Using geoisostasy phenomena,the author has got the answers for some questions about tsunami physical nature.Equilibrium state conception of the rotated Earth as the planet(geoisostasy)was shown on theⅩⅩⅧsession of ...Using geoisostasy phenomena,the author has got the answers for some questions about tsunami physical nature.Equilibrium state conception of the rotated Earth as the planet(geoisostasy)was shown on theⅩⅩⅧsession of the International Geological Congress for the first time.According to geoisostasy conception there are some conditions that must fulfill tsunami development:(1)ocean-floor tectonic motions must have significant vertical components;(2) vertical displacements of tectonic blocks must展开更多
For our investigation we have 235 measurements done in the east part of Democratic Republic of Congo by P.Herrinck during a magnetic survey including the graben region from the parallel joining Goma city and Mahagi ci...For our investigation we have 235 measurements done in the east part of Democratic Republic of Congo by P.Herrinck during a magnetic survey including the graben region from the parallel joining Goma city and Mahagi city, the region between Albert and Aka lakes, and the route from Aba to Kinsagani. During the surveys the density of recording points has been selected according to the importance of anomalies. In this way, the offset was 1 km where the disturbance was high in Goma city and 20 km have been sufficient along the route from Aba to Kinsagani. For the topographic and isostatic reductions only one cartographic document has been chosen that was the international map of the scale 1/1 000 000 which presents a certain characteristic of homogeneity.展开更多
The application of the seismic reflection method is often limited in complex terrain areas. The problem is the incorrect correction of time-shift caused by topography. To apply normal moveout (NMO) correction to refle...The application of the seismic reflection method is often limited in complex terrain areas. The problem is the incorrect correction of time-shift caused by topography. To apply normal moveout (NMO) correction to reflection data correctly, static corrections are necessary to be applied in advance for the compensation of the time distortions of topography and the time-delays from near-surface weathered layers. For environment and engineering investigation, weathered layers are our targets so that the static correction mainly serves the adjustment of time-shift due to an undulating surface. In practice, seismic reflected raypaths are assumed to be almost vertical through the near-surface layers because they have much lower velocities than layers below. This assumption is typically acceptable in most cases since it results in little residual error for small elevation changes and small offsets in reflection events. Although static algorithms based on choosing a floating datum related to common midpoint gathers or residual surface-consistent functions are available and effective, errors caused by the assumption of vertical raypaths often generate pseudo indications of structures. This paper presents the comparison of applying corrections based on the vertical raypaths and bias (non-vertical) raypaths. It also provides an approach of combining elevation and NMO corrections. The advantages of the approach are demonstrated by a synthetic example of multi-coverage seismic reflection surveys on rough topography.展开更多
The oolitic shoals of the Triassic carbonate platform margin in the Yudongzi (鱼洞子) outcrop of Erlangmiao (二郎庙) area in the northwestern Sichuan (四川) basin present a scarce opportunity to quantitatively d...The oolitic shoals of the Triassic carbonate platform margin in the Yudongzi (鱼洞子) outcrop of Erlangmiao (二郎庙) area in the northwestern Sichuan (四川) basin present a scarce opportunity to quantitatively describe their diagenesis and its effects on the acoustic velocity. Using a detailed field geologic survey, profiles illustration of typical depositional system, and systematic testing, five types of diagenesis have been identified in the oolitic shoals: micritization, cementation, compaction and pressolution, dissolution, and dolomitisation. The cementation is composed of four subtypes (micrite cements, fibrous calcite cements, granular calcite cements, and blocky calcite cements). The dissolution is formed from three subtypes (freshwater selective dissolution, burial non-selective dissolution, and burial selective dissolution). The dolomitisation is composed of three subtypes (fine-crystalline dolomites, microcrystalline dolomites, and medium-crystalline dolomites). In order to quantitatively describe the diagenetic fabric of oolitic shoals, the micritic grain content, calcite cement content, mean pore diameter, pore types, dolomite content, and dolomite types have been evaluated. Based on these data, the relationship between the acoustic velocity and diagenesis of oolitic shoals hasbeen established. The results show that the diagenetic fabric is linearly related with the acoustic velocity, and the general trend observed is as expected a decrease of velocity as the micritic grain content, mean pore diameter and dolomite content increase, or the sparite cement content decreases. This study will demonstrate that the transformation of diagenetic facies will probably make the petrophysicai properties ofEffects of Diagenesis on the Acoustic Velocity of the Triassic Oolitic Shoals in the Yudongzi Outcropthe oolitic shoals regularly changed. The reflection configuration of diagenetic facies in the oolitic shoals can be shown in the synthetic seismic model simulated according to the P-wave impedance and S-wave impedance.展开更多
文摘Using geoisostasy phenomena,the author has got the answers for some questions about tsunami physical nature.Equilibrium state conception of the rotated Earth as the planet(geoisostasy)was shown on theⅩⅩⅧsession of the International Geological Congress for the first time.According to geoisostasy conception there are some conditions that must fulfill tsunami development:(1)ocean-floor tectonic motions must have significant vertical components;(2) vertical displacements of tectonic blocks must
文摘For our investigation we have 235 measurements done in the east part of Democratic Republic of Congo by P.Herrinck during a magnetic survey including the graben region from the parallel joining Goma city and Mahagi city, the region between Albert and Aka lakes, and the route from Aba to Kinsagani. During the surveys the density of recording points has been selected according to the importance of anomalies. In this way, the offset was 1 km where the disturbance was high in Goma city and 20 km have been sufficient along the route from Aba to Kinsagani. For the topographic and isostatic reductions only one cartographic document has been chosen that was the international map of the scale 1/1 000 000 which presents a certain characteristic of homogeneity.
