Calculating Skempton constant of aquifer from volume strain and water level response to seismic waves at Changping seismic station

Based on linear poroelastic theory of ideal poroelastic media, we apply the mathematic expression between pore pressure and volume strain for well-aquifer system to analyzing the observed data of water level and volume strain changes aroused by Sumatra MS8.7 (determined by China Seismic Networks Center) seismic waves at Changping, Beijing, station on December 26, 2004 from both time and frequency domain. The response coefficients of water level fluctuation to volume strain are also calculated when seismic waves were passing through confined aquifer. A method for estimating Skempton constant B is put forward, which provide an approach for understanding of the characteristics of aquifer.     

Application of Wavelet Decomposition to Removing Barometric and Tidal Response in Borehole Water Level

Wavelet decomposition is used to analyze barometric fluctuation and earth tidal response in borehole water level changes. We apply wavelet analysis method to the decomposition of barometric fluctuation and earth tidal response into several temporal series in different frequency ranges. Barometric and tidal coefficients in different frequency ranges are computed with least squares method to remove barometric and tidal response. Comparing this method with general linear regression analysis method, we find wavelet analysis method can efficiently remove barometric and earth tidal response in borehole water level. Wavelet analysis method is based on wave theory and vibration theories. It not only considers the frequency characteristic of the observed data but also the temporal characteristic, and it can get barometric and tidal coefficients in different frequency ranges. This method has definite physical meaning.     

A new LS+AR model with additional error correction for polar motion forecast

Polar motion depicts the slow changes in the locations of the poles due to the earth’s internal instantaneous axis of rotation. The LS+AR model is recognized as one of the best models for polar motion prediction.Through statistical analysis of the time series of the LS+AR model’s short-term prediction residuals,we found that there is a good correlation of model prediction residuals between adjacent terms.These indicate that the preceding model prediction residuals and experiential adjustment matrixes can be used to correct the next prediction results,thereby forming a new LS+AR model with additional error correction that applies to polar motion prediction.Simulated predictions using this new model revealed that the proposed method can improve the accuracy and reliability of polar motion prediction.In fact,the accuracies of ultra short-term and short-term predictions using the new model were equal to the international best level at present.     

The ONAD method for solving the SH-wave equation and simulation of the SH-wave propagation in the Earth’s mantle

The optimal nearly-analytic discrete(ONAD) method is a new numerical method developed in recent years for solving the wave equation.Compared with other methods,such as popularly-used finite-difference methods,the ONAD method can effectively suppress the numerical dispersion when coarse grids are used.In this paper,the ONAD method is extended to solve the 2-dimensional SH-wave equation in the spherical coordinates.To investigate the accuracy and the efficiency of the ONAD method,we compare the numerical results calculated by the ONAD method and other methods for both the homogeneous model and the inhomogeneous IASP91 model.The comparisons indicate that the ONAD method for solving the SH-wave equation in the spherical coordinates has the advantages of less numerical dispersion,small memory requirement for computer codes,and fast calculation.As an application,we use the ONAD method to simulate the SH-wave propagating between the Earth’s surface and the core-mantle boundary(CMB).Meanwhile,we investigate the SH-wave propagating in the mantle through analyzing the wave-field snapshots in different times and synthetic seismograms.     

Studying surface structure in desert areas using multiple kinds of surface wave data

Shallow surface wave methods are mostly used for investigation of the surface velocity structure in environmental and engineering geophysics in non-desert areas. For the special geological features of the Takelamagan Desert area, we use the multi-channel analysis of surface wave （MASW） method to process multi-channel shallow surface wave records to determine the near surface velocity structure in the desert area. We also process, analyze, and compare the surface waves in many-trace records extracted from the oil exploration shot gathers in the area. We show that the MASW method can determine detailed shallow velocity structure in desert areas and the many-trace records can be used to get detailed deep geological structure. The combination of the two different datasets can obtain the exact velocity structure upper 60 m depth in the survey area.     

Estimation of characteristic parameters m region-time-length algorithm and its application

On the basis of gap＇s temporal-spatial characteristics in and around source area before an earthquake, we propose a method to estimate characteristic parameters （characteristic distance and time） in the region-time-length （RTL） algorithm and introduce the method of correlation coefficient developed by some authors in 2006 to determine the characteristic parameters. The anomalous seismic activities before four moderately strong earthquakes occurred in the northwestern and southwestern China in recent years are studied by the two methods. The results show that the method to estimate characteristic parameters advanced in this paper is a simple one, which possesses a physical meaning and is well applicable to the four moderately strong earthquakes studied.     

弱各向异性介质中的P-SV波近似反射系数计算

We introduce the Thomsen anisotropic parameters into the approximate linear reflection coefficient equation for P-SV wave in weakly anisotropic HTI media. From this we get a new, more effective, and practical reflection coefficient equation. We performed forward modeling to AVO attributes, obtaining excellent results. The combined AVO attribute analysis of PP and PS reflection data can greatly reduce ambiguity, obtain better petrophysical parameters, and improve parameter accuracy.     

