Tidal stress triggering effects of earthquakes based on various tectonic regions in China and related astronomical characteristics

Dividing the China's Mainland into different tectonic stress regions,we calculate tidal stress components along the seismic compressive and extensional principal stress axes at every earthquake's focus in different tectonic stress regions.Tidal stress triggering effect on every earthquake fault is analyzed.Based on this,the lunar-solar location parameters on the occurring times of earthquakes which suffered tidal triggering effects are calculated,and the distribution patterns of the lunar-solar location parameters in different tectonic stress regions are obtained.The results indicate that earthquake tidal triggering effects and related astronomical characteristics are dependent on the properties of regional tectonic stress and the geographic locations of earthquake faults.

A Modification to Vertical Distribution of Tidal Flow Reynolds Stress in Shallow Sea

Tidal flow is a periodic movement of unsteady and non-uniform, which has acceleration and deceleration process obviously, especially in coastal shallow waters. Many researches show that vertical distribution of tidal flow Reynolds stress deviated from linear distribution. The parabolic distribution of the tidal flow Reynolds stress was proposed by Song et al. （2009）. Although the model fills better with field observations and indoor experimental data, it has the lower truncated series expansion of tidal flow Reynolds stress, and the description of the distribution is not very comprehensive By introducing the motion equation of tidal flow and improving the parabolic distribution established by Song et al. （2009）, the cubic distribution of the tidal flow Reynolds stress is proposed. The cubic distribution is verified well by field data （Bowden and Fairbairn, 1952; Bowden et al., 1959; Rippeth et al., 2002） and experimental data （Anwar and Atkins, 1980）, is consistent with the numerical model results of Kuo et al. （1996）, and is compared with the parabolic distribution of the tidal flow Reynolds stress. It is shown that this cubic distribution is not only better than the parabolic distribution, but also can better reflect the basic features of Reynolds stress deviating from linear distribution downward with the tidal flow acceleration and upward with the tidal flow deceleration, for the foundation of further study on the velocity profile of tidal flow.

Vertical Distribution of Tidal Flow Reynolds Stress in Shallow Sea

Based on the results of the tidal flow Reynolds stresses of the field observations, indoor experiments, and numerical models, the parabolic distribution of the tidal flow Reynolds stress is proposed and its coefficients are determined theoretically in this paper. Having been well verified with the field data and experimental data, the proposed distribution of Reynolds stress is also compared with numerical model results, and a good agreement is obtained, showing that this distribution can well reflect the basic features of Reynolds stress deviating from the linear distribution that is downward when the tidal flow is of acceleration, upward when the tidal flow is of deceleration. Its dynamics cause is also discussed preliminarily and the influence of the water depth is pointed out from the definition of Reynolds stress, turbulent generation, transmission, and so on. The established expression for the vertical distribution of the tidal flow Reynolds stress is not only simple and explicit, but can also well reflect the features of the tidal flow acceleration and deceleration for further study on the velocity profile of tidal flow.

Ice-volcanism due to tidal stress on Europa

Tectonism would be driven by tidal heat onEuropa, and there may be ice-volcano on the surface ofactive Europa. We assume that ice-volcano would spurt out due to tidal stress, and calculate the velocity and height of the spurt in scale. We also find out the approximate distribution of the active volcanoes on Europa.

A Preliminary Study on the Use of NCEP Temperature Images and Additive Tectonic Stress from Astro-Tidal-Triggering to Forecast Short-Impending Earthquakes

