With artificial heating term (*Q*_{hf}) added in the electron energy equation of SAMI2 model, the disturbance amplitude of electron temperature and density along field line is simulated. The effects of disturbances under different heating conditions are also compared. The results show that the terrestrial ionospheric plasma can be heated by powerful high-frequency radio waves, which can result in the rising of the temperature of electron in the whole field line, especially at the heated spot where electron temperature enhances more than 3 times; the pressure balance is broken as the increase in the electron temperature, which leads to plasma diffusion and then perturbation of electron density occurred; electron density gradient perpendicular to magnetic field line changes in accordance with the perturbation of electron density; the perturbation amplitude of electron temperature and density decreases during the heating time, which gradually becomes saturated. Electron temperature and density have a nonlinear relationship with the intensity of heating source.

The distribution, saturation, and hydrate indicator of free gas beneath gas hydrate stability zone have been the difficulty in the research of gas hydrate. Amplitude versus offset (AVO) and rock physics can be used to quantitatively interpret free gas saturation. In this paper, seismic data, acquired at K-G basin, India, are processed to preserve true amplitude information. Based on the logging data and horizon calibration, free gas saturation of NGHP01-10A is assessed with effective medium theory and AVO modeling. It is found that free gas saturation is related to its distribution patterns. Assessments of free gas saturation in homogeneous and patchy distribution are 0.3%∼0.4% and 3%∼4%, respectively. The results show good agreement with the crossplot of Poisson's ratio which are calculated from the measurement at NGHP01-10D. Free gas is further deduced to be homogeneous distribution on the base of dry frame Poisson's ratio with the saturation of 0.3%∼0.4%.

Edge detection plays an important role in the interpretation of potential field data. Many traditional methods are employed to outline the edges. However, some of them cannot equalize the amplitude of the edges of shallow and deep geological bodies simultaneously; some of them although can balance the anomaly amplitude, the identified edges include some additional false edge information, especially when the measured anomalies contain both positive and negative anomalies simultaneously. Some methods used to avoid this disadvantage are subjective to some extent. In order to solve these problems, this paper proposed a new method called enhanced analytic sinal tilt angle to identify the edges of geological bodies. The new method is tested with synthetic gravity anomaly, which shows that the new method can not only identify the edges of shallow and deep geological bodies clearly and precisely, also can avoid bringing some additional false edges. Finally, we apply the new method to real measured gravity data in Sichuan basin, China, obtaining good results.

Coal elasticity is one of the important mechanical characteristics reflecting the material composition and structure of coal. Under the constraint of drilling and well logging, applying seismic exploration to predict elastic characteristics of the coal seams would be of important engineering significance for coal mining and CBM reservoir evaluation and development. In this regard, ultrasonic experiment of coal samples is the basis to realize the seismic inversion of physical properties of coal seam. In this paper, based on 30 pieces of six kinds of metamorphic raw coals collected from six mining areas of Yima, Fukang, Huainan, Pingdingshan, Hebi and Jiaozuo in China, laboratory ultrasonic measurements of these coal samples were respectively conducted in three directions of strike, dip and perpendicular to the beddings of coal seam under room temperature and pressure. The experimental results show: the samples’ velocities of both pressure wave (P-wave) and shear wave (S-wave) decrease in turn in the three directions; there are obvious anisotropies of velocities, and the average anisotropy of P-wave velocity is stronger than S-wave's. Moreover, larger differences exist among both quality factors and modules of elasticity in the three directions, and the S-wave quality factors are greater than P-wave's; with exception of Poisson's ratio, modules of elasticity of coal are less than those common sedimentary rocks. Through the experiment and analysis, it can be demonstrated that Gardener and Castagna formulas are not suitable to represent relations of coal elastic parameters in China's coal fields, and two empirical formulas with higher precision are statistically given.

It is difficult to calculate reservoir parameters of tight sand reservoirs using conventional interpretation methods, due to their complex lithology and variable pore structure. An optimization log interpretation method is able to take full advantage of the log data and geological information. Therefore, it is an effective method to evaluate tight sand reservoirs. In this study, in order to calculate the reservoir parameters of tight sand reservoirs, an appropriate interpretation model needed to be first established according to the reservoirs’ characteristics. Then, the interpretation parameters were chosen, and the specific form of the objective function was determined. Next, an optimization algorithm was adopted to search for the optimal solution. A bacterial foraging algorithm (BFA) is a newly developed algorithm which has strong global search capabilities. It simulates the behavior of the colon bacillus which swims with flagella for food in the human gut. However, since it slowly converges in the later part of the optimization, it was combined in this study with a complex algorithm (CM) for constituting a BFA-CM hybrid algorithm, in order to improve the precision and efficiency of the search process. Also in this study, the unknown reservoir parameters of the optimization log interpretation method were determined using a genetic algorithm (GA), particle swarm optimization (PSO), BFA algorithm, and BFA-CM hybrid algorithm, respectively. The calculation results showed that, when compared with the GA and PSO, the errors of the porosity and the component content calculated by the BFA were minimal. However, the calculation result curves were found to be inconsistent. Therefore, by combining a BFA algorithm with a CM algorithm to constitute a BFA-CM hybrid algorithm for calculating reservoir parameters, the accuracy was improved, and the curves became more stable. The results of the BFA-CM optimization log interpretation method verified that the objective function value was *F* ≈ 0. Also, the sonic, neutron, and density log theoretical value curves (AC0, CNL0, DEN0) fell within the confidence interval, which indicated that a system deviation influence did not exist, and that the optimization results were reasonable and credible. When compared with the other algorithms, the BFA-CM hybrid algorithm displayed unique advantages during the process of calculating the unknown parameters with the optimization log interpretation method. Its calculation results were of high accuracy and stability, and the efficiency was also improved. The experimental results showed that the BFA-CM optimization logging interpretation method was able to accurately calculate the tight sandstone reservoir parameters, and could therefore be applied to actual production practices.

