposed in this paper.Based on the spectral integral form of the kernel function,the unbounded term can be isolated and extracted from the hyper-singular kernel function by using the method of subtracted and added back in wave number domain.Finally,based on the inverse transformation from the frequency domain to the time domain,the time histories of crack opening displacement under constant stress drop can be determined.Three rupture models(simultaneous rupture model,symmetric bilaterally-propagating model and unilaterally propagating model) with specified time histories of stress drop are considered in this paper.Even though these three models will cause the same final slip shapes because of the same constant stress drop,the associated slip time functions differ significantly from each other during the rupture process.     

Characteristic of crustal structure in the Shulu fault basin and its vicinity

（王椿镛，张先康，林中洋，李学清）ＣｈａｒａｃｔｅｒｉｓｔｉｃｏｆｃｒｕｓｔａｌｓｔｒｕｃｔｕｒｅｉｎｔｈｅＳｈｕｌｕｆａｕｌｔｂａｓｉｎａｎｄｉｔｓｖｉｃｉｎｉｔｙ￥Ｃｈｕｎ－ＹｏｎｇＷＡＮＧＩ；Ｘｉａｎ－ＫａｎｇＺＨＡＮＧ；Ｚｈｏｎｇ－ＹａｎｇＬ...     

Crustal structure in Xiaojiang fault zone and its vicinity

Based on the integrative interpretation of travel-time data and amplitude information obtained from the deep seismic sounding experiment on the Chuxiong-Luoping profile,eastern Yunnan province,carried out in January of 2005,we present a 2-D P wave velocity structure along the profile. The crustal structure shows remarkable contrasts between the two sides of the Xiaojiang fault zone,although the whole profile is situated within the Yangtze platform. The average P wave velocities of the crust on the west and ...     

The propagation of a single shear crack: A displacement discontinuity model

Numerical studies using the displacement discontinuity method show that a single shear crack under compression propagates in its own direction, because such propagation results in the maximum release of strain energy. The methods of linear elastic fracture mechanics may not be used for such a closed crack, and the stress intensity factors are meaningless in that case. Laboratory observations of propagation by means of kinks at an angle of approximately 70° to the crack may be due to heterogeneities, to the effect of a preexisting crack, to end effects, to microcracking, or to some combination of these factors. Such kinks may thus be local phenomena which cannot release most of the strain energy, and are not incompatible with our numerical results which are based on a global energy balance.     

地壳介质各向异性电性本构关系讨论

讨论了地壳介质中常见的两类电性各向异性。推导了长波长条件下薄中向异性电导率张量;提出了一种新的电导率物理模型并由此推导了与ＥＤＡ裂隙相适应的各向异性电导率张量。从直流电法和大地电磁测深法的角度分别讨论了这两种电性各向异性所显现的地表视电阻率、阻抗和电位特征。     

Trajectory of fault-plane-induced tensile crack in relation to the primary stress field

Summary The predetermination of the trajectory of a tensile crack induced at the tip of a stress-free fault plane (open slit, in two dimensional approximation) was investigated. Both the primary field of the tensile component of principal stress and the primary field of the strain energy density factor were computed and compared with the trajectory of the subsequent tensile crack. It was found that it is not the field of the strain energy density factor, but the field of the tensile component of principal stress which determines the trajectory of the tensile crack. Moreover, this field is responsible for the trajectory of the tensile crack not only in its seismoactive phase of its development, but also in the following aseismic stage characterized by slow stable growth.     

The subsurface structure of the AIRA caldera and its vicinity in Southern Kyushu, Japan

Southern Kyushu, Japan, includes a chain of large and small calderas and active volcanoes, and the greatest part of it is covered with thick pyroclastic ejecta. The regional and local structures of this area are discussed from the standpoint of physical volcanology, with consideration of all available data.The regional structure of this area is examined in the light of gravity and geomagnetic anomalies. Two layers of the earth's uppermost crust are defined by spectrum analysis of the gravity anomalies. These two layers are identical with the two identified by seismicwave velocities. The Bouguer gravity anomalies are relatively high and rather monotonous over outcrops of the Mesozoic basement and the granite, but are relatively low and perturbed over calderas and caldera-like structures. Two low-gravity anomalies in Kagoshima Bay are remarkable. One is circular, with its center on the Aira caldera. The other is elongated between the Satsuma and Oosumi peninsulas. The southern end of the latter anomaly is occupied by the Ata caldera. Discussion of the gravity anomalies of the Aira caldera suggests that the subsurface basement has a funnel shape and is overlain by ‘fallback’. The sub bottom geology of the caldera suggests that it is formed by a few smaller depressions, though the distribution of the overall gravity anomalies is parallel with its shape.The southern part of Kagoshima Bay is characterized by a graben-like topography and low-gravity anomalies and, moreover, by several calderas. The middle part, between the Aira and Ata calderas, may have a graben-like structure. A profile crossing the bay through Sakurajima volcano is modeled on the basis of results from drilling and gravity surveys. The basement has a graben-like structure and is filled with coarse and low-density deposits, and the structure continues northwards to the Aira caldera with a funnel shape.A comparison of this area with the Taupo-Rotorua depression in New Zealand and Lake Toba in Indonesia, leads the authors to the conclusion that such major volcanic depressions may have been formed by amalgamation of a series of caldera-like structures which were formed by multiple violent explosions accompanied by ejection of a tremendous amount of pyroclastic material.     