Application Effect of CEMP in the Foreland Basin on the Western Edge of Ordos

Foreland basins on the western edge of Ordos are characterized by typical loess geomorphologic features. Its surface is severely cut, and its underground geological structures are complicated.Making use of the advantage of CEMP in exploration in frontland as well as successful multi-year exploration experiences in West China, we first employed the CEMP method to conduct exploration on the western edge of the Ordos basin and its surrounding areas. The practices proved that rich and reliable geological results have been achieved with the CEMP method in complicated areas covered with loess. This can provide important evidence for researching the contact relationship among basins and mountains, structural feature of target layers and predict favourable areas.     

The Program Application on the Relative Method of Fuzzy Mathematics

The method of fuzzy mathematics for simultaneous assessment of time and intensity of earthquake hazards has been studied.This method is based on fundamental statistical indices of regional seismicity.Applying the retrieval method of fuzzy information,we can classify the time and intensity into several intervals and classes of seismic activity,then the possible time interval of large earthquakes with magnitude of M≥Ms can be estimated in a given region.Based on the preceding idea,an FRPP program is constructed.For the automatic data processing when this method is used,it is very important to design the statistical process of each index decomposition so that the program could be fit to a different sample discussed.There are some functions in the FRPP program.The man-made impact on results is reduced to the minimum as far as possible.Computation time is saved.There is a menu on which time interval,index,intensity class,and output data all can be selected.The catalog input that can be displayed on the scre     

Impact history and origin of lunar meteorite Northwest Africa 15528

No samples from the Moon’s far side have been returned to Earth. Thus, lunar meteorite study can deepen the understanding of the Moon’s far side(if we can identify which lunar meteorites came from the Moon’s far side). The Northwest Africa(NWA) 15528 meteorite is a lunar feldspathic regolith breccia meteorite and we speculated it might originate from the Feldspathic Highlands Terrane(FHT) on the far side of the Moon. Here, we report detailed petrography, major and trace elements, and noble gas(H...     

PROSPECTING FOR THE HIDDEN ACTIVE FAULT BY MEASURING THE 218p0 AND 210p0

A method of prospecting for the concealed active fault by simultaneous measuring both 218Po and 210Po is introduced.It is a radioactive prospecting.The concentration of radon near the fault can be determined from the activities of its daughters 218Po and 210Po.At the fault,there is a good passage for gases,and the radioative gas from crustal depths can be easy to get to the surface.As a result,the level of the radioactivity there is quite high,but low at both sides far from there.The     

Mohr space and its application to the activation prediction of pre-existing weakness

The activation coefficient equations in the"activation criterion of pre-existing weakness"are relatively complex and not easy to apply to specific applications.The relative activity of pre-existing weaknesses is often critical in geological analysis.The Mohr circle can be used only in two-dimensional stress analysis.By applying the"activation criterion of pre-existing weakness"and combining it with numerical analysis,we establish the correspondence between the pole(n,n)of a pre-existing weakness plane and its orientation in"Mohr space".As a result,the normal stress(n)and shear stress(n)of a pre-existing weakness plane can be readily expressed in Mohr space.Furthermore,we introduce the method and procedures for predicting the activation and relative activation of pre-existing weaknesses in Mohr space.Finally,we apply the Mohr space method and compare the predictions to sandbox modeling results and 3D seismic data.The results show that Mohr space can be used in stress analysis to estimate the activation of a pre-existing weakness in any triaxial stress state.     

Research on 3D marine electromagnetic interferometry with synthetic sources for suppressing the airwave interference

In order to suppress the airwave noise in marine controlled-source electromagnetic （CSEM） data, we propose a 3D deconvolution （3DD） interferometry method with a synthetic aperture source and obtain the relative anomaly coefficient （RAC） of the EM field reflection responses to show the degree for suppressing the airwave. We analyze the potential of the proposed method for suppressing the airwave, and compare the proposed method with traditional methods in their effectiveness. A method to select synthetic source length is derived and the effect of the water depth on RAC is examined via numerical simulations. The results suggest that 3DD interferometry method with a synthetic source can effectively suppress the airwave and enhance the potential of marine CSEM to hydrocarbon exploration.     

Research on model testing of a new ultrasonic multi-wav detecting method

The traditional crack exploring method with echo (reflected wave) in metals is called the ″single-wave de-tecting method″ that uses a probe of single weight. This method is not able to detect directly the size and shape of the crack and the result can only be obtained by relative comparison, that is to compare the echo amplitudes of the unknown quantity (crack) with the known quantity (regular artificial crack) to determine the equivalent size and shape of a certain crack. In this way, the s…     

Theory and Method for Identifying Well Water Level Anomalies in a Groundwater Overdraft Area

The overexploitation of underground water leads to the continuous drawdown of groundwater levels, change of water quality and dry-up in dynamic water level observation wells. Due to land subsidence, the well pipes uplift and the observation piping systems are damaged. These environmental geology problems can present serious difficulties for the identification of earthquake anomalies by groundwater level observation. Basied on hydrogeological theories and methods, the paper analyzes the relations of the water balance state of aquifers with stress-strain conditions and the water level regime, and then discusses preliminarily the theory and method for identifying well water level anomalies in a groundwater overdraft area. The result shows that we can accurately judge the nature of the anomaly according to the diffusion character of the drawdown funnel in the well area in combination with the aforementioned theory and method and multi-year variation patterns obtained from existing data. The results of the research are helpful for distinguishing the influence of single centralized water pumping from the long-term overdraft of water on the water level, correctly recognizing water level anomalies in the groundwater overdraft area and increasing the level of earthquake analysis and prediction.     

