The types, influencing factors and their evolutions of focused fluid flow systems in the northern South China Sea (SCS) are deeply studied based on high-resolution 3D and 2D seismic data. These systems include mud volcanoes, mud diapirs, gas chimneys, pipes, polygonal faults and tectonic faults. They are influenced by both tectonism and sedimentation. The gas chimneys, mud diapirs and mud volcanoes may have relationship of unidirectional evolution and we can separate them from whether the sediments are involved and whether the sediments or fluids erupt into the seawater or not. Finally, a development model of focused fluid flow systems in the northern SCS is proposed. Because their great importance for the deep-water resource exploration (hydrocarbon and gas hydrate), they should receive much attention from now on.
{"title":"Focused fluid flow systems and their implications for hydrocarbon and gas hydrate accumulations in the deep-water basins of the northern South China Sea","authors":"Sun Qi-liang, Wu Shiguo, Chen Duan-xin, Mi Lijun","doi":"10.6038/CJG20141217","DOIUrl":"https://doi.org/10.6038/CJG20141217","url":null,"abstract":"The types, influencing factors and their evolutions of focused fluid flow systems in the northern South China Sea (SCS) are deeply studied based on high-resolution 3D and 2D seismic data. These systems include mud volcanoes, mud diapirs, gas chimneys, pipes, polygonal faults and tectonic faults. They are influenced by both tectonism and sedimentation. The gas chimneys, mud diapirs and mud volcanoes may have relationship of unidirectional evolution and we can separate them from whether the sediments are involved and whether the sediments or fluids erupt into the seawater or not. Finally, a development model of focused fluid flow systems in the northern SCS is proposed. Because their great importance for the deep-water resource exploration (hydrocarbon and gas hydrate), they should receive much attention from now on.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2014-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71078980","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Yangmao Wen, Caijun Xu, Zhenhong Li, Y. Liu, W. Feng, X. Shan
On 12 May 2008,an M_w7.9 earthquake occurred on the Longmenshan fault system at the eastern margin of the Qinghai-Tihet Plateau near Wenchuan City.Here we obtained the ionospheric perturbations in Japanese ALOS/PALSAR images covering the epicenter of Wenchuan earthquake from the corresponding azimuth offsets,and determined highly precise and continuous InSAR surface displacements using those that are not strongly affected by ionospheric perturbations.Combing with the GPS coseismic deformation,a joint model considering both coseismic and postseismic phases is constructed to study the coseismic slip distribution of the Wenchuan earthquake and the viscous structure of the Longmenshan region.The best-fitting slip model suggests that the earthquake is an event with very complex fault rupture.The slips of Hongkou,Yuejiashan,Beichuan,and Hanwang segments are dominated by the thrust movement and the Qingchuan segment experiences a dominant right-lateral strike slip.The major slip occurred mainly at the depth of less than 10 km,with a maximum slip of 10.7 m on the northeastern Hongkou segment.The determined geodetic moment is approximately 9.28 × 10~(20) N ? m(M_w7.91),which is consistent with the results of seismology.The mid to lower crustal viscosity derived from the joint model in a Maxwell half-space is 2×10~(18) Pa ? s,which places a strong low bound on viscosity in the Longmenshan region.Postseismic displacements time series covering a longer time span might have the potential to improve this constraint.
