A strong earthquake(Mw6.9)occurred in the Gorda plate off the northwestern coast of California in March 10,2014(Beijing Time).The rupture process of the earthquake is determined by the waveform inversion method using far-field body waveform records provided by IRIS.Afterthat,we analyze the reason why the earthquake did not cause serious hazards and trigger tsunami,and provide new evidence to the research of dynamics study in the area.The focal mechanism of the earthquake is obtained by dislocation source model utilizing 19far-field P vertical waveform records with uniform azimuth coverage and 13near-field P-wave initial motions.Based on the obtained focal mechanism,we get the strike angle of fault rupture surface combined with the geological structure background.In the following finite fault inversion,the fault surface is divided into 17×9subfaults to simulate the temporal and spatial distribution of the slips,along with the use of 18far-field P vertical waveform records and 21 farfield SH tangent waveform records,then we can retrieve the rupture process of the earthquake using waveform inversion method with the multi-reflection effect under consideration.Based on the seawater-layered model,the focal mechanism solution based on the shear dislocation source model indicates that this event occurred on the rupture plane(strike angle 323°,dip angle 86.1°,rake angle-180°,focal depth 10.6km)is a high-angle strike-slip faulting.The rupture process is rather simple,the distribution of major slips is concentered in the region of35km×9km above the source,the rupture lasts about 19 seconds,the average rupture velocity is about 2.7km·s-1,the larger slips distribute along the strike direction,and the maximum slip is 249 cm.The earthquake is an Mw6.9strike-slip event with steep dip angle that occurs in the Gorda plate.The earthquake is a pure strike-slip faulting event occurring beneath the seabed,the fault surface is nearly vertical,so it did not cause great damage to the cities off the coast.Since the earthquake does not change the topography of the seafloor in the rupture process,so there is no big displacement of seawater,thus,it won′t trigger a large-scale tsunami.
{"title":"Rupture process of March 10, 2014, M(w)6. 9 Earthquake in the northwestern coast of California","authors":"L. Cao, J. Hao, Weimin Wang, Z. Yao","doi":"10.6038/CJG20150117","DOIUrl":"https://doi.org/10.6038/CJG20150117","url":null,"abstract":"A strong earthquake(Mw6.9)occurred in the Gorda plate off the northwestern coast of California in March 10,2014(Beijing Time).The rupture process of the earthquake is determined by the waveform inversion method using far-field body waveform records provided by IRIS.Afterthat,we analyze the reason why the earthquake did not cause serious hazards and trigger tsunami,and provide new evidence to the research of dynamics study in the area.The focal mechanism of the earthquake is obtained by dislocation source model utilizing 19far-field P vertical waveform records with uniform azimuth coverage and 13near-field P-wave initial motions.Based on the obtained focal mechanism,we get the strike angle of fault rupture surface combined with the geological structure background.In the following finite fault inversion,the fault surface is divided into 17×9subfaults to simulate the temporal and spatial distribution of the slips,along with the use of 18far-field P vertical waveform records and 21 farfield SH tangent waveform records,then we can retrieve the rupture process of the earthquake using waveform inversion method with the multi-reflection effect under consideration.Based on the seawater-layered model,the focal mechanism solution based on the shear dislocation source model indicates that this event occurred on the rupture plane(strike angle 323°,dip angle 86.1°,rake angle-180°,focal depth 10.6km)is a high-angle strike-slip faulting.The rupture process is rather simple,the distribution of major slips is concentered in the region of35km×9km above the source,the rupture lasts about 19 seconds,the average rupture velocity is about 2.7km·s-1,the larger slips distribute along the strike direction,and the maximum slip is 249 cm.The earthquake is an Mw6.9strike-slip event with steep dip angle that occurs in the Gorda plate.The earthquake is a pure strike-slip faulting event occurring beneath the seabed,the fault surface is nearly vertical,so it did not cause great damage to the cities off the coast.Since the earthquake does not change the topography of the seafloor in the rupture process,so there is no big displacement of seawater,thus,it won′t trigger a large-scale tsunami.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"58 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71078702","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 relief of the metamorphosed basement of the Precambrian and the thickness variation of the overlying sedimentary cover are very important for geology and exploration of energy and resources. The magnetic difference between these two layers permits geophysicists to estimate the magnetic basement depth using aeromagnetic data. The work is based on such data acquired by AGRS's aero geophysical surveys for more than 30 years over China mainland, covering more than 30 basins and areas. Our purpose is to compile the magnetic basement depth map for China mainland on a scale 1:1000000 with the data converted into the same coordinate system and scale. The resultant map shows that using E105° line as a boundary, the covers are thick in sedimentary depression areas of western China, mainly distributed in the Tarim basin, Junggar basin, Qaidam basin and Tibet area. While, in east China, mainly distributed in the Songliao basin, Erlian basin, Ordos, southern North China, Sichuan basin, and South Yellow Sea-Subei basin, such covers are relatively thin in sedimentary depression areas, of which the largest thickness is located in the southwest of the Sichuan basin and the western edge of the Ordos basin. These characteristics are associated with the metamorphosed basement of Precambrian and depth changes of irruptive rocks body with certain scales, and reflect sedimentary covers' thickness and status. They allow us to intuitively observe depths and sizes of various types of sedimentary basins and sedimentary depression areas, and provide direct evidence for exploration of oil and gas reservoirs on the basements.