Estimation of characteristic parameters in region-time-length algorithm and its application

On the basis of gap's temporal-spatial characteristics in and around source area before an earthquake, we propose a method to estimate characteristic parameters (characteristic distance and time) in the region-time-length (RTL) algorithm and introduce the method of correlation coefficient developed by some authors in 2006 to determine the characteristic parameters. The anomalous seismic activities before four moderately strong earthquakes occurred in the northwestern and southwestern China in recent years are studied by the two methods. The results show that the method to estimate characteristic parameters advanced in this paper is a simple one, which possesses a physical meaning and is well applicable to the four moderately strong earthquakes studied.     

Simulation and retrieval for spaceborne aerosol and cloud high spectral resolution lidar of China

Clouds and aerosols can significantly affect global climate change and the atmospheric environment,and observing them three-dimensionally with high spatial and temporal resolutions is a long-standing issue.Spaceborne lidars are effective instruments for the vertical detection of clouds and aerosols globally.Numerous Mie scattering lidars were successfully launched and widely used,such as the Cloud-Aerosol Lidar with Orthogonal Polarization(CALIOP)and Geoscience Laser Altimeter System.However,the retrieval of Mie scattering lidar data is an ill-posed problem that introduces a large uncertainty.The spaceborne Aerosol and Cloud High Spectral Resolution Lidar(ACHSRL)of China is currently under development and scheduled for launch in the near future.The ACHSRL attracted extensive attention,because it can separate Mie and Rayleigh scattering signals and avoid ill-posed retrieval.In this study,we conducted ACHSRL signal simulation and retrieval to explore the potential of the ACHSRL.First,we proposed a simplified scheme for retrieving optical parameters,which reduced the number of equations and intermediate variables of the traditional method and avoided false extrema in the backscatter coefficient retrieval.Additionally,the experiments showed that the backscatter coefficient retrieval was overestimated owing to the influence of the Poisson noise but can be corrected.Second,we examined the feasibility of the strategy of“first retrieving the lidar ratio then retrieving the extinction coefficient”to improve the extinction coefficient retrieval.We found that the retrieval error in the simulated cases can be reduced to less than 1%of the original retrieval error.Furthermore,we discussed the influence of the uncertainty of the iodine filter transmittance on the retrieval of the optical parameters and found that the average relative error was less than 1‰.Finally,we conducted simulation and retrieval based on the atmospheric parameters measured by the CALIOP.Results showed that the relative error in the backscatter and extinction coefficients at night was 12%and 28%for test cases,respectively,which was superior to that in the backscatter and extinction coefficients of the corresponding CALIOP product(i.e.,75%and 82%).This research is significant and useful for the development and application of satellite lidars in the future.     

Study on simulating strong ground motion by fractal stochastic method

The time history of strong ground motion can be synthesized by empirical Green′s function (EGF) method. Firstly a large seismic event is discretized into a series of subevents; secondly recordings of earthquakes with proper size and spatial distribution are chosen as time history (EGF) of those subevents; finally the EGFs are summated to get the time history of ground motion caused by the large event. It is certain for the regions with abundant strong earthquake records to calculate broad…     

Numerical Simulation of the Binchuan Airgun Source Affected by Water Body

The numerical simulation of the influence of a reservoir water body on the Binchuan airgun source could provide a theoretical basis to analyze the data obtained from the active source detection and inversion of regional interior medium structures. Based on a medium model containing limited water body, we use the finite different method to simulate the effect of the water level, excitation energy and focal depth. The results show that the influence on the waveform amplitude caused by the water level changing is very large near the water body, and that a high water level or large amplitude change can have a larger effect. However, for stations beyond a certain epicentral distance, the influence will be weakened and kept stable. As for the Binchuan airgun source, amplitude fluctuation caused by the water level changing becomes very small(±0.05 times) after propagating a certain distance, so we can remove the influence of the water level changing by referring to the numerical simulation result. Wave amplitude increases linearly with the excitation energy and focal depth, therefore, the greater the energy and the deeper the focal depth, the better the effect of the excitation, and is more conducive in detecting remote and deep penetration underground structures.     

From active fault segmentation to risks of earthquake hazards and property and life losses——A case study from the Xianshuihe-Xiaojiang fault zone

Strong earthquakes generally rupture along active faults, and associated ground motion can cause earthquake disasters, property losses, and casualties from kilometers to tens of kilometers away. Therefore, one of the most effective ways to find earthquake’s dangerous parts of faults is to study the seismic hazards on fault segments. After that, we can also evaluate the probabilities of landslides hazard, property losses, and casualties. In this study, using fault slip rates and magnitude-frequen...