2008年5月12日，汶川附近青藏高原东缘龙门山断裂带发生里氏7.9级地震。本文从覆盖汶川地震震中的日本ALOS/PALSAR影像的方位角偏移量获取电离层扰动，并利用不受电离层扰动强烈影响的影像获得高精度、连续的InSAR地表位移。结合GPS同震变形，建立了考虑同震和震后相位的联合模型，研究了汶川地震同震滑动分布和龙门山地区的粘性结构。最佳拟合滑动模型表明，这次地震是一次非常复杂的断层破裂事件。虹口段、岳家山段、北川段、汉旺段的滑移以逆冲运动为主，青川段以右侧走滑为主。主要滑移发生在10 km以下，虹口段东北部最大滑移量为10.7 m。测得的大地力矩约为9.28 × 10~(20) N ?m(M_w7.91)，这与地震学的结果一致。在麦克斯韦半空间中，由结合部模型导出的中下地壳粘度为2×10~(18) Pa ?这使得龙门山地区的黏度有很强的下限。覆盖更长的时间跨度的震后位移时间序列可能有可能改善这一限制。
{"title":"Coseismic and postseismic deformation of the 2008 Wenchuan Earthquake from InSAR","authors":"Yangmao Wen, Caijun Xu, Zhenhong Li, Y. Liu, W. Feng, X. Shan","doi":"10.6038/CJG20140613","DOIUrl":"https://doi.org/10.6038/CJG20140613","url":null,"abstract":"On 12 May 2008,an M_w7.9 earthquake occurred on the Longmenshan fault system at the eastern margin of the Qinghai-Tihet Plateau near Wenchuan City.Here we obtained the ionospheric perturbations in Japanese ALOS/PALSAR images covering the epicenter of Wenchuan earthquake from the corresponding azimuth offsets,and determined highly precise and continuous InSAR surface displacements using those that are not strongly affected by ionospheric perturbations.Combing with the GPS coseismic deformation,a joint model considering both coseismic and postseismic phases is constructed to study the coseismic slip distribution of the Wenchuan earthquake and the viscous structure of the Longmenshan region.The best-fitting slip model suggests that the earthquake is an event with very complex fault rupture.The slips of Hongkou,Yuejiashan,Beichuan,and Hanwang segments are dominated by the thrust movement and the Qingchuan segment experiences a dominant right-lateral strike slip.The major slip occurred mainly at the depth of less than 10 km,with a maximum slip of 10.7 m on the northeastern Hongkou segment.The determined geodetic moment is approximately 9.28 × 10~(20) N ? m(M_w7.91),which is consistent with the results of seismology.The mid to lower crustal viscosity derived from the joint model in a Maxwell half-space is 2×10~(18) Pa ? s,which places a strong low bound on viscosity in the Longmenshan region.Postseismic displacements time series covering a longer time span might have the potential to improve this constraint.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"1 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2014-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71078229","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The present study calculated the thermal structure,the distribution of buoyancy,and P-wave velocity anomalies in Japan Trench subduction zone using finite difference method,and predicted the range of metastable olivine according to whole and layered mantle convection models.We analyzed the influences of multiple coefficients,such as thermal conductivity,thermal expansion,and heat sources on the thermal structure.The relation between the buoyancy of subduction zone and its shape were also discussed.Interesting results for layered mantle convection model demonstrated that the modeled P-wave velocity anomalies not only matched seismic tomography results much better,but also highly correlated to the distribution of deep-focus earthquakes in Japan Trench subduction zone.The areas of metastable olivine inside slabs became larger with decreasing values of thermal conductivity and thermal expansion coefficients and ignoring phase change heating and shear heating would also induce larger areas of modeled metastable olivine.The maximum value of negative buoyancy reached the depth of about400 km.The metastable olivine resulted in the decrease of negative buoyancy,or even positive buoyancy within the subduction zone against the penetration of the subduction zone into the 660 km discontinuity.
{"title":"Thermal structure of Japan Trench subduction zone and deep-focus earthquakes","authors":"Chen Zhang, Shuangxi Zhang, E. Carminati, B. Gao","doi":"10.6038/CJG20141009","DOIUrl":"https://doi.org/10.6038/CJG20141009","url":null,"abstract":"The present study calculated the thermal structure,the distribution of buoyancy,and P-wave velocity anomalies in Japan Trench subduction zone using finite difference method,and predicted the range of metastable olivine according to whole and layered mantle convection models.We analyzed the influences of multiple coefficients,such as thermal conductivity,thermal expansion,and heat sources on the thermal structure.The relation between the buoyancy of subduction zone and its shape were also discussed.Interesting results for layered mantle convection model demonstrated that the modeled P-wave velocity anomalies not only matched seismic tomography results much better,but also highly correlated to the distribution of deep-focus earthquakes in Japan Trench subduction zone.The areas of metastable olivine inside slabs became larger with decreasing values of thermal conductivity and thermal expansion coefficients and ignoring phase change heating and shear heating would also induce larger areas of modeled metastable olivine.The maximum value of negative buoyancy reached the depth of about400 km.The metastable olivine resulted in the decrease of negative buoyancy,or even positive buoyancy within the subduction zone against the penetration of the subduction zone into the 660 km discontinuity.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":"3208-3217"},"PeriodicalIF":1.4,"publicationDate":"2014-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71079028","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
T. Xu, M. Zhang, Xiaobo Tian, Yong Zheng, Z. Bai, Chenglong Wu, Zhongjie Zhang, J. Teng
On August 3,2014,an M_s 6.5 earthquake occurred in Ludian County,Yunnan.The Ludian earthquake ruptured along the NE-orie.nted Zhaotong-Lianfeng fault zone,western margin of the Yangtze block.However,there was no seismic sounding profile across the Zhaotong—Lianfeng fault zone up to now.Since the distance from Lijiang—Panzhihua—Qingzhen active source seismic sounding profile to the Ludian earthquake source region is within50 km,we can handle the wide-angle seismic data to reveal the upper crustal velocity structure in this area,and provide the velocity model of upper crust for the earthquake locating and focal mechanism inversion of Ludian earthquake sequence,etc.The velocity profile shows that the crustal velocity around the Xiaojiang fault is lower than its periphery,thus the rheological strength of the upper crust beneath the Xiaojiang fault is speculated to be weaker than its surrounding areas.Considering the high strain rate along the Xiaojiang fault,it is possible to accumulate great strain and strong stress in the Xiaojiang fault zone and its surrounding faults.Thus we should pay attention to the potential risk of strong earthquakes on the Xiaojiang fault and its nearby Ludian—Zhaotong fault.
