Based on a plenty of exploration achievements in Xihu sag, it is found that the oil reservoir is distributed in the upper stratum, while the gas is distributed in the lower stratum, with the pattern of more resources in the southern fields than those in northern ones. Through the analysis of the geochemical parameters of the condensate and condensate gas in Xihu sag, it is concluded that the condensate and condensate gas are the same for their genetic type and maturity, and are generated from the coal measures source rocks of Pinghu Formation. Based on the research results of reservoir type, oil and gas accumulation time,and trap forming time in the western slope and central inversion belts, it is believed that the oil and gas filled in Pinghu Formation in the western slope belt, and then migrated to Huagang Formation due to the late fault opening. Because the pressure was reduced in Huagang Formation, gas was lost, and finally the condensate reservoir was formed in Huagang Formation. In the central inversion zone, due to the late trap, oil and gas underwent one time reservoir accumulation, and then migrated to Huagang Formation through faults. Because the low pressure in the upper part of Huagang Formation, oil and gas were separated with gas dispersing, thus the pure condensate reservoir was formed. According to the research on the attributes of oil/gas accumulation and distribution, we can get the conclusion as follows:the reservoir distribution is controlled by the gas-generation center, and the abundance is controlled by faults; the distributing interface between condensate oil reservoir and condensate gas reservoir is controlled by overpressure in the west slope belt.

Taking high resolution sequence stratigraphy as a guidance, combined with episodic tectonic evolution characteristics of Tainan depression, the author analyzed the Permian stratigraphic sequences of Tainan depression by using core observation, oil test data, geophysical and geochemical data. The studies show that the filling characteristics of stratigraphic sequences, source rocks and reservoir distribution are controlled by tectonic evolution with significant stages. The lithology stacking patterns and sedimentary distribution are controlled by the structural characteristics:during the LSC1 deposition period, the southern Sleep Tarot Mountains rose, the northern steep slope developed fan delta and underwater fan deposits, and the southern gentle slope developed braided river delta sedimentary system; during the LSC2 deposition period, the western Luxi uplift and eastern Takequan uplift gradually formed, and the provenance decreased in the south, but increased in the east and west; during the LSC3 deposition period, the northern Bogda Mountains rose, the strata tilted from north to south, the provenance gradually developed in the north, the fan delta developed on the short axis of the fault depression, and the fan delta sedimentary system-braided river delta sedimentary system-lacustrine depositional system transited gradually on the long axis of the fault depression. Through the analysis of the sequence stratigraphy of source rocks and reservoirs, the author believes that the mudstones developed in the late stage of LSC2 transgressive system tract and early stage of high system tract are the main hydrocarbon rocks, and the sandstones developed in the upper LSC3 low water level system tract are the main reservoirs of oil and gas.

The lithology, physical property, and diagenetic facies of the Chang 7 tight sandstone reservoirs in Ganquan-Fuxian area of Ordos basin were studied by using core analysis, thin section identification, SEM, and logging data. The lithology of the Chang 7 tight sandstone reservoir is mainly feldspar sandstone, with porosity between 3% and 10%, and permeability between 0.05 and 0.60 mD. Five types of digenetic facies were identified based on the type and strength of diagenesis combined with the features of diagenetic minerals, the characteristics of pore development, and its impact on reservoir property. They are medium compacted chlorite cementation native intergranular pore facies, medium compacted corrosion of unstable components solved pore facies, strongly compacted weakly dissolved microporous facies, strongly compacted illite cemented tight facies, and strongly compacted calcareous cemented tight facies. Natural gamma ray and acoustic logging are sensitive to diagenetic facies. A logging identification model was established by using the logging data of the study area, and the "dominant facies" method was used to predict the distribution of diagenetic facies. The result shows that the diagenesis is relatively tight, and plays a controlling role in oil accumulation.