Taking the three earthquakes which occurred in Tibet, China during the period of July 12 to August 25, 2004 as an example,the paper analyses the M_S≥6.0 earthquakes that occurred in China and M_S≥7.0 earthquakes that occurred overseas since May of 2003 by combining the image data from the National Center for Environmental Prediction of America(NCEP)with the additive tectonic stress from astro-tidal-triggering (ATSA) and makes the following conclusions: The abnormal temperature image data of NCEP can better reflect the spatial-temporal evolution process of tectonic earthquake activity; The ATSA has an evident triggering effect on the activity of a fault when the terra stress is in critical status; using the NCEP images and the ATSA to forecast short-impending earthquake is a new concept; The three earthquakes occurred during the same phase of the respective ATSA cycle, i.e. that occurred at the time when the ATSA reached the relatively steady end of a peak, rather than at the time when the variation rate was maximal. In addition, the author discovered that the occurrence time of other earthquake cases during 2003～2004 in Tibet was also in the same phase of the above-mentioned cycles, and therefore, further study of this feature is needed with more earthquake cases in other areas over longer periods of time.

Effect of tidal stress on fault nucleation and failure of the 2007 Ms6.4 Ning＇er earthquake

Based on calculations of the tidal Coulomb failure stress and investigations of the correlation between the Earth tide and the Ning'er earthquake sequence, the processes of fault nucleation and failure were simulated. In these simulations we consider the influence of tidal stresses using the rate- and state-dependent friction laws. Furthermore, the effects on tidal triggering due to the stress amplitude and periodic oscillation properties were investigated, and the triggering effects between the tidal normal and tidal shear stresses were compared. The results showed that the Ning'er earthquake sequence was a physical consequence of tidal effects. A transition period T_0 exists between the nucleation and failure processes of a seismic fault. When the period T of stress is equal to or becomes larger than T_0, the fault response becomes dependent on the periodic features of the loading stress; however, for T < T_0, the response of the fault is nearly independent of the period. Both the tidal normal and tidal shear stresses have similar effect in the nucleation and failure processes; the clock changes generally increase with the maximum amplitudes of the tidal stresses. Tidal normal and tidal shear stresses with positive amplitudes mainly induce earthquake triggering; however, the triggering effects induced by negative tidal stresses are smaller and faults are not sensitive to negative tidal stresses. Our results primarily reveal the physical mechanisms of tidal stress triggering.

Relationship between M_S≥7.0 Earthquakes in the Chinese Mainland and Tidal Coulomb Failure Stress

In this paper,we focused on earthquakes with M S≥7.0 in the Chinese mainland from1900 to 2012,calculated the lunisolar tidal Coulomb failure stress on the seismic fault plane and got the tidal phase through Schuster's test,then quantitatively analyzed the correlation between strong earthquakes in the Chinese mainland and tidal Coulomb failure stress.Research shows that among 57 strong earthquakes with focal mechanism solutions,over 71.9%took place within the tidal loading phase,with the p-value of 3.83%,indicating that strong earthquakes with M S≥7.0 in Chinese mainland have a certain correlation with lunisolar tidal Coulomb failure stress.In the active period,the p-value is4.56%,75.5%of earthquakes occurred in the tidal loading phase zone,and 50%of earthquakes occurred in the quiescence period,indicating that strong earthquakes in the active period were obviously triggered with the tidal Coulomb failure stress loading.

基于LURR的前震分析方法及其在川滇地区的应用

加卸载响应比(Load-Unload Response Ratio,LURR)是基于岩石介质本构关系动态变化提出的一种中短期地震预测方法,然而,在实践应用中存在构造剪应力方向难以确定的问题.本文以前震为研究对象,发展了一种确定构造剪切应力方向的新思路.当4级以上地震发生后,通过沿该地震滑动方向计算库仑破坏应力(CFS)的变化,判断其固体潮加卸载状态,探测后续强震发生的可能性.以川滇地区(20°N—35°N,96°E—106°E)为研究区域,分析2000年以来所有6级以上地震的4级以上前震的加卸载状态发现,大部分4级以上前震发生在加载阶段.进一步分析近10年来所有4级以上地震的加卸载状态发现,非前震则更易发生在卸载阶段.结合概率增益分析可知,(1)若原震区连续发生至少2个4级以上地震,且均位于固体潮加载过程,后续发生强震的可能性较大;(2)当地震位于卸载过程,原震区发生更强地震的可能性要低于平时的背景地震活动水平.此外,对2022年11月以来的4级以上地震加卸载状态分析推测,川东南、滇南、滇西北地区应力积累水平较高,需要重点关注强震危险性.

