Ying-Kang Li, G. Rui, Yao Yutao, Shengxin Mi, Wen-hui Li, Xiao-Song Xiong, Jian-Wei Gao
The survey of seismic refraction and wide-angle reflection from Zhangjiakou to China-Mongolia border is about 600 km long, which begins from the North China Plate, crosses Xing'an Mongolian orogenic belt and ends at the Siberian plate. The recordings of seismic wave field are composed of 8 shootings. Each shooting is generated from an explosion of 1.5 tons and received by 300 detectors along the survey. The qualities of received seismic wave field of P-wave are good for most of the shootings. The data collected from the experiment of seismic refraction and wide-angle reflection have been processed, analyzed and modeled. There are six seismic phases in the data: the arrivals of refracted and reflected seismic waves from the sediments and basements (Pg), the arrival of reflected seismic wave from the bottom of the upper crust (P2), the arrival of reflected seismic wave from the inner of middle crust (P3), the arrival of reflected seismic wave from the bottom of middle crust (P4), the arrival of reflected seismic wave from the inner of lower crust (P5) which exists only in the area between Xianghuang Qi and Sonid Youqi, and the arrival of reflected seismic wave from the Moho (Pm). The velocity distribution of crust is obtained using the seismic dynamics ray method (seis88). The results show that (1) there are local high velocity anomalies in the upper crust between the North China Plate and Inner Mongolia orogenic belt, as well as in the upper crust between the Inner Mongolia orogenic belt and Siberian plate, and there are also a lot of Paleozoic granite and ultramafic rock which are exposed at the surface of those places. (2) In the middle and lower crusts, the velocity of seismic wave in the northern margin of the North China plate is big, which is in the range of 6.3∼6.7 km/s, and in the southern margin of the Siberian Plate the velocity is relatively small and it is in the range of 6.1∼6.7 km/s. The velocity variation between the margins of the two areas is small. The reason for the velocity variations in different regions is that there exit the rugged undulation interfaces in middle and lower crusts, the splicing and substance exchanges between different land and sea blocks, which are caused by the crustal shortening and orogenic uplifting in the Inner Mongolia orogenic belt. (3) The Moho varies gently both in the south of F2 fault and in the north of F4 fault, and the depth of Moho is in the range of 40∼42 km. There exist double Moho boundaries between F2 and F4 faults. The Moho1 uplifts obviously, its depth is 33.5 km and the layer velocity is in the range of 6.6∼6.7 km/s. The Moho2 concaves downward obviously, the deepest boundary of it reaches 47 km and the layer velocity is in the range of 6.7∼6.9 km/s, which may be caused by the material exchange between the crust and mantle. Based on the characteristics of the Moho boundaries, the authors consider that the south area of double Moho boundaries is the northern margin of the North China pla
{"title":"Crustal Velocity Structure from the Northern Margin of the North China Craton to the Southern Margin of the Siberian Plate","authors":"Ying-Kang Li, G. Rui, Yao Yutao, Shengxin Mi, Wen-hui Li, Xiao-Song Xiong, Jian-Wei Gao","doi":"10.1002/CJG2.20083","DOIUrl":"https://doi.org/10.1002/CJG2.20083","url":null,"abstract":"The survey of seismic refraction and wide-angle reflection from Zhangjiakou to China-Mongolia border is about 600 km long, which begins from the North China Plate, crosses Xing'an Mongolian orogenic belt and ends at the Siberian plate. The recordings of seismic wave field are composed of 8 shootings. Each shooting is generated from an explosion of 1.5 tons and received by 300 detectors along the survey. The qualities of received seismic wave field of P-wave are good for most of the shootings. The data collected from the experiment of seismic refraction and wide-angle reflection have been processed, analyzed and modeled. There are six seismic phases in the data: the arrivals of refracted and reflected seismic waves from the sediments and basements (Pg), the arrival of reflected seismic wave from the bottom of the upper crust (P2), the arrival of reflected seismic wave from the inner of middle crust (P3), the arrival of reflected seismic wave from the bottom of middle crust (P4), the arrival of reflected seismic wave from the inner of lower crust (P5) which exists only in the area between Xianghuang Qi and Sonid Youqi, and the arrival of reflected seismic wave from the Moho (Pm). The velocity distribution of crust is obtained