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1.
The construction of S-wave velocity models of marine sediments down to hundreds of meters below the seafloor is important in a number of disciplines. One of the most significant trends in marine geophysics is to use interface waves to estimate shallow shear velocities which play an important role in determining the shallow crustal structure. In marine settings, the waves trapped near the fluid–solid interface are called Scholte waves, and this is the subject of the study. In 1998, there were experiments on the Ninetyeast Ridge (Central Indian Ocean) to study the shallow seismic structure at the drilled site. The data were acquired by both ocean bottom seismometer and ocean bottom hydrophone. A new type of seafloor implosion sources has been used in this experiment, which successfully excited fast and high frequency (>500 Hz) body waves and slow, intermediate frequency (<20 Hz) Scholte waves. The fundamental and first higher mode Scholte waves have both been excited by the implosion source. Here, the Scholte waves are investigated with a full waveform modeling and a group velocity inversion approach. Shear wave velocities for the uppermost layers of the region are inferred and results from the different methods are compared. We find that the full waveform modeling is important to understand the intrinsic attenuation of the Scholte waves between 1 and 20 Hz. The modeling shows that the S-wave velocity varies from 195 to 350 m/s in the first 16 m of the uppermost layer. Depths levels of high S-wave impedance contrasts compare well to the layer depth derived from a P-wave analysis as well as from drilling data. As expected, the P- to S-wave velocity ratio is very high in the uppermost 16 m of the seafloor and the Poisson ratio is nearly 0.5. Depth levels of high S-wave impedance contrasts are comparable to the layer depth derived from drilling data.  相似文献   

2.
A new set of three-dimensional velocity models beneath Mt. Etna volcano is derived in the present work. We have used P- and S-wave arrivals from local earthquakes recorded at permanent and temporary seismic networks installed since 1980. A set of 1249 earthquakes recorded at more than four seismic stations was selected for traveltime inversion. The velocity models obtained by using different data selection criteria and parametrization display similar basic features, showing a high P-wave velocity at shallow depth in the SE quadrant, in close connection with a high gravimetric Bouguer anomaly. This area shares a low Vp/Vs ratio. High P-wave velocities and high Vp/Vs ratios are obtained along the central conduits, suggesting the presence of dense, intrusive magmatic bodies extending to a depth of about 20 km. The central intrusive core is surrounded by lower P-wave velocities. The relocated earthquake hypocenters also display the presence of an outward dipping brittle region, away from the central conduits, surrounding a ductile zone spatially related to the high P-wave velocity anomalies located in proximity to the central craters.  相似文献   

3.
深反射地震剖面法为了获取深部结构特征常常采取大的偏移距采集数据.目前公开发表的相关资料中,鲜有利用深反射地震炮集数据获取近地表的结构特征.为此,本文通过正演测试了相关数据处理流程,即利用有限差分正演了起伏地表模型的大偏移距地震单炮弹性波场特征,通过共检波点域面波信号F-K频谱叠加构建新方法,从深反射地震数据集中提取了高品质的多阶面波频散曲线,再利用多阶面波联合反演获得了近地表的结构特征.在前述正演流程基础上,利用跨越班公湖—怒江缝合带的SinoProbe深反射地震剖面中的实际炮集数据,求取了基阶和一阶瑞利波频散曲线,联合反演后得到近地表横波速度结构.该结果与初至波走时反演获取的纵波速度结构具有较好的一致性,且在近地表的浅层分辨率较纵波速度结构特征更高,而更与已有地质认识相吻合.本文提供的相关数据处理流程表明利用深反射地震炮集数据,也能够获取近地表浅层的横波速度结构.  相似文献   

