Q. Yao, Xi-wei Xu, H. Xing, Jia Cheng, Guoyan Jiang, Weiyu Ma, Jie Liu, Wen Yang
On April 25th, 2015, the moment magnitude (M-w) 7. 8 Gorkha earthquake, Nepal occurred in Himalaya orogenic belt, which seems insufficient to release the accumulated energy as suggested previously. The following seismic risk assessments are mostly based on the two dimensional or pseudo-three dimensional inversions of tectonic deformation. Here we analyze the relationship between the main shock and biggest aftershock of the 2015 Gorkha earthquake sequence, and its unevenness in time and space. Combining focal mechanism solutions, crustal velocity structure, relocated aftershocks, and inversion results from InSAR, we construct a three dimensional model which changes along both the strike and dip directions of the Main Himalayan Thrust. The finite element method with nonlinear friction is used to calculate the fault behavior and block deformation in one earthquake recurrence period. Comparison between the forward calculation results and the co-seismic deformation observed from InSAR, and co-seismic slip inverted from deformation observations, and time-space evolution of historical earthquakes revealed that the three dimension model is close to the reality. The results suggest two potential seismic risk regions in the future: a big earthquake might be located in the east of the 1934 Bihar-Nepal M-w similar to 8. 1 earthquake, and a moderate to major event might take place to the southeast of the aftershock M(w)7. 3 earthquake.
{"title":"3D seismogenic model of the 2015 Gorkha earthquake and subsequent seismic risk","authors":"Q. Yao, Xi-wei Xu, H. Xing, Jia Cheng, Guoyan Jiang, Weiyu Ma, Jie Liu, Wen Yang","doi":"10.6038/CJG2018L0371","DOIUrl":"https://doi.org/10.6038/CJG2018L0371","url":null,"abstract":"On April 25th, 2015, the moment magnitude (M-w) 7. 8 Gorkha earthquake, Nepal occurred in Himalaya orogenic belt, which seems insufficient to release the accumulated energy as suggested previously. The following seismic risk assessments are mostly based on the two dimensional or pseudo-three dimensional inversions of tectonic deformation. Here we analyze the relationship between the main shock and biggest aftershock of the 2015 Gorkha earthquake sequence, and its unevenness in time and space. Combining focal mechanism solutions, crustal velocity structure, relocated aftershocks, and inversion results from InSAR, we construct a three dimensional model which changes along both the strike and dip directions of the Main Himalayan Thrust. The finite element method with nonlinear friction is used to calculate the fault behavior and block deformation in one earthquake recurrence period. Comparison between the forward calculation results and the co-seismic deformation observed from InSAR, and co-seismic slip inverted from deformation observations, and time-space evolution of historical earthquakes revealed that the three dimension model is close to the reality. The results suggest two potential seismic risk regions in the future: a big earthquake might be located in the east of the 1934 Bihar-Nepal M-w similar to 8. 1 earthquake, and a moderate to major event might take place to the southeast of the aftershock M(w)7. 3 earthquake.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"14 1 1","pages":"2332-2343"},"PeriodicalIF":1.4,"publicationDate":"2018-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89787138","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}
H. Qian, J. Mechie, Changqing Yu, Deutsches GeoForschungsZentrum Publikationen aller GIPP-unte Projekte
{"title":"The spherical analytic relocation technique and its application to local seismic tomography in Longmenshan area","authors":"H. Qian, J. Mechie, Changqing Yu, Deutsches GeoForschungsZentrum Publikationen aller GIPP-unte Projekte","doi":"10.6038/CJG2018M0149","DOIUrl":"https://doi.org/10.6038/CJG2018M0149","url":null,"abstract":"","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"28 1","pages":"2011-2021"},"PeriodicalIF":1.4,"publicationDate":"2018-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74917786","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}