{"title":"Upper crustal velocity of Lijiang-Qingzhen profile and its relationship with the seismogenic environment of the M_s6.5 Ludian earthquake","authors":"T. Xu, M. Zhang, Xiaobo Tian, Yong Zheng, Z. Bai, Chenglong Wu, Zhongjie Zhang, J. Teng","doi":"10.6038/CJG20140932","DOIUrl":"https://doi.org/10.6038/CJG20140932","url":null,"abstract":"On August 3,2014,an M_s 6.5 earthquake occurred in Ludian County,Yunnan.The Ludian earthquake ruptured along the NE-orie.nted Zhaotong-Lianfeng fault zone,western margin of the Yangtze block.However,there was no seismic sounding profile across the Zhaotong—Lianfeng fault zone up to now.Since the distance from Lijiang—Panzhihua—Qingzhen active source seismic sounding profile to the Ludian earthquake source region is within50 km,we can handle the wide-angle seismic data to reveal the upper crustal velocity structure in this area,and provide the velocity model of upper crust for the earthquake locating and focal mechanism inversion of Ludian earthquake sequence,etc.The velocity profile shows that the crustal velocity around the Xiaojiang fault is lower than its periphery,thus the rheological strength of the upper crust beneath the Xiaojiang fault is speculated to be weaker than its surrounding areas.Considering the high strain rate along the Xiaojiang fault,it is possible to accumulate great strain and strong stress in the Xiaojiang fault zone and its surrounding faults.Thus we should pay attention to the potential risk of strong earthquakes on the Xiaojiang fault and its nearby Ludian—Zhaotong fault.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"54 1","pages":"3069-3089"},"PeriodicalIF":1.4,"publicationDate":"2014-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71078320","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Su Zheng, C. Yun-Cheng, Y. Rui, Wu Nengyou, Chen Duo-fu, Yang Sheng-xiong, Wang Hong-bin
The Shenhu area on the northern continental slope of the South China Sea is considered as a promising target for gas hydrate exploration and exploitation. Its special hydrate occurrence makes it difficult to explain and quantitatively describe its formation mechanism by using the deposition rates and fluid flow conditions at present. Its formation evolution mode and controlling factors are unclear yet. In this paper a dynamic model for the hydrate accumulation is constructed with two controlling parameters, i.e. the sedimentation rate and fluid water flow rate. The model is used to simulate the hydrate accumulation in the Shenhu area and testified with saturation data derived from salinity. Finally, a hydrate formation pattern in the Shenhu area is built based on the investigation of tectonic activities and the dynamics of hydrate accumulation in the area. The model indicates that Shenhu hydrates were developed from the hydrates formed in late tectonic activities during the late Pliocene Epoch-early Pleistocene Epoch. The gas hydrate formation in the Shenhu area has a typical dual pattern. In the first stage the hydrate grew in fractured sediments formed by tectonic activities 1. 5 Ma. The water flow rate was up to 50 m/ka, and abundant methane gas was carried into the hydrate stability zone and led to a rapid hydrate formation. The hydrate saturation went up to 20% in the duration of 40 ka. In the second stage of the following 1. 5 Mas, permeability of the sediment reduced sharply due to the sedimentation of clay silts. Fluid flux was 0. 7 m/ka and methane supply was inadequate. Thus hydrates could not form in shallow sediments and only grew slowly on the base of the hydrate stability zone, and then formed the feature of hydrate occurrence observed currently in the Shenhu area. And also the resource amount of hydrate continued reducing.