不同含水率与静置时间下滩涂土壤流变特性试验

为了研究贝类养殖的滩涂土壤的流变属性和结构稳定性,采用旋转流变仪对不同含水率和不同静置时间的滩涂土壤进行了流变试验,通过单因素试验研究了各因素对滩涂土壤流变特性的影响,并分析了土壤剪切过程中的变化机理。同时,通过Response Surface Methodology中的Central Composite Design试验建立了屈服应力与含水率和静置时间之间的数值模型,并比较了含水率和静置时间对屈服应力产生的影响。结果表明:1)剪切过程中滩涂试样经过了弹塑性阶段、固液转化阶段和流体阶段,滩涂土壤表现出了静置时间越长,固液转化阶段就越长的性质,且剪切过程中表现出剪切稀化的性质。2)静置时间的增加会导致整体剪切应力和屈服应力同时增加,含水率的增加会导致整体剪切应力和屈服应力的降低,且滩涂土壤存在一个含水率分界点,此含水率分界点在64.5%~67.0%之间,当超过这个含水率分界点的试样的静置时间超过31 h时,试样的屈服应力基本不会再发生较大的波动,大小在2240~4380 Pa之间,此外,静置时间在0~53 h之间且含水率在62.0%~69.5%之间的试样的屈服应力在1870~5410 Pa之间。3)含水率对屈服应力的影响比静置时间的影响更加显著,模型的R^(2)为0.9534,并且在验证试验中,屈服应力的测量值与预测值之间的误差在15.0%以内,都说明了数值模型的可靠性。研究定性和定量地表征了滩涂土壤的流变特性,为滩涂贝类采收机械的研发和优化提供参考。

Distribution of Polychaete Assemblage in Relation to Natural Environmental Variation and Anthropogenic Stress

Polychaete are diverse species of the soft-bottom community, and are often used as indicators in environment monitoring programs. However, the effects of anthropogenic activities and natural environmental variation on polychaete assemblage are rarely addressed. The goals of this study are to identify the effects of natural environmental variation and anthropogenic stress on polychaete assemblage, and to explore the relationship between the polychaete assemblage structure and anthropogenic stress without considering the natural environmental variation. Based on the data collected from the surveys conducted in the tidal flat of Jiaozhou Bay, the relationship between polychaete assemblage structure and environmental variables was determined using multivariate statistical methods including hierarchical cluster analysis, multidimensional scaling(MDS) and canonical correspondence analysis(CCA). The results showed that the polychaete assemblage was dominated by two species, Amphictene japonica and Heteromastus filiformis, and could be divided into two subgroups characterized by high and low species abundance. CCA illustrated that the natural environmental variables including water temperature and the distance from coast had primary effects on the polychaete assemblage structure; while stress of contaminants, such as As and Hg, had the secondary influences; and stress from the aquacultured species, mainly Ruditapes philippinarum, had a limited effect. Colinearity between the natural environmental variables and anthropogenic stress variables caused a critical divergence in the interpretation of CCA results, which highlighted the risk of a lack of information in environment assessment. Glycinde gurjanovae, Sternaspis scutata and Eulalia bilineata may serve as the ‘contamination indicators', which need to be confirmed in future studies.