基金ThispaperisfundedbytheNaturalScienceFoundationofHubeiProvince ,China (No .2 0 0 1ABB0 0 3)
文摘The application of the seismic reflection method is often limited in complex terrain areas. The problem is the incorrect correction of time-shift caused by topography. To apply normal moveout (NMO) correction to reflection data correctly, static corrections are necessary to be applied in advance for the compensation of the time distortions of topography and the time-delays from near-surface weathered layers. For environment and engineering investigation, weathered layers are our targets so that the static correction mainly serves the adjustment of time-shift due to an undulating surface. In practice, seismic reflected raypaths are assumed to be almost vertical through the near-surface layers because they have much lower velocities than layers below. This assumption is typically acceptable in most cases since it results in little residual error for small elevation changes and small offsets in reflection events. Although static algorithms based on choosing a floating datum related to common midpoint gathers or residual surface-consistent functions are available and effective, errors caused by the assumption of vertical raypaths often generate pseudo indications of structures. This paper presents the comparison of applying corrections based on the vertical raypaths and bias (non-vertical) raypaths. It also provides an approach of combining elevation and NMO corrections. The advantages of the approach are demonstrated by a synthetic example of multi-coverage seismic reflection surveys on rough topography.
基金supported by the SINOPEC Forward Looking Project of China (No. YPH08114)
文摘The oolitic shoals of the Triassic carbonate platform margin in the Yudongzi (鱼洞子) outcrop of Erlangmiao (二郎庙) area in the northwestern Sichuan (四川) basin present a scarce opportunity to quantitatively describe their diagenesis and its effects on the acoustic velocity. Using a detailed field geologic survey, profiles illustration of typical depositional system, and systematic testing, five types of diagenesis have been identified in the oolitic shoals: micritization, cementation, compaction and pressolution, dissolution, and dolomitisation. The cementation is composed of four subtypes (micrite cements, fibrous calcite cements, granular calcite cements, and blocky calcite cements). The dissolution is formed from three subtypes (freshwater selective dissolution, burial non-selective dissolution, and burial selective dissolution). The dolomitisation is composed of three subtypes (fine-crystalline dolomites, microcrystalline dolomites, and medium-crystalline dolomites). In order to quantitatively describe the diagenetic fabric of oolitic shoals, the micritic grain content, calcite cement content, mean pore diameter, pore types, dolomite content, and dolomite types have been evaluated. Based on these data, the relationship between the acoustic velocity and diagenesis of oolitic shoals hasbeen established. The results show that the diagenetic fabric is linearly related with the acoustic velocity, and the general trend observed is as expected a decrease of velocity as the micritic grain content, mean pore diameter and dolomite content increase, or the sparite cement content decreases. This study will demonstrate that the transformation of diagenetic facies will probably make the petrophysicai properties ofEffects of Diagenesis on the Acoustic Velocity of the Triassic Oolitic Shoals in the Yudongzi Outcropthe oolitic shoals regularly changed. The reflection configuration of diagenetic facies in the oolitic shoals can be shown in the synthetic seismic model simulated according to the P-wave impedance and S-wave impedance.