The Sulige gas-field in the Ordos basin covers a wide range of natural gas, but the gas content varies greatly. In order to investigate the migration characteristics under the influence of gas-water interaction, 13 samples from the 8th member of Permian Xiashihezi Formation and the 1st member of Permian Shanxi Formation in the Shaan Well 234-235 area were selected and studied based on the gas water relative flow analyses. The results show that the fluid permeability of reservoir in the target horizon is poor. The reservoirs with typeⅠgas-water phase permeability curve are hardly seen; while the reservoirs with typeⅡgas-water phase permeability curve are the preferred layers for exploration and development. The movable gas porosity equals to the storage space of recoverable gas, which has a positive correlation with movable fluid porosity, porosity, movable fluid saturation, permeability, effective pore volume, effective throat volume, quartz volume fraction, and carbonate volume fraction. The maximum effective gas-phase permeability equals to the gas flow capacity, which has a positive correlation with the first seven factors mentioned above; while the volume fraction of clay minerals plays a negative role both in the storage space of the recoverable gas and the gas flow capacity.

In order to analyze the formation physicochemical conditions and tectonic environment of the Hegenshan ophiolite in Inner Mongolia, the unaltered chromites from the Chonggenshan ophiolite were chosen to study their mineralogy and mineral geochemistry. The result shows that the chromites consist of Cr₂O₃ (38.86%-39.12%), Al₂O₃ (26.56%-26.92%),and TFeO (17.37%-17.50%), Cr^# values of 49.34-49.58, Mg^#values of 68.82-69.73, Yfe values of 6.62-6.97,and Fe^2+#values of 30.27-31.18, without texture zoning. They are aluminum-rich chromites. The average crystallization temperature and pressure of the chromite are estimated to be 1 396.88℃ and 3.35 GPa, respectively, indicating its formation depth of about 103.72 km. It is inferred that the Chonggenshan chromite-hosting peridotite was derived from the garnet lherzolites in depleted upper mantle with oxygen fugacities from FMQ+1.41 to FMQ+1.45 lg units (average FMQ +1.43 lg units), and partial melting degree of the mantle from 20.93% to 20.95% (average 20.94%). The chromites show the characteristics of super-subduction zone. We believe that the Chonggenshan ophiolite was formed in the background of intra-oceanic back-arc basin in the subduction zone.

In this research, the detrital zircon LA-ICP-MS U-Pb from the ore-hosting strata of gold deposits is studied in Alxa Tebai area. The concordant age of the youngest detrital zircons is concentrated in 525-461 Ma with the peak age of (473±3) Ma. The maximum sedimentary age of this set of strata is around the Middle Ordovician. Considering the Carboniferous Bembatu Formation, combined with the regional fault contacts and the massive emplaced Early Permian granites, the age of ore-bearing strata is roughly limited to the Middle Ordovician-Early Permian, rather than the Mesoproterozoic-Neoproterozoic as thought by predecessors. The source analysis shows that these Paleoproterozoic-Ordovician clastic zircons are most likely derived from the metamorphic basement of the Alxa massif and the magmatic arc of the syn-orogenic continental margin. The ore-bearing strata may have been formed in the background of the early subduction of Ordovician fore-arc basins, which is closely related to the Central Asian orogenic event.

Dapinggou gold deposit is one of the typical gold deposits in Northern Altun. The deposit is characterized by K-feldspar quartz vein-type and altered rock-type mineralization. The gold mineralization occurs within near the E-W ductile shear zone with the K-feldspar leptynite of Archaean Milan Group as the principal host rock. The ore minerals are mainly pyrite, with minor limonite and natural gold. The measured δ¹⁸O_VSMOW values for the gold-bearing quartz range from 12.4‰ to 15.3‰, the estimated δ¹⁸O_H2O fluid values range from 7.4‰ to 10.3‰, and the δD_VSMOW values of fluid inclusions in quartz range from-97‰ to -66‰, indicating that the ore-forming fluid is dominated by metamorphic sources. The δ³⁴S_VCDT values of sulfide minerals range from 6.9‰ to 8.3‰ in accordance with those of the typical orogenic gold deposits. The ²⁰⁶Pb/²⁰⁴Pb ratios of sulfides range from 18.310 1 to 19.373 9, ²⁰⁷Pb/²⁰⁴Pb ratios from 15.587 2 to 15.654 1, and the ²⁰⁸Pb/²⁰⁴Pb ratios from 38.119 1 to 39.143 9, indicating the lead source of sulfide the same as the orogenic type. It is proposed that Dapinggou gold deposit can be classified as the orogenic gold deposit, the gold formation is controlled by the near EW secondary fault and the ductile shear zone, the metallogenic material is derived from the Archaean metamorphic rocks, and the ore-forming fluids are mainly metamorphic fluids.

