The Change in Outgoing Long-wave Radiation before the Ludian Ms6.5 Earthquake Based on Tidal Force Niche Cycles

The cycle process of the tidal force niche for the Ludian M_S6.5 earthquake occurring in Ludian County, Yunnan Province, China on August 3, 2014 was calculated. The earthquake occurred near the middle point phase. It indicates that the type of seismogenic fault that the tide force acted on belongs to the thrust fault. According to the tidal niche cycle,the abnormal OLR( Outgoing Long-wave Radiation) change was analyzed based on NOAA satellite data around the whole land area of China before and after the earthquake.The result shows that the OLR changed evidently with tide force change. Temporally,the change went through the evolution process of initial OLR rise → strengthening → abnormal peaking → attenuation → returning to normal; and spatially,the abnormal area wound its way along the Zhaotong-Ludian fault and went through a scattered → conversion →scattered process. This process is similar to the change process of rock breaking under stress loading. The results indicate that the tidal force of a celestial body could trigger an earthquake when the tectonic stress reaches its critical breaking point and the OLR anomaly is proportional to the seismic tectonic stress change. It is of great use to combine OLR and tidal force in earthquake precursory observation.

Study on Correlation of Tidal Forces with Global Great Earthquakes

The correlation between the celestial tidal forces and earthquakes has been a controversial problem, although its research history is very long. This paper analyzes the relation between the tidal forces and all the earthquakes of magnitudes no less than 7.0 which occurred in the entire world from year 1900.0 to 2000.0 by calculating tidal forces and the run tests which yields the runs of earthquakes near the extreme and non-extreme values of the tidal forces. It is shown that the occurrence of an earthquake is relevant to the tidal forces. From the analysis of the relation between the ecliptic longitudes of the lunar ascending node and the seismic activities of the principal seismic belts and regions in the world, it is also shown that the lunar node tide is possibly one of the important astronomical contributing factors of the seismic activities there. The results enrich and support the relevant study of the relation between celestial tidal forces and earthquakes.

Evidence of earthquakes triggered by the tidal force of the sun and the moon——On the temporal characteristics of the earthquakes in Xingtai,Hejian and Tangshan

Studies by many scientists show that Hebei, China is an area with strong correlation between the tidal force and the occurrences of major earthquakes, the Xingtai earthquake of 1966, the Hejian earthquake of 1967 and the Tangshan earthquake of 1976 were triggered by the tidal force, in this paper the study on the common characteristics of their occurrence times confirms these facts. The computed times of maximum horizontal of the semi diurnal solid tide tidal force show that the occurrence times of the above mentioned earthquakes were close to the times of maximum horizontal tidal force of the semi diurnal solid tide at new moon or full moon. The Longyao earthquake of M =6.8, the Ningjin earthquake of M =7.2 and the Hejian earthquake of M =6.3 occurred tens of minutes after the maximum horizontal tidal force of the semi diurnal solid tides, and the Tangshan earthquake of M =7.8 occurred 16 minutes before the maximum horizontal tidal force. The tidal forces were directed to the west. This is their temporal characteristic. It is generally accepted that the 1969 Bohai earthquake of M =7.4 and the 1975 Haicheng earthquake were not triggered by the tidal force. These events did not show such characteristics. The temporal characteristics of the earthquakes indicate that the occurrences of these events were not random, but were controlled by the tidal force from the sun and the moon, and triggered by the tidal force. These facts agree with the triggering mechanism of the tidal force, are evidences of earthquakes triggered by tidal force.

A Study on Tidal Force Triggering of the Wenchuan M_S8.0 Earthquake and Its Strong Aftershocks

By calculating the azimuth, phase angle and change rate of tidal force, and contrasting their rupture types, we find that in 6 of 11 reverse faulting earthquakes, the angles between the direction of the horizontal tidal force and compressive principal stress are within 33°, the vertical phase angles of all 8 strike-slip earthquakes are in the upward peak section and the vertical phase angles of two extensional normal faulting earthquakes are in the downward peak section. According to the above statistics, the mechanism of tidal force triggering of the Wenchnan Ms8. 0 Earthquake and its strong aftershocks is discussed.