4.
Array measurements of microtremors were carried out at thirty sites in Damascus city, Syria to estimate S-wave velocity structures of shallow soil formations for site effect analysis. The microtremor data were recorded by 6 vertical-component seismometers distributed along the circumferences of two circles as well as a 3-component seismometer deployed in the center. The phase velocities were estimated at each site from the vertical components of recorded microtremor data by using the Spatial Autocorrelation method. Then, Genetic Simulated Annealing Algorithm technique was applied for inversion of the phase velocities to estimate 1-D S-wave velocity structures beneath the sites. The inverted Vs profiles are not uniform in Damascus city and the results show that a shallow soft layer (∼200 m/s) appears in the eastern part of the city as well as the central part along Barada River. This layer controls the amplification distribution in the city with a high amplification mainly observed at the locations having this layer. The inversion results also show that the depth to the engineering bedrock (∼750 m/s) is very shallow along the foothills of Mt. Qasyoun in the north-west. Then the depth increases towards the east and the south. The maximum depth to the engineering bedrock (∼80 m) was observed in the southern part of Damascus. To validate the results of the inversions, the spectral ratios between the horizontal and vertical components (H/V) of the recorded microtremor data at the central seismometer were compared with the computed ellipticities of the fundamental-mode Rayleigh-waves based on the respective Vs structure. The results show a good agreement in a period range of 0.05 s to 0.5 s. In this period range, the dominant peaks of the H/V ratios are due to the overall effect of the velocity contrasts between the shallow layers representing the subsurface S-wave velocity structure. Moreover, the average S-wave velocity for the top 10 m of soils (VS10) shows a better correlation with the averaged site amplification in a period range of 0.05 s to 0.5 s than VS30 which indicates that VS10 can be a better proxy for high-frequency site amplification in the case of Damascus city.  相似文献   

5.
High-resolution three-dimensional V P and V P /V S images in the Longtan reservoir area were obtained from local earthquake data by using 3,178 events with total 24,153 P-wave and 23,987 S-wave arrivals collected from 23 seismic stations. The tomographic images show that significant V P heterogeneities can be seen at layers of different depth in the Longtan reservoir area. Low-V P anomalies both beneath and around the main rivers in the reservoir area may be related to the composition of rocks which are mainly deposit carbonate and arenaceous shale, which contributes to water saturation. We deduced that the high porosity rocks beneath the main rivers may be fully saturated with water. The phenomenon that V P is relatively high in the area which is 10–20?km away from the rivers indicates that horizontal saturation of water is limited within a small range of area that is about 10–20?km from the main rivers. The characteristic is significant that seismicity in the Longtan reservoir area is coincident with the distribution of the low-V P area. V P /V S tomographic images show that V P /V S ranges from 1.8 to 2.05 in shallow layers above 4?km depth beneath the Longtan reservoir, suggesting the properties of the rocks are limestone and shale. At the depth of 7?km, the distribution of V P /V S image varies quite remarkably, especially in the dam area. This demonstrates that the range of influence by the saturation of water in the media below the reservoir surface can reach 4–7?km depth in the dam area.  相似文献   

6.
Using the P-and S-wave arrivals from the 150 earthquakes distributed in Tibetan Plateau and its neighboring areas, recorded by Tibetan seismic network, Sichuan seismic network, WWSSN and the mobile network situated in Tibetan Plateau, we have obtained the average P-and S-wave velocity models of the crust and upper mantle for this region:
(1)  The crust of 70 km average thickness can be divided into two main layers: 16 km thick upper crust with P-wave velocity 5.55 km/s and S-wave velocity 3.25 km/s; and 54 km thick lower crust with P-wave velocity 6.52 km/s and S-wave velocity 3.76 km/s.
(2)  The p-wave velocity at the upper most mantle is 7.97 km/s, and the S-wave 4.55 km/s. The low velocity layer in the upper mantle occurs approximately at 140 km deep with a thickness of about 55–62 km. The prominent velocity gradient beneath the LVZ is comparable to the gradient above it.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, Supp., 573–579, 1992.  相似文献   

7.
The high level of seismic activity in eastern Turkey is thought to be mainly associated with the continuing collision of the Arabian and Eurasian tectonic plates. The determination of a detailed three-dimensional (3D) structure is crucial for a better understanding of this on-going collision or subduction process; therefore, a body wave tomographic inversion technique was performed on the region. The tomographic inversion used high quality arrival times from earthquakes occurring in the region from 1999 to 2001 recorded by a temporary 29 station broadband IRIS-PASSCAL array operated by research groups from the Universities of Bo?azi?i (Turkey) and Cornell (USA). The data was inverted and consisted of 3,114 P- and 2,298 S-wave arrival times from 252 local events with magnitudes (M D) ranging from 2.5 to 4.8. The stability and resolution of the results were qualitatively assessed by two synthetic tests: a spike test and checkerboard resolution test and it was found that the models were well resolved for most parts of the imaged domain. The tomographic inversion results reveal significant lateral heterogeneities in the study area to a depth of ~20?km. The P- and S-wave velocity models are consistent with each other and provide evidence for marked heterogeneities in the upper crustal structure beneath eastern Turkey. One of the most important features in the acquired tomographic images is the high velocity anomalies, which are generally parallel to the main tectonic units in the region, existing at shallow depths. This may relate to the existence of ophiolitic units at shallow depths. The other feature is that low velocities are widely dispersed through the 3D structure beneath the region at deeper crustal depths. This feature can be an indicator of the mantle upwelling or support the hypothesis that the Anatolian Plateau is underlain by a partially molten uppermost mantle.  相似文献   