Study on the double-logarithmic profile of tidal flow velocity in the near-bed layers

Tidal current velocity profile in the near-bed layers has been widely studied. The results showed that velocity profile in the near-bed layer obviously departure from the traditional logarithmic profile, due to the acceleration or deceleration. Although the logarithmic linear profile can reduce the rate of deviation from this, only it is a lower-order approximate solution. In this paper, considering the unsteady and non-linear features of tidal motion, the double logarithmic profile near-bed layers in estuarine and coastal waters is established on the assumption that the turbulent shear stress along the water depth was parabolic distribution, and on the basis of Prandtl＇s mixing length theory and yon Karman＇s self-similar theory. Having been verified the data observed at the West Solent in the south of England, and comparison of the logarithmic linear profile, it found that the double logarithmic profile is more precious than the latter. At last, the discussed results showed that： （1） The parabolic distribution of the tidal shear stresses verified good by the field data and experimental data, can be better reflected the basic features of the tidal shear stress deviating from linear distribution that is downward when to accelerate, upward when to decelerate. （2） The traditional logarithmic velocity profile is the zero-order approximation solution of the double logarithmic profile, the logarithmic linear profile is the first order, and the logarithmic parabolic profile is the second order. （3） Ignoring the conditions of diffusion and convection in the tida movement, the double logarithmic profile can reflect the tidal properties of acceleration or deceleration, so that the calculation of the friction velocity and roughness length are more reasonable. When the acceleration or the deceleration is about zero, the double logarithmic profile becomes the logarithmic profile.

Mechanical Response of Saturated Geological Rock Mass under Tidal Force

In this paper,the mechanical response of saturated geological rock under tidal force is explored by poroelastic theory.First,we use the free energy formula of saturated rock under a tidal force to study the relationships of pore pressure with stress,and stress with strain.Then we analyze the relationship between rock strain and tidal potential by the equilibrium differential equations of saturated rock under tidal force.Finally,we derive the physical relationship between the two parameters (pore pressure and tidal mean stress) of saturated rock and tidal potential.The relationship shows that:pore pressure is directly proportional with tidal potential,but tidal mean stress of saturated rock is inversely proportional with tidal potential.The ratio coefficient is related not only to the Lame coefficients of rock skeletons,but also to the Biot modulus.By using this model to analyze observational well water level of C-18 well which locates in Huili,Sichuan Province,the well level response coefficient (D) was estimated.This way,we derive the Skempton coefficient (B),the coefficient A and C which refer to the response coefficients of pore pressure and tidal stress to tidal potential respectively.Then we compare the differences among each coefficient in coupling and uncoupling conditions.It shows that for saturated rocks,the response of stress and pore pressure to earth tides is a product of coupling,and it is necessary to take into account the coupling effect when we study the mechanical response.The model will provide the basis not only for the study of mechanics and hydrodynamics of well-confined aquifer systems,and the mechanics of faulting under tidal force,but also for quantitative research of the triggering mechanism of tidal forces.

Numerical calculation of hydrodynamic characteristics of tidal currents for submarine excavation engineering in coastal area

In coastal areas with complicated flow movement, deposition and scour readily occur in submarine excavation projects. In this study, a smallscale model, with a high resolution in the vertical direction, was used to simulate the tidal current around a submarine excavation project. The finite volume method was used to solve Navier-Stokes equations and the Reynolds stress transport equation, and the entire process of the tidal current was simulated with unstructured meshes, generated in the irregular shape area, and structured meshes, generated in other water areas.The meshes near the bottom and free surface were densified with a minimum layer thickness of 0.05 m. The volume of fluid method was used to track the free surface, the volume fraction of cells on the upstream boundary was obtained from the volume fraction of adjacent cells, and that on the downstream boundary was determined by the water level process. The numerical results agree with the observed data, and some conclusions can be drawn: after the foundation trench excavation, the flow velocity decreases quite a bit through the foundation trench, with reverse flow occurring on the lee slope in the foundation trench; the swirling flow impedes inflow, leading to the occurrence of dammed water above the foundation trench; the turbulent motion is stronger during ebbing than in other tidal stages, the range with the maximum value of turbulent viscosity, occurring on the south side of the foundation trench at maximum ebbing, is greater than those in other tidal stages in a tidal cycle, and the maximum value of Reynolds shear stress occurs on the south side of the foundation trench at maximum ebbing in a tidal cycle. The numerical calculation method shows a strong performance in simulation of the hydrodynamic characteristics of tidal currents in the foundation trench, providing a basis for submarine engineering construction in coastal areas.

