Earthquake prediction is a worldwide scientific problem with high complexity. Guided by the problems in our country’s practice for more than 50 years, relying on the natural phenomena revealed by it, from the perspective of philosophy of science and methodology, we review the methods of empirical induction, reductionist dynamics, induction-deduction and complex dynamic systems. The important role of epistemological factors in prediction is discussed through the examples of the Wenchuan and Tangshan earthquakes. In the new era of earth system science, it is suggested that the evolution of complex dynamic systems of continental deformation and seismic behavior, and that image (pattern) dynamics of bridges for empirical and numerical prediction be taken as the natural view and methodology of earthquake prediction. Although imperfect, it is closer to nature’s holistic, evolutionary and non-linear nature, and can contain and connect various ideas and methods. It is both forward-looking and operable. Earthquakes are predictable and uncertain. There is still considerable room for innovation in forecasting, prediction and disaster mitigation.
In this paper, we show that harmonic analysis results of solid tide observations cannot confirm that gravitational interaction speed is the same as the speed of light. First, from the aspects of the theory of gravity tide, the solid tide theory value and the observed value are synchronized. There is no time lag in harmonic analysis. Second, celestial tidal force is only related to gravitation and has nothing to do with the speed of light. Third, tidal factors only reflect the physical changes in the earth’s medium and the phase difference reflects the elasticity and viscosity of the viscoelastic medium; they have nothing to do with the time lag between universal gravitation and light. Fourth, during the concrete process of analysis, there are too many artificial astronomical operations of corrections, and some corrections may be used improperly in two papers of professor Tang and professor Luo. Fifth, gravity and gravitational waves are two different concepts. Gravity is a spatial property in the interaction of two objects, it is an attribute of the two interacting objects, which does not propagate; Gravity waves are space-time ripples, under specified conditions, which radiation of waves from an oscillating source at the speed of light, and energy loss via radiation of gravitational waves. It is pointed out that the theory of earth tide implies two hypotheses: the speed of gravity is the same as the speed of light, and the time lag between universal gravitation and light is the same as the phase difference of harmonic analysis results, as in two papers of professor Tang and professor Luo. The two hypotheses are incorrect, and the conclusion that gravitation is transmitted at the speed of light cannot be established.Gravity doesn’t take time to propagate.
We use the cross-fault deformation measurement data of Tan-Lu fault zone in Anhui section and “Huoshan seismic window”, and calculate each line observation data for nearly 20 years utilizing the method of fault deformation accumulation rate and annual sliding velocity ratio. We analyze the fault activity, energy accumulation, and evolution characteristics of whole space in the study area, comb the various points across the fault deformation characteristics of the fault zone and the change process, and discuss the relation between fault activity and moderate earthquakes in Anhui province and adjacent areas from the angle of space distribution to the time evolution characteristics. Our results show that: 1) The cumulative rate of fault deformation in the Anhui section of the Tan-Lu fault zone is higher than that of the “Huoshan seismic window”. Before the earthquake, there are high-value clusters, regional boundaries, high-density low-value gradient zones, etc., showing the background of stress accumulation before the earthquake. 2) The fault activity in Anhui area is obviously affected by the overall activity of the Tanlu fault zone, and the regional and periodic changes are significant. (3) The annual slip rate of fault deformation has a certain indication effect on the judgment of earthquake activity, mainly as before the earthquake. The characteristics of high-value anomalies of 2 months to 1 year, and group anomalies of multiple points, increase with increased magnitude.
We select the seismic phase reports of Tangshan region by Hebei digital seismic network from 2008 to 2018 and calculate the wave velocity ratio by multi station-multi earthquake method and single station-multi earthquake method. We then analyze the characteristics of wave velocity ratio change combined with seismic activity. The results show that using the velocity ratio by multi station-multi earthquake method is more stable, but the results by the single station-multi earthquake method show more detail, and low value anomaly appears in varying degrees before ML≥4.5 earthquakes in the Tangshan region. The locations of abnormal stations correspond to earthquakes, to some extent.
The Niger delta displays the classic, well-developed zones of a large delta province with an onshore to shelfal zone of growth fault-controlled depocenters, a well-developed belt of “shale diapirs” around the outer shelf-slope area, and a fold and thrust belt in the slope area. The upper extensional zone develops different loading and the subsequent formation of large growth fault, most of which are normal and listric. A middle translational zone is dominated by mud diapirs and shale ridges beneath the upper slope. The thrust belt is characterized by oceanward verging, commonly imbricated, thrusts and folds. On the basis of the structural characteristics, we analyze the forming mechanism of the structure. We reveal the structural characteristics of the M region on the conversion zone in Niger delta, and the structure of the research area is divided into three types, based on evolution and features. On this basis, it is proposed that the main traps in the study area are tectonic-lithologic traps. This paper provides new theoretical guidance for deep water exploration in Niger delta basin.
