Carbon and nitrogen stable isotopes are useful tracers for distinguishing marine and terrestrial plant sources of sedimentary organic matter(OM),and for identifying OM from different types of plants.By analyzing the c...Carbon and nitrogen stable isotopes are useful tracers for distinguishing marine and terrestrial plant sources of sedimentary organic matter(OM),and for identifying OM from different types of plants.By analyzing the carbon and nitrogen stable isotopes of marine and riverine sediments from Bohai Bay and its catchment,we were able to identify the source of OM in these sediments.The stable carbon isotope values of Bohai Bay sediments were between-22.94‰ and-23.90‰,while those of riverine sediments were from-24.45‰ to-32.50‰.Marine algae were the main source of OM in Bohai Bay sediments.However,lacustrine algae were the main source of riverine sediments,not terrestrial OM.The nitrogen isotopes in Bohai Bay sediments decreased in eastward direction,with increasing distance from the coastline,which suggested a higher degree of impact from human activities along the coast.展开更多
Sediment cores （-40-100 cm） were collected at 12 locations in the western Bohai Bay, the Haihe River estuary, the Yongding River estuary and the Tianjin Harbor, China, during 24-26 July 2007, and analyzed for ^7Be a...Sediment cores （-40-100 cm） were collected at 12 locations in the western Bohai Bay, the Haihe River estuary, the Yongding River estuary and the Tianjin Harbor, China, during 24-26 July 2007, and analyzed for ^7Be and ^210pb activities. Due to localized hydrodynamic patterns and frequent disturbance from dredging activities, steady-state sedimentation features were not observed in this study. As demonstrated in the VBe and ^210pb profiles, the temporal and spatial variations of these radionuclides support a non-steady state depositional environment in the study area. By comparing ^7Be and ^210pb inventories in the sediments with those of the atmospheric source, we found that： 1） sediments dredged from the Tianjin Harbor or eroded from nearby estuarine and coastal areas are retained in the western Bohai Bay for relatively short intervals （several months）, as reflected in the relatively high ^7Be inventories in the western Bohai Bay; 2） over the long-term （years to decades）, ^210Pb inventories in the sediments imply that there is a net on-shore transport of sediments, and the sediments are mass-balanced in the entire study area. Overall, our results suggest that the sediments are retained in the estuaries and the western Bohai Bay despite local variability in sediment dynamics and disturbance due to human activities.展开更多
This paper analyzes the seismicity and seismic risk distribution in the Bohai Sea. Based on the seismic design parameters of 46 platforms in the Bohai Sea, a statistic analysis is made on the ratios of the peak accele...This paper analyzes the seismicity and seismic risk distribution in the Bohai Sea. Based on the seismic design parameters of 46 platforms in the Bohai Sea, a statistic analysis is made on the ratios of the peak accelerations for different probability levels. In accordance with the two-stage design method, a scheme of two design seismic levels is proposed, and two fortification goals are established respectively for strength level earthquakes and ductility level earthquakes. Through analogy and comparison to the Chinese seismic code for buildings, it is proposed that the probability level for the strength and ductility level earthquakes takes return periods of 200a and 1000～2500a respectively, and we further expounded on its rationality. Finally, the fortification parameters in the sub-regions of Bohai Sea area are given in the light of seismic risk zonation and ground motion division. This article is a summary of experiences from many years of offshore platform seismic fortification work, and an exploratory study on the seismic fortification standards of offshore platforms in China, which may provide some references for the establishment of the standard.展开更多
Based on the rotation in the entire block and homogeneous strain model ( REHSM) ,we firstly analyze the motion and deformation features across the southern part of Tancheng- Lujiang fault zone from GPS velocity fields...Based on the rotation in the entire block and homogeneous strain model ( REHSM) ,we firstly analyze the motion and deformation features across the southern part of Tancheng- Lujiang fault zone from GPS velocity fields in period of 1999 ～ 2001,2001 ～ 2004,2004 ～ 2007 and 2007 ～ 2009. The results show a dextral strike-slip feature in the Weifang- Tancheng segment and sinistral strike-slip in the Tancheng-Lujiang segment. And the deformation perpendicular to the Tancheng-Lujiang fault zone alternates between tension and compression in different time-intervals. Then we resolve the relative rigid motion of blocks around Bohai Bay to the Circum-Bohai Sea area by deducting the entire rigid motion of the Circum-Bohai Sea area. We find that the Yanshan-Bohai seismic belt split this area into two parts,the northern part moving NW,and the other SE.展开更多