{"title":"Characteristics of Magnetic Basement Depth Beneath China Mainland","authors":"Xiong Sheng-qing, Ding Yan‐Yun, Li Zhan-kui","doi":"10.1002/CJG2.20156","DOIUrl":"https://doi.org/10.1002/CJG2.20156","url":null,"abstract":"The relief of the metamorphosed basement of the Precambrian and the thickness variation of the overlying sedimentary cover are very important for geology and exploration of energy and resources. The magnetic difference between these two layers permits geophysicists to estimate the magnetic basement depth using aeromagnetic data. The work is based on such data acquired by AGRS's aero geophysical surveys for more than 30 years over China mainland, covering more than 30 basins and areas. Our purpose is to compile the magnetic basement depth map for China mainland on a scale 1:1000000 with the data converted into the same coordinate system and scale. The resultant map shows that using E105° line as a boundary, the covers are thick in sedimentary depression areas of western China, mainly distributed in the Tarim basin, Junggar basin, Qaidam basin and Tibet area. While, in east China, mainly distributed in the Songliao basin, Erlian basin, Ordos, southern North China, Sichuan basin, and South Yellow Sea-Subei basin, such covers are relatively thin in sedimentary depression areas, of which the largest thickness is located in the southwest of the Sichuan basin and the western edge of the Ordos basin. These characteristics are associated with the metamorphosed basement of Precambrian and depth changes of irruptive rocks body with certain scales, and reflect sedimentary covers' thickness and status. They allow us to intuitively observe depths and sizes of various types of sedimentary basins and sedimentary depression areas, and provide direct evidence for exploration of oil and gas reservoirs on the basements.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"58 1","pages":"69-82"},"PeriodicalIF":1.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20156","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51220511","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. Qing-quan, Tan Juan, Wang Lanning, W. Min, Zhao Qi-Geng
A global ocean carbon cycle circulation model which was developed by the National Climate Center, China Meteorological Administration is presented and the basic performance of this model is analyzed and evaluated in this paper. This model is a global three-dimensional (3D) ocean carbon cycle circulation model, with 40 layers in vertical direction, and biogeochemical processes developed on the basis of the global ocean circulation model MOM4 (Modular Ocean Model version 4) of the US Geophysical Fluid Dynamics Laboratory (GFDL), which is abbreviated as MOM4_L40 (Modular Ocean Model Version 4 with 40 Levels). This model has been integrated for over 1000 years under climate field forcing. The results indicate that, when compared with the observations, this model can more effectively simulate the surface and vertical distribution characteristics of the ocean temperature, salinity, total carbon dioxide, total alkalinity, and total phosphate levels. The simulated distribution of the total CO2 in the ocean is basically consistent with observations, of which a low-value zone exists on the surface, beneath which is a high-value zone from 10°S to 60°N. However, the simulations above 2000 m are smaller than observations while simulations below 2000 m are larger than observations. In general, the MOM4_L40 model is found to be a reliable tool for the simulation and research of oceanic carbon cycle processes.