The influence of explicit tidal forcing in a climate ocean circulation model

The eight main tidal constituents have been implemented in the global ocean general circulation model with approximate 1° horizontal resolution.Compared with the observation data,the patterns of the tidal amplitudes and phases had been simulated fairly well.The responses of mean circulation,temperature and salinity are further investigated in the global sense.When implementing the tidal forcing,wind-driven circulations are reduced,especially those in coastal regions.It is also found that the upper cell transport of the Atlantic meridional overturning circulation（AMOC） reduces significantly,while its deep cell transport is slightly enhanced from 9×106m3/s to 10×106 m3/s.The changes of circulations are all related to the increase of a bottom friction and a vertical viscosity due to the tidal forcing.The temperature and salinity of the model are also significantly affected by the tidal forcing through the enhanced bottom friction,mixing and the changes in mean circulation.The largest changes occur in the coastal regions,where the water is cooled and freshened.In the open ocean,the changes are divided into three layers：cooled and freshened on the surface and below 3 000 m,and warmed and salted in the middle in the open ocean.In the upper two layers,the changes are mainly caused by the enhanced mixing,as warm and salty water sinks and cold and fresh water rises;whereas in the deep layer,the enhancement of the deep overturning circulation accounts for the cold and fresh changes in the deep ocean.

The impact of oceanic processes on the transient climate response: a tidal forcing experiment

In this study, the impact of oceanic processes on the sensitivity of transient climate change is investigated using two sets of coupled experiments with and without tidal forcing, which are termed ExpTide and ExpControl,respectively. After introducing tidal forcing, the transient climate response(TCR) decreases from 2.32 K to 1.90 K,and the surface air temperature warming at high latitudes decreases by 29%. Large ocean heat uptake efficiency and heat storage can explain the low TCR in ExpTide. Approximately 21% more heat is stored in the ocean in ExpTide(1.10×10^24 J) than in ExpControl(0.91×10^24 J). Most of the large ocean warming occurs in the upper 1 000 m between 60°S and 60°N, primarily in the Atlantic and Southern Oceans. This ocean warming is closely related to the Atlantic Meridional Overturning Circulation(AMOC). The initial transport at mid-and high latitudes and the decline in the AMOC observed in ExpTide are both larger than those observed in ExpControl. The spatial structures of AMOC are also different with and without tidal forcing in present experiments. The AMOC in ExpTide has a large northward extension. We also investigated the relationship between AMOC and TCR suggested by previous studies using the present experiments.

Tide simulation using the mild-slope equation with Coriolis force and bottom friction

Since the mild-slope equation was derived by Berkhoff （1972）,the researchers considered various mechanism to simplify and improve the equation,which has been widely used for coastal wave field calculation.Recently,some scholars applied the mild-slope equation in simulating the tidal motion,which proves that the equation is capable to calculate the tide in actual terrain.But in their studies,they made a lot of simplifications,and did not consider the effects of Coriolis force and bottom friction on tidal wave.In this paper,the first-order linear mild-slope equations are deduced from Kirby mild-slope equation including wave and current interaction.Then,referring to the method of wave equations’ modification,the Coriolis force and bottom friction term are considered,and the effects of which have been performed with the radial sand ridges topography.Finally,the results show that the modified mild-slope equation can be used to simulate tidal motion,and the calculations agree well with the measurements,thus the applicability and validity of the mild-slope equation on tidal simulation are further proved.

Expiratory Flow Limitation and Its Relation to Dyspnea and Lung Hyperinflation in Patients with Chronic Obstructive Pulmonary Disease: Analysis Using the Forced Expiratory Flow-Volume Curve and Critique

Background: Tidal expiratory flow limitation (tEFL) is defined as absence of increase in air flow during forced expiration compared to tidal breathing and is related to dyspnea at rest and minimal exertion in patients with chronic airflow limitation (CAL). Tidal EFL has not been expressed as a continuous variable (0% - 100%) in previous analyses. Objective: To relate the magnitude of tEFL to spirometric values and Modified Medical Research Council (MMRC) score and Asthma Control Test (ACT). Methods: Tidal EFL was computed as percent of the tidal volume (0% - 100%) spanned (intersected) by the forced expiratory-volume curve. Results: Of 353 patients screened, 192 (114 M, 78 F) patients (136 with COPD, 56 with asthma) had CAL. Overall characteristics: (mean ± SD) age 59 ± 11 years, BMI 28 ± 7, FVC (% pred) 85 ± 20, FEV1 (% pred) 66 ± 21, FEV1/FVC 55% ± 10%, RV (% pred) 147 ± 42. Tidal EFL in patients with tEFL was 53% ± 39%. Using univariate analysis, strongest correlations were between tEFL and FVC and between tEFL and RV in patients with BMI < 30 kg/m2. In patients with nonreversible CAL, tEFL was positively associated with increasing MMRC, negatively with spirometric measurements, and positively with RV/TLC. In asthmatics, ACT scores were higher in patients with mean BMI ≥ 28 kg/m2 (p < 0.00014) and RV/TLC values > 40% (p < 0.03). Conclusions: Dyspnea is strongly associated with tEFL and lung function, particularly in patients with nonreversible CAL. Air trapping and BMI contribute to tEFL.