土体动力一维非线性本构关系剖析与评价

土体动力一维非线性本构关系是场地及地基动力响应、土工数值分析的关键。回顾和总结了国内外的发展状况及研究进展,对其分析方法、等幅循环荷载到不规则荷载的扩展及应用规则、试验阻尼比的等效、滞回曲线形状等核心问题进行剖析、评价和探讨,并对各种模型的优缺点进行了比较和讨论,着重介绍了最近研究结果。最后指出未来发展方向及有待进一步研究的问题。     

Study and review on crust-mantle velocity structure in Bohai Bay and its vicinity

Introduction Bohai Bay, along with its adjacent areas, is one of the seismically active areas in North China. Understanding its crust/upper-mantle structural characteristics and lateral heterogeneity of the medium in this area is of great significance to the study of seismogenic environment, thus improvimg the level of earthquake prediction. For years, scientists have studied the area by gravity and magnetic methods (FENG, et al, 1989), geothermal field (WU, et al, 1988; TIAN, ZHANG, 19…     

Coulomb constitutive laws for friction: Contrasts in frictional behavior for distributed and localized shear

We describe slip-rate dependent friction laws based on the Coulomb failure criteria. Frictional rate dependence is attributed to a rate dependence of cohesionc and friction angle . We show that differences in the stress states developed during sliding result in different Coulomb friction laws for distributed shear within a thick gouge layer versus localized shear within a narrow shear band or between bare rock surfaces. For shear within gouge, shear strength is given by =c cos + _n sin, whereas for shear between bare rock surfaces the shear strength is =c cos + _n tan, where and _n are shear and normal stress, respectively. In the context of rate-dependent Coulomb friction laws, these differences mean that for a given material and rate dependence of the Coulomb parameters, pervasive shear may exhibit velocity strengthening frictional behavior while localized shear exhibits velocity weakening behavior. We derive from experimental data the slip-rate dependence and evolution ofc and for distributed and localized shear. The data show a positive rate dependence for distributed shear and a negative rate dependence for localized shear, indicating that the rate dependence ofc and are not the same for distributed and localized shear, even after accounting for differences in stress state. Our analysis is consistent with the well-known association of instability with shear localization in simulated fault gouge and the observation that bare rock surfaces exhibit predominantly velocity weakening frictional behavior whereas simulated fault gouge exhibits velocity strengthening followed by a transition to velocity weakening with increasing displacement. Natural faults also exhibit displacement dependent frictional behavior and thus the results may prove useful in understanding the seismic evolution of faulting.     

Diagnosing the effective parameters of the ionospheric fine structure from statistical characteristics of radio waves in the vicinity of a regular caustic

This paper is concerned with the oblique propagation of decametric radio waves in the ionosphere with random electron density irregularities. Effective parameters are introduced for calculating the influence of irregularities on the wave field structure. A technique is proposed for determining these parameters from measurements of statistical characteristics of the signal in the vicinity of a regular caustic. The technique uses asymptotic expressions obtained using the interference integral method and perturbation theory, as well as matching them to the numerical solution on the basis of the method of characteristics. A global semi-empirical model that is updated for current ionospheric conditions is used to specify the background medium. The proposed technique has been tested using data from a number of mid-latitude paths. Results obtained in this study testify that the technique deserves a practical implementation.     

Heavy metal accumulation in the vicinity of a desalination plant

The brine effluent produced by a flash distillation desalination plant contains elevated levels of some heavy metals. The effluent produced from such a plant operating in Jersey during the summer months leads to increased metal concentrations in limpets and some Fucus species. This is most evident with copper which remains at elevated levels during the winter period of plant inactivity, probably due to the copper coating retained on boulders and pebbles on the upper shore.     

Dynamic displacements and stresses in the vicinity of a cylindrical cavity embedded in a half-space

The two-dimensional response of a viscoelastic half-space containing a buried, unlined, infinitely long cylindrical cavity of circular cross-section subjected to harmonic plane SH, P, SV and Rayleigh waves is obtained by an indirect boundary integral method based on the two-dimensional Green's functions for a viscoelastic half-space. An extensive critical review of the existing numerical results obtained by other techniques is presented together with some new numerical results describing the motion on the ground surface and the motion and stresses on the wall of the cavity for P, SV, SH and Rayleigh waves.     