本文介绍了由中国气象局国家气候中心开发的全球海洋碳循环模型，并对该模型的基本性能进行了分析和评价。该模式是在美国地球物理流体动力学实验室(GFDL)的全球海洋环流模式MOM4 (Modular ocean model version 4 with 40 Levels)(简称MOM4_L40)基础上开发的全球三维(3D)海洋碳循环循环模式，垂直方向40层，生物地球化学过程。该模式在气候场强迫作用下已集成了1000多年。结果表明，与观测结果相比，该模式能更有效地模拟海洋温度、盐度、总二氧化碳、总碱度和总磷酸盐水平的表面和垂直分布特征。模拟得到的海洋总CO2分布与观测值基本一致，表层存在低值区，表层以下为10°S ~ 60°N范围内的高值区。2000 m以上的模拟值小于观测值，2000 m以下的模拟值大于观测值。总体而言，MOM4_L40模式是模拟和研究海洋碳循环过程的可靠工具。
{"title":"Simulation of the Natural Distribution of Carbon and Nutrients in the Ocean Based on the Global Ocean Carbon Cycle Model MOM4_L40","authors":"L. Qing-quan, Tan Juan, Wang Lanning, W. Min, Zhao Qi-Geng","doi":"10.1002/CJG2.20151","DOIUrl":"https://doi.org/10.1002/CJG2.20151","url":null,"abstract":"A global ocean carbon cycle circulation model which was developed by the National Climate Center, China Meteorological Administration is presented and the basic performance of this model is analyzed and evaluated in this paper. This model is a global three-dimensional (3D) ocean carbon cycle circulation model, with 40 layers in vertical direction, and biogeochemical processes developed on the basis of the global ocean circulation model MOM4 (Modular Ocean Model version 4) of the US Geophysical Fluid Dynamics Laboratory (GFDL), which is abbreviated as MOM4_L40 (Modular Ocean Model Version 4 with 40 Levels). This model has been integrated for over 1000 years under climate field forcing. The results indicate that, when compared with the observations, this model can more effectively simulate the surface and vertical distribution characteristics of the ocean temperature, salinity, total carbon dioxide, total alkalinity, and total phosphate levels. The simulated distribution of the total CO2 in the ocean is basically consistent with observations, of which a low-value zone exists on the surface, beneath which is a high-value zone from 10°S to 60°N. However, the simulations above 2000 m are smaller than observations while simulations below 2000 m are larger than observations. In general, the MOM4_L40 model is found to be a reliable tool for the simulation and research of oceanic carbon cycle processes.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"58 1","pages":"1-19"},"PeriodicalIF":1.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20151","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51220317","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}
G. Deng, F. Liang, Xt Li, Junmeng Zhao, Hb Liu, X. Wang
In processing of deep seismic reflection data,when the frequency band difference between the weak useful signal and noise both from the deep subsurface is very small and hard to distinguish,the traditional method of filtering will be limited.To solve this problem,we apply different spectral decomposition methods respectively to experimental data and real data and compare the results from these methods.Our purpose is to find an effective way to protect weak signals during processing deep seismic reflection data.The spectral decomposition method is based on the discrete Fourier transform,which uses the signal frequency-amplitude spectrum and other information to generate a high-resolution seismic image.Typically,it is used to identify the lateral distribution of media properties,solve spectrum changes within complex media and local phase instability and other issues,such as locating faults and small-scale complex fractures.S transform as a new time-frequency analysis method,which is a generalization of STFT developed by Stockwell in 1994,has the ability to automatically adjust the resolution.This method has been widely applied to exploration seismic,MT and other geophysical datasets in recent years.It has become one of the effective methods in noise suppressing during geophysical data processing.Comparing deep seismic reflection data with conventional oil reflection seismic data,in order to probe deep structure,this approach employs a large number of explosives,long observing systems,leading to a phenomenon that valid signals from the deep and noise are mixed together both in the time domain and frequency domain.Considering these characteristics of deep reflection data,this paper combines spectral decomposition with S transform technology.First we design a simple pulse function experimental data to confirm the validity of the S transform method.Then we illustrate the effect of spectral decomposition which is influenced by choosing frequency analysis methods and the transform window function which determines the strength of the resolving power of the method.On this basis,S transform spectrum decomposition is applied to a single channel of deep reflection seismic data and the stacked profile,then the application results of traditional transform spectral decomposition and S transform spectral decomposition are compared.Comparison of single channel data shows that compared with traditional spectral decomposition,the S transform spectral decomposition method is able to automatically adjust the resolution,accurately calibrate frequency component of weak signals at different times in deep reflection seismic data.Application to stacked profile data shows that the stacked profile results obtained by the S transform spectral decomposition and those from other spectral decomposition method are largely consistent,while the results of S transform spectral decomposition clearlydepict the characteristics of low-frequency details which are superimposed by noise in