井水位潮汐响应与小地震调制作用的关系

地下流体在地震孕育和发生过程中发挥着至关重要的作用。文中从黑龙江地区18个水位观测井中,筛选出2016年以来符合一定条件的延寿台、通河台、肇东台、甘南台和绥化北林台的井水位数据,应用维尼迪柯夫调和分析方法进行潮汐分析,得到井水位潮汐响应全日波群中的周日波潮汐因子,分析了吉林松原宁江M_(S)5.0、M_(S)5.7、M_(S)5.1地震前后周日波的高值异常变化特征,并结合震源区M_(L)≥3.0小地震调制比异常,进一步探讨了周日波异常与小地震调制作用的关系。结果显示:1)周日波潮汐因子背景变化相对稳定,异常更容易被识别,具有较高的信噪比。2)吉林松原宁江地震前,井水位潮汐响应的周日波异常具有准同步性和形态一致性,主要表现为3个及以上台站的配套性异常。3)吉林松原宁江地震发生在周日波高值配套性异常结束后的2.6个月内,最短仅为7d,具有明显的短临特征,且异常持续时间、异常幅度与震级大小相关。4)吉林松原宁江地震前震源区M_L≥3.0小地震调制比存在低值异常,主要表现为短临特征,井水位潮汐响应的周日波异常反映构造内部应力状态的改变,小地震调制比则能更好地揭示震源区构造应力达到或接近临界状态,对二者进行联合分析有助于识别和捕捉地震前兆短临异常。

不同潮气量机械通气对急性呼吸窘迫综合征大鼠肺纤维化的作用机制

目的 旨在评估不同潮气量机械通气对急性呼吸窘迫综合征(ARDS)大鼠早期肺纤维化的影响,并初步探讨可能的相关机制。方法 通过尾静脉注射油酸来构建ARDS大鼠模型。对照组(n=10)大鼠给予等量等渗盐水。将建模成功的ARDS模型大鼠根据随机数字表法分为模型组、小潮气量组和大潮气量组,每组10只。采用HE染色和Masson染色评估肺组织损伤和肺组织纤维化。采用酶联免疫吸附实验检测肺组织I型胶原蛋白(COL I)、羟脯氨酸(HYP)和转化生长因子(TGF-β1)的含量。采用蛋白免疫印迹检测核因子类胡萝卜素2相关因子2(Nrf2)信号通路相关蛋白。结果 与对照组相比,模型组大鼠的PaO2/FiO2明显降低,而肺W/D值明显升高(P<0.05)。与模型组相比,小潮气量组和大潮气量组大鼠的PaO2/FiO2和肺W/D值均明显升高(P<0.05)。模型组大鼠的肺组织损伤评分、肺纤维化评分、COL I、Hyp和TGF-β1水平、α-平滑肌肌动蛋白(α-SMA)蛋白表达均明显升高(P<0.05),而E-cadherin、Nrf2、血红素氧合酶-1(HO-1)和醌氧化还原酶-1(NQO-1)蛋白表达均明显降低(P<0.05)。与模型组相比,大潮气量组大鼠的肺组织损伤评分、肺纤维化评分、COL I、Hyp和TGF-β1水平、α-SMA蛋白表达均明显升高(P<0.05),而E-cadherin、Nrf2、HO-1和NQO-1蛋白表达均明显降低(P<0.05)。结论 大潮气量机械通气加重ARDS大鼠的肺组织损伤和早期肺纤维化可能是通过抑制Nrf2信号通路的活化来诱导氧化应激、促进上皮间充质转变来实现。小潮气量机械通气可能更有益于ARDS急性期的治疗。