8.
First-arrival traveltime tomography was applied to high-resolution seismic data acquired over a known quick-clay landslide scar near the Göta River in southwest Sweden in order to reveal the geometry and physical properties of clay-related normally consolidated sediments. Investigated area proved to be a challenging environment for tomographic imaging because of large P-wave velocity variations, ranging from 500 to 6000 m/s, and relatively steeply-dipping bedrock. Despite these challenges, P-wave velocity models were obtained down to ca. 150 m for two key 2D seismic profiles (each about 500-m long) intersecting over the landslide scar. The models portrait the sandwich-like structure of marine clays and coarse-grained consolidated sediments, but the estimated resolution (20 m) is too small to distinguish thin layers within this structure. Modelled velocity structures match well the results of reflection seismic processing and resistivity tomography available along the same profiles.  相似文献   

9.
The liquefaction potential of soils is traditionally assessed through geotechnical approaches based on the calculation of the cyclical stress ratio (CSR) induced by the expected earthquake and the ‘resistance’ provided by the soil, which is quantified through standard penetration (SPT), cone penetration (CPT), or similar tests. In more recent years, attempts to assess the liquefaction potential have also been made through measurement of shear wave velocity (VS) in boreholes or from the surface. The latter approach has the advantage of being non-invasive and low cost and of surveying lines rather than single points. However, the resolution of seismic surface techniques is lower than that of borehole techniques and it is still debated whether it is sufficient to assess the liquefaction potential.In this paper we focus our attention on surface seismic techniques (specifically the popular passive and active seismic techniques based on the correlation of surface waves such as ReMiTM, MASW, ESAC, SSAP, etc.) and explore their performance in assessing the liquefaction susceptibility of soils. The experimental dataset is provided by the two main seismic events of ML=5.9 and 5.8 (MW=6.1, MW=6.0) that struck the Emilia-Romagna region (Northern Italy) on May 20 and 29, 2012, after which extensive liquefaction phenomena were documented in an area of 1200 km2.The CPT and drillings available in the area allow us to classify the soils into four classes: A) shallow liquefied sandy soils, B) shallow non-liquefied sandy soils, C) deep non-liquefied sandy soils, and D) clayey–silty soils, and to determine that on average class A soils presented a higher sand content at the depth of 5–8 m compared to class B soils, where sand was dominant in the upper 5 m. Surface wave active–passive surveys were performed at 84 sites, and it was found that they were capable of discriminating among only three soil classes, since class A and B soils showed exactly the same VS distribution, and it is possible to show both experimentally and theoretically that they appear not to have sufficient resolution to address the seismic liquefaction issue.As a last step, we applied the state-of-the art CSR–VS method to assess the liquefaction potential of sandy deposits and we found that it failed in the studied area. This might be due to the insufficient resolution of the surface wave methods in assessing the Vs of thin layers and to the fact that Vs scales with the square root of the shear modulus, which implies an intrinsic lower sensitivity of Vs to the shear resistance of the soil compared to parameters traditionally measured with the penetration tests. However, it also emerged that the pure observation of the surface wave dispersion curves at their simplest level (i.e. in the frequency domain, with no inversion) is still potentially informative and can be used to identify the sites where more detailed surveys to assess the liquefaction potential are recommended.  相似文献   