Tidal force effects and bound orbits in null naked singularity spacetime

Naked singularities form during the gravitational collapse of inhomogeneous matter clouds.The final nature of the singularity depends on the initial conditions of the matter properties and types of matter profiles.These naked singularities can also be divided into two types:null-like and timelike singularities.The spacelike singularity of the Schwarzschild black hole can be distinguished from the null and timelike naked singularity spacetimes.In light of this,we investigate the precession of timelike bound orbits in the null naked singularity spacetime,as well as tidal force effects and geodesic deviation features.As a result,we find that the orbital precession of the timelike bound orbits in null naked singularity spacetime could be distinguished from the Schwarzschild precession case.The radial component of the tidal force has an intriguing profile,whereas the angular component has a profile that is comparable to that of a Schwarzschild black hole scenario.The geodesic deviation equation is then solved numerically,yielding results that resemble Schwarzschild black holes.These characteristic features can then be used to discern among these singularities.

Estimating peak response frequencies in a tidal band in the seas adjacent to China with a numerical model

A numerical method is designed to examine the response properties of real sea areas to open ocean forcing. The application of this method to modeling the China＇s adjacent seas shows that the Bohai Sea has a highest peak response frequency （PRF） of 1.52 d^-1; the northern Yellow Sea has a PRF of 1.69 d^-1; the Gyeonggi Bay has a high amplitude gain plateau in the frequency band roughly from 1.7 to 2.7 d^-1; the Yellow Sea （includ- ing the Gyeonggi Bay）, the East China Sea shelf and the Taiwan Strait have a common high amplitude gain band with frequencies around 1.76 to 1.78 d^-1 and are shown to be a system that responds to the open ocean forcing in favor of amplifying the waves with frequencies in this band; the Beibu Gulf, the Gulf of Thailand and the South China Sea deep basin have PRFs of 0.91, 1.01 and 0.98 d^-1 respectively. In addition, the East China Sea has a Poincare mode PRF of 3.91 d^-1. The PRFs of the Bohal Sea, the northern Yellow Sea, the Bei- bu Gulf and the South China Sea can be explained by a classical quarter （half for the Bohai Sea） wavelength resonance theory. The results show that further investigations are needed for the response dynamics of the Yellow Sea-East China Sea-Taiwan Strait system, the East China Sea Poincare mode, the Talwan Strait, and the Gulf of Thailand.

Modified Saint-Venant equations for flow simulation in tidal rivers

Flow in tidal rivers periodically propagates upstream or downstream under tidal influence. Hydrodynamic models based on the Saint-Venant equations （the SVN model） are extensively used to model tidal rivers. A force-corrected term expressed as the combination of flow velocity and the change rate of the tidal fevel was developed to represent tidal effects in the SVN model. A momentum equation incorporating with the corrected term was derived based on Newton＇s second law. By combing the modified momentum equation with the continuity equation, an improved SVN model for tidal rivers （the ISVN model） was constructed. The simulation of a tidal reach of the Qiantang River shows that the ISVN model performs better than the SVN model. It indicates that the corrected force derived for tidal effects is reasonable; the ISVN model provides an appropriate enhancement of the SVN model for flow simulation of tidal rivers.

A Review on Tidal Triggering of Earthquakes

Research of tidal triggering of earthquakes in recent years is systematically reviewed,focusing on the relationship between the phases of the moon and seismic activity,earthquakes triggered by tidal forces and its components,based on the large sample statistics to discuss the tidal triggering of an earthquake.The relationship between the phase of the moon and seismic activity is a preliminary study of tidal triggering of earthquakes,and the modulation ratio is a quantitative description of it.Using the resolution of tidal stress to study seismic activity is a way to reveal the relationship between the tides and earthquakes from the mechanics point of view.Large sample statistics is another way to study the relationship between the tidal and earthquake from the view of statistics.In many statistical methods,Schuster's test is used more widely,which takes many factors into account,such as focal mechanism,tidal stress,and statistical tests to quantitatively analyze the tidal triggering effect on earthquakes.

Improved Numerical Computing Method for the 3D Tidally Induced Lagrangian Residual Current and Its Application in a Model Bay with a Longitudinal Topography

An improved method for computing the three-dimensional(3 D)first-order Lagrangian residual velocity(uL)is estab-lished.The method computes tidal body force using the harmonic constants of the zeroth-order tidal current.Compared with using the tidal-averaging method to compute the tidal body force,the proposed method filters out the clutter other than the single-frequency tidal input from the open boundary and obtains uL that is more consistent with the analytic solution.Based on the new method,uL is calculated for a wide bay with a longitudinal topography.The strength and pattern of uL are mostly determined by the parts of the tidal body force related to the vertical mixing of the Stokes’drift and the Coriolis effect,with a minor contribution from the advection effect.The geometrical shape of the bay can influence uL through the topographic gradient.The magnitude of uL increases with the increases in tidal energy input and vertical eddy viscosity and decreases in terms of the bottom friction coefficient.