A typical turquoise mineralization belt is distributed in Ma'anshan City of Anhui Province. The genesis of these turquoise deposits remains controversial. In this study, a detailed field geological survey and indoor observation of the Bijiashan turquoise deposits were carried out. The mineralogy and petro-chemistry of the turquoise minerals were analyzed by using microscope, electron probe, SEM, ICP-MS and other methods. The main minerals of Bijiashan turquoise deposit consist of turquoise with a small amount of quartz, pyrite, feldspars, pyrophyllite, limonite and jarosite. Turquoise is microcrystalline aggregate with gelatinous structure. The SEM micromorphology shows that the platelike crystallite aggregates of turquoise are parallel or staggered. The symbiotic pyrites with turquoise are characterized by medium-low temperature hydrothermal cubes, pentagonal dodecahedron and polymorphic crystal. In the chart of Co-Ni content relationship, the samples mainly distributed in magma and hydrothermal area. The δ³⁴S isotope ranges from 8.3‰ to 11.9 ‰, which indicates that the sulphur was derived from a deep magmatic and sedimentary source, and the ore-forming fluid was formed by mixed atmospheric precipitation and deep magmatic water. Combined with the mineral assemblage, mineral forming sequence, symbiotic pyrite mineralization, and ore-forming fluid, Bijiashan turquoise deposit is a medium-low temperature hydrothermally metasomatic deposit formed by volcanic eruption.

The Chang'an gold deposit,is one of the large classic gold deposits in the south Ailaoshan metallogenic belt, where many vein-type alkaline rocks appeared. In this paper,we present new data of the zircon U-Pb geochronology,trace element,and Hf isotope of these alkaline rocks from the Chang'an gold deposit to constrain their age and origin;furthermore,to discuss the formation mechanism of the gold deposit.The LA-ICP-MS zircon U-Pb isotope data show that these alkaline rocks formed in the Late Eocene(37.0-35.0 Ma).According to the chemistry of trace element,Hf isotope,and zircon saturation temperature,they were mainly derived from igneous zone in the lower crust,but a small amount of sediment material was formed during 1 648.5-34.8 Ma in the upper crust. Further,these alkaline rocks are the results of the partial melting of lower crust which were heated by the under-plated hot basic-ultrabasic melt induced by the ductile shear activity of Ailaoshan. Combined with the previous data of the stable isotopes of ore-forming fluid,we suggest that the forming of alkaline rocks and gold mineralization are independent events which occurred under the same geological setting,and the ductile shear activity of Ailaoshan was triggered by the southeastward escape of Tibetan Plateau during the collision of Indian plate and Euro-Asia plate.

Through a LA-ICP-MS U-Pb dating of zircons from four diabase dykes in Wulonggou ore concentrated areas, we found that the most zircons are the inherited zircons. The zircons with the latest age represent those from the magmatic crystallization of diabase veins with an average age of (242.8±2.1) Ma (the Middle Triassic). The four diabase dykes are calc-alkaline -high calc-alkaline with w(SiO₂) range of 42.82%-52.94%,w(Na₂O) range of 1.98%-4.51% and w(K₂O) range of 0.70%-2.04%. V, Cr, Ni and the other trace elements in the four dikes are positively correlated with MgO mass fraction, and the mass fraction is small. This results indicate that the fractional crystallizations of the olivine and pyroxene occurred during the magmatic process. The trace elements are characterized by relatively rich in LILE (Rb, Ba, Eu), LREE, depleted of HFSE, Nb/La is 0.39-0.50, Nb/Ta is 12.16-16.69, and Zr/Hf is 45.82-47.06. These features are quite different from those of the magma derived from the depleted asthenosphere mantle. In conclusion, the Middle Triassic diabase dikes in Wulonggou ore concentrated areas may be derived from the partial melting of the lithospheric mantle, reconstructed by the subduction plate fluids and contaminated by the crust.