using the seismic dynamics ray method (seis88). The results show that (1) there are local high velocity anomalies in the upper crust between the North China Plate and Inner Mongolia orogenic belt, as well as in the upper crust between the Inner Mongolia orogenic belt and Siberian plate, and there are also a lot of Paleozoic granite and ultramafic rock which are exposed at the surface of those places. (2) In the middle and lower crusts, the velocity of seismic wave in the northern margin of the North China plate is big, which is in the range of 6.3∼6.7 km/s, and in the southern margin of the Siberian Plate the velocity is relatively small and it is in the range of 6.1∼6.7 km/s. The velocity variation between the margins of the two areas is small. The reason for the velocity variations in different regions is that there exit the rugged undulation interfaces in middle and lower crusts, the splicing and substance exchanges between different land and sea blocks, which are caused by the crustal shortening and orogenic uplifting in the Inner Mongolia orogenic belt. (3) The Moho varies gently both in the south of F2 fault and in the north of F4 fault, and the depth of Moho is in the range of 40∼42 km. There exist double Moho boundaries between F2 and F4 faults. The Moho1 uplifts obviously, its depth is 33.5 km and the layer velocity is in the range of 6.6∼6.7 km/s. The Moho2 concaves downward obviously, the deepest boundary of it reaches 47 km and the layer velocity is in the range of 6.7∼6.9 km/s, which may be caused by the material exchange between the crust and mantle. Based on the characteristics of the Moho boundaries, the authors consider that the south area of double Moho boundaries is the northern margin of the North China pla","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":"48-63"},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20083","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51212479","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}
Based on the brittle failure theory of multiple locked patches in a seismogenic fault system and the associated prediction method developed by us, we have released a medium- and long-term prediction of future strong earthquakes in the Yutian seismic zone of Xinjiang, including the magnitude, location, critical Benioff strain, and focal depth. Comparison shows that these parameters are almost identical with the Yutian Ms7.3 event in Xinjiang on 12 February 2014, which indicates that our previous prediction is credible. Meanwhile, our analysis suggest that the most immediate cause leading to Yutian Ms7.3 earthquake is attributed to the Yutian-Cele ML 6.6 earthquake swarm in 2008.
{"title":"Review of the Prospective Prediction of the 2014 Yutian Ms7.3 Earthquake in Xinjiang and Analysis of its Postseismic Trend","authors":"Q. Siqing, Xue Lei, Li Pei, L. Guo-liang","doi":"10.1002/CJG2.20090","DOIUrl":"https://doi.org/10.1002/CJG2.20090","url":null,"abstract":"Based on the brittle failure theory of multiple locked patches in a seismogenic fault system and the associated prediction method developed by us, we have released a medium- and long-term prediction of future strong earthquakes in the Yutian seismic zone of Xinjiang, including the magnitude, location, critical Benioff strain, and focal depth. Comparison shows that these parameters are almost identical with the Yutian Ms7.3 event in Xinjiang on 12 February 2014, which indicates that our previous prediction is credible. Meanwhile, our analysis suggest that the most immediate cause leading to Yutian Ms7.3 earthquake is attributed to the Yutian-Cele ML 6.6 earthquake swarm in 2008.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":"127-132"},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20090","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51213281","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 paper presents a recursive filter designed from the second order transfer function of a velocity-flat-response seismometer by impulse invariance. This filter includes less coefficients than that designed by bilinear transformation and its usage is more convenient. Numeric experiments using this recursive filter have been done for deconvolution and simulation. A short period record was also simulated for a real broadband record of an earthquake. All the simulated results are well consistent with real system records. Some relative azimuth measurements of seismometers with the cross correlation analysis method have been conducted with the aids of simulation. The results are closer to absolute measurements by the north finder than that without simulation.