The logging evaluations of tuffaceous sandstone reservoirs are always difficult problems. The existence of tuff results in the great variations in reservoir pore structures, and the associated physical properties, which greatly influence the formation parameters. Therefore, the effects of tuff on saturation models cannot be ignored. This study took the tuffaceous sandstone reservoirs in the X depression of the Hailar-Tamtsag Basin as an example. Based on the differences of the response characteristics between the tuff and shale, the component content was calculated using a method which combined a bacterial foraging algorithm and a particle swarm optimization algorithm. The experimental data of the cation exchange capacity (CEC) proved that the tuff had conductivity. Then, the resistivity of the tuff was obtained using the relationship between the CEC and the resistivity, which was then used to calculate the saturation. Finally, a new method was proposed to calculate the saturation of a tuffaceous sandstone reservoir, and was referred to as a CEC ratio method. The calculation results of this method were found to have a good application effect.

To analyze the applicability of double rotation (DR), planar fit (PF) and fetch planar fit (FPF) over complicated terrain, turbulent data from the Semi-Arid Climate and Environment Observatory of Lanzhou University (SACOL) are used. A parameterization scheme is provided in integral turbulent characteristics (ITC) test for SACOL data. The overall quality after data processing and quality control including sonic temperature correction, coordinate rotations, WPL correction (correction for density fluctuations), stationarity test and ITC test shows that about 45%∼62% of the total data are of high quality for friction velocity (*u*_{*}), 66%∼68% for sensible heat flux, 62%∼65% for latent heat flux and 52%∼54% for CO_{2} flux. The proportion of the high quality of *u*_{*} obtained by DR is 17% higher than PF, while the proportion of high quality data of the latter three kinds of fluxes obtained by PF is 2%∼3% higher than DR. The differences between PF and FPF are mainly in *u*_{*}. Comparing the three coordinate rotations in the dominant wind direction, DR still obtains the best quality of *u*_{*}. The use of DR is recommended in the complicated terrain for reducing calculation and improving the data quality.

This study statistically investigates the temporal and spatial variations of plasma convection velocity (*V*_{y}) and thermospheric zonal wind velocity (*U*_{y}) in the range of –4 hour (h) and +2 h MLT relative to substorm onsets (MLT onset) with both CHAMP and DMSP (F13, F15) satellites observations from 2001 to 2005. It shows that *V*_{y} increase significantly in all MLT sectors and the latitudes of the peak values move equatorward in 1.5 h after substorm onsets. In the subsequent 1.5 h *V*_{y} decrease in intensity and the peaks retreat poleward, which shows that the onsets of substorm can enhance the plasma convection velocity dramatically. The relative increase of *V*_{y} is largest from –2 h to MLT onset, which indicates that the substorm mainly affects the thermosphere in the westward 0∼2 h MLT sector. *U*_{y} increases steadily in 3 hours after substorm onsets, with a 1.5 h delay relative to *V*_{y} in response to the substorm onsets.

For the 2001 *M*_{S}8.1 Kunlun earthquake, which was one of the largest events occurred around the Tibet plateau, a large controversy still exists about its rupture detail. In this paper, we invert the co-seismic GPS and InSAR data for a robust finite-fault model of the Kunlun earthquake based on a realistic fault geometry buried in a layered earth structure. The inversion is based on the constrained least-squares principle and realized using the steepest decent method (SDM). The different data sets are weighted according to their variance and spatial coverage. The results show that the slip maximum can reach up to ∼6.9 m and is located at 35.76° N and 93.40° E. The main rupture area is located at the shallow depth above 20 km. The inverted shallow slip agrees with the surface rupture observed by the field survey, and the whole slip pattern appears generally consistent with the results obtained from previous geological and seismic wave studies.