This study aims to construct the volcanic edifices,and discuss the characteristics of the different volcanic edifices and the reservoir of Yingcheng Formation in the southern area of Songliao Basin. The volcanic edifices of the study area are divided into 3 kinds and 9 types (trachytic lava, basaltic lava, andesitic lava, dacitic lava, rhyolitic lava, basaltic clastic rock, andesitic clastic rock, rhyolitic clastic rock,and composite volcanic edifices). In addition, the statistics of different reservoir types and porosity suggest that the rhyolitic composite volcanic edifices have the best reservoir characteristics, and the solution pores are important pore type; rhyolitic clastic volcanic edifices have the worse and the worst reservoir characteristics belong to the rhyolitic lava. The reservoir in Changling fault depression is divided into three types:high porosity-high permeability reservoir, middle porosity-middle permeability reservoir, and low porosity-low permeability reservoir. The favorable reservoir is mainly affected by lithofacies rather than lithology.

The Badu Group in Suichang-Dazhe region of southwestern Zhejiang underwent metamorphism and deformation under the influence of Indosinian metamorphic event. Through a detailed field investigation and lithofacies study, it can be divided into three metamorphism-deformation sequences:for S₁ deformation period,the residual tight folds are recorded by NW-trending gneisses,and the symbiotic mineral assemblages are garnet metamorphic phenocrysts with inclusion minerals of garnet+biotite+quartz (argillaceous) and garnet + amphibole+plagioclase+quartz (feldspar) distributed directionally; for S₂ deformation period,the regional wide-gentle folds and NE-trending gently inclined permeable gneisses are developed,and the symbiotic mineral assemblages are garnet metamorphic phenocrysts and matrix minerals of garnet+biotite+silica+quartz+K-feldspar+plagioclase (argillaceous) and garnet+K-feldspar+plagioclase+biotite+quartz (feldspar); for S₃ deformation period,the NE-trending steeply inclined permeable gneisses and ductile-brittle fractures are mostly filled by granite porphyry veins, and the symbiotic mineral assemblages are garnet metamorphic phenocrysts and their retrograde edge minerals of garnet+cordierite+sillimanite+plagioclase+biotite+quartz+K-feldspar (argillaceous) and amphibole+plagioclase+biotite+ilmenite (feldspar). Combined with the previous research results, the peak metamorphic degree of Indosinian metamorphic event of Badu Group reached granulite facies,showing a clockwise near isothermal decompression (ITD) type p-T evolution track. The S₁-S₃ metamorphism and deformation reflect the evolution from subduction collision to rapid re-cooling. The zircon U-Pb dating results of granite porphyry restrict the completion time of the evolution process to 229.7 Ma, which may be the response of southwestern Zhejiang to the subduction-collision between the Indosinian-South China-North China plate to the Paleo-Tethyan Ocean during Indosinian.

In order to explore the accumulation range of debris flow, a numerical simulation of the Lamazhazi debris flow in Miyun County, Beijing was carried out by using the LAHARZ software combined with the 1:10 000 DEM map of the small drainage basin. The authors utilized the data of volume and accumulation area of debris flow in some areas of China, and obtained a new statistical model for debris flow volume and its accumulation area. The optimal river threshold was determined to be 15 000 through comparing the simulated river channel with the actual river channel; combined with the on-site survey statistical and rainfall historical data, the debris flow volume thresholds for 10, 20, 50, and 100 years under heavy rain were determined to be 56 500, 72 900, 94 200, and 113 100 m³, respectively. The corresponding accumulation area of the debris flow trench is predicted as follows:the area of the debris flow under the condition of once-in-a-century rainstorm is 48 729 m², and the longest distance is about 490 m, which has an impact on the downstream villages.