Research on distinguishing method and mechanism of tidal deformation anomalies before large earthquakes

By analyzing the digital tilt tidal observations at Yongsheng station and strain tidal observations at Houma station, this paper suggests that the solid tidal force might trigger tiny abrupt deformation when the seismogenic system enters into an instable critical state. The step and abrupt changes correlate to a certain extent to the direction of tidal force and the orientation and size of tidal shear stress along the fault strike. In the paper, we study for the first time the relationship between deformation anomaly and additional tidal stress in order to approach the physical mechanism of anomalies appeared immediately before earthquakes and the distinguishing method.

强涌潮水流条件下直立圆柱体的涌潮作用力试验研究

为厘清强涌潮河口直立式圆柱体受到的涌潮作用力与涌潮水流条件、圆柱直径的关系,通过涌潮水槽模型试验研究了三种直径直立圆柱在不同潮前水深、涌潮高度条件下的涌潮作用力。结果表明,强涌潮的涌潮作用力为直立圆柱受到冲击力叠加该时刻的水流绕流阻力、圆柱前后水位压差力。通过数据回归分析,得到了一个无量纲涌潮作用力计算公式。该公式表明,涌潮作用力分析计算除了要考虑涌潮高度、圆柱直径外,潮前水深也是关键因素,且涌潮作用力与圆柱直径之间存在显著的非线性关系。

现行黄河口分汊河道的分流特征及其影响机制

自2013年黄河尾闾河道出汊形成双槽入海的河口汊道,控制了河口流量的分配,但其分流特征及其影响机制尚不清楚。本文基于Delft3D构建了黄河口汊道的水动力三维数值模型,模拟了不同工况下河口汊道的分流特征,揭示了其影响机制。结果表明:河口汊道的分流不对称性随流量的增加而减小,流量增加加大了东汊与北汊河道的水位梯度差,使得从东汊河道的流量增量较北汊河道大,河流流量的分配更加均匀。潮汐作用增强了河口汊道的流量不对称性,而随着径流量的增加,潮汐的增强作用逐渐减弱。这主要由于在半日潮的作用下,东汊和北汊河道水位梯度的差异,形成河口潮汐的“东阻北促”效应,增强了河口汊道的分流不对称性。

Astronomic background of global huge earthquakes at beginning of 21st century

Since the beginning of the 21st century,major earthquakes have frequently occurred worldwide.To explore the impact of astronomical factors on earthquakes,in this study,the statistical analysis method of correlation is used to systematically analyze the effects of astronomical factors,such as solar activity,Earth’s rotation,lunar declination angle,celestial tidal force,and other phenomena on M≥8 global earthquakes at the beginning of the 21st century.With regard to solar activity,this study focuses on the analysis of the 11-year and century cycles of solar activity.The causal relationship of the Earth’s rotation is not obvious in this work and previous works;in contrast,the valley period of the solar activity century cycle may be an important astronomical factor leading to the frequent occurrence of global earthquakes at the beginning of the 21st century.This topic warrants further study.

Tidal Forces in Dyonic Reissner-Nrdstrom Black Hole

This paper investigates the tidal as well as magnetic charge effects produced in dyonic Reissner-Nordstroom black hole.We evaluate Newtonian radial acceleration using radial geodesics for freely falling test particles.We establish system of equations governing radial and angular tidal forces using geodesic deviation equation and discuss their solutions for bodies falling freely towards this black hole.The radial tidal force turns out to be compressing outside the event horizon whereas the angular tidal force changes sign between event and Cauchy horizons unlike Schwarzschild black hole.The radial geodesic component starts decreasing in dyonic Reissner-Nordstroom black hole unlike Schwarzschild case.We conclude that magnetic charge strongly affects the radial as well as angular components of tidal force.

RELATIONSHIP BETWEEN THE VARIATION OF LUNISOLAR TIDAL FORCE AND EARTHQUAKES IN TAI WAN

The paper presents a discussion of the relationship between the variance ratio of the lunisolar tidal force prior to and after the attacks of the major earthquakes (Ms≥7.0) in Taiwan Province, China in the 20th century. It concludes that a close connection exists between them: the variance of the lunisolar tidal force might be a trigger to the occurrence of disastrous earthquakes in the Province.

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．