{"title":"S-transform spectrum decomposition technique in the application of the extraction of weak seismic signals","authors":"G. Deng, F. Liang, Xt Li, Junmeng Zhao, Hb Liu, X. Wang","doi":"10.6038/CJG20151221","DOIUrl":"https://doi.org/10.6038/CJG20151221","url":null,"abstract":"In processing of deep seismic reflection data,when the frequency band difference between the weak useful signal and noise both from the deep subsurface is very small and hard to distinguish,the traditional method of filtering will be limited.To solve this problem,we apply different spectral decomposition methods respectively to experimental data and real data and compare the results from these methods.Our purpose is to find an effective way to protect weak signals during processing deep seismic reflection data.The spectral decomposition method is based on the discrete Fourier transform,which uses the signal frequency-amplitude spectrum and other information to generate a high-resolution seismic image.Typically,it is used to identify the lateral distribution of media properties,solve spectrum changes within complex media and local phase instability and other issues,such as locating faults and small-scale complex fractures.S transform as a new time-frequency analysis method,which is a generalization of STFT developed by Stockwell in 1994,has the ability to automatically adjust the resolution.This method has been widely applied to exploration seismic,MT and other geophysical datasets in recent years.It has become one of the effective methods in noise suppressing during geophysical data processing.Comparing deep seismic reflection data with conventional oil reflection seismic data,in order to probe deep structure,this approach employs a large number of explosives,long observing systems,leading to a phenomenon that valid signals from the deep and noise are mixed together both in the time domain and frequency domain.Considering these characteristics of deep reflection data,this paper combines spectral decomposition with S transform technology.First we design a simple pulse function experimental data to confirm the validity of the S transform method.Then we illustrate the effect of spectral decomposition which is influenced by choosing frequency analysis methods and the transform window function which determines the strength of the resolving power of the method.On this basis,S transform spectrum decomposition is applied to a single channel of deep reflection seismic data and the stacked profile,then the application results of traditional transform spectral decomposition and S transform spectral decomposition are compared.Comparison of single channel data shows that compared with traditional spectral decomposition,the S transform spectral decomposition method is able to automatically adjust the resolution,accurately calibrate frequency component of weak signals at different times in deep reflection seismic data.Application to stacked profile data shows that the stacked profile results obtained by the S transform spectral decomposition and those from other spectral decomposition method are largely consistent,while the results of S transform spectral decomposition clearlydepict the characteristics of low-frequency details which are superimposed by noise in","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"58 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71079268","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}
On July 22,2013,a major earthquake(MS6.6)occurred on the boundary of Minxian and Zhangxian in Gansu province,with its epicenter near the Lintan-Dangchang fault.Based on the finite fault model constructed,the rupturing process of this earthquake was determined by the waveform method using 12 near source strong motion three-component records provided by China Earthquake Data Center.Strike,dip angle,and rake angle of seismogenic fault as well as focal depth are supposed to be known before the waveform inversion based on a finite fault model.The focal mechanism of the earthquake is obtained by a dislocation source model utilizing 30far-field P vertical waveform records with uniform azimuth coverage and 12near-field P-wave initial motions.Geometric parameters of the seismogenic fault plane and focal depth adopted in the inversion were determined by considering information such as results of different institutions and scholars,waveform fitting obtained by treating two nodal planes as fault planes,and strike of existing faults in this area.The strike is300.2°,dip angle is 66°,slip angle is 47.7°,focal depth is 7km.In the process of invertingrupture process of this earthquake using strong motion records,Green′s function was calculated by f-k integration and source parameters over the fault,including slip amount,slip rake,rise time and rupture velocity,which were inverted by simulated annealing method.In order to check the accuracy of source parameters deduced by strong motion records,we use the deduced source parameters to calculate the far-field synthetic waveforms and then compare them with observed ones.Results show that slip over the seismogenic fault is centralized nearby the focal source,maximum slip is around 80 cm,and no slip on the surface of ground.This earthquake is dominated by over-thrust with sinistral strike-slip component,consistent with other faults in this area.The rupturing ended at 8s.Seismic moment M0 is 1.60×1025dyn·cm,moment magnitude MWis 6.1.Considering the strike of the seismogenic fault and aftershocks′distribution matches with Lintan-Dangchang fault,rake and dip of seismogenic fault are also similar to those of eastern part of Lintan-Dangchang fault,we deduce this earthquake was related with the north forward extrusion of the east Kunlun fault and resulted from the further activity of the Minxian-Dangchang fault.