{"title":"Deconvolution and Simulation of Seismic Records in the Time Domain and Application to the Relative Measurements of Seismometer Azimuths","authors":"Xie Jian-bo","doi":"10.1002/CJG2.20082","DOIUrl":"https://doi.org/10.1002/CJG2.20082","url":null,"abstract":"This paper presents a recursive filter designed from the second order transfer function of a velocity-flat-response seismometer by impulse invariance. This filter includes less coefficients than that designed by bilinear transformation and its usage is more convenient. Numeric experiments using this recursive filter have been done for deconvolution and simulation. A short period record was also simulated for a real broadband record of an earthquake. All the simulated results are well consistent with real system records. Some relative azimuth measurements of seismometers with the cross correlation analysis method have been conducted with the aids of simulation. The results are closer to absolute measurements by the north finder than that without simulation.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"5 1","pages":"35-47"},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20082","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51212929","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}
Ke-Shi Chen, C. Gumiaux, R. Augier, Yan Chen, Yan-Hui Mei, Wei Lin, Qingchen Wang
Fold-and-thrust belts are hot topics in the research of orogens. However, the single geological or geophysical discipline often provides multisolutions on the geometry of a fold-and-thrust belt. We introduce here a multidisciplinary method combining geological and geophysical methods, take the Hutubi River section as a case to study the geometry of the fold-and-thrust belt in the northern piedmont of Tianshan. Firstly, we have carefully taken geological survey and got structural data on the surface. Secondly, petroleum seismic profile was re-interpreted based on the surface data and drilled wells. However, the seismic profile is absent in the contact zone between the mountain and the Junggar basin. We therefore carried out gravity measurements and forward modeling along this profile with the densities of the basement and sediments. The result shows that the northern flank fault of Tianshan doesn't exist along the Hutubi River profile, and the basin sediments could be continually followed from the basin to the mountain interior. This indicates that the tectonic structures in the contact zones between the mountain and the basin are variable, as the western section in the Jingou River section shows that the Tianshan basement thrusts northward on the basin sediments. Based on the balance-section technology, the restored section shows 4. 8 km of shortening. Comparing with previous results, this indicates the heterogeneous deformation along the northern piedmont of Tianshan. It also implies that this multidisciplinary method could be widely used in the fold-and-thrust belt.
{"title":"A multidiscipline method of geological survey,seismic profile and gravity measurement applied to fold-and-thrust belt:a case study along the Hutubi River in the northern piedmont of Tianshan","authors":"Ke-Shi Chen, C. Gumiaux, R. Augier, Yan Chen, Yan-Hui Mei, Wei Lin, Qingchen Wang","doi":"10.6038/CJG20140108","DOIUrl":"https://doi.org/10.6038/CJG20140108","url":null,"abstract":"Fold-and-thrust belts are hot topics in the research of orogens. However, the single geological or geophysical discipline often provides multisolutions on the geometry of a fold-and-thrust belt. We introduce here a multidisciplinary method combining geological and geophysical methods, take the Hutubi River section as a case to study the geometry of the fold-and-thrust belt in the northern piedmont of Tianshan. Firstly, we have carefully taken geological survey and got structural data on the surface. Secondly, petroleum seismic profile was re-interpreted based on the surface data and drilled wells. However, the seismic profile is absent in the contact zone between the mountain and the Junggar basin. We therefore carried out gravity measurements and forward modeling along this profile with the densities of the basement and sediments. The result shows that the northern flank fault of Tianshan doesn't exist along the Hutubi River profile, and the basin sediments could be continually followed from the basin to the mountain interior. This indicates that the tectonic structures in the contact zones between the mountain and the basin are variable, as the western section in the Jingou River section shows that the Tianshan basement thrusts northward on the basin sediments. Based on the balance-section technology, the restored section shows 4. 8 km of shortening. Comparing with previous results, this indicates the heterogeneous deformation along the northern piedmont of Tianshan. It also implies that this multidisciplinary method could be widely used in the fold-and-thrust belt.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":"75-87"},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71078153","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}