{"title":"Research on the formation model of gas hydrate deposits in the Shenhu Area,northern South China Sea","authors":"Su Zheng, C. Yun-Cheng, Y. Rui, Wu Nengyou, Chen Duo-fu, Yang Sheng-xiong, Wang Hong-bin","doi":"10.6038/CJG20140529","DOIUrl":"https://doi.org/10.6038/CJG20140529","url":null,"abstract":"The Shenhu area on the northern continental slope of the South China Sea is considered as a promising target for gas hydrate exploration and exploitation. Its special hydrate occurrence makes it difficult to explain and quantitatively describe its formation mechanism by using the deposition rates and fluid flow conditions at present. Its formation evolution mode and controlling factors are unclear yet. In this paper a dynamic model for the hydrate accumulation is constructed with two controlling parameters, i.e. the sedimentation rate and fluid water flow rate. The model is used to simulate the hydrate accumulation in the Shenhu area and testified with saturation data derived from salinity. Finally, a hydrate formation pattern in the Shenhu area is built based on the investigation of tectonic activities and the dynamics of hydrate accumulation in the area. The model indicates that Shenhu hydrates were developed from the hydrates formed in late tectonic activities during the late Pliocene Epoch-early Pleistocene Epoch. The gas hydrate formation in the Shenhu area has a typical dual pattern. In the first stage the hydrate grew in fractured sediments formed by tectonic activities 1. 5 Ma. The water flow rate was up to 50 m/ka, and abundant methane gas was carried into the hydrate stability zone and led to a rapid hydrate formation. The hydrate saturation went up to 20% in the duration of 40 ka. In the second stage of the following 1. 5 Mas, permeability of the sediment reduced sharply due to the sedimentation of clay silts. Fluid flux was 0. 7 m/ka and methane supply was inadequate. Thus hydrates could not form in shallow sediments and only grew slowly on the base of the hydrate stability zone, and then formed the feature of hydrate occurrence observed currently in the Shenhu area. And also the resource amount of hydrate continued reducing.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2014-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71078165","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
J. Liang, L. Zhang, P. Tian, X. Cao, H.B. Wang, Bi
This paper examines the impact of low-level jets (LLJs) on the turbulent in nocturnal boundary layer, using the data collected by eddy covariance ( EC) and boundary layer meteorological measurement systems at the Semi-Arid Climate and Environment Observatory of Lanzhou University(SACOL). The Weather Research and Forecasting model is used to understand flow structure characteristics in the stable boundary layer over the complex terrain of the Loess Plateau. Over the complex terrain of the Loess Plateau, the formation and maintaining of LLJs may be related to the local circulation caused by topography in a stable boundary layer. The presence of LLJs results in strong turbulence and weak stability with gradient Richardson number (Ri) less than 0. 25 by the strong shear. On the other hand, synchronous observations show that 65.4% are strong stable stratification of Ri>0. 3,in the absence of jet activity. The contribution from non-stationary motions results in sharp increasing in the low frequency end of power spectra for horizontal wind speed. Compared with the no/weak LLJs situations, the turbulent kinetic energy doubles when strong LLJs occur. Vertical transportation of turbulent kinetic energy has an order of magnitude increase in value,and the turbulent is transported downward from aloft in the boundary layer,about -3 X 10(-3) m(3) . s(-3). This means that the pollutants may be transported downward and accumulated at the bottom of boundary layer.