{"title":"Rupture process of the Minxian-Zhangxian, Gansu, China M(S)6. 6 earthquake on 22 July 2013","authors":"M. Sun, Weimin Wang, X. Wang, Jk He","doi":"10.6038/cjg20150607","DOIUrl":"https://doi.org/10.6038/cjg20150607","url":null,"abstract":"On July 22,2013,a major earthquake(MS6.6)occurred on the boundary of Minxian and Zhangxian in Gansu province,with its epicenter near the Lintan-Dangchang fault.Based on the finite fault model constructed,the rupturing process of this earthquake was determined by the waveform method using 12 near source strong motion three-component records provided by China Earthquake Data Center.Strike,dip angle,and rake angle of seismogenic fault as well as focal depth are supposed to be known before the waveform inversion based on a finite fault model.The focal mechanism of the earthquake is obtained by a dislocation source model utilizing 30far-field P vertical waveform records with uniform azimuth coverage and 12near-field P-wave initial motions.Geometric parameters of the seismogenic fault plane and focal depth adopted in the inversion were determined by considering information such as results of different institutions and scholars,waveform fitting obtained by treating two nodal planes as fault planes,and strike of existing faults in this area.The strike is300.2°,dip angle is 66°,slip angle is 47.7°,focal depth is 7km.In the process of invertingrupture process of this earthquake using strong motion records,Green′s function was calculated by f-k integration and source parameters over the fault,including slip amount,slip rake,rise time and rupture velocity,which were inverted by simulated annealing method.In order to check the accuracy of source parameters deduced by strong motion records,we use the deduced source parameters to calculate the far-field synthetic waveforms and then compare them with observed ones.Results show that slip over the seismogenic fault is centralized nearby the focal source,maximum slip is around 80 cm,and no slip on the surface of ground.This earthquake is dominated by over-thrust with sinistral strike-slip component,consistent with other faults in this area.The rupturing ended at 8s.Seismic moment M0 is 1.60×1025dyn·cm,moment magnitude MWis 6.1.Considering the strike of the seismogenic fault and aftershocks′distribution matches with Lintan-Dangchang fault,rake and dip of seismogenic fault are also similar to those of eastern part of Lintan-Dangchang fault,we deduce this earthquake was related with the north forward extrusion of the east Kunlun fault and resulted from the further activity of the Minxian-Dangchang fault.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"58 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71079274","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}
Y. Li, W. Feng, J. Zhang, Zhenhong Li, Y. Tian, W. Jiang, Y. Luo
On 24 August 2014, an Mw 6.1 earthquake occurred in the Napa Valley shook a large area of northern San Francisco Bay, California, USA. An interferometric pair acquired from the newly launched ESA’s Sentinel-1A satellite was used to map the coseismic displacements, and then combined with GPS coseismic displacements to determine its fault geometry and slip distribution. The Sentinel-1A interferogram shows that this earthquake produced significant ground displacements with maximum uplift and subsidence of 10 cm in the satellite light of sight (LOS). The best-fit slip model in the joint inversion suggests that the major coseismic slip is concentrated on a right-lateral fault with a strike of 344° ,a dip of 80° and an average rake angle of -146.5°. The maximum slip of ~1.1 m at a depth of ~4 km, suggesting that shallow slip deficit happened during the mainshock. The accumulative seismic moment is up to 1.5x1018 N.m, equivalent to a magnitude of Mw 6.1. The seismic energy estimated using InSAR and GPS is less than that obtained by InSAR only, which might be due to considerable postseismic displacements included in the Sentinel-1A coseismic interferogram. The fault is believed to be part of the West Napa fault system, but little attenetion has been paid before the quake. Summary
{"title":"Coseismic slip of the 2014 M w 6.1 Napa, California earthquake revealed by Sentinel-1A InSAR","authors":"Y. Li, W. Feng, J. Zhang, Zhenhong Li, Y. Tian, W. Jiang, Y. Luo","doi":"10.6038/CJG20150712","DOIUrl":"https://doi.org/10.6038/CJG20150712","url":null,"abstract":"On 24 August 2014, an Mw 6.1 earthquake occurred in the Napa Valley shook a large area of northern San Francisco Bay, California, USA. An interferometric pair acquired from the newly launched ESA’s Sentinel-1A satellite was used to map the coseismic displacements, and then combined with GPS coseismic displacements to determine its fault geometry and slip distribution. The Sentinel-1A interferogram shows that this earthquake produced significant ground displacements with maximum uplift and subsidence of 10 cm in the satellite light of sight (LOS). The best-fit slip model in the joint inversion suggests that the major coseismic slip is concentrated on a right-lateral fault with a strike of 344° ,a dip of 80° and an average rake angle of -146.5°. The maximum slip of ~1.1 m at a depth of ~4 km, suggesting that shallow slip deficit happened during the mainshock. The accumulative seismic moment is up to 1.5x1018 N.m, equivalent to a magnitude of Mw 6.1. The seismic energy estimated using InSAR and GPS is less than that obtained by InSAR only, which might be due to considerable postseismic displacements included in the Sentinel-1A coseismic interferogram. The fault is believed to be part of the West Napa fault system, but little attenetion has been paid before the quake. Summary","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"13 1","pages":""},"PeriodicalIF":1.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83196047","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}