Affected by the Qinghai-Tibet Plateau tectonic structures and the warm-humid climate during the Last Glacial Epoch,the Jinsha River was incised into deep valley, on which numerous large-scale landslides are distributed and revived under the effects of rainfall and water-level fluctuation. In this study,the Baisheng landslide was studied using field investigation and geo-mechanical analysis for its formation evolution,geo-mechanical model and stable mechanism of rainfall-type water-level fluctuation slopes in deep-incised river valleys. According to the study results,the geological evolution and sliding processes of landslides are divided into six stages,including the initial status,unloading and degradation of rocks,extrusion and plastic flow,instability triggered by rainfalls,disintegration and compaction of deposit,and local resurrection by water-level fluctuation in the front of landslide. The stability of slopes gradually reduces due to unloading of rocks, water softening, and creepage by rainfalls or water fluctuation of reservoir. The slopes are stable when the stability coefficient is 1.12 under the natural condition; while landslides failure when the stability coefficient is 0.98 under heavy rain conditions and fluctuation of reservoir water level.

The Qinghai-Tibetan Plateau suture zone lies between the continental blocks of the India plate and the Eurasian plate, where the geological conditions are complex,and the tectonic movement is strong. The Lhasa-Nyingchi Line of Sichuan-Tibet Railway is almost along the Yarlung Zangbo suture, and its high ground stress causes problems frequently. At present, the study on in-situ stress of the tunnel in plate suture zone is relatively rare. The in-situ stress measurement of the tunnels along the railway was carried out by hollow inclusion stress-relief method, and the in-situ stresses with several typical projects such as Chengdu-Lanzhou Railway, Lanzhou-Chongqing Railway, and Jinping Hydropower Station were analyzed and compared with each other. The results show that the tunnels along the Lhasa-Nyingchi Railway have large buried depth, and the prominent tectonic stress shows as maximum horizontal principal stress > vertical principal stress > minimum horizontal principal stress. The average lateral pressure coefficient distribution is relatively concentrated (1.0-1.5), and at a high level. Most of the maximum principal stresses are between 20-50 MPa, the gradient between maximum principal stress and burial depth is 0.033 7 MPa/m, and the direction of maximum principal stress is NNW-NNE. It is suggested that the invert structure should be used to reduce the stress concentration at the foot of tunnel wall.

In order to study the influence of deep foundation pit excavation on the surrounding environment, the excavation process of a deep foundation pit in Changchun was numerically simulated for its effect on the surrounding buildings by using Midas GTS/NX software. Compared with the on-site monitoring records, the changes of the surrounding environment were discussed. The results show that the calculated results are basically consistent with the measured results; the deep foundation pit excavation caused a displacement of the enclosure structure towards the foundation pit, and the maximum displacement is 10.8 mm, 2.9 mm larger than that of the actual monitoring data of 7.9 mm; for the shallow foundation in the buildings, the settlement and surface settlement of the buildings are different from those of a foundation pit at 0.6H-0.8H (excavation depth of foundation pit), and the building settlement is uneven.

Accurate determination of the location of freshwater and saltwater interface is the premise of evaluation of saltwater intrusion. Hydrochemical analysis method and geophysical investigation method are the main methods to determine the location of freshwater and saltwater interface. In order to overcome the huge waste of human, material and financial resources caused by using only one traditional method, take the saltwater intrusion area south of Xiaoqing River in Guangrao County, southwestern coast of Laizhou Bay as the research object. Based on comprehensive analysis of the current situation of groundwater exploitation and the results of hydrochemical monitoring in the area, three typical sections were selected, and field electrical conductivity method in hydrochemical method was used to rapidly determine the approximate location of the freshwater and saltwater interface. Then, high-density resistivity method was used to rapidly and accurately determine the spatial distribution of freshwater and saltwater interface between saltwater and freshwater monitoring wells. Results show that if the electrical conductivity of underground water in this area is greater than 1.61 mS/cm, it can be considered that the area is intruded by saltwater. The apparent resistivity of the freshwater and saltwater interface is 11-13 Ω·m. The saltwater body near the freshwater and saltwater interface is tongue-shaped and mainly occurs in shallow groundwater within 13 m below the surface.