The loading tides are calculated by means of the Green's function method based on a high-resolution regional ocean tide model, the TOPO7.0 global ocean tide model, and the Gutenberg-Bullen A Earth model. The resul...The loading tides are calculated by means of the Green's function method based on a high-resolution regional ocean tide model, the TOPO7.0 global ocean tide model, and the Gutenberg-Bullen A Earth model. The results show that the maximal amplitude of M2 vertical displacement loading (VDL) tide in the Bohai, Yellow, and East China Seas exceeding 28mm appears 150km off the Zhejiang coast; the second maximum exceeding 20mm appears in Inchon Bay; and the third maximum exceeding 14mm is located in the northeast of the North Yellow Sea. The maximal amplitudes of S2 VDL tide at the above three locations exceed 10, 8, and 4mm, respectively. The maximal amplitudes of the K1 and O1 VDL tides, exceeding 13 and 10 mm respectively, appear near the central and north Ryukyu Islands; the amplitudes tend to decease toward the inward areas. The phases of semidiurnal VDL tides are basically opposite to those of corresponding ocean tides. The phases of diurnal VDL tides are basically opposite to those of corresponding ocean tides in the most part of the East China Sea and the eastern part of the South Yellow Sea. This anti-phase relationship generally does not hold in the rest parts of the Bohai and Yellow Seas. The distribution patterns of self-attraction and loading (SAL) tides are very similar to those of VDL tides. The SAL tides have amplitudes about 1.2-1.7 times of the corresponding VDL tides and their phases are basically opposite to the corresponding VDL tides. The maximal amplitude of M2 SAL tide also appears off the Zhejiang coast, with a magnitude exceeding 42mm.展开更多
基金Supported by the National Natural Science Foundation of China(No.41273068)the Tianjin Research Program of Applied Science and Advanced Technology(No.11JCZDJC24100)
文摘Carbon and nitrogen stable isotopes are useful tracers for distinguishing marine and terrestrial plant sources of sedimentary organic matter(OM),and for identifying OM from different types of plants.By analyzing the carbon and nitrogen stable isotopes of marine and riverine sediments from Bohai Bay and its catchment,we were able to identify the source of OM in these sediments.The stable carbon isotope values of Bohai Bay sediments were between-22.94‰ and-23.90‰,while those of riverine sediments were from-24.45‰ to-32.50‰.Marine algae were the main source of OM in Bohai Bay sediments.However,lacustrine algae were the main source of riverine sediments,not terrestrial OM.The nitrogen isotopes in Bohai Bay sediments decreased in eastward direction,with increasing distance from the coastline,which suggested a higher degree of impact from human activities along the coast.
基金Supported by the New Jersey Sea Grant (No. 6560-0000, H. Feng)the Tianjin Science and Technology Committee (No. 06YFGHHZ01500)
文摘Sediment cores （-40-100 cm） were collected at 12 locations in the western Bohai Bay, the Haihe River estuary, the Yongding River estuary and the Tianjin Harbor, China, during 24-26 July 2007, and analyzed for ^7Be and ^210pb activities. Due to localized hydrodynamic patterns and frequent disturbance from dredging activities, steady-state sedimentation features were not observed in this study. As demonstrated in the VBe and ^210pb profiles, the temporal and spatial variations of these radionuclides support a non-steady state depositional environment in the study area. By comparing ^7Be and ^210pb inventories in the sediments with those of the atmospheric source, we found that： 1） sediments dredged from the Tianjin Harbor or eroded from nearby estuarine and coastal areas are retained in the western Bohai Bay for relatively short intervals （several months）, as reflected in the relatively high ^7Be inventories in the western Bohai Bay; 2） over the long-term （years to decades）, ^210Pb inventories in the sediments imply that there is a net on-shore transport of sediments, and the sediments are mass-balanced in the entire study area. Overall, our results suggest that the sediments are retained in the estuaries and the western Bohai Bay despite local variability in sediment dynamics and disturbance due to human activities.