利用兰州大学半干旱气候与环境观测站(SACOL)涡动相关(EC)和边界层气象测量系统采集的数据，研究了低层急流对夜间边界层湍流的影响。利用气象研究与预报模型对黄土高原复杂地形上稳定边界层的流动结构特征进行了研究。在地形复杂的黄土高原上，低涡的形成和维持可能与稳定边界层地形引起的局地环流有关。llj的存在导致湍流强，稳定性弱，梯度理查德森数(Ri)小于0。25 .受强剪切。另一方面，同步观测表明65.4%为强稳定层理。3、在没有喷射活动的情况下。非平稳运动的贡献导致水平风速功率谱的低频端急剧增加。与无/弱llj情况相比，强llj发生时湍流动能增加了一倍。湍流动能垂直输运的数值增加了一个数量级，湍流在边界层中从高空向下输运，约为-3 X 10(-3) m(3)。(3)。这意味着污染物可能向下运移并在边界层底部积聚。
{"title":"Impact of low-level jets on turbulent in nocturnal boundary layer over complex terrain of the Loess Plateau","authors":"J. Liang, L. Zhang, P. Tian, X. Cao, H.B. Wang, Bi","doi":"10.6038/CJG20140504","DOIUrl":"https://doi.org/10.6038/CJG20140504","url":null,"abstract":"This paper examines the impact of low-level jets (LLJs) on the turbulent in nocturnal boundary layer, using the data collected by eddy covariance ( EC) and boundary layer meteorological measurement systems at the Semi-Arid Climate and Environment Observatory of Lanzhou University(SACOL). The Weather Research and Forecasting model is used to understand flow structure characteristics in the stable boundary layer over the complex terrain of the Loess Plateau. Over the complex terrain of the Loess Plateau, the formation and maintaining of LLJs may be related to the local circulation caused by topography in a stable boundary layer. The presence of LLJs results in strong turbulence and weak stability with gradient Richardson number (Ri) less than 0. 25 by the strong shear. On the other hand, synchronous observations show that 65.4% are strong stable stratification of Ri>0. 3,in the absence of jet activity. The contribution from non-stationary motions results in sharp increasing in the low frequency end of power spectra for horizontal wind speed. Compared with the no/weak LLJs situations, the turbulent kinetic energy doubles when strong LLJs occur. Vertical transportation of turbulent kinetic energy has an order of magnitude increase in value,and the turbulent is transported downward from aloft in the boundary layer,about -3 X 10(-3) m(3) . s(-3). This means that the pollutants may be transported downward and accumulated at the bottom of boundary layer.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2014-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71078133","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ye Yueming, Zhao Changlei, Zhuang Xijin, Guo Shu-Juan, Qian Jin
In conventional seismic data processing, multiple reflection waves are regarded as noise which should be removed from seismic data in order to avoid misunderstanding. In fact, multiples are also signals which contribute to part of subsurface structure illumination and imaging. In this paper, we analyzed the artifact generating mechanism and phenomenon caused by multiples in conventional one-way equation based pre-stack depth migration. In order to realize multiple imaging based on one-way wave equation, the boundary condition of one-way wave-equation based pre-stack depth migration was modified. It means that the input source wave field and recorded wave field are replaced by the record containing multiples and predicted surface correlated multiples, respectively. Then we stacked the pre-stack depth migration results from primaries and multiples based on the matching operator which is obtained from the norm II least-square energy difference methods. Imaging with multiples is a good compensation to imaging to that with primaries. The test on a simple model shows the validity of our method. Finally, jointed imaging with primaries and multiples was performed on the Sigsbee2B model. The results show that the imaging of the steep salt boundary was improved dramatically.
{"title":"Migration of surface correlated multiples based on one-way wave equation","authors":"Ye Yueming, Zhao Changlei, Zhuang Xijin, Guo Shu-Juan, Qian Jin","doi":"10.6038/CJG20140421","DOIUrl":"https://doi.org/10.6038/CJG20140421","url":null,"abstract":"In conventional seismic data processing, multiple reflection waves are regarded as noise which should be removed from seismic data in order to avoid misunderstanding. In fact, multiples are also signals which contribute to part of subsurface structure illumination and imaging. In this paper, we analyzed the artifact generating mechanism and phenomenon caused by multiples in conventional one-way equation based pre-stack depth migration. In order to realize multiple imaging based on one-way wave equation, the boundary condition of one-way wave-equation based pre-stack depth migration was modified. It means that the input source wave field and recorded wave field are replaced by the record containing multiples and predicted surface correlated multiples, respectively. Then we stacked the pre-stack depth migration results from primaries and multiples based on the matching operator which is obtained from the norm II least-square energy difference methods. Imaging with multiples is a good compensation to imaging to that with primaries. The test on a simple model shows the validity of our method. Finally, jointed imaging with primaries and multiples was performed on the Sigsbee2B model. The results show that the imaging of the steep salt boundary was improved dramatically.