10.
The pressure dependence of P- and S-wave velocities, velocity anisotropy, shear wave splitting and crack-porosity has been investigated in a number of samples from different crustal rock types for dry and wet (water saturated) conditions. At atmospheric pressure, P-wave velocities of the saturated, low-porosity rocks (< 1%) are significantly higher than in dry rocks, whereas the differences for S-wave velocities are less pronounced. The effect of intercrystalline fluids on seismic properties at increased pressure conditions is particularly reflected by the variation of the Poisson's ratio because P-wave velocities are more sensitive to fluids than S-wave velocities in the low-porosity rocks. Based on the experimental data, the respective crack-density parameter (), which is a measure of the number of flat cracks per volume unit contained within the background medium (crack-free matrix), has been calculated for dry and saturated conditions. There is a good correlation between the calculated crack-densities and crack-porosities derived from the experimentally determined volumetric strain curves. The shear wave velocity data, along with the shear wave polarisation referred to a orthogonal reference system, have been used to derive the spatial orientation of effective oriented cracks within a foliated biotite gneiss. The experimental data are in reasonable agreement with the self consistent model of O'Connell and Budiansky (1974). Taking the various lithologies into account, it is clear from the present study, that combined seismic measurements ofV p andV s , using theV p V s -ratio, may give evidence for fluids on grain boundaries and, in addition, may provide an estimate on the in-situ crack-densities.  相似文献   

11.
We have explored 1D S-wave velocity profiles of shallow and deep soil layers over a basement at strong motion stations in Eskisehir Province, Turkey. Microtremor array explorations were conducted at eight strong motion stations in the area to know shallow 1D S-wave velocity models. Rayleigh wave phase velocity at a frequency range from 3 to 30 Hz was estimated with the spatial autocorrelation analysis of array records of vertical microtremors at each station. Individual phase velocity was inverted to a shallow S-wave velocity profile. Low-velocity layers were identified at the stations in the basin. Site amplification factors from S-wave parts of earthquake records that had been estimated at the strong motion stations by Yamanaka et al. (2017) were inverted to the S-wave velocities and Q-values of the sedimentary layers. The depths to the basement with an S-wave velocity of 2.2 km/s are about 1 km in the central part of the basin, while the basement becomes shallow as 0.3 km in the marginal part of the basin. We finally discussed the effects of the shallow and deep sedimentary layers on the 1D S-wave amplification characteristics using the revealed profiles. It is found that the shallow soil layers have no significant effects in the amplification at a frequency range lower than 3 Hz in the area.  相似文献   

12.
The InterPACIFIC project was aimed at assessing the reliability, resolution, and variability of geophysical methods in estimating the shear-wave velocity profile for seismic ground response analyses. Three different subsoil conditions, which can be broadly defined as soft-soil, stiff-soil, and hard-rock, were investigated. At each site, several participants performed and interpreted invasive measurements of shear wave velocity (Vs) and compression wave velocity (Vp) in the same boreholes. Additionally, participants in the project analysed a common surface-wave dataset using their preferred strategies for processing and inversion to obtain Vs profiles. The most significant difference between the invasive borehole methods and non-invasive surface wave methods is related to resolution of thin layers and abrupt contrasts, which is inherently better for invasive methods. However, similar variability is observed in the estimated invasive and non-invasive Vs profiles, underscoring the need to account for such uncertainty in site response studies. VS,30 estimates are comparable between invasive and non-invasive methods, confirming that the higher resolution provided by invasive methods is quite irrelevant for computing this parameter.  相似文献   

13.
Several parameters are needed to describe the converted-wave （C-wave） moveout in processing multi-component seismic data, because of asymmetric raypaths and anisotropy. As the number of parameters increases, the converted wave data processing and analysis becomes more complex. This paper develops a new moveout equation with two parameters for C-waves in vertical transverse isotropy （VTI） media. The two parameters are the C-wave stacking velocity （Vc2） and the squared velocity ratio （7v,i） between the horizontal P-wave velocity and C-wave stacking velocity. The new equation has fewer parameters, but retains the same applicability as previous ones. The applicability of the new equation and the accuracy of the parameter estimation are checked using model and real data. The form of the new equation is the same as that for layered isotropic media. The new equation can simplify the procedure for C-wave processing and parameter estimation in VTI media, and can be applied to real C-wave processing and interpretation. Accurate Vc2 and Yvti can be deduced from C-wave data alone using the double-scanning method, and the velocity ratio model is suitable for event matching between P- and C-wave data.  相似文献   