基金Supported by Special Scientific Research of Public Welfare Profession of Ministry of Finance,the People's Republic of China(200708055)
文摘This paper analyzes the seismicity and seismic risk distribution in the Bohai Sea. Based on the seismic design parameters of 46 platforms in the Bohai Sea, a statistic analysis is made on the ratios of the peak accelerations for different probability levels. In accordance with the two-stage design method, a scheme of two design seismic levels is proposed, and two fortification goals are established respectively for strength level earthquakes and ductility level earthquakes. Through analogy and comparison to the Chinese seismic code for buildings, it is proposed that the probability level for the strength and ductility level earthquakes takes return periods of 200a and 1000～2500a respectively, and we further expounded on its rationality. Finally, the fortification parameters in the sub-regions of Bohai Sea area are given in the light of seismic risk zonation and ground motion division. This article is a summary of experiences from many years of offshore platform seismic fortification work, and an exploratory study on the seismic fortification standards of offshore platforms in China, which may provide some references for the establishment of the standard.
基金sponsored by the Basic Research Project of Institute of Earthquake Science,China Earthquake Administration ( 2011IES010102)
文摘Based on the rotation in the entire block and homogeneous strain model ( REHSM) ,we firstly analyze the motion and deformation features across the southern part of Tancheng- Lujiang fault zone from GPS velocity fields in period of 1999 ～ 2001,2001 ～ 2004,2004 ～ 2007 and 2007 ～ 2009. The results show a dextral strike-slip feature in the Weifang- Tancheng segment and sinistral strike-slip in the Tancheng-Lujiang segment. And the deformation perpendicular to the Tancheng-Lujiang fault zone alternates between tension and compression in different time-intervals. Then we resolve the relative rigid motion of blocks around Bohai Bay to the Circum-Bohai Sea area by deducting the entire rigid motion of the Circum-Bohai Sea area. We find that the Yanshan-Bohai seismic belt split this area into two parts,the northern part moving NW,and the other SE.
基金supported by National Natural Science Foundation of China (Grant Nos. 40676009 and 40606006)Qingdao Science and Technology Basic Research Program (Grant No. 11-1-4-98-JCH)
文摘The loading tides are calculated by means of the Green's function method based on a high-resolution regional ocean tide model, the TOPO7.0 global ocean tide model, and the Gutenberg-Bullen A Earth model. The results show that the maximal amplitude of M2 vertical displacement loading (VDL) tide in the Bohai, Yellow, and East China Seas exceeding 28mm appears 150km off the Zhejiang coast; the second maximum exceeding 20mm appears in Inchon Bay; and the third maximum exceeding 14mm is located in the northeast of the North Yellow Sea. The maximal amplitudes of S2 VDL tide at the above three locations exceed 10, 8, and 4mm, respectively. The maximal amplitudes of the K1 and O1 VDL tides, exceeding 13 and 10 mm respectively, appear near the central and north Ryukyu Islands; the amplitudes tend to decease toward the inward areas. The phases of semidiurnal VDL tides are basically opposite to those of corresponding ocean tides. The phases of diurnal VDL tides are basically opposite to those of corresponding ocean tides in the most part of the East China Sea and the eastern part of the South Yellow Sea. This anti-phase relationship generally does not hold in the rest parts of the Bohai and Yellow Seas. The distribution patterns of self-attraction and loading (SAL) tides are very similar to those of VDL tides. The SAL tides have amplitudes about 1.2-1.7 times of the corresponding VDL tides and their phases are basically opposite to the corresponding VDL tides. The maximal amplitude of M2 SAL tide also appears off the Zhejiang coast, with a magnitude exceeding 42mm.