In the marine controlled-source electromagnetic (CSEM) survey, the receivers are usually placed at the seafloor. The resistivity contrast between the seawater and seafloor sediments is large, which can cause difficulties in numerical modeling of CSEM fields at receiver locations. In this paper, we present an improved interpolating method for calculating electric and magnetic fields at the seafloor with a resistivity contrast. This method is applied to the 2. 5 dimensional (2. 5D) frequency-domain CSEM modeling with towed transmitters and receivers located at the seafloor. Considering the discontinuity of the normal electric fields, we use the normal current electric density for interpolation. We simulate the 2. 5D marine CSEM responses by the staggered finite-difference (SFD) method with Fourier transform to the strike direction. The final SFD equations are solved by the direct solver MUMPS (MUltifrontal Massively Parallel Sparse direct Solver). To avoid the source singularities, the secondary-field approach is used and the primary fields excited by the electric dipole source can be calculated quasi-analytically for the one-dimensional (1D) layered background model. We focus on interpolating of electric and magnetic fields in the wavenumber domain to the receiver locations at the seafloor interface between the conductive seawater and resistive seafloor formation. The secondary electric and magnetic fields are used for interpolation instead of the total fields for high numerical accuracy. After performing the inverse Fourier transform to the wavenumbers, the electric and magnetic fields in the space domain are obtained. To check the accuracy of our 2. 5D marine CSEM SFD modeling algorithm with the improved receiver interpolating technique, we compare our results with both the 1D analytical results and the adaptive finite element results. The SFD numerical results are approved to be accurate. We also compare the numerical accuracy between our improved interpolation scheme and others, i.e., the conventional linear interpolation and the rigorous interpolation. The proposed interpolation only utilizes the nodes below/above the seafloor interface, and is proved to be much more accurate than the other two interpolating methods used.
在海洋可控源电磁(CSEM)测量中，接收机通常放置在海底。海水和海底沉积物的电阻率差异较大，这给接收点的CSEM场数值模拟带来了困难。本文提出了一种改进的利用电阻率对比法计算海底电场和磁场的插值方法。该方法适用于2。5维(2)5D)频率域CSEM建模，位于海底的拖曳发射器和接收器。考虑到法向电场的不连续，我们采用法向电流电密度进行插值。我们模拟2。用交错有限差分法(SFD)对走向进行傅里叶变换，得到5D海洋CSEM的响应。最后用直接求解器MUMPS (multifront Massively Parallel Sparse direct solver)求解SFD方程。为了避免源的奇异性，采用二次场方法，对一维分层背景模型进行了电偶极子源激发的一次场的拟解析计算。我们的重点是将波数域的电场和磁场插值到位于导电海水和电阻性海底地层之间的海底界面上的接收器位置。为了提高数值精度，采用二次电场和磁场代替总电场进行插值。对波数进行傅里叶反变换后，得到了空间域中的电场和磁场。来检查我们的2的准确性。采用改进的接收机插值技术对5D海洋CSEM SFD建模算法进行了比较，并与一维解析结果和自适应有限元结果进行了比较。结果表明，SFD数值计算结果是准确的。本文还比较了改进后的插补方案与传统线性插补方案和严格插补方案的数值精度。所提出的插值方法仅利用了海底界面下方/上方的节点，并且被证明比其他两种插值方法要准确得多。
{"title":"2.5D marine CSEM modeling in the frequency-domain based on an improved interpolation scheme at receiver positions","authors":"Gang Li, Yuguo Li, B. Han, S. Duan","doi":"10.6038/CJG20171228","DOIUrl":"https://doi.org/10.6038/CJG20171228","url":null,"abstract":"In the marine controlled-source electromagnetic (CSEM) survey, the receivers are usually placed at the seafloor. The resistivity contrast between the seawater and seafloor sediments is large, which can cause difficulties in numerical modeling of CSEM fields at receiver locations. In this paper, we present an improved interpolating method for calculating electric and magnetic fields at the seafloor with a resistivity contrast. This method is applied to the 2. 5 dimensional (2. 5D) frequency-domain CSEM modeling with towed transmitters and receivers located at the seafloor. Considering the discontinuity of the normal electric fields, we use the normal current electric density for interpolation. We simulate the 2. 5D marine CSEM responses by the staggered finite-difference (SFD) method with Fourier transform to the strike direction. The final SFD equations are solved by the direct solver MUMPS (MUltifrontal Massively Parallel Sparse direct Solver). To avoid the source singularities, the secondary-field approach is used and the primary fields excited by the electric dipole source can be calculated quasi-analytically for the one-dimensional (1D) layered background model. We focus on interpolating of electric and magnetic fields in the wavenumber domain to the receiver locations at the seafloor interface between the conductive seawater and resistive seafloor formation. The secondary electric and magnetic fields are used for interpolation instead of the total fields for high numerical accuracy. After performing the inverse Fourier transform to the wavenumbers, the electric and magnetic fields in the space domain are obtained. \u0000 \u0000To check the accuracy of our 2. 