14.
In recent years, numerous induced seismic events have occurred in the proximity of the natural gas field in Northern Germany. To monitor the seismicity and to asses the seismic hazard potential, a local monitoring network was installed in the area. Focusing on the seismicity hazard assessment, a major challenge is the characterisation of potential site effects due to local soil characteristics. This is quantitatively performed by estimating the shear-wave velocity (V s) variation with subsurface layer thickness. Such local effects can only be covered with a coarse spatial resolution due to the limited number of monitoring stations. Profiles were determined at three test sites (Langwedel, Walle and Bomlitz) by using a combined approach of small aperture 2D array ambient noise and small-scale active 1D measurements. The high-resolution frequency-wavenumber (HRFK), spatial autocorrelation (SPAC) and multichannel analysis of surface waves (MASW) methods were applied to the recorded ambient noise and active seismic data using various array sizes supplemented by the active measurements. This jointly allowed obtaining phase velocity dispersion curves covering a wide frequency range from 2 up to 32 Hz. The inversion of the obtained dispersion curves results in average S-wave velocity profiles down to depths of 70 m, identifying thin near-surface layers of a few meters as well as thicker layers of tens of meters in greater depth. A comparison with available borehole data shows a good correlation with the layering. Additionally, to asses the impact of a seismic event at the test sites, PGV estimations for various seismic events were performed. The final results of the test surveys demonstrate that the combined approach represents a suitable tool for near-surface characterisation, which can be used to improve the seismic hazard assessment in the area of the natural gas fields in Northern Germany.  相似文献   

15.
An ScP phase reflected and converted at the core–mantle boundary (CMB) beneath the region east of the Philippine Islands shows clear pre- and postcursors, recorded on short-period seismic networks in Japan. These waveform variations can be explained by interaction of the ScP wavefield with thin layers at the CMB. The results of forward modeling of double-array stacks reveal two different structural heterogeneities in the lowermost mantle beneath the region east of the Philippine Islands. One of the structures represents a decreased velocity, and increased density across the reflector at the lowermost ～10 km of the mantle, with P- and S-wave velocity reductions of 5–10% and ～30%, respectively, and an increase in density of 5–10%. Another structure consists of a pair of reflectors at ～10 km and ～5 km above the CMB, both of which are characterized by reduced P- and S-wave velocities. The upper reflector is the interface of a low-velocity zone in which P- and S-wave velocities decrease of 10% and 30%, respectively, accompanied by an extremely large increase in density (20–25%). The lower reflector is characterized by a 25% reduction in S-wave velocity relative to the above low-velocity layer, as well as a 5% decrease in P-wave velocity and no change in density. The nature of the low-velocity zone detected locally at the CMB is comparable with that of ultra-low-velocity zones (ULVZs) observed by various seismic probes in the South Pacific and Central America. Extensive observations of the ULVZ beneath the region east of the Philippine Islands indicate massive partial melting at the bottom of the mantle. Low-S-velocity basal layer partly detected within the ULVZ may be resulting from core–mantle chemical interactions, driven by massive partial melting.  相似文献   

16.
Subsurface lithology and seismic site classification of Lucknow urban center located in the central part of the Indo-Gangetic Basin (IGB) are presented based on detailed shallow subsurface investigations and borehole analysis. These are done by carrying out 47 seismic surface wave tests using multichannel analysis of surface waves (MASW) and 23 boreholes drilled up to 30 m with standard penetration test (SPT) N values. Subsurface lithology profiles drawn from the drilled boreholes show low- to medium-compressibility clay and silty to poorly graded sand available till depth of 30 m. In addition, deeper boreholes (depth >150 m) were collected from the Lucknow Jal Nigam (Water Corporation), Government of Uttar Pradesh to understand deeper subsoil stratification. Deeper boreholes in this paper refer to those with depth over 150 m. These reports show the presence of clay mix with sand and Kankar at some locations till a depth of 150 m, followed by layers of sand, clay, and Kankar up to 400 m. Based on the available details, shallow and deeper cross-sections through Lucknow are presented. Shear wave velocity (SWV) and N-SPT values were measured for the study area using MASW and SPT testing. Measured SWV and N-SPT values for the same locations were found to be comparable. These values were used to estimate 30 m average values of N-SPT (N 30) and SWV (V s 30 ) for seismic site classification of the study area as per the National Earthquake Hazards Reduction Program (NEHRP) soil classification system. Based on the NEHRP classification, the entire study area is classified into site class C and D based on V s 30 and site class D and E based on N 30. The issue of larger amplification during future seismic events is highlighted for a major part of the study area which comes under site class D and E. Also, the mismatch of site classes based on N 30 and V s 30 raises the question of the suitability of the NEHRP classification system for the study region. Further, 17 sets of SPT and SWV data are used to develop a correlation between N-SPT and SWV. This represents a first attempt of seismic site classification and correlation between N-SPT and SWV in the Indo-Gangetic Basin.  相似文献   