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2014-04-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71078557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This study is a systematic analysis on the environmental magnetic properties, soil texture and distribution of heavy metals content in topsoil sampled from typical oasis cities in desert like Wuhai, Shizuishan and Yinchuan. The results indicated that the topsoil in Wuhai and Shizuishan is typical sandy soil, while that in Yinchuan is sandy loam. Magnetic properties of topsoil samples are all predominated by ferrimagnetic magnetic mineral (magnetite) of coarse pseudo single domain (PSD)-multi domain (MD) particles with magnetic susceptibility of 152 X 10(-8), 104X10(-8), and 117x10(-8)m(3).kg(-1) respectively for the three cities. The magnetic mineral content and magnetic particles size in topsoil samples of Wuhai are significantly higher than that of Shizuishan and Yinchuan. Pollution Load Index (PLI) of heavy metals (Cr, Cu, Pb, Zn, Fe) showed that there is slight pollution in the three cities. Dotted distribution of high values of magnetic susceptibility and Pollution Load Index is shown in nonindustrial area, whilst planar distribution with high value is shown in industrial area. The correlation coefficient between magnetic parameters and heavy metals of topsoil in Wuhai is significantly higher than that in Shizuishan and Yinchuan, which suggests that magnetic parameters are more advantageous for evaluation on pollution degree in regions with single pollution source. There is an increase by the same degree in magnetic susceptibility in parallel with the increase of Pollution Load Index, despite of the significant difference of magnetic properties among three cities. Therefore, magnetic susceptibility can be used as the unified and effective substitute indicator to evaluate the pollution degree of heavy metals in topsoil of Ningxia plain.
{"title":"Magnetic properties of urban soils from typical oasis cities and their environmental implications","authors":"Bo‐Lin Wang, D. Xia, Y. Yu, J. Jia, Sj Xu","doi":"10.6038/CJG20140319","DOIUrl":"https://doi.org/10.6038/CJG20140319","url":null,"abstract":"This study is a systematic analysis on the environmental magnetic properties, soil texture and distribution of heavy metals content in topsoil sampled from typical oasis cities in desert like Wuhai, Shizuishan and Yinchuan. The results indicated that the topsoil in Wuhai and Shizuishan is typical sandy soil, while that in Yinchuan is sandy loam. Magnetic properties of topsoil samples are all predominated by ferrimagnetic magnetic mineral (magnetite) of coarse pseudo single domain (PSD)-multi domain (MD) particles with magnetic susceptibility of 152 X 10(-8), 104X10(-8), and 117x10(-8)m(3).kg(-1) respectively for the three cities. The magnetic mineral content and magnetic particles size in topsoil samples of Wuhai are significantly higher than that of Shizuishan and Yinchuan. Pollution Load Index (PLI) of heavy metals (Cr, Cu, Pb, Zn, Fe) showed that there is slight pollution in the three cities. Dotted distribution of high values of magnetic susceptibility and Pollution Load Index is shown in nonindustrial area, whilst planar distribution with high value is shown in industrial area. The correlation coefficient between magnetic parameters and heavy metals of topsoil in Wuhai is significantly higher than that in Shizuishan and Yinchuan, which suggests that magnetic parameters are more advantageous for evaluation on pollution degree in regions with single pollution source. There is an increase by the same degree in magnetic susceptibility in parallel with the increase of Pollution Load Index, despite of the significant difference of magnetic properties among three cities. Therefore, magnetic susceptibility can be used as the unified and effective substitute indicator to evaluate the pollution degree of heavy metals in topsoil of Ningxia plain.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2014-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71078357","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Near-source co-seismic displacement field of the 20 April 2013 Ms7.0 Lushan, Sichuan earthquake is estimated from digital strong-motion records after correction for their baseline errors using an improved empirical method and compared with the GPS observations. Furthermore, different slip models of the earthquake are inverted from the GPS and strong-motion based displacement data separately and jointly, which are in good agreement. Both show that the earthquake is dominated by the thrust mechanism (also a few left-lateral dislocations). The maximum horizontal and vertical co-seismic displacements reached 4.9 cm and 4.4 cm at station 51YAM and 51QLY, respectively. The fault slips are mainly distributed around the first event and in an area of about 30 km along the strike and 25 km along the dip. The moment magnitude is estimated to be Mw6.7, and the peak slip is about 1.14 m for strong motion data and 1.09 m for GPS. The surface rupture should be very small. Finally, we discuss the minimum requirements on the strong-motion data that ensure a reliable recovery of the co-seismic displacement data and corresponding problems in the current strong-motion networks in China.