Z. Di, Qiu Ning, Wang Zhangwen, Wang Zhenfeng, Sun Zhen
Rifting of the Qiongdongnan basin initiated in the Cenozoic above the Pre-Cenozoic basement which was overprinted by rifting basin tectonics soon after becoming part of a rifted passive continental margin of the South China Sea. Using integrated data of sedimentary horizons,wells,seismic reflection,and the observed gravity field,we constructed a crust-scale structural model of the Qiongdongnan basin.Many characteristics of this model reflect the tectonostratigraphic history of the basin.The structural and isopach maps of the basin allow us to retrace the well-established history of the basin comprising a dominant structural trend ofgradually shifting depocentre from the Paleogene sequence(45Ma~23.3Ma)to the Neogene to Quaternary sequence(23.3 Ma~present)towards the west or southwest.The present-day configuration of the basin implies that the basin fill of Cenozoic sediments becomes thinner towards the east.By integrating several reflection seismic profiles,interval velocity and performing gravity modeling, we have modeled the sub-sedimentary basement of the Qiongdongnan basin.The results show some high-velocity bodies in the lower part of crust(vP7.0 km ·s-1),and most probably is igneous magma underplated to the lower stretched continental crust during the final rifting and early spreading phase.The crystalline continental crust spans from the weakly stretched domains(as thick as about 25km)near the continental shelf to the extremely thinned domains(of less than 2.8km thickness)in the central depression,representing the continental margin rifting process in the Qiongdongnan basin.The estimated distribution of the crustal extension factor(β)of the basin shows that the factor in central depression is maximum value(6.0),while that in northern and southern side wings is minimum value(2.0).This model can shed light on future numerical simulation researches,including the reconstruction of the evolutionary processes from the rifted basin to the passive margin one and the evolution of the thermal field of the basin.
{"title":"Tectonostratigraphic structure and crustal extension of the Qiongdongnan basin,northern South China Sea","authors":"Z. Di, Qiu Ning, Wang Zhangwen, Wang Zhenfeng, Sun Zhen","doi":"10.6038/CJG20141008","DOIUrl":"https://doi.org/10.6038/CJG20141008","url":null,"abstract":"Rifting of the Qiongdongnan basin initiated in the Cenozoic above the Pre-Cenozoic basement which was overprinted by rifting basin tectonics soon after becoming part of a rifted passive continental margin of the South China Sea. Using integrated data of sedimentary horizons,wells,seismic reflection,and the observed gravity field,we constructed a crust-scale structural model of the Qiongdongnan basin.Many characteristics of this model reflect the tectonostratigraphic history of the basin.The structural and isopach maps of the basin allow us to retrace the well-established history of the basin comprising a dominant structural trend ofgradually shifting depocentre from the Paleogene sequence(45Ma~23.3Ma)to the Neogene to Quaternary sequence(23.3 Ma~present)towards the west or southwest.The present-day configuration of the basin implies that the basin fill of Cenozoic sediments becomes thinner towards the east.By integrating several reflection seismic profiles,interval velocity and performing gravity modeling, we have modeled the sub-sedimentary basement of the Qiongdongnan basin.The results show some high-velocity bodies in the lower part of crust(vP7.0 km ·s-1),and most probably is igneous magma underplated to the lower stretched continental crust during the final rifting and early spreading phase.The crystalline continental crust spans from the weakly stretched domains(as thick as about 25km)near the continental shelf to the extremely thinned domains(of less than 2.8km thickness)in the central depression,representing the continental margin rifting process in the Qiongdongnan basin.The estimated distribution of the crustal extension factor(β)of the basin shows that the factor in central depression is maximum value(6.0),while that in northern and southern side wings is minimum value(2.0).This model can shed light on future numerical simulation researches,including the reconstruction of the evolutionary processes from the rifted basin to the passive margin one and the evolution of the thermal field of the basin.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"1 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71078818","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}
Shi Chun-hua, Guo Dong, L. Hui, Zheng Bin, Liu Renqiang
We studied a deep convection in the warm sector and abnormal subtropical front caused by a cutoff low over East Asia in June 2009 by using cloud profile radar data from Cloudsat, temperature of black body from FY2C, atmospheric compositions from Aura/MLS, meteorological data from the ECMWF and HYSPLIT4 trajectory model. The analysis shows that for the sake of the background of southern trough, there is a weaker rainfall from the inner fronts, while nearly 1000km-scale deep convection occurs in the warm sector. At the nearly mature stage of the low, the subtropical front induced by the cutoff low is abnormally developing throughout the whole troposphere, which is due to the warm and humid air from southwest gathering along the subtropical front. After rapid eastward movement of the front into the rain belt of the warm sector, the strong ascending branch of thermal indirect secondary circulation across the frontal zone enhances deep convection at the colder part below the front. But it is difficult to sustain because the supplement of water vapor is blocked by the abnormal front. Furthermore, intense stratosphere-troposphere exchange occurs in the abnormal subtropical front zone due to the convective injection into stratospheric intrusions. On the scatter plot of ozone and water vapor these are two special gathering areas with both high (low) concentrations of the two species.
{"title":"Stratosphere‐Troposphere Exchange Corresponding to a Deep Convection in the Warm Sector and Abnormal Subtropical Front Induced by a Cutoff Low over East Asia","authors":"Shi Chun-hua, Guo Dong, L. Hui, Zheng Bin, Liu Renqiang","doi":"10.1002/CJG2.20079","DOIUrl":"https://doi.org/10.1002/CJG2.20079","url":null,"abstract":"We studied a deep convection in the warm sector and abnormal subtropical front caused by a cutoff low over East Asia in June 2009 by using cloud profile radar data from Cloudsat, temperature of black body from FY2C, atmospheric compositions from Aura/MLS, meteorological data from the ECMWF and HYSPLIT4 trajectory model. The analysis shows that for the sake of the background of southern trough, there is a weaker rainfall from the inner fronts, while nearly 1000km-scale deep convection occurs in the warm sector. At the nearly mature stage of the low, the subtropical front induced by the cutoff low is abnormally developing throughout the whole troposphere, which is due to the warm and humid air from southwest gathering along the subtropical front. After rapid eastward movement of the front into the rain belt of the warm sector, the strong ascending branch of thermal indirect secondary circulation across the frontal zone enhances deep convection at the colder part below the front. But it is difficult to sustain because the supplement of water vapor is blocked by the abnormal front. Furthermore, intense stratosphere-troposphere exchange occurs in the abnormal subtropical front zone due to the convective injection into stratospheric intrusions. On the scatter plot of ozone and water vapor these are two special gathering areas with both high (low) concentrations of the two species.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"40 1","pages":"1-10"},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20079","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51212173","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}
As the subsurface medium is widely viscous, it is necessary to compensate absorption and to correct dispersion of seismic waves in true-amplitude pre-stack imaging. The instability problem encountered in conventional inverse-Q migration hinders the application of the method. In this work, imaging was treated as a linear inverse problem named least-squares reverse time migration (LSRTM). Firstly, we linearized the wave equation and defined the cost function. Then based on the derived equations of the adjoint wave propagation operator, iterative solution was derived using the adjoint-state method. At last dynamical phase encoding technology was used to reduce computation cost. This method breaks a new way for imaging in visco-acoustic media while avoiding the instability problem. The true-amplitude imaging results can be obtained while compensating absorption and correcting dispersion automatically. It is also a good way to suppress the imaging noise and correct amplitude unbalance caused by geometrical spreading or weak illumination. Compared with conventional reverse time migration (RTM), this method can yield results with higher resolution and lower imaging noise. The validity of the method was demonstrated by the numerical test on synthetic seismic data.
