Reliable thickness of sedimentary layers is essential for seismic hazard assessment in active fault zones, especially in regions prone to strong earthquakes. This study analyzed the seismic ambient noise data recorded...Reliable thickness of sedimentary layers is essential for seismic hazard assessment in active fault zones, especially in regions prone to strong earthquakes. This study analyzed the seismic ambient noise data recorded by 60 short-period seismic stations deployed at the Jishishan earthquake source and adjacent areas. The base-order resonance frequencies of sedimentary layers beneath the stations were determined using the horizontal-to-vertical spectral ratio method on ambient noise with diff erent frequencies. Then, a resonance-thickness formula was applied to estimate the sedimentary layer thickness at each station. Finally, the entire regional sediment thickness was obtained via interpolation. The thickness of the sedimentary layer beneath each station was estimated using the equation of the relationship between resonance frequency and sedimentary layer thickness, and fi nally, the distribution of sedimentary layer thickness in the whole region was obtained by interpolation. Results reveal notable spatial variations in sediment thickness in the source and adjacent areas. The shallow sedimentary layer in the source area is relatively thick at approximately 100 m, whereas that in Liugou Village, which is the most severely damaged area, is approximately 150-180 m. In the western region, specifically along the western edge of the Jishishan Mountain rupture and the Pourouliuhe-Cheunhua Nanshan rupture zone, the shallow sedimentary layer is approximately 30-60 m. A comparison between the distribution of seismic secondary hazards and sedimentary layer thickness highlights a strong correlation between these hazards and the amplifi cation eff ects of seismic waves. In regions with thicker sedimentary layers, ground shaking is signifi cantly amplifi ed, resulting in more serious seismic secondary hazards. In addition, the study confi rmed that secondary hazards, such as landslides and liquefaction, were more prevalent in regions with thicker sedimentary layers. These fi ndings provide an important reference for post-earthquake reconstruction, seismic risk assessment, and the development of regional disaster prevention and mitigation strategies..展开更多
The finite element method （FEM） was used to simulate sediment hydrodynamics at the Beidaihe International Yacht Club, and a two-dimensional model was established. The sediment movement and deposition were analyzed u...The finite element method （FEM） was used to simulate sediment hydrodynamics at the Beidaihe International Yacht Club, and a two-dimensional model was established. The sediment movement and deposition were analyzed under many tidal conditions in conjunction with the hydrological regime of the Daihe River. The peak value of the sediment deposition thickness appears in the main channel and around the estuary. The sediment deposition thickness is essentially constant and relatively small in the project area. The sediment deposition thickness in the main channel, in the yachting area, and around the hotel is greater than the other areas in the project. Regular excavation and dredging of the channel is the best measure for mitigating the sedimentation.展开更多
According to Vening Meinesz-Moritz （VMM） global inverse isostatic problem, either the Moho density contrast （crust-mantle density contrast） or the Moho geometry can be estimated by solv- ing a non-linear Fredholm ...According to Vening Meinesz-Moritz （VMM） global inverse isostatic problem, either the Moho density contrast （crust-mantle density contrast） or the Moho geometry can be estimated by solv- ing a non-linear Fredholm integral equation of the first kind. Here solutions to the two Moho parame- ters are presented by combining the global geopotential model （GOCO-03S）, topography （DTM2006） and a seismic crust model, the latter being the recent digital global crustal model （CRUST1.0） with a resolution of 1°×1°. The numerical results show that the estimated Moho density contrast varies from 21 to 637 kg/m3, with a global average of 321 kg/m^3, and the estimated Moho depth varies from 6 to 86 km with a global average of 24 km. Comparing the Moho density contrasts estimated using our least-squares method and those derived by the CRUST1.0, CRUST2.0, and PREM models shows that our estimate agrees fairly well with CRUST1.0 model and rather poor with other models. The estimated Moho depths by our least-squares method and the CRUST1.0 model agree to 4.8 km in RMS and with the GEMMA1.0 based model to 6.3 km.展开更多
Wadi El Assiuti represents a promising area for agricultural development and building new communities far from the overpopulated areas in the Nile Val-ley. An integrated approach of satellite-based data and geophysica...Wadi El Assiuti represents a promising area for agricultural development and building new communities far from the overpopulated areas in the Nile Val-ley. An integrated approach of satellite-based data and geophysical data with borehole data was used for defining the area of interest, the sediment thick-ness, delineating the subsurface structures, and mapping the depth to the basement rocks, and defining the groundwater aquifers. Findings are: 1) Dramatic changes are detected in the anthropogenic activities at the entrance area of the wadi, making stress and heavy exploitation of the groundwater resources. However, the central and northeastern regions show no development;2) Several structural trends in the directions of NNW, NW, NE, and E-W are cutting the basement rocks and sedimentary cover;3) The depth to the basement rocks is increasing eastward from ~2.24 km to ~4.84 km;4) Three groundwater-bearing reservoirs are represented by the shallow Qua-ternary, the fractured limestone, and the deep Nubian sandstone aquifers;5) The deep-seated faults are affecting the area and rising groundwater from the deeper Nubian aquifer along its sub-vertical trend;and 6) The results are in-formative and used to define the suitable sites for water well drilling.展开更多
