Using seismic data of about one year recorded by 18 broadband stations of ASCENT project, we obtained 2547 receiver func- tions in the northeastern Tibetan Plateau. The Moho depths under 14 stations were calculated by...Using seismic data of about one year recorded by 18 broadband stations of ASCENT project, we obtained 2547 receiver func- tions in the northeastern Tibetan Plateau. The Moho depths under 14 stations were calculated by applying the H-x domain search algorithm. The Moho depths under the stations with lower signal-noise ratio （SNR） were estimated by the time delay of the PS conversion. Results show that the Moho depth varies in a range of -40--60 kin. The Moho near the Haiyuan fault is vague, and its depth is larger than those on its two sides. In the Qinling-Qilian Block, the Moho becomes shallower gradually from west to east. To the east of 105~E, the average depth of the Moho is 45 km, whereas the west is 50 km or even deeper. Combining our results with surface wave research, we suggest a boundary between the Qinling and the Qilian Mountains at around 105~E. S wave velocities beneath 15 stations have been obtained through a linear inversion by using Crust2.0 as an ini- tial model, and the crustal thickness that was derived by H-x domain search algorithm was also taken into account. The results are very similar to the results of previous active source studies. The resulting figure indicates that low velocity layers devel- oped in the middle and lower crust beneath the transition zone of the Tibet Block and western Qinling, which may be related to regional faults and deep earth dynamics. The velocity of the middle and lower crust increases from the Songpan Block to the northeastern margin of Tibetan Plateau. Based on the velocity of the crust, the distribution of the low velocity zone and the composition of the curst （Poisson＇s ratio）, we infer that the crust thickening results from the crust shortening along the direc- tion of compression.展开更多
The northeastern margin of the South China Sea (SCS), developed from continental rifting and breakup, is usually thought of as a non-volcanic margin. However, post-spreading volcanism is massive and lower crustal high...The northeastern margin of the South China Sea (SCS), developed from continental rifting and breakup, is usually thought of as a non-volcanic margin. However, post-spreading volcanism is massive and lower crustal high-velocity anomalies are widespread, which complicate the nature of the margin here. To better understand crustal seismic velocities, lithology, and geophysical properties, we present an S-wave velocity (VS) model and a VP/VS model for the northeastern margin by using an existing P-wave velocity (VP) model as the starting model for 2-D kinematic S-wave forward ray tracing. The Mesozoic sedimentary sequence has lower VP/VS ratios than the Cenozoic sequence;in between is a main interface of P-S conversion. Two isolated high-velocity zones (HVZ) are found in the lower crust of the continental slope, showing S-wave velocities of 4.0–4.2 km/s and VP/VS ratios of 1.73–1.78. These values indicate a mafic composition, most likely of amphibolite facies. Also, a VP/VS versus VP plot indicates a magnesium-rich gabbro facies from post-spreading mantle melting at temperatures higher than normal. A third high-velocity zone (VP : 7.0–7.8 km/s;VP/VS: 1.85–1.96), 70-km wide and 4-km thick in the continent-ocean transition zone, is most likely to be a consequence of serpentinization of upwelled upper mantle. Seismic velocity structures and also gravity anomalies indicate that mantle upwelling/ serpentinization could be the most severe in the northeasternmost continent-ocean boundary of the SCS. Empirical relationships between seismic velocity and degree of serpentinization suggest that serpentinite content decreases with depth, from 43% in the lower crust to 37% into the mantle.展开更多
为更好地指导船舶滚装通道的结构轻量化设计,对当前滚装船滚装通道结构设计标准进行梳理。在国际标准方面,聚焦国际海事组织(International Maritime Organization,IMO)和国际船级社协会(International Association of Classification S...为更好地指导船舶滚装通道的结构轻量化设计,对当前滚装船滚装通道结构设计标准进行梳理。在国际标准方面,聚焦国际海事组织(International Maritime Organization,IMO)和国际船级社协会(International Association of Classification Societies,IACS)的相关技术要求;在行业技术标准方面,重点关注各国船级社的相关技术要求。对滚装通道结构设计中的关键技术进行分项阐述,并以中国船级社(China Classification Society,CCS)滚装通道结构设计的技术要求为例,解析其结构分析及衡准要点。研究成果可为船舶滚装通道的结构轻量化设计提供一定参考。展开更多