{"title":"Least‐Squares Reverse Time Migration in Visco‐Acoustic Media","authors":"L. Zhenchun, Guo Zhen-bo, Tian Kun","doi":"10.1002/CJG2.20085","DOIUrl":"https://doi.org/10.1002/CJG2.20085","url":null,"abstract":"As the subsurface medium is widely viscous, it is necessary to compensate absorption and to correct dispersion of seismic waves in true-amplitude pre-stack imaging. The instability problem encountered in conventional inverse-Q migration hinders the application of the method. In this work, imaging was treated as a linear inverse problem named least-squares reverse time migration (LSRTM). Firstly, we linearized the wave equation and defined the cost function. Then based on the derived equations of the adjoint wave propagation operator, iterative solution was derived using the adjoint-state method. At last dynamical phase encoding technology was used to reduce computation cost. This method breaks a new way for imaging in visco-acoustic media while avoiding the instability problem. The true-amplitude imaging results can be obtained while compensating absorption and correcting dispersion automatically. It is also a good way to suppress the imaging noise and correct amplitude unbalance caused by geometrical spreading or weak illumination. Compared with conventional reverse time migration (RTM), this method can yield results with higher resolution and lower imaging noise. The validity of the method was demonstrated by the numerical test on synthetic seismic data.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":"79-94"},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20085","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51212592","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}
F. Juan, Meng Xiaohong, Chen Zhaoxi, Shi Lei, Wu Yue, Fan Zhen-jun
Based on the Fourier transform, the Parker-Oldenburg algorithm in the frequency domain was extended to the three-dimensional case in which the density changes with depth. From this, a gravity interface inversion formula was derived in which the assumed density varies laterally and vertically. Iterative convergence is assured by fixing a particular depth as the datum plane below the surface to reduce the interface fluctuation. The results of an example of synthetic gravity data indicate that the proposed method has high precision and rapid convergence, with high practical value for the inversion of density interfaces. This method was also used to determine the Moho depth beneath northern China. The results were verified by seismic sounding data.
{"title":"Research and Application of Three‐Dimensional Density Interface Inversion","authors":"F. Juan, Meng Xiaohong, Chen Zhaoxi, Shi Lei, Wu Yue, Fan Zhen-jun","doi":"10.1002/CJG2.20086","DOIUrl":"https://doi.org/10.1002/CJG2.20086","url":null,"abstract":"Based on the Fourier transform, the Parker-Oldenburg algorithm in the frequency domain was extended to the three-dimensional case in which the density changes with depth. From this, a gravity interface inversion formula was derived in which the assumed density varies laterally and vertically. Iterative convergence is assured by fixing a particular depth as the datum plane below the surface to reduce the interface fluctuation. The results of an example of synthetic gravity data indicate that the proposed method has high precision and rapid convergence, with high practical value for the inversion of density interfaces. This method was also used to determine the Moho depth beneath northern China. The results were verified by seismic sounding data.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":"95-102"},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20086","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51212652","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}
Penetration depth is one of key technical parameters in the airborne time-domain electromagnetic system (ATEM), which plays an important role in system design as well as data interpretation. When the difference of conductivity between the target layer and host rock is small or the anomaly response of the target layer is not obvious, the conventional method for estimating penetration depth is no longer applicable. To overcome this drawback, this study suggests a new approach. It simulates the diffusion processes of the induced electric field in a uniform half-space model or a layering model and determines the transient position of the field with the largest amplitude in the subsurface. Then it defines that the depth of this position is the penetration depth of the system, where the measured response value is equal to the given noise level. Taking the China helicopter time-domain electromagnetic system I (CHTEM-I), developed independently by our own forces, as the example, this work presents the application of this new method. It compares calculation results under various conditions, produces relation curves of penetration depth, flight height and noise level, and explores how to enhance the penetration depth of the system. The results show that the system can probe down depth 300 m in the case that noise level is proportional to t−05 when the half-space model has conductivity in 0.000295∼0.0422 S/m. This depth estimation method is not affected by factors such as layer thickness and magnitude of conductivity difference between the target layer and host rock, and thus very applicable. It is of significance to design including estimation of penetration depth for various time-domain airborne electromagnetic systems.