Gravity currents exist widely in nature and engineering. In this study, a series of laboratory experiments were conducted to investigate lock-release gravity currents through vegetation patches into different ambient environments. The head position, front velocity and entrainment coefficient of gravity currents were analyzed by using the images acquired by a high-speed camera. The results show that the front velocity in linearly stratification environments is smaller than that in constant-density ambient. Both stratified environment and vegetation patches can inhibit the entrainment between gravity current and ambient water. As stratified environment and vegetation patches exist simultaneously, the mixing and entrainment of gravity currents are related to the ratio α of vegetation height to water depth. When α=0.43, the entrainment and mixing between gravity current and ambient water are the strongest. The particle image velocimetry (PIV) technique was applied to study the velocity and vorticity fields in detail. The results show that the stratification environment can restrain the development of the vorticity both at the upper and lower interfaces between current and ambient water. However, when α=0.20, i.e. some gravity currents climbs to the top of vegetation patches, the combined effects of the stratified water and the vegetation patch strengthen the vorticity near the top of vegetation patches.

A T-H-M (thermal-hydraulic-mechanical) coupling mechanical model considering the effect of thermal convection and thermal conduction is built to study the influence of fracture-network spacing on temperature of reservoir rock mass during water injection for HDR geothermal reservoirs. Taking the horizontal well with multiple-fracture-network geothermal development as an example, the fracture-network and its surrounding rocks are regarded as an equivalent porous medium, the coupling of H-M coupling and thermal convection is achieved by the secondary development of ABAQUS. The simulation results show that the temperature change of the reservoir rock mass falls into three stages during water injection:in the initial temperature maintaining stage, the rock mass temperature remains initial, and there is no effect of different fracture-networks spacings on the temperature of overall reservoir rock mass; in the temperature rapid declining stage, the temperature decline of the reservoir rock mass shows a negative exponential with the water injection time, and the fracture-network spacings are positively correlated with the temperature of reservoir rock mass; the third stage is the temperature slow and steady declining stage, at the beginning of this stage, the relationship between the fracture-network spacings and the temperature of reservoir rock mass are consistent with that in the temperature rapid declining stage, however, at the end of this stage, the fracture-network spacings are negatively correlated with the temperature of reservoir rock mass. In space, the smaller the fracture-network spacing, the greater the gradient temperature changes of reservoir rock mass in the area where rock mass temperature is high; while the smaller the fracture-network spacing, the smaller the gradient temperature changes of reservoir rock mass in the area where rock mass temperature is low.

Traditional surfactant flushing technology has some disadvantages such as low elution efficiency, difficult control of liquid transport, and contaminated area extension. Colloidal gas aphrons (CGAs) can effectively avoid these problems with the characteristics of light density, small particle size, and good fluidity. Pressure can be used as a crucial parameter in the remediation process to efficiently reflect the CGAs migration distribution. One-dimensional and two-dimensional models were designed in this research to discuss the effects of medium grain size, moisture content, and polymer (xanthan gum) addition on the pressure of the system and the transport patterns of CGAs in soil. The results demonstrated that with the increase of the medium grain size, moisture content, and xanthan gum concentration, the pressure of the system decreased. Besides, the results of the CGAs injection into soil from a single point on one side of the simulated tank indicated that the migration traces in the medium was nearly semicircular and CGAs distributed uniformly in the coverage area, which effectively overcame the influence of gravity to its distribution in the medium. With the increase of medium grain size, the CGAs sweep efficiency increased first and then decreased. The maximum value of sweep efficiency reached 34.77% when the medium grain size was 0.8-1.0 mm. The moisture content augmentation of the medium also stimulated the increase of the sweep efficiency. Moreover, the addition of xanthan gum significantly improved the sweep efficiency of CGAs:when the mass concentration of xanthan gum was 500 mg/L, the sweep efficiency reached 40.28%,which is 1.48 times greater than that without xanthan gum addition.