Based on the geothermal and gravitation methods, this paper investigated the rheological and thermal structure of the lithosphere under the northern margin of South China Sea. The result shows that the temperature of ...Based on the geothermal and gravitation methods, this paper investigated the rheological and thermal structure of the lithosphere under the northern margin of South China Sea. The result shows that the temperature of the upper crust is 150–300°C lower than that of the lower crust, and the viscous coefficient of the upper crust is 2–3 orders of magnitude larger than that of the lower crust. It reveals that the upper crust is characterized by brittle deformation while the lower crust by ductile deformation. A channel of lower-viscosity should be formed between the upper and lower crust when the lithosphere is scattered and spreads out toward ocean from northwest to southeast along the northern margin of South China Sea. And, a brittle deformation takes place in the upper part of the lithosphere while a ductile deformation takes place in the lower part of the lithosphere due to different viscous coefficients and temperature. The layered deformation leads the faulted blocks to rotate along the faulting and the marginal grabens to appear in the northern margin of South China Sea in Cenozoic tectonic expansion.展开更多
To study the deep dynamic mechanism leading to the difference in rifting pattern and basin structure from shelf to oceanic basin in passive continental margin, we constructed long geological sections across the shelf,...To study the deep dynamic mechanism leading to the difference in rifting pattern and basin structure from shelf to oceanic basin in passive continental margin, we constructed long geological sections across the shelf, slope and oceanic basin using new seismic data. Integrated gravity-magnetic inversion and interpretation of these sections were made with the advanced dissection method. Results show that the basement composition changes from intermediate-acid intrusive rocks in the shelf to intermediate-basic rocks in the slope. The Moho surface shoals gradually from 31 km in the shelf to 22.5 km in the uplift and then 19 km in the slope and finally to 13 km in the oceanic basin. The crust thickness also decreases gradually from 30 km in the northern fault belt to 9 km in the oceanic basin. The crustal stretching factor increases from the shelf toward the oceanic basin, with the strongest extension under the sags and the oceanic basin. The intensity of mantle upwelling controlled the style of basin structures from shelf to oceanic basin. In the Zhu 1 depression on the shelf, the crust is nearly normal, the brittle and cold upper crust mainly controlled the fault development; so the combinative grabens with single symmetric graben are characteristic. In the slope, the crust thinned with a large stretching factor, affected by the mantle upwelling. The ductile deformation controlled the faults, so there developed an asymmetric complex graben in the Baiyun （白云） sag.展开更多
基金financially supported by National Natural Science Foundation of China(Grant No.40930317)CHINARE2012-02-02+1 种基金Project SinoProbe-02-03the NSFC Innovation Research Group Fund(Grant No.41021001)
文摘Using seismic data of about one year recorded by 18 broadband stations of ASCENT project, we obtained 2547 receiver func- tions in the northeastern Tibetan Plateau. The Moho depths under 14 stations were calculated by applying the H-x domain search algorithm. The Moho depths under the stations with lower signal-noise ratio （SNR） were estimated by the time delay of the PS conversion. Results show that the Moho depth varies in a range of -40--60 kin. The Moho near the Haiyuan fault is vague, and its depth is larger than those on its two sides. In the Qinling-Qilian Block, the Moho becomes shallower gradually from west to east. To the east of 105~E, the average depth of the Moho is 45 km, whereas the west is 50 km or even deeper. Combining our results with surface wave research, we suggest a boundary between the Qinling and the Qilian Mountains at around 105~E. S wave velocities beneath 15 stations have been obtained through a linear inversion by using Crust2.0 as an ini- tial model, and the crustal thickness that was derived by H-x domain search algorithm was also taken into account. The results are very similar to the results of previous active source studies. The resulting figure indicates that low velocity layers devel- oped in the middle and lower crust beneath the transition zone of the Tibet Block and western Qinling, which may be related to regional faults and deep earth dynamics. The velocity of the middle and lower crust increases from the Songpan Block to the northeastern margin of Tibetan Plateau. Based on the velocity of the crust, the distribution of the low velocity zone and the composition of the curst （Poisson＇s ratio）, we infer that the crust thickening results from the crust shortening along the direc- tion of compression.
基金South China Sea Institute of Oceanology (SCSIO) for providing R/V Shiyan-2 to carry out this experiment,sponsored by Oceanographic Research Vessel Sharing Plan (NORC2016-08) of National Natural Science Foundation of Chinafunded by National Natural Science Foundation of China (Grant Nos. 41776057, 41761134051, 91858213, 41730532 and 91428039)
文摘The northeastern margin of the South China Sea (SCS), developed from continental rifting and breakup, is usually thought of as a non-volcanic margin. However, post-spreading volcanism is massive and lower crustal high-velocity anomalies are widespread, which complicate the nature of the margin here. To better understand crustal seismic velocities, lithology, and geophysical properties, we present an S-wave velocity (VS) model and a VP/VS model for the northeastern margin by using an existing P-wave velocity (VP) model as the starting model for 2-D kinematic S-wave forward ray tracing. The Mesozoic sedimentary sequence has lower VP/VS ratios than the Cenozoic sequence;in between is a main interface of P-S conversion. Two isolated high-velocity zones (HVZ) are found in the lower crust of the continental slope, showing S-wave velocities of 4.0–4.2 km/s and VP/VS ratios of 1.73–1.78. These values indicate a mafic composition, most likely of amphibolite facies. Also, a VP/VS versus VP plot indicates a magnesium-rich gabbro facies from post-spreading mantle melting at temperatures higher than normal. A third high-velocity zone (VP : 7.0–7.8 km/s;VP/VS: 1.85–1.96), 70-km wide and 4-km thick in the continent-ocean transition zone, is most likely to be a consequence of serpentinization of upwelled upper mantle. Seismic velocity structures and also gravity anomalies indicate that mantle upwelling/ serpentinization could be the most severe in the northeasternmost continent-ocean boundary of the SCS. Empirical relationships between seismic velocity and degree of serpentinization suggest that serpentinite content decreases with depth, from 43% in the lower crust to 37% into the mantle.
文摘为更好地指导船舶滚装通道的结构轻量化设计,对当前滚装船滚装通道结构设计标准进行梳理。在国际标准方面,聚焦国际海事组织(International Maritime Organization,IMO)和国际船级社协会(International Association of Classification Societies,IACS)的相关技术要求;在行业技术标准方面,重点关注各国船级社的相关技术要求。对滚装通道结构设计中的关键技术进行分项阐述,并以中国船级社(China Classification Society,CCS)滚装通道结构设计的技术要求为例,解析其结构分析及衡准要点。研究成果可为船舶滚装通道的结构轻量化设计提供一定参考。
基金the National Natural Science Foundation of China (Grant Nos.49732005, 49733011) and the Chinese Academy of Sciences (Grant No. KZ951-A1-401). We wish to thank Prof. Xu Houze and Lu Yang for their contribution in gravitational model. The authors also than
文摘Based on the geothermal and gravitation methods, this paper investigated the rheological and thermal structure of the lithosphere under the northern margin of South China Sea. The result shows that the temperature of the upper crust is 150–300°C lower than that of the lower crust, and the viscous coefficient of the upper crust is 2–3 orders of magnitude larger than that of the lower crust. It reveals that the upper crust is characterized by brittle deformation while the lower crust by ductile deformation. A channel of lower-viscosity should be formed between the upper and lower crust when the lithosphere is scattered and spreads out toward ocean from northwest to southeast along the northern margin of South China Sea. And, a brittle deformation takes place in the upper part of the lithosphere while a ductile deformation takes place in the lower part of the lithosphere due to different viscous coefficients and temperature. The layered deformation leads the faulted blocks to rotate along the faulting and the marginal grabens to appear in the northern margin of South China Sea in Cenozoic tectonic expansion.
基金supported by the National Natural Science Foundation of China (No. 40238060)
文摘To study the deep dynamic mechanism leading to the difference in rifting pattern and basin structure from shelf to oceanic basin in passive continental margin, we constructed long geological sections across the shelf, slope and oceanic basin using new seismic data. Integrated gravity-magnetic inversion and interpretation of these sections were made with the advanced dissection method. Results show that the basement composition changes from intermediate-acid intrusive rocks in the shelf to intermediate-basic rocks in the slope. The Moho surface shoals gradually from 31 km in the shelf to 22.5 km in the uplift and then 19 km in the slope and finally to 13 km in the oceanic basin. The crust thickness also decreases gradually from 30 km in the northern fault belt to 9 km in the oceanic basin. The crustal stretching factor increases from the shelf toward the oceanic basin, with the strongest extension under the sags and the oceanic basin. The intensity of mantle upwelling controlled the style of basin structures from shelf to oceanic basin. In the Zhu 1 depression on the shelf, the crust is nearly normal, the brittle and cold upper crust mainly controlled the fault development; so the combinative grabens with single symmetric graben are characteristic. In the slope, the crust thinned with a large stretching factor, affected by the mantle upwelling. The ductile deformation controlled the faults, so there developed an asymmetric complex graben in the Baiyun （白云） sag.