In cross-fault deformation measurement data processing, it is common to use unequally spaced raw data for calculations, leading to a series of problems, such as time calculation, synchronization, master-slave relations, comparability, etc. For these questions, we design a cross-fault deformation data calculation method from reasonable and optimal requirements, examining their adaptability in various algorithms. Our research contributes to the improvement and development of cross-fault deformation measurement data processing.
By using the GPS horizontal velocity field of 2009-2015 and the negative dislocation model of DEFNODE, we invert for fault locking and fault slip deficit of the Red river fault zone, and analyze the potential seismic danger, combining with the results of precision positioning of small earthquakes. The results show that the fitting results of GPS horizontal observation value and the simulated value are good, and there is also a certain correlation between the distribution of minor earthquakes and the degree of fault locking. The inversion results show that the middle section of the Red river fault is different from the south to north, and that the northern part is basically completely locked. The fault slip deficit rate is relatively large, which has the potential danger of a larger earthquake, and the degree of locking of the southern fault is much weaker. The locking degree of other sections of the Red river fault are also much weaker, and there are no strong blocking states in these sections, especially in the southern section of the fault zone. The fracture is basically transformed from the locking state to the creep state at 2-5 km depth, the fault slip deficit rate is relatively small, and the possibility of larger earthquakes in this section is much smaller.
On January 23, 2018, a 7.9-magnitude earthquake occurred in the gulf of Alaska. The Okada model is used to calculate the initial tsunami field information, and the COMCOT model is used to simulate the tsunami propagation. The simulated amplitude and arrival time of the tsunami wave are compared with the measurements at the DARTs station. The amplitude difference is within 4 cm, and the time difference is within 4 minutes; furthermore, the simulation results agree with the measurements, which reveals that the intensity of the tsunami caused by the Alaska earthquake is weak and reflects that the selection of the parameters of the initial tsunami field is reasonable and effective. Also, the results of tsunami simulation are reliable.
The partial errors-in-variables model of variance component estimation precision evaluation theory needs improvement, so we apply the SUT sampling method to the minimum norm quadratic unbiased estimation of Partial EIV model. Using the variance component estimation modified stochastic model, we then use it as a priori information to obtain the weighted mean and second-order precision information by the SUT sampling method. Considering the deviation of the nonlinear model, the deviation correction is carried out, and the second-order precision information is calculated by the SUT method. An experiment shows that combining SUT method and variance component estimation to deal with Partial EIV model can effectively avoid complicated derivation operation, and gets more accurate parameter values and reasonable second-order accuracy information. It also shows the necessity of deviation correction.
A new random walk process considering between-epoch variations of ionospheric delays is employed. GPS data sets collected from 170 globally distributed stations of the International GPS Service(IGS) network in a one-month period(July 2016) are exclusively processed in static and simulated kinematic modes. The convergence time and positioning accuracy are used as indicators to validate the stochastic modeling for ionospheric parameters. For the convergence performance, the proposed model is not affected by the spectral density of the random walk process, while the convergence performance is much better than the traditional random walk process at the small spectral density. Positioning accuracy derived from the proposed model and the white noise process are comparable, with an average RMS of 5 cm in static mode, and 8 cm in kinematic mode.
Due to uneven distribution of the international GNSS service (IGS) organization tracking stations in high latitudes, the observation data used for ionospheric fitting modeling are uneven and incomplete, leading to inadequate modeling accuracy of the total ionospheric content in this region. When the ionospheric fit model is established using observation data from these IGS tracking stations, the grid output values of the ionospheric fitting model contain a large number of negative and zero values, which are contrary to the actual physical meaning of the ionosphere. Aiming at this problem, we adopt the ionospheric grid output negative point, zero point to join inequality constraint conditions, and the inequality constraint least square method, to calculate parameters of optimization. Experimental results show that the algorithm shows a significant improvement in reducing the large number of zeros and negative values in the sparse high-latitude areas, and modeling accuracy of the global ionosphere model is also improved.
This paper calculates ZTD for Galileo, GPS and GPS/Galileo, with PPP ZTD estimation method using observation data from 14 MGEX stations. The RMSs of Galileo-GPS ZTD differences range from 8 mm to 16 mm. The average of RMSs of total stations is 12.3 mm, which proves that Galileo-ZTD agrees well with GPS-ZTD and that the accuracy of Galileo real-time ZTD is satisfactory. Meanwhile, IGS final ZTD products are adopted to assess the performance of each solution. The result shows that the accuracy is improved by 5%－35% when compared to GPS single solutions, and 25%－51% to Galileo single solutions.
We propose a method based on weighted mean temperature derived from GPT2w to retrieve precipitable water vapor, and analyze the influence of the weighted mean temperature with systematic correction derived from GPT2w on precipitable water vapor. The results show that the precision of precipitable water vapor based on weighted mean temperature derived from GPT2w is comparable with that of precipitable water vapor based on weighted mean temperature by Bevis formula, and that weighted mean temperature with systematic correction has little influence on precipitable water vapor, the improvement rate is less than 1%.