Affected by the collisional orogeny of Indian-Asian land-continent,the fracture structure developed in the Zhaxikang ore-concentrating area. The Pb-Zn polymetallic ore bodies in the area are occurred in the Lower Jurassic Ridang Formation. The vein-like and lenticular ore-bearing rock consists of carbonate-bearing slate, calcareous slate and tectonic breccias and the ore body is strictly controlled by the near N-S and N-E fractures. In order to understand the tectonic conditions and the relationships of the Zhaxikang ore area between tectonic and mineralization, the author processes the data obtained from the 1:50 000 gravity and magnetic measurement with upward extension, indicating that the ore-concentrating area has the anti-L abnormal partition feature and known deposits are in the low-magnetic and low-heavy areas, and there are many hidden rock masses in the deep. Then processes the data with horizontal derivative, horizontal gradient modulus and vertical second-order derivative,interpreting the four main faults in the ore-concentrating area and a secondary fault the fault is the main ore-control fault. It is proposed that the main fault or the secondary fault trap area is a favorable ore-forming area, and four ore-forming favorable areas are delineated, combined with chronological geology and geochemical characteristics discusses the relationships of the framework and mineralization. It is believed that when there is a certain structural framework, there is potential for prospecting.

Convolutional perfectly matched layer (CPML) absorbing boundary is a method for efficiently processing artificial boundary reflection waves in numerical simulation of wave equations. Based on the traditional first-order system CPML absorption boundary conditions, the authors generalized and deduced the new CPML boundary conditions of the second-order system. Different from the CPML boundary conditions of the conventional second-order system, the core idea of the new boundary is to ignore the space-varying characteristics of partial attenuation factors in the complex-frequency domain, so as to avoid of the generation of complex convolution in the time domain, and then to obtain a second-order scalar wave equation based on CPML absorption conditions,which is then applied to the second-order scalar wave numerical simulation. Through the uniform medium model test, the memory usage of the new second-order system CPML absorbing boundary is less than that of the conventional second-order system CPML and SPML, and the effect of absorbing boundary of the new second-order system CPML is slightly inferior to the conventional second-order system CPML, but they all have obvious advantages over SPML. The stability of the new boundary conditions and the advantages in efficiency are verified by the test of layered model and Marmousi model.

Utilization of high frequency surface waves to invert S-wave velocity has been a hotspot in shallow seismic engineering research. To deeply understand the ability of high-frequency surface waves (Rayleigh waves and Love waves) to invert S-wave velocity, in this study, the high-order staggered-grid finite-difference method is used to simulate the Rayleigh and Love waves of a two-layer model. The t-p transformation is adopted to generate the dispersion energy image. Compared with Rayleigh waves, the Love waves dispersion energy of different modes is extremely consistent, which shows that multi-mode inversion is easier to achieve. The generalized pattern search is then realized by linear mapping to achieve the variable-thickness inversion of base mode and multi-mode Rayleigh waves and Love waves of a four-layer model with a weak interlayer. If the initial model is extremely poor, compared to Love waves,the base mode inversion of Rayleigh waves cannot reconstruct the feature of strata with a weak interlayer, which can be attained by multi-mode inversion of Rayleigh waves. Base mode and multi-mode inversion of Love waves can reconstruct this feature. Even when the Poisson's ratio of the stratum is much different from the estimated value, the multi-mode inversion of Rayleigh waves can still reconstruct the stratum structure. However, the multi-mode dispersion curve of Rayleigh waves always has the phenomenon of mode kissing, leading to misjudge. The Love-wave inversion does not require an estimated value of Poisson's ratio, and there is no mode kissing. A series of examples show that an addition of high-mode Rayleigh waves can significantly improve the accuracy of the shear wave velocity evaluation results;although an addition of high-mode Love waves would make the inversion system too sensitive to the parameters of anomalous strata above the half space, making the parameters excessive, it can improve the ability significantly to evaluate the shear wave velocity of the half space. Finally, the analysis of field Love-wave data is realized by using this method.