Temperature is a key parameter of controlling hydrocarbon generation of source rocks. Elevated temperature resulted from tectonothermal events may significantly affect hydrocarbon generation. Based on geology, fission track analysis, apatite U-Th/He and volcanic rock isotopic age data, it is found that there existed Indosinian (T_{3}-J_{2}) and Yanshanian (J_{3}-K_{1}) tectonothermal events in Lower Yangtze area and the sedimentary basins reached their peak heat flow at about 130∼110 Ma. The maximum heat flows obtained from thermal history reconstruction based on vitrinite reflectance are ∼94 mW·m^{–2} and ∼78 mW·m^{–2} in Jurong and Taixing areas respectively, with an increasing trend from east to west. Hydrocarbon generation history reconstruction based on the EASY%Ro model shows that the dominating gas generation periods of the Cambrian source rock are the Early Permian-Late Triassic and the Late Triassic-Early Cretaceous in Changzhou and Jurong areas respectively. Because of the dual effects from the foreland sediments deposited in T_{3}-J_{1–2} and the magmatism thermal event in the Early Cretaceous, the marine source rocks reached their maximum temperature at the end of Early Cretaceous. The temperature of the marine source rocks was no longer elevated owing to the decreased heat flow since the Late Cretaceous, though, in some parts of the Jurong, Taixing and Changzhou areas, subsidence occurred and burial depth increased during the K2-E period. Therefore, the secondary hydrocarbon generation of the marine source rocks is not a widespread process in central Lower Yangtze area.

The application of multiple waves is an important content of marine exploration, and eliminating or utilizing the multiple waves is one of the significant topics in the processing of seismic data. However, little work is concerned with the multiple waves of Ocean Bottom Seismometer (OBS) wide-angle seismic survey and taking advantage of them to improve the ability of seismic imaging. This study attempts to understand the characteristics of the secondary Pg phases and analyze the applications of seismic imaging in OBS wide angle seismic survey.

We firstly identify and know the secondary Pg phases from synthetic seismogram sections and record waveforms then calculate and analyze particle motions of primary Pg and secondary Pg phases through the azimuth angle rotation. After understanding the secondary Pg phases, we get the propagation path by the theoretical model simulation and calculation of measured data with the P wave travel forward modeling method based on the RAYINVR. In addition, improving the seismic imaging is expected, so we used the theoretical model and the actual model of OBS2010 to show the work of the crustal structure imaging.

The secondary Pg phases roughly parallel and follow closely the primary Pg phase, and are characterized by continuous, clear phase and strong amplitude. An obvious vibration is observed behind the vibration of the primary Pg with stronger amplitude, which is supposed to be the secondary Pg phase. On the basis of particle motions, the secondary Pg phases belong to the P-wave seismic phase. The travel-time fitting of the possible propagation path based on the test data gave three different results: (a) the χ^{2} value is 14.921 when the reflecting layer is water layer and sediment; (b) the χ^{2} value is 193.264 when the reflecting layer is the single water layer; and (c) the χ^{2} value is 1.786 when the reflecting layer is the single sediment. After theoretical investigation and data tests, we have the following conclusions: (1) the secondary Pg phases are characterized by P-wave; (2) the secondary Pg phases are mainly from the reflection between the sediments, which (3) greatly increase the constraint on the basement, and (4) improve the imaging resolution of the sediments and the upper crust.

Time-lapse, or 4D, seismic technology is a tool to monitor underground change for oil field maximum recovery or other purpose especially associated to human being activities. Repeatability is a key issue for time-lapse seismic and geometry repeatability is a fundamental element to essentially affect the repeatability. There were many practices to improve repeatability during data processing, but geometry repeatability needs to be acquired during monitor data acquisition phase. Theory and practice shows that geometry repeatability determined in acquisition cannot be thoroughly improved in processing. Thus, geometry repeatability analysis is important. Multi-trace geometry repeatability rises from practical situation. Multi-trace geometry repeatability is important for overall geometry repeatability evaluation. The difference or repeatability of time-lapse seismic data is evaluated by normalized RMS difference (NRMS). The definition of multi-trace repeatability can be derived from NRMS for time-lapse seismic/4D seismic data, showing that multi-trace repeatability is weighted RMS of all single traces. Noting that the uncertainty of the match between monitor data and baseline data and that probable data size difference between monitor and baseline, the repeatability of the best baseline-based match with imaginary data for mismatch was employed. Derived from previous researches, the linear model of relationship between seismic data repeatability and geometry repeatability was established, and the weighted RMS geometry repeatability of the best baseline-based match with extrapolation for mismatch was obtained as the equivalent of the repeatability of the best baseline-based match with imaginary data for mismatch. The weighting coefficient is determined on the basis of NMO and its stretch. Application study was also conducted based on real data to demonstrate that the new geometry repeatability can be utilized to valuate geometry repeatability during 4D monitor seismic data acquisition. The application study showed that one display of the multi-trace geometry repeatability upon best baseline-based match with extrapolation for mismatch can indicate repeatability and effect of fold of coverage simultaneously. The calculation in application was simplified for speed improvement, which is not yet the main point in this article.