5D marine CSEM SFD modeling algorithm with the improved receiver interpolating technique, we compare our results with both the 1D analytical results and the adaptive finite element results. The SFD numerical results are approved to be accurate. \u0000 \u0000We also compare the numerical accuracy between our improved interpolation scheme and others, i.e., the conventional linear interpolation and the rigorous interpolation. The proposed interpolation only utilizes the nodes below/above the seafloor interface, and is proved to be much more accurate than the other two interpolating methods used.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"1 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2017-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43775464","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 shale gas reservoir storage space mainly includes micro pores and cracks of micron and nano scale. Owing to the complex pore network, as well as high content of kerogen and clay minerals in shale matrix and existence of conductive minerals, especially pyrite, the shale reservoir conductive mechanism is quite different from that of conventional reservoir, and the I-Sw curve obtained by core electricity experiment is non-linear which makes traditional evaluation models such as Archie's law not suitable. Aiming at these issues, according to actual core experiment and CT scan data, a three dimensional percolation network is established with randomized algorithm and the node voltage and current are calculated through over-relaxation iteration algorithm. With this network, the reasons for non-Archie property and the influence factors of shale reservoir are analyzed. Simulation results show that pore structure, shape and size, mineral composition and formation water resistivity have different effects on the reservoir resistivity. By changing the setting value, single-correlation between the reservoir resistivity and these factors can be built, and percolation correction model is also developed to calculate shale reservoir water saturation. The method has achieved a good effect in a certain shale gas field in Sichuan, China, which presents a good application prospect and provides a new thought on solving complex problems in shale gas field exploration and development with network simulation methods.
{"title":"SHALE RESERVOIR CONDUCTIVE MECHANISM SIMULATION BASED ON PERCOLATION NETWORK","authors":"Zhao Jun, Dai Xinyun, Lu Yi-fan, Tang Shen-Hua","doi":"10.1002/CJG2.30045","DOIUrl":"https://doi.org/10.1002/CJG2.30045","url":null,"abstract":"The shale gas reservoir storage space mainly includes micro pores and cracks of micron and nano scale. Owing to the complex pore network, as well as high content of kerogen and clay minerals in shale matrix and existence of conductive minerals, especially pyrite, the shale reservoir conductive mechanism is quite different from that of conventional reservoir, and the I-Sw curve obtained by core electricity experiment is non-linear which makes traditional evaluation models such as Archie's law not suitable. Aiming at these issues, according to actual core experiment and CT scan data, a three dimensional percolation network is established with randomized algorithm and the node voltage and current are calculated through over-relaxation iteration algorithm. With this network, the reasons for non-Archie property and the influence factors of shale reservoir are analyzed. Simulation results show that pore structure, shape and size, mineral composition and formation water resistivity have different effects on the reservoir resistivity. By changing the setting value, single-correlation between the reservoir resistivity and these factors can be built, and percolation correction model is also developed to calculate shale reservoir water saturation. The method has achieved a good effect in a certain shale gas field in Sichuan, China, which presents a good application prospect and provides a new thought on solving complex problems in shale gas field exploration and development with network simulation methods.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"60 1","pages":"275-285"},"PeriodicalIF":1.4,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.30045","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45231740","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}
L. Fei, Xiao Feng, Zhang Shengkai, E. Dongchen, C. Xiao, Hao Weifeng, Yuan Lexian, Zuo Yao-Wen
Digital elevation models (DEMs) are of fundamental importance to many geoscientific and environmental studies in Antarctic and due to relatively poor coverage by ground based surveys, the main data source for constructing an Antarctic DEM is satellite altimetry. The newest operating satellite-borne altimeter with ice applications is the ESA satellite CryoSat-2, which was launched in April 2010. CryoSat-2 provides altimetry data up to a latitude of 88°S/N, which is a significant improvement to previous satellite-borne altimeters. Based on two full cycles of CryoSat-2 observations acquired between December 2012 and January 2015, we derived a new DEM for the Antarctic Ice Sheet. The accuracy of generated DEM depends largely on the interpolation method adopted and five widely used interpolation methods were compared using the Cross Validation method. The Kriging method yielded better estimates for the Antarctic Ice Sheet and was adopted when constructing the final DEM. For the CryoSat-2 LRM data we followed an iterative approach to correct for the surface slope, and the slope correction was applied to each data point using the relocation method. Data gap beyond the latitudinal limit of the CryoSat-2 mission (88°S) was filled by contour data from Antarctic Digital Database (ADD). Finally, we present a new Antarctic DEM with a pixel size of 1 km×1 km. The accuracy of the final DEM was assessed by ICESat, IceBridge and GPS data and compared with four widely used Antarctic DEMs namely Bamber 1 km DEM, ICESat DEM, RAMPv2 DEM and JLB97 DEM. The results show that the CryoSat-2 DEM has an uncertainty of 0.73±8.398 m. The vertical accuracy of the DEM is better than 1 m at domes, better than 4 m for the ice shelves, better than 10 m for the interior ice sheet and over 150 m for the rugged mountainous and coastal areas.
{"title":"DEM DEVELOPMENT AND PRECISION ANALYSIS FOR ANTARCTIC ICE SHEET USING CRYOSAT-2 ALTIMETRY DATA","authors":"L. Fei, Xiao Feng, Zhang Shengkai, E. Dongchen, C. Xiao, Hao Weifeng, Yuan Lexian, Zuo Yao-Wen","doi":"10.1002/CJG2.30041","DOIUrl":"https://doi.org/10.1002/CJG2.30041","url":null,"abstract":"Digital elevation models (DEMs) are of fundamental importance to many geoscientific and environmental studies in Antarctic and due to relatively poor coverage by ground based surveys, the main data source for constructing an Antarctic DEM is satellite altimetry. The newest operating satellite-borne altimeter with ice applications is the ESA satellite CryoSat-2, which was launched in April 2010. CryoSat-2 provides altimetry data up to a latitude of 88°S/N, which is a significant improvement to previous satellite-borne altimeters. Based on two full cycles of CryoSat-2 observations acquired between December 2012 and January 2015, we derived a new DEM for the Antarctic Ice Sheet. The accuracy of generated DEM depends largely on the interpolation method adopted and five widely used interpolation methods were compared using the Cross Validation method. The Kriging method yielded better estimates for the Antarctic Ice Sheet and was adopted when constructing the final DEM. For the CryoSat-2 LRM data we followed an iterative approach to correct for the surface slope, and the slope correction was applied to each data point using the relocation method. Data gap beyond the latitudinal limit of the CryoSat-2 mission (88°S) was filled by contour data from Antarctic Digital Database (ADD). Finally, we present a new Antarctic DEM with a pixel size of 1 km×1 km. The accuracy of the final DEM was assessed by ICESat, IceBridge and GPS data and compared with four widely used Antarctic DEMs namely Bamber 1 km DEM, ICESat DEM, RAMPv2 DEM and JLB97 DEM. The results show that the CryoSat-2 DEM has an uncertainty of 0.73±8.398 m. The vertical accuracy of the DEM is better than 1 m at domes, better than 4 m for the ice shelves, better than 10 m for the interior ice sheet and over 150 m for the rugged mountainous and coastal areas.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"60 1","pages":"231-243"},"PeriodicalIF":1.4,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.30041","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49092900","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}
We restore the seismic source spectrums of 1012 earthquakes (2.0 ≤ ML ≤ 5.0) in the mid-northern part of Sichuan-Yunnan seismic block between January 1, 2009 and December 31, 2015, then calculate the source parameters (e.g., seismic moments M0, focal scale r and stress drop Δσ) and fit the calibration relationship between these parameters. Based on the regional seismic tectonic background, the distribution of active faults and seismicity, the study area is divided into four statistical units. For each unit the stress distribution characteristics, change of stress drop with location, correlation between the stress-strain loading and the dynamic process of regional deformation, are discussed respectively. The results show that seismic moments M0 are consistent with the magnitude-moment relation that lgM0 = 0.92ML + 10.46. The relationship between stress drop and magnitude is consistent with the result gained by Nuttli that intraplate earthquake follows the ISD model, with a statistical relationship lgΔσ = 0.31 lgM0 – 3.92. Seismic source stress drop results show the following, (1) The stress at the end of the Jinshajiang fault is low, the overall sliding rate of the fault unit is high, and strong earthquake activity is very rare. In the fault belt consisting of three secondary faults, stress-strain loading deceases gradually from northwest to southeast along Litang fault, the northwest section which is relatively locked is more likely to accumulate strain than southeast section. (2) Stress drop of Xianshuihe fault zone is divided by Kangding, the southern section is low and northern section is high. Southern section (Kangding-Shimian) is difficult to accumulate higher strain in the short term, but in northern section (Garze-Kangding), moderate and strong earthquakes have not filled the gaps of seismic moment release, there is still a high stress accumulation in partial section. (3) High stress-drop events were concentrated on Anninghe-Zemuhe fault zone, strain accumulation of this unit is strong, and stress level is the highest, earthquake risk is high. (4) On Lijiang-Xiaojinhe fault zone, stress drop characteristics of different magnitude earthquakes are not the same, which is related to complex tectonic setting, the specific reasons still need to be discussed deeply. Stress background in the Muli area is low and may be affected by the local tectonic environment. The study also shows that, (1) Stress drops display a systematic change with different faults and locations, high stress-drop events occur mostly in the fault intersection area. Faults without locking condition and mainly creeping are mainly characterized by low stress drop. (2) Contrasting to what is commonly thought that “strike-slip faults are not easy to accumulate stress”, Xianshuihe fault zone and Anninghe-Zemuhe fault zone all exhibit high stress levels, which may be due to that the magnitude and intensity of medium-strong earthquakes are not enough to release the accumulated en
{"title":"REGIONAL CHARACTERISTICS OF STRESS STATE OF MAIN SEISMIC ACTIVE FAULTS IN MID‐NORTHERN PART OF SICHUAN‐YUNNAN BLOCK","authors":"Wu Weiwei, Wu Peng, W. Yaling, Sun Wei","doi":"10.1002/CJG2.30043","DOIUrl":"https://doi.org/10.1002/CJG2.30043","url":null,"abstract":"We restore the seismic source spectrums of 1012 earthquakes (2.0 ≤ ML ≤ 5.0) in the mid-northern part of Sichuan-Yunnan seismic block between January 1, 2009 and December 31, 2015, then calculate the source parameters (e.g., seismic moments M0, focal scale r and stress drop Δσ) and fit the calibration relationship between these parameters. Based on the regional seismic tectonic background, the distribution of active faults and seismicity, the study area is divided into four statistical units. For each unit the stress distribution characteristics, change of stress drop with location, correlation between the stress-strain loading and the dynamic process of regional deformation, are discussed respectively. The results show that seismic moments M0 are consistent with the magnitude-moment relation that lgM0 = 0.92ML + 10.46. The relationship between stress drop and magnitude is consistent with the result gained by Nuttli that intraplate earthquake follows the ISD model, with a statistical relationship lgΔσ = 0.31 lgM0 – 3.92. \u0000 \u0000Seismic source stress drop results show the following, (1) The stress at the end of the Jinshajiang fault is low, the overall sliding rate of the fault unit is high, and strong earthquake activity is very rare. In the fault belt consisting of three secondary faults, stress-strain loading deceases gradually from northwest to southeast along Litang fault, the northwest section which is relatively locked is more likely to accumulate strain than southeast section. (2) Stress drop of Xianshuihe fault zone is divided by Kangding, the southern section is low and northern section is high. Southern section (Kangding-Shimian) is difficult to accumulate higher strain in the short term, but in northern section (Garze-Kangding), moderate and strong earthquakes have not filled the gaps of seismic moment release, there is still a high stress accumulation in partial section. (3) High stress-drop events were concentrated on Anninghe-Zemuhe fault zone, strain accumulation of this unit is strong, and stress level is the highest, earthquake risk is high. (4) On Lijiang-Xiaojinhe fault zone, stress drop characteristics of different magnitude earthquakes are not the same, which is related to complex tectonic setting, the specific reasons still need to be discussed deeply. Stress background in the Muli area is low and may be affected by the local tectonic environment. The study also shows that, (1) Stress drops display a systematic change with different faults and locations, high stress-drop events occur mostly in the fault intersection area. Faults without locking condition and mainly creeping are mainly characterized by low stress drop. (2) Contrasting to what is commonly thought that “strike-slip faults are not easy to accumulate stress”, Xianshuihe fault zone and Anninghe-Zemuhe fault zone all exhibit high stress levels, which may be due to that the magnitude and intensity of medium-strong earthquakes are not enough to release the accumulated en","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"28 4","pages":"254-265"},"PeriodicalIF":1.4,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.30043","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41268081","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}
Fan Xiao-ping, He Yi-cheng, Wang Jun-fei, Yang Yun
Broadband teleseismic waveform data from 10 earthquakes recorded by 134 digital seismic stations were selected to study the seismic scattering strength of the crust in the middle-south segment of the Tancheng-Lujiang fault zone by teleseismic fluctuation wave field method. The results show that strong transverse inhomogeneity exists beneath the middle-south segment of the Tancheng-Lujiang fault zone, and that the spatial distributions of seismic scattering strength exhibit conformity between the upper and lower crusts. Strong seismic scattering strength is found beneath the north China block and the Qinling-Dabie fold system, whereas weak seismic scattering strength is found under the Yangtze block. The peak value of seismic scattering strength is mainly distributed in Lu'an, Junan, Jiashan, and Yantai, among others. The tectonic blocks are correlated with seismic scattering strength. Different blocks show different seismic scattering strengths. Seismic scattering strength, which can be divided into three segments, shows a segmental feature along the Tancheng-Lujiang fault zone. The first segment is from Weifang to Linyi, the second is from Linyi to Jiashan, and the third is from Jianshan to Jiujiang. Earthquake activity is strongly correlated with seismic scattering strength, and the epicenters of moderate earthquakes are located along the gradient zone of seismic scattering strength. Many smaller earthquakes occur along the high gradients of seismic scattering strength throughout the Tancheng-Lujiang fault zone, such as the segment of Linyi to Jiashan, and the segment of Jianshan to Jiujiang. However, the segment of Linyi to Jiashan with fewer earthquakes shows a low gradient of seismic scattering strength. Seismic scattering strength shows coherency with tectonic blocks, deep fault structure, and earthquake activity. Thus, seismic scattering strength reflects the different physical properties of a medium in the crust and is also related to the physical morphology of the medium, substance migration, and variations in stress-strain environment in the deep structure.