Qiu Na, Chen Yanhong, W. Wenbin, Gong Jiancun, Liu Siqing
The study of the ionosphere responses to Corotating Interaction Regions(CIRs)and Coronal Mass Ejections(CMEs)got much attentions in rencent years.With the comparison of different types of ionosphere response caused by different disturbance sources from solar activity and interplanetary solar wind,morphological changes and physical process of ionospheric storms can be understood more impressively and comprehensively.It provides a possibility to predict ionospheric disturbance states according to different solar wind conditions in advance as well.GPS-TEC data at a mid-latitude station(131°E,35°N)are used to analyze the ionosphere response during geomagnetic disturbances induced by 109 CIRs and 45 CMEs over the period 2001 to 2009.Firstly,the TEC difference are determined to achieve the information of ionospheric positive or negative storms during the CIR and CME events.The definition of a ionosphericstorms is relative TEC greater than or equal to 15% and persisting for more than 4hours;Secondly,year dependence,seasonal dependence,time delay between ionospheric storms and geomagnetic storms,geomantic storm intensity dependence and time duration of ionospheric storms are analyzed in detail.Analysis results indicate that the types of ionospheric storms vary in different phases of a solar cycle.CIR-driven positive and positive-negative storms are more likely to occur in the declining phase of the solar cycle,while negative phase storms more in solar maximum and negative-positive storms mainly in solar minimum.CME-driven positive storms and negative storms mostly occur in solar maximum.There is no remarkable seasonal difference for the occurrence of different types of ionospheric storms except the positive-negative storms most likely to occur in summer.The time delays between geomagnetic disturbances and the start time of ionospheric storms are-6to 6hours in general,but CIR-driven ionopsheric storms involve in a wider range with a time delay of-12 to 24hours and CME-driven storms is delayed from-6to6 hours.Moreover,for CIR-driven ionospheric storms,positive and negative storms mostly occur in main phase of magnetic storms,positive-negative storms mostly in initial and main phase,and negative-positive storms mainly in initial phase.For CME-driven storms,positive,negative and positive-negative storms basically occur in main phase.Our investigation also demonstrates certain correlation between the types of ionospheric storms and the AE maximum indices.Ionopsheric negative storms often occur in stronger geomagnetic activity,with the AE maximum intensity between 800 to 1200nT while positive-negative storms tend to occur with AE maximum intensity higher than 400 nT.Compared to CIR driven storms,AE maximum value during CME driven storms is higher.The duration of CIR-driven storms is longer(1to 6days)than that of CME-driven storms(1to 4days).The ionosphere response to interplanetary conditions contribute to the study the ionospheric disturbance.Statistical anal
{"title":"Statistical analysis of the ionosphere response to the CIR and CME in Mid-latitude regions","authors":"Qiu Na, Chen Yanhong, W. Wenbin, Gong Jiancun, Liu Siqing","doi":"10.6038/CJG20150704","DOIUrl":"https://doi.org/10.6038/CJG20150704","url":null,"abstract":"The study of the ionosphere responses to Corotating Interaction Regions(CIRs)and Coronal Mass Ejections(CMEs)got much attentions in rencent years.With the comparison of different types of ionosphere response caused by different disturbance sources from solar activity and interplanetary solar wind,morphological changes and physical process of ionospheric storms can be understood more impressively and comprehensively.It provides a possibility to predict ionospheric disturbance states according to different solar wind conditions in advance as well.GPS-TEC data at a mid-latitude station(131°E,35°N)are used to analyze the ionosphere response during geomagnetic disturbances induced by 109 CIRs and 45 CMEs over the period 2001 to 2009.Firstly,the TEC difference are determined to achieve the information of ionospheric positive or negative storms during the CIR and CME events.The definition of a ionosphericstorms is relative TEC greater than or equal to 15% and persisting for more than 4hours;Secondly,year dependence,seasonal dependence,time delay between ionospