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.

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.

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.

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.

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.

Discussion on Geodynamics of Three-body Motion

To determine the Earth＇s dynamics and their equations, which are crucial for Earth science research, this paper analyzes the interaction forces in the motion of a three-body system（namely, fixed, active, and passive points）, based on the orbital motion. The mathematical derivation has been conducted strictly according to trigonometric functions with time and space as variables. In spatial transformation, related data items are simplified and replaced reasonably and necessarily according to the physical phenomenon to conduct derivations of planar to spatial transformation, through which the motion point has universal significance. Moreover, the polynomial equation for the dynamics has been obtained. Results indicate that the polynomial expression for the dynamics comprises the tidal force, the powerful mid-latitude Force（PML Force）, and gravitation. Gravitation analysis shows that it is proportional to the dynamics quality, the size of the angular velocity of their deviation from the progenitor-paternal orbital plane＇s center position, and the square of the progenitor orbital plane＇s distance. However, it is inversely proportional to the distance of the paternal orbital plane and not related to another body＇s quality. Some past errors are addressed and some constructive conclusions are offered in the discussion of gravitation.

Two Ocean Tides per Day: Why?

Ocean semi-diurnal tides are suggested qualitatively to be more accurately explained by the vertical tide generating forces of the sun and moon, not by the historically standard horizontal components. It is proposed that the sea level elevations created sequentially at the eastern and then western ocean coastal boundaries propagate seaward as shallow water surface gravity waves and interact without mutual disturbance. In that manner two tides per day are created. Horizontal tide forces generate horizontal ocean currents with speeds of 5 mph at the most. Shallow water tide waves move at about 500 mph in open waters and therefore come much closer to being in tune with the sun and moon transiting across the sky.

Tidal effects of a dark matter halo around a galactic black hole

We investigate tidal forces and geodesic deviation motion in the spacetime of a black hole in a galaxy with a dark matter halo.Our results show that tidal forces and geodesic deviation motion depend on the mass of the dark matter halo and the typical lengthscale of the galaxy.The effect of the typical lengthscale of the galaxy on the tidal force is opposite to that of dark matter mass.With increasing dark matter mass,the radial tidal force increases in the region far from the black hole but decreases in the region near the black hole.Furthermore,the absolute value of angular tidal force monotonously increases with the dark matter halo mass.The angular tidal force also depends on the particle energy,and the effects of dark matter become more distinct for the test particle at higher energies,which differs from the behavior observed in typical static black hole spacetimes.We also present the change in the geodesic deviation vector with dark matter halo mass and the typical lengthscale of a galaxy under two types of initial conditions.