{"title":"CRUST SEISMIC SCATTERING STRENGTH BENEATH THE MIDDLE‐SOUTH SEGMENT OF THE TANCHENG‐LUJIANG FAULT ZONE","authors":"Fan Xiao-ping, He Yi-cheng, Wang Jun-fei, Yang Yun","doi":"10.1002/CJG2.30042","DOIUrl":"https://doi.org/10.1002/CJG2.30042","url":null,"abstract":"Broadband teleseismic waveform data from 10 earthquakes recorded by 134 digital seismic stations were selected to study the seismic scattering strength of the crust in the middle-south segment of the Tancheng-Lujiang fault zone by teleseismic fluctuation wave field method. The results show that strong transverse inhomogeneity exists beneath the middle-south segment of the Tancheng-Lujiang fault zone, and that the spatial distributions of seismic scattering strength exhibit conformity between the upper and lower crusts. Strong seismic scattering strength is found beneath the north China block and the Qinling-Dabie fold system, whereas weak seismic scattering strength is found under the Yangtze block. The peak value of seismic scattering strength is mainly distributed in Lu'an, Junan, Jiashan, and Yantai, among others. The tectonic blocks are correlated with seismic scattering strength. Different blocks show different seismic scattering strengths. Seismic scattering strength, which can be divided into three segments, shows a segmental feature along the Tancheng-Lujiang fault zone. The first segment is from Weifang to Linyi, the second is from Linyi to Jiashan, and the third is from Jianshan to Jiujiang. Earthquake activity is strongly correlated with seismic scattering strength, and the epicenters of moderate earthquakes are located along the gradient zone of seismic scattering strength. Many smaller earthquakes occur along the high gradients of seismic scattering strength throughout the Tancheng-Lujiang fault zone, such as the segment of Linyi to Jiashan, and the segment of Jianshan to Jiujiang. However, the segment of Linyi to Jiashan with fewer earthquakes shows a low gradient of seismic scattering strength. Seismic scattering strength shows coherency with tectonic blocks, deep fault structure, and earthquake activity. Thus, seismic scattering strength reflects the different physical properties of a medium in the crust and is also related to the physical morphology of the medium, substance migration, and variations in stress-strain environment in the deep structure.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"60 1","pages":"244-253"},"PeriodicalIF":1.4,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.30042","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47456380","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}
Directly from the second order differential equations of satellite motion, the linearized orbital perturbation differential equations for CHAMP-like satellites are derived after introducing the reference orbit, and then introducing the omitted terms into the linearized orbital perturbation differential equations, the orbital perturbation differential equations with nonlinear corrections are derived. The accuracies for the orbital perturbation differential equations are estimated and the following results are obtained: if the measurement errors of the satellite positions and the non-gravitational accelerations are less than 3 cm and 3 × 10−10 m·s−2 respectively, the linearized orbital perturbation differential equations and the equations with nonlinear corrections can hold the accuracies 3 × 10−10 m·s−2 only when ρ ≤ 4.7 m and ρ ≤ 4.14 × 103 m respectively, where ρ is the distance between the satellite orbit and the reference one. Hence, compared with the linearized orbital perturbation differential equations, the equations with nonlinear corrections are suitable to establish normal system of equations of the gravity field's spherical harmonic coefficients in long time span. The solving method for the orbital perturbation differential equations is also given with the help of the superposition principle in the paper. At last, some imitation examples for CHAMP and GRACE missions are computed, and the results illustrate that the orbital perturbation differential equations with nonlinear corrections have higher accuracies than the linearized ones.
{"title":"ORBITAL PERTURBATION DIFFERENTIAL EQUATIONS WITH NON‐LINEAR CORRECTIONS FOR CHAMP‐LIKE SATELLITE","authors":"Yuan Jin-hai, Zhu Yong-chao, Meng Xiang-chao","doi":"10.1002/CJG2.30046","DOIUrl":"https://doi.org/10.1002/CJG2.30046","url":null,"abstract":"Directly from the second order differential equations of satellite motion, the linearized orbital perturbation differential equations for CHAMP-like satellites are derived after introducing the reference orbit, and then introducing the omitted terms into the linearized orbital perturbation differential equations, the orbital perturbation differential equations with nonlinear corrections are derived. The accuracies for the orbital perturbation differential equations are estimated and the following results are obtained: if the measurement errors of the satellite positions and the non-gravitational accelerations are less than 3 cm and 3 × 10−10 m·s−2 respectively, the linearized orbital perturbation differential equations and the equations with nonlinear corrections can hold the accuracies 3 × 10−10 m·s−2 only when ρ ≤ 4.7 m and ρ ≤ 4.14 × 103 m respectively, where ρ is the distance between the satellite orbit and the reference one. Hence, compared with the linearized orbital perturbation differential equations, the equations with nonlinear corrections are suitable to establish normal system of equations of the gravity field's spherical harmonic coefficients in long time span. The solving method for the orbital perturbation differential equations is also given with the help of the superposition principle in the paper. At last, some imitation examples for CHAMP and GRACE missions are computed, and the results illustrate that the orbital perturbation differential equations with nonlinear corrections have higher accuracies than the linearized ones.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"60 1","pages":"286-299"},"PeriodicalIF":1.4,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.30046","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47370413","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}
Chen Gao-xiang, Fu Li-yun, YU Geng‐Xin, Guan Xi‐Zhu, Ge Shuang-cheng
{"title":"A QUANTITATIVE ANALYSIS METHOD FOR THE SEISMIC GEOLOGICAL COMPLEXITY OF NEAR SURFACE","authors":"Chen Gao-xiang, Fu Li-yun, YU Geng‐Xin, Guan Xi‐Zhu, Ge Shuang-cheng","doi":"10.1002/CJG2.30047","DOIUrl":"https://doi.org/10.1002/CJG2.30047","url":null,"abstract":"","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"60 1","pages":"300-312"},"PeriodicalIF":1.4,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.30047","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41530952","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}
Zhou Jiang-cun, Sun He-ping, Xu Jianqiao, Cui Xiao-ming, Chen Xiao-dong
Earthquakes not only release seismic-wave energy, which decays eventually, but also give rise to permanent deformation in the Earth. This permanent deformation causes gravitational potential energy (GPE) change. Previous researches showed that the GPE change is a good indicator of extensional and compressional tectonics. In this paper, we first proposed an effective method to compute co-seismic GPE change for a SNREI (spherically symmetric Non-rotational Elastic Isotropic) Earth according to the point dislocation theory. This method is applicable to both shear and tensile earthquakes. We then applied this method to compute the contributions from earthquakes occurred over Tibetan plateau area from 1976 to 2013 to the crustal GPE change. The results show that earthquakes occurred in central and western part of Tibetan plateau caused the crustal GPE to decrease while those in eastern part caused it to increase, which correspond to extensional and compressional tectonic status, respectively, in this area. Furthermore, the impact of earthquakes occurred from 1999 to 2013 was larger than that of earthquakes occurred from 1976 to 1998.
{"title":"CO‐SEISMIC GRAVITATIONAL POTENTIAL ENERGY CHANGE AND ITS TECTONIC IMPLICATIONS: A CASE STUDY IN TIBETAN PLATEAU AREA","authors":"Zhou Jiang-cun, Sun He-ping, Xu Jianqiao, Cui Xiao-ming, Chen Xiao-dong","doi":"10.1002/CJG2.30048","DOIUrl":"https://doi.org/10.1002/CJG2.30048","url":null,"abstract":"Earthquakes not only release seismic-wave energy, which decays eventually, but also give rise to permanent deformation in the Earth. This permanent deformation causes gravitational potential energy (GPE) change. Previous researches showed that the GPE change is a good indicator of extensional and compressional tectonics. In this paper, we first proposed an effective method to compute co-seismic GPE change for a SNREI (spherically symmetric Non-rotational Elastic Isotropic) Earth according to the point dislocation theory. This method is applicable to both shear and tensile earthquakes. We then applied this method to compute the contributions from earthquakes occurred over Tibetan plateau area from 1976 to 2013 to the crustal GPE change. The results show that earthquakes occurred in central and western part of Tibetan plateau caused the crustal GPE to decrease while those in eastern part caused it to increase, which correspond to extensional and compressional tectonic status, respectively, in this area. Furthermore, the impact of earthquakes occurred from 1999 to 2013 was larger than that of earthquakes occurred from 1976 to 1998.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"60 1","pages":"313-320"},"PeriodicalIF":1.4,"publicationDate":"2017-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.30048","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46293723","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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