Mechanism and modeling of the land subsidence are complex because of the complicate geological background in Beijing, China. This paper analyzed the spatial relationship between land subsidence and three factors, incl...Mechanism and modeling of the land subsidence are complex because of the complicate geological background in Beijing, China. This paper analyzed the spatial relationship between land subsidence and three factors, including the change of groundwater level, the thickness of compressible sediments and the building area by using remote sensing and GIS tools in the upper-middle part of alluvial-proluvial plain fan of the Chaobai River in Beijing. Based on the spatial analysis of the land subsidence and three factors, there exist significant non-linear relationship between the vertical displacement and three factors. The Back Propagation Neural Network (BPN) model combined with Genetic Algorithm (GA) was used to simulate regional distribution of the land subsidence. Results showed that at field scale, the groundwater level and land subsidence showed a significant linear relationship. However, at regional scale, the spatial distribution of groundwater depletion funnel did not overlap with the land subsidence funnel. As to the factor of compressible strata, the places with the biggest compressible strata thickness did not have the largest vertical displacement. The distributions of building area and land subsidence have no obvious spatial relationships. The BPN-GA model simulation results illustrated that the accuracy of the trained model during fifty years is acceptable with an error of 51% of verification data less than 20 mm and the average of the absolute error about 32 mm. The BPN model could be utilized to simulate the general distribution of land subsidence in the study area. Overall, this work contributes to better understand the complex relationship between the land subsidence and three influencing factors. And the distribution of the land subsidence can be simulated by the trained BPN-GA model with the limited available dada and acceptable accuracy.展开更多
Groundwater inundation occurs when rivers with high water levels are hydraulically connected to the adjacent riversides.Huge barrages constructed in South Korea have caused the river water levels and groundwater level...Groundwater inundation occurs when rivers with high water levels are hydraulically connected to the adjacent riversides.Huge barrages constructed in South Korea have caused the river water levels and groundwater levels in the riversides to increase.We used a discriminant model with seven input variables,namely the sediment thickness,difference between the land elevation and river water level,difference between the groundwater and river water levels,soil drainage type,topsoil texture,subsoil texture,and hydrological soil feature classification,to develop a map of the groundwater inundation vulnerability along the basins of the Nakdong River.We estimated the groundwater levels in unmonitored areas with a linear regression model developed from the relationship between the distance from the river and the depth to the groundwater in 91 monitoring wells.We produced a grid map for the vulnerability with an optimum grid size of 100 m.We validated the groundwater inundation vulnerability map by comparing highly susceptible areas with swampy fields observed in a field survey.This result indicates that the vulnerability map will be helpful to forecast and prepare inundation in the riversides during the rainy season when the river water levels are inevitably high.展开更多
基金jointly supported by the National Natural Science Foundation of China (42204061)Special Fund for Basic Research Operations of the Institute of Geophysics,China Earthquake Administration (0419501)+1 种基金the Gansu Jishishan6.2 magnitude earthquake scientific investigation (DQJB23Y45) programthe Sichuan Provincial Natural Science Foundation (2023NSFSC0768,2023NSFSC0770)。
文摘Reliable thickness of sedimentary layers is essential for seismic hazard assessment in active fault zones, especially in regions prone to strong earthquakes. This study analyzed the seismic ambient noise data recorded by 60 short-period seismic stations deployed at the Jishishan earthquake source and adjacent areas. The base-order resonance frequencies of sedimentary layers beneath the stations were determined using the horizontal-to-vertical spectral ratio method on ambient noise with diff erent frequencies. Then, a resonance-thickness formula was applied to estimate the sedimentary layer thickness at each station. Finally, the entire regional sediment thickness was obtained via interpolation. The thickness of the sedimentary layer beneath each station was estimated using the equation of the relationship between resonance frequency and sedimentary layer thickness, and fi nally, the distribution of sedimentary layer thickness in the whole region was obtained by interpolation. Results reveal notable spatial variations in sediment thickness in the source and adjacent areas. The shallow sedimentary layer in the source area is relatively thick at approximately 100 m, whereas that in Liugou Village, which is the most severely damaged area, is approximately 150-180 m. In the western region, specifically along the western edge of the Jishishan Mountain rupture and the Pourouliuhe-Cheunhua Nanshan rupture zone, the shallow sedimentary layer is approximately 30-60 m. A comparison between the distribution of seismic secondary hazards and sedimentary layer thickness highlights a strong correlation between these hazards and the amplifi cation eff ects of seismic waves. In regions with thicker sedimentary layers, ground shaking is signifi cantly amplifi ed, resulting in more serious seismic secondary hazards. In addition, the study confi rmed that secondary hazards, such as landslides and liquefaction, were more prevalent in regions with thicker sedimentary layers. These fi ndings provide an important reference for post-earthquake reconstruction, seismic risk assessment, and the development of regional disaster prevention and mitigation strategies..
文摘The finite element method （FEM） was used to simulate sediment hydrodynamics at the Beidaihe International Yacht Club, and a two-dimensional model was established. The sediment movement and deposition were analyzed under many tidal conditions in conjunction with the hydrological regime of the Daihe River. The peak value of the sediment deposition thickness appears in the main channel and around the estuary. The sediment deposition thickness is essentially constant and relatively small in the project area. The sediment deposition thickness in the main channel, in the yachting area, and around the hotel is greater than the other areas in the project. Regular excavation and dredging of the channel is the best measure for mitigating the sedimentation.
文摘According to Vening Meinesz-Moritz （VMM） global inverse isostatic problem, either the Moho density contrast （crust-mantle density contrast） or the Moho geometry can be estimated by solv- ing a non-linear Fredholm integral equation of the first kind. Here solutions to the two Moho parame- ters are presented by combining the global geopotential model （GOCO-03S）, topography （DTM2006） and a seismic crust model, the latter being the recent digital global crustal model （CRUST1.0） with a resolution of 1°×1°. The numerical results show that the estimated Moho density contrast varies from 21 to 637 kg/m3, with a global average of 321 kg/m^3, and the estimated Moho depth varies from 6 to 86 km with a global average of 24 km. Comparing the Moho density contrasts estimated using our least-squares method and those derived by the CRUST1.0, CRUST2.0, and PREM models shows that our estimate agrees fairly well with CRUST1.0 model and rather poor with other models. The estimated Moho depths by our least-squares method and the CRUST1.0 model agree to 4.8 km in RMS and with the GEMMA1.0 based model to 6.3 km.
文摘Wadi El Assiuti represents a promising area for agricultural development and building new communities far from the overpopulated areas in the Nile Val-ley. An integrated approach of satellite-based data and geophysical data with borehole data was used for defining the area of interest, the sediment thick-ness, delineating the subsurface structures, and mapping the depth to the basement rocks, and defining the groundwater aquifers. Findings are: 1) Dramatic changes are detected in the anthropogenic activities at the entrance area of the wadi, making stress and heavy exploitation of the groundwater resources. However, the central and northeastern regions show no development;2) Several structural trends in the directions of NNW, NW, NE, and E-W are cutting the basement rocks and sedimentary cover;3) The depth to the basement rocks is increasing eastward from ~2.24 km to ~4.84 km;4) Three groundwater-bearing reservoirs are represented by the shallow Qua-ternary, the fractured limestone, and the deep Nubian sandstone aquifers;5) The deep-seated faults are affecting the area and rising groundwater from the deeper Nubian aquifer along its sub-vertical trend;and 6) The results are in-formative and used to define the suitable sites for water well drilling.
基金Under the auspices of National Natural Science Foundation of China(No.41201420,41130744)Beijing Nova Program(No.Z111106054511097)Foundation of Beijing Municipal Commission of Education(No.KM201110028016)
文摘Mechanism and modeling of the land subsidence are complex because of the complicate geological background in Beijing, China. This paper analyzed the spatial relationship between land subsidence and three factors, including the change of groundwater level, the thickness of compressible sediments and the building area by using remote sensing and GIS tools in the upper-middle part of alluvial-proluvial plain fan of the Chaobai River in Beijing. Based on the spatial analysis of the land subsidence and three factors, there exist significant non-linear relationship between the vertical displacement and three factors. The Back Propagation Neural Network (BPN) model combined with Genetic Algorithm (GA) was used to simulate regional distribution of the land subsidence. Results showed that at field scale, the groundwater level and land subsidence showed a significant linear relationship. However, at regional scale, the spatial distribution of groundwater depletion funnel did not overlap with the land subsidence funnel. As to the factor of compressible strata, the places with the biggest compressible strata thickness did not have the largest vertical displacement. The distributions of building area and land subsidence have no obvious spatial relationships. The BPN-GA model simulation results illustrated that the accuracy of the trained model during fifty years is acceptable with an error of 51% of verification data less than 20 mm and the average of the absolute error about 32 mm. The BPN model could be utilized to simulate the general distribution of land subsidence in the study area. Overall, this work contributes to better understand the complex relationship between the land subsidence and three influencing factors. And the distribution of the land subsidence can be simulated by the trained BPN-GA model with the limited available dada and acceptable accuracy.
基金supported by the Daejeon University Research Grants(2016)scheme.
文摘Groundwater inundation occurs when rivers with high water levels are hydraulically connected to the adjacent riversides.Huge barrages constructed in South Korea have caused the river water levels and groundwater levels in the riversides to increase.We used a discriminant model with seven input variables,namely the sediment thickness,difference between the land elevation and river water level,difference between the groundwater and river water levels,soil drainage type,topsoil texture,subsoil texture,and hydrological soil feature classification,to develop a map of the groundwater inundation vulnerability along the basins of the Nakdong River.We estimated the groundwater levels in unmonitored areas with a linear regression model developed from the relationship between the distance from the river and the depth to the groundwater in 91 monitoring wells.We produced a grid map for the vulnerability with an optimum grid size of 100 m.We validated the groundwater inundation vulnerability map by comparing highly susceptible areas with swampy fields observed in a field survey.This result indicates that the vulnerability map will be helpful to forecast and prepare inundation in the riversides during the rainy season when the river water levels are inevitably high.