17.
To better understand the relationship between crustal heterogeneity and seismotectonics in the National Capital Region (NCR), Delhi, India, we carried out local P- and S-velocity tomography beneath the NCR. First arrival times of the first P- and S-wave from 275 crustal earthquakes recorded by the Seismic Telemetry Network in and around Delhi of the India Meteorological Department, India, are inverted to obtain crustal P-, S-velocity and V P /V S variations in the region. Our tomographic images of the upper crust reflect well the surface geological and tectonic features. The Delhi fold belt is identified as low V P, high V S and low V P/V S. The Sohna hot spring region is appearing as low V P, low V S and high V P /V S correlating with the possible presence of fluid-filled rocks. The crustal seismicity is distributed in both the high- and low-velocity zones, but most distinctly in the low V P /V S region.  相似文献   

18.
井间高分辨率纵横波层析成像研究井间油藏   总被引：3，自引：1，他引：2       下载免费PDF全文
瞿辰  杨文采  于常青 《地球物理学报》2010,53(12):2944-2954
采用视速度-偏振井间波场分离法分离得到纵波和横波波场,使用跨孔地震走时层析成像级联方法计算井间纵波和横波速度结构以及泊松比空间分布.综合纵横波速度、泊松比和测井参数,分析两井间岩性和储层特性.数值模型试验表明该方法垂直分辨率达到主频波长的1/4,并能准确分辨倾斜断层和垂直断层.处理相同纵波资料结果表明本文方法分辨率远远高于以往的井间走时层析成像方法,比井间声波层析成像分辨率更高.使用该方法处理垦71区井间资料,得到同台同源纵波和横波速度结构和泊松比分布.泊松比的低/高变化与测井参数指示的砂/泥岩层基本吻合.根据泊松比分布,参考岩石地震物理学测试数据,可以区分井间介质中的泥岩层、砂岩层,以及砂岩层中的饱水和饱油区,确定储层的连通性,圈定井间的剩余油藏.  相似文献   

19.
Contrasts in elastic parameters can be estimated directly from seismic data using offset-dependent information in the PP reflection coefficient. A linear approximation to the PP reflection coefficient including three coefficients is fitted to the data, and relative contrasts in various elastic parameters are obtained from linear combinations of the estimated coefficients. Linearized elastic parameter sections for the contrasts in P-wave impedance, P-wave velocity, density, plane-wave modulus, and the change in bulk modulus and shear modulus normalized with the plane-wave modulus are estimated. If the average P- to S-wave velocity ratio is known, linearized parameter sections including the contrast in the average P- to S-wave velocity ratio and a fluid factor section can be computed. Applied to synthetic data, visual comparison of the estimated and true elastic parameter sections agree qualitatively, and the results are confirmed by an analysis of the standard deviation of the estimated parameters. The parameter sections obtained by inversion of a shallow seismic anomaly in the Barents Sea are promising, but the reliability is uncertain because neither well data nor regional trends are available.  相似文献   

20.
Shear-wave velocity is a key parameter for calibrating monitoring time-lapse 4D seismic data during CO2-EOR (Enhanced Oil Recovery) and CO2 sequestration. However, actual S-wave velocity data are lacking, especially in 4D data for CO2 sequestration because wells are closed after the CO2 injection and seismic monitoring is continued but no well log data are acquired. When CO2 is injected into a reservoir, the pressure and saturation of the reservoirs change as well as the elastic parameters of the reservoir rocks. We propose a method to predict the S-wave velocity in reservoirs at different pressures and porosities based on the Hertz–Mindlin and Gassmann equations. Because the coordination number is unknown in the Hertz–Mindlin equation, we propose a new method to predict it. Thus, we use data at different CO2 injection stages in the Gao89 well block, Shengli Oilfield. First, the sand and mud beds are separated based on the structural characteristics of the thin sand beds and then the S-wave velocity as a function of reservoir pressure and porosity is calculated. Finally, synthetic seismic seismograms are generated based on the predicted P- and S-wave velocities at different stages of CO2 injection.  相似文献   

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