Thermal regimes and regional metamorphism in the vicinity of overthrust faults: an example of shear heating and inverted metamorphic zonation from southern California

Thermal models are developed and temperature-depth profiles computed to account for the development of sharply inverted metamorphic zonations and estimatedP-T conditions beneath deep-seated thrust faults, with particular reference to the metamorphism of the Pelona Schist-Vincent Thrust system of southern California.Models dependent only upon conductive redistribution of heat from an initially hot upper plate are inadequate to account for the observed temperature distributions and theP-T time constraints can only be satisfied if a total shear heating of 3 hfu or more occurs in the region of the thrusts. These heating rates are consistent with known rates of plate movement, shear stresses along major fault zones, and shear strengths of rocks.Petrological constraints indicate the likelihood of buffering of the maximum temperature attained by shear heating due to marked reduction of shear strengths of rocks upon increase of temperature and release of water during metamorphic dehydration reactions.These models may be of general applicability to inverted metamorphic zonations, notably those beneath obducted Newfoundland ophiolites, and are consistent with our present understanding of the thermal properties of the upper parts of subduction zones.     

The typical seismic behavior in the vicinity of a large earthquake

The Global Centroid Moment Tensor catalog (GCMT) was used to construct the spatio-temporal generalized vicinity of a large earthquake (GVLE) and to investigate the behavior of seismicity in GVLE. The vicinity is made of earthquakes falling into the zone of influence of a large number (100, 300, or 1000) of largest earthquakes. The GVLE construction aims at enlarging the available statistics, diminishing a strong random component, and revealing typical features of pre- and post-shock seismic activity in more detail. As a result of the GVLE construction, the character of fore- and aftershock cascades was examined in more detail than was possible without of the use of the GVLE approach. As well, several anomalies in the behavior exhibited by a variety of earthquake parameters were identified. The amplitudes of all these anomalies increase with the approaching time of the generalized large earthquake (GLE) as the logarithm of the time interval from the GLE occurrence. Most of the discussed anomalies agree with common features well expected in the evolution of instability. In addition to these common type precursors, one earthquake-specific precursor was found. The decrease in mean earthquake depth presumably occurring in a smaller GVLE probably provides evidence of a deep fluid being involved in the process. The typical features in the evolution of shear instability as revealed in GVLE agree with results obtained in laboratory studies of acoustic emission (AE). The majority of the anomalies in earthquake parameters appear to have a secondary character, largely connected with an increase in mean magnitude and decreasing fraction of moderate size events (mw5.0–6.0) in the immediate GLE vicinity. This deficit of moderate size events could hardly be caused entirely by their incomplete reporting and can presumably reflect some features in the evolution of seismic instability.     

Calibrating function and station corrections forPKP waves in the vicinity of a caustic

Summary The homogeneous Magnitude System (HMS), developed by Vank, Kondorskaya and Christoskov, is used to calculate station corrections, magnitudes and a calibrating function for short-period PKP waves in the distance interval of 143° to 148°. The data basis consists of a set of 26 Tuamotu underground explosions and their records at 14 Central European seismic stations. The station magnitudes, calculated in this way show a smaller dispersion than the uncorrected (usual) values.     

框支剪力墙耗能结构抗震性能研究

框支剪力墙结构容易在底部形成大空间,可以满足变化多样的使用要求。但框支剪力墙结构易在底部形成薄弱层,不利于抗震。通过在底部设置RC耗能柱及限位斜撑的框支剪力墙结构模型的模拟地震振动台试验和有限元数值模拟分析,得到了框支剪力墙耗能结构的加速度、位移、剪力等在地震作用下的反应规律。验证了在中小地震时RC耗能柱充分耗能,在大震时RC耗能柱耗能、限位斜撑防止结构倒坍的耗能柱-限位斜撑体系的抗震设计思想。     

东北亚跃进山拼贴带及邻域岩石圈结构特征的地电学证据

为进一步查清东北亚完达山地体与两侧的佳木斯地块、兴凯地块间接触关系以及对跃进山拼贴带域沉积盆地油气条件的控制作用,布设5条MT剖面,计长1104 km.结果显示:(1)研究区地电学结构主要特征为佳木斯地块从中部向南北两方向,这一稳定地块的“高阻核”减薄,兴凯地块的高阻块体自东而西逐渐加深增厚,完达山地体在南部具有较多的高阻块体,向北渐少.(2)完达山地体西南端呈一“牛角”形状范围把佳木斯地块和兴凯地块分开;与原认识的完达山地体、佳木斯地块在同江-宝清-当壁一带贴合的位置相比,从宝清开始向南移至麻山-桦林一带.(3)完达山地体构造成因包括两部分,一是俯冲引起的拼贴,二是软流圈物质的热上涌;佳木斯地块内所存在的“高阻核”边界可能是该地块东界.(4)4个沉积盆地除勃利盆地外,另外3个盆地的基底间或存在规模不大的高阻块,大多范围分布着高导带,对盆地的成烃环境是有利的.     

改进框架支撑模型对剪力墙结构抗震性能的模拟

通过改变基本单元的数量m,本文提出的改进框架支撑模型不仅适用于不同层高宽比和材料的剪力墙结构,而且适用于框支、开洞等不同形式的剪力墙结构。通过对框支配筋砌块砌体剪力墙KZW-2子结构拟动力试验的模拟结果表明,改进框架支撑模型能有效地模拟剪力墙结构在地震作用下的弹塑性变形性能。