τ-p transform is a classic projection transform method, which is widely used in seismic data processing such as signal-noise separation, seismic trace interpolation, and plane wave decomposition based on different ray parameters. However, the precision and resolution of τ-p transform are limited by mathematical inverse problems, and it is necessary to study the methods to accelerate the calculation speed of τ-p transform or to design relevant filter, while maintaining high precision. We propose two τ-p transform methods based on radial trace transform and slope decomposition respectively. In this paper,we demonstrate the fundamental theory of the two methods and compare them with conventional τ-p transform. Using fast Fourier transform and radial trace transform, the τ-p transform method can efficiently reduce the time consumption. Utilizing stable slope decomposition algorithm, the τ-p transform method can perform high resolution τ-p transform,and provide redundant transformation dimension (τ-x-p domain),which enable the design of filter operator more flexible. The numerical experiments show that these two proposed methods are superior to the conventional τ-p transform in calculation speed and reconstruction accuracy. The field-data examples for ground-roll noise suppression confirm that the two methods can provide more effective and flexible implementations for seismic data processing.

Acoustic parameters such as sound velocity, density, and porous structure of seafloor sediments are important for describing seabed, and are necessary for engineering application in sound field numerical prediction and coastal engineering. Based on the backscattering characteristics of the seabed, we extended the diffraction CT technique and re-deduced the relationship between the target scattering intensity and the relevant image spectral sample of the bistatic system. Quartet structure generation set is used to construct the image model of the sound field. When LFM wave is incident from a single direction, the image inversion is retrieved by using the finite sparse sample of the bistatic sound field. The frequency interval and direction number, which affect the acoustic parameter accuracy, are obtained. The porosity and mean impedance indices of sediments are further inversed. Compared with the classical numerical calculation method, the computational efficiency of this method is increased by about two orders of magnitude.

Studying the pattern and driving factors of urban and rural land use change is conducive to the sustainable development of regional land resources. Taking Changchun City as an example, combined with manual interpretation, the overall accuracy of the Landsat satellite supervised classification images in 1997, 2007 and 2017, is 93.06%, 90.70%,and 94.12%, respectively. From 1997 to 2017, the grassland, cultivated land and other land area decreased by 354.74 km², 922.11 km²,and 55.35 km² respectively, and the construction land, water area, and forest land increased by 1 154.14 km², 70.38 km², and 107.54 km² respectively. The overall trend is that the construction land expanded to the periphery and encroached on the area of other land types. Based on the 2007 classification data, combined with the driving factors of land use change of terrain, traffic location and social economy, the land use pattern was simulated for 2017 with FLUS (future land use simulation) model. The simulation is in good agreement with the real results. The simulation accuracy is 85.10%, Kappa coefficient is 0.821 2, and the verification model and the driving factors are reliable and consistent with the trend of land use change. The model is used to predict the land use pattern of 2027, showing that the construction land will slowly invade the area of cultivated land, forest land, grassland and other land around the town, and the area of forest land and water will increase.

Effective data preprocessing is essential to an online coastal wetland ecological internet of things (IoT) observation system. Outliers always occur due to the limitations of measuring methods and harsh environmental conditions, which challenge data applications. Based on the ecological observation data of Chongming Dongtan wetland in Shanghai, the outliers were divided into three types:abnormal values, abnormal fluctuation,and abnormal events. Integrating the interactions between indicators of coastal wetlands, we proposed a preprocessing method for the outliers of the coastal wetland ecological IoT system based on the residual probabilistic outlier detection algorithm, look-up table, and multi-indicator time series model. Compared with the traditional methods, this method can not only ensure the accuracy of outlier detection, but also better distinguish abnormal events from sensor problems to reduce false positives. Through the analysis of more than 50 000 data records of nine indicators, two abnormal events and 0.18%-8.12% abnormal values and abnormal fluctuations were detected with the threshold of 10^-8-10^-20. Through the analysis of the preprocessed data, we find that the observation principle and observation season will affect the stability of sensors, and the human activities in the observation area are the main factors causing abnormal events.