利用改进的经验方法对2013年4月20日四川芦山Ms7.0地震的基线误差进行校正后，估计了数字强震记录的近源同震位移场，并与GPS观测结果进行了比较。利用GPS和强震位移资料分别和联合反演了不同的地震滑动模型，结果吻合较好。两者都表明地震以逆冲机制为主(也有少量左旋位错)。51YAM和51QLY站的最大水平和垂直同震位移分别达到4.9 cm和4.4 cm。断层滑动主要分布在第一次活动周围，沿走向约30 km，沿倾角约25 km的范围内。估计矩震级为Mw6.7，强震数据的峰值滑移约为1.14 m, GPS数据的峰值滑移约为1.09 m。表面破裂应该非常小。最后，讨论了中国目前强震台网中保证同震位移数据可靠恢复的强震数据的最低要求及相应问题。
{"title":"Slip Model and Co‐Seismic Displacement Field Derived from Near‐Source Strong Motion Records of the Lushan Ms7.0 Earthquake on 20 April 2013","authors":"Jin Ming-Pei, Wang Rong-jiang, Tu Hong-wei","doi":"10.1002/CJG2.20081","DOIUrl":"https://doi.org/10.1002/CJG2.20081","url":null,"abstract":"Near-source co-seismic displacement field of the 20 April 2013 Ms7.0 Lushan, Sichuan earthquake is estimated from digital strong-motion records after correction for their baseline errors using an improved empirical method and compared with the GPS observations. Furthermore, different slip models of the earthquake are inverted from the GPS and strong-motion based displacement data separately and jointly, which are in good agreement. Both show that the earthquake is dominated by the thrust mechanism (also a few left-lateral dislocations). The maximum horizontal and vertical co-seismic displacements reached 4.9 cm and 4.4 cm at station 51YAM and 51QLY, respectively. The fault slips are mainly distributed around the first event and in an area of about 30 km along the strike and 25 km along the dip. The moment magnitude is estimated to be Mw6.7, and the peak slip is about 1.14 m for strong motion data and 1.09 m for GPS. The surface rupture should be very small. Finally, we discuss the minimum requirements on the strong-motion data that ensure a reliable recovery of the co-seismic displacement data and corresponding problems in the current strong-motion networks in China.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":"25-34"},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20081","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51212262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Airborne time-domain electromagnetic (ATEM) data usually contain natural and cultural noise, which can lower data quality, influence inversion accuracy or even lead to incorrect interpretation if it is not removed from data using an appropriate filter. To solve this problem, this work suggests a denosing method based on kernel principal component analysis. Firstly, it extracts the principal component from stacked decay curves. Then the useful signals, which are associated with subsurface media, and noise are separated using the energy ratio. Finally, these signals are used to perform reconstruction. This method can not only remove natural noise such as spikes or oscillation caused by sferies, but also effectively suppress cultural noise. Using this method and the AeroTEM software, the real ATEM data from a helicopter survey is processed separately. Comparison of the results shows that the denoising effect of the method suggested by this paper is superior to that of the AeroTEM software.
{"title":"A Denoising Method Based on Kernel Principal Component Analysis for Airborne Time‐Domain Electromagnetic Data","authors":"Chen Bin, Lu Cong-de, Liu Guang-ding","doi":"10.1002/CJG2.20087","DOIUrl":"https://doi.org/10.1002/CJG2.20087","url":null,"abstract":"Airborne time-domain electromagnetic (ATEM) data usually contain natural and cultural noise, which can lower data quality, influence inversion accuracy or even lead to incorrect interpretation if it is not removed from data using an appropriate filter. To solve this problem, this work suggests a denosing method based on kernel principal component analysis. Firstly, it extracts the principal component from stacked decay curves. Then the useful signals, which are associated with subsurface media, and noise are separated using the energy ratio. Finally, these signals are used to perform reconstruction. This method can not only remove natural noise such as spikes or oscillation caused by sferies, but also effectively suppress cultural noise. Using this method and the AeroTEM software, the real ATEM data from a helicopter survey is processed separately. Comparison of the results shows that the denoising effect of the method suggested by this paper is superior to that of the AeroTEM software.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":"103-111"},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20087","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51212685","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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