引潮力与潮汐应力对强震触发的研究

本文讨论了在构造应力水平达到岩石破裂临界值时引潮力、潮汐附加应力的动态变化与地震序列之间的关系，选用了中国大陆1970年以来7级以上地震序列资料，分析了引潮力水平分量动态变化与强震发震时间之间的关系，结果显示在一定时空范围内前震、主震及余震序列发震时刻的引潮力存在优势方向，多数地震发震时刻与选取时段引潮力水平分量的方位角相位比平均值仅为35％；对于构造复杂地区，结果显示引潮力水平分量的方位角不仅存在一个优势方向，还明显存在其他优势方向，可能与发震构造有关．根据1966～1976年中国九大地震震源机制解计算潮汐正应力和滑动方向的剪应力及其变化率，结果显示多数地震发震时刻潮汐剪应力接近最大值．

不同类型地震断层上的固体潮汐库仑破裂应力特征

计算和研究了不同类型地震断层上的潮汐库仑破裂应力及其随纬度变化特征;通过对全球20395个地震断层发震时潮汐库仑破裂应力的计算,研究了受到潮汐库仑破裂应力促滑作用的不同类型地震断层的纬度分布特征.结果表明,断层上潮汐库仑破裂应力的性质和特征与断层的类型、走向和位置密切相关,同一时间段内不同类型地震断层土的潮汐库仑破裂应力变化特征不同,同一断层在不同纬度处的潮汐库仑破裂应力的大小和符号都存在较大的差别.潮汐库仑破裂应力对断层的促滑作用,对正断层在低纬和中纬地区较突出、对逆断层在中高纬地区较明显、对走滑断层随纬度增加而减小.

潮汐应力对发震断层作用的统计分析

计算了中国及邻区1069个地震震源处沿主压应力P轴和主张力T轴方向的潮汐应力分量,并分析了这些量对发震断层的作用方式,按纬度区域统计了与潮汐应力促滑作用有关的发震断层类型以及它们与潮汐应力作用方式的关系,得到了如下结论:与潮汐应力促滑作用有关的发震断层数的比例随区域纬度增加有减小趋势。其中,走滑型断层的比例在低纬区较大,而倾滑斜滑型断层的比例在中高纬度区较大;对发震断层有促滑作用的潮汐应力作用方式分增压型和减压型。对整个统计区域而言,与增压型潮汐应力促滑作用有关的发震断层数比例大于与减压型潮汐应力促滑作用有关的发震断层;对不同的纬度区域,不同的潮汐应力作用方式与之促滑的断层类型也有不同的分布特征。

地震主应力方向的附加潮汐应力计算及其对发震断层的作用方式研究

通过对地震震源处沿主压应力P轴和主张应力T轴方向的附加潮汐应力分量的计算 ,在岩石力学莫尔—库仑准则的基础上分析了附加潮汐应力对发震断层的作用方式。分析和计算表明 ,对发震断层有促滑作用的附加潮汐应力作用方式分增压型和减压型 ,增压型潮汐应力增大断层面上的正压力和剪应力 ,促使断层达到破裂滑动条件 ,减压型潮汐应力在一定条件下能降低断层面上的破裂滑动强度 ,同样能促使断层的运动。计算实例显示 ,大部分发震断层受到了附加潮汐应力的增压型或减压型促滑作用。

天文潮汐与地震

从三个方面综述了天文潮汐与地震关系的研究，内容包括，日、月、地球的相对位置与地震；天文潮汐的周期、相位与地震；天文潮汐应力与地震。日、月、地球的相对位置与地震和天文潮汐周期与地震的研究均属于从体积力的角度考虑问题，主要是从宏观角度揭示地震发生时的日月位置分布有何规律性，揭示地震发生时间丛集在潮汐周期变化过程中的相位或时段以及地震活动的潮汐周期。天文潮汐应力与地震的研究从引潮力在地球内部震源处产生的潮汐应力角度出发，着重研究不同类型性质的发震断层与潮汐应力触发的关系，从物理意义上讲，该研究较深层次地切入了问题的实质。分析了采用某些方法和样本研究结果不一致性的原因，并提出了进一步研究的方向。