In the paper, we describe in detail the observation principle, then introduce the design of a new model AC geo-electrical resistivity measurement system. Finally, we show the preliminary experimental results, carried out in Jiangning observatory, Jiangsu province. These experimental results show that AC geo-electrical resistivity observation method can decrease the electromagnetic interference caused by the environment, meeting geo-electrical resistivity observation requirements.It is proved that the AC geo-electrical resistivity observation method could obtain high signal-noise ratio when working in strong interference observation environment, especially to decrease the interference caused by subway.
In this study, we use gravity observation data from two stations in Lanzhou and Gaotai from 2011 to 2015. The MS6.6 earthquake, which occurred at the junction of Minxian and Zhangxian on July 22, 2013, is taken as the research object. The detrended fluctuation analysis method is used to deal with the continuous observation data of the two stations, and to try to extract anomaly information on gravity before the earthquake. The results show, with 9.4 times the standard deviation of the fractal index of the station as abnormal threshold, that there is a similar abnormal increase process before the earthquake on the gravity fractal index of the two stations. This indicates the gravity variation before the earthquake, has a continuous feature and shows a long-range correlation. This may be important information related to the earthquake. The study of this gravity fractal exponent is only preliminary and exploratory. Combined with the research results of other scholars, it is preliminarily speculated that this abnormal change may be related to the material migration in the middle and lower crust and even the upper mantle.
With three Burris relative gravimeters, we study the effect of feedback scale factor in the meter system on relative gravity observation results. The study indicates there are linear relationships between the feedback scale factor and meter readings of Burris. The larger FBK correlation, the larger change of meter readings, and the positive or negative FBK correlation, determine the direction of gravimeter readings variation as feedback scale factor increases. When the three Burris gravimeters are employed to survey a gravity difference that is 17 mGal between two sites, there are variations of gravity difference, although the changes of feedback scale factor are similar and the largest variation is 0.140 mGal. When one Burris gravimeter is used to measure a gravity difference between two sites, where the FBK correlations are -14.7 mGal and 2.2 mGal, the change of measured gravity difference is larger than 0.300 mGal, if the feedback scale factor changes 2%.
Based on comprehensive collection and systematical analysis of China water temperature observatory dynamics in 2008 within nearly 300 wells, we first ascertain the relationship between water temperature dynamics and earth tide and analyze anomalous change before and after the May 12th Wenchuan MS8.0 earthquake. Second, we clear the normal drill water temperature dynamics in year time and the basic features of temperature tidal effects, determining that there are 14 abnormal wells before earthquake. We summarize anomaly patterns and the spatial-temporal characteristics, analyzing coseismic corresponding characteristics of 125 wells. Finally, we further demonstrate possibilities and problems in water temperature and seismic monitoring, and come up with upgrading the hydrothermal observation network to a geothermal observation network, to explore the new ideas in the study of the relationship between crust thermal and seismic activities.
Using the AlphaGUARD P2000 portable measuring radon instrument to regularly measure the soil radon of the Baodi fault, we determine a scientific and effective soil radon observation method for the area, and analyze the relationship between soil radon concentration and influencing factors, including soil property and moisture, fault structure and activity. We obtain the characteristics of data changes in the research area of the Baodi fault, which has reference value for the application of soil radon observation in seismic monitoring and fault activity tracking. In addition, these results further provide new observation methods and application examples for earthquake situation tracking and anomaly identification.
In this paper, the soil radon(Rn) concentration of the Gaoqiao fault zone is measured. The soil radon concentration characteristics of two lines in Gongjiaqiao and Zhongyangpo are analyzed, and the results, combined with the structural sections, shows the location, scale and other characteristics of the fracture. The results show that the background values of radon concentration in soil are 34 138 Bq/m3 and 26 960 Bq/m3. The lower limits of the high value are 53 580 Bq/m3 and 53 322 Bq/m3, and the anomalous areas indicate that the fracture at Gongjiaqiao is not more than 60 meters and not less than 40 meters at Zhongyangpo.
The PBO borehole strainmeter reaches 1 sps sampling. With the Mexico 8.1 earthquake on September 8, 2017 as an example, we analyze the seismic signals of 14 strainmeters and seismeters, showing that the seismic waves recorded by strainmeters meet the radiation law of transmission. The characteristics of the coseismic response of strainmeters and seismeters based on S-transform are analyzed for stations with different epicenter distances, and the coseismic responses of the strainmeters are very coherent with the seismeters’ signals. The frequency of the strainmeters is mainly below 025 Hz. After seismic time series data calculation, we find that, in the coseismic phase, the main direction of strain points to the epicenter.