{"title":"Estimating Penetration Depth of the CHTEM‐I System by the Diffusive Electric Field Method","authors":"Chen Bin, Mao Li-feng, Liu Guang-ding","doi":"10.1002/CJG2.20088","DOIUrl":"https://doi.org/10.1002/CJG2.20088","url":null,"abstract":"Penetration depth is one of key technical parameters in the airborne time-domain electromagnetic system (ATEM), which plays an important role in system design as well as data interpretation. When the difference of conductivity between the target layer and host rock is small or the anomaly response of the target layer is not obvious, the conventional method for estimating penetration depth is no longer applicable. To overcome this drawback, this study suggests a new approach. It simulates the diffusion processes of the induced electric field in a uniform half-space model or a layering model and determines the transient position of the field with the largest amplitude in the subsurface. Then it defines that the depth of this position is the penetration depth of the system, where the measured response value is equal to the given noise level. Taking the China helicopter time-domain electromagnetic system I (CHTEM-I), developed independently by our own forces, as the example, this work presents the application of this new method. It compares calculation results under various conditions, produces relation curves of penetration depth, flight height and noise level, and explores how to enhance the penetration depth of the system. The results show that the system can probe down depth 300 m in the case that noise level is proportional to t−05 when the half-space model has conductivity in 0.000295∼0.0422 S/m. This depth estimation method is not affected by factors such as layer thickness and magnitude of conductivity difference between the target layer and host rock, and thus very applicable. It is of significance to design including estimation of penetration depth for various time-domain airborne electromagnetic systems.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"57 1","pages":"112-119"},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20088","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51212752","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}
Lab ultrasonic measurements to metamorphic kinds of coal reveal the relation between the maximum vitrinite reflectance and ultrasonic quality factor. And then the relations between ultrasonic velocities and quality factors, including the anisotropic characteristics of quality factors are analyzed. The results show that there are good linear correlations between the maximum vitrinite reflectance and P- and S-wave quality factors, between velocities in direction perpendicular to seams and quality factors, and between the P- wave quality and S-wave's quality factors in direction vertical to seams. Moreover, there are stronger anisotropies in seismic quality factors than velocities. Comparison of the measured S-wave Q values with estimated values, based on a theoretical formula, indicates an only 7.2% relative error in this method. It proves that this theoretical formula can be applied to attenuation compensation of the converted shear wave in processing of multi-component seismic data.
{"title":"Quality Factor Characteristics of Six Metamorphic Kinds of Coal in China","authors":"Xu Xiao-kai, Wang Yun, Meng Zhao-ping","doi":"10.1002/CJG2.20089","DOIUrl":"https://doi.org/10.1002/CJG2.20089","url":null,"abstract":"Lab ultrasonic measurements to metamorphic kinds of coal reveal the relation between the maximum vitrinite reflectance and ultrasonic quality factor. And then the relations between ultrasonic velocities and quality factors, including the anisotropic characteristics of quality factors are analyzed. The results show that there are good linear correlations between the maximum vitrinite reflectance and P- and S-wave quality factors, between velocities in direction perpendicular to seams and quality factors, and between the P- wave quality and S-wave's quality factors in direction vertical to seams. Moreover, there are stronger anisotropies in seismic quality factors than velocities. Comparison of the measured S-wave Q values with estimated values, based on a theoretical formula, indicates an only 7.2% relative error in this method. It proves that this theoretical formula can be applied to attenuation compensation of the converted shear wave in processing of multi-component seismic data.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"11 1","pages":"120-126"},"PeriodicalIF":1.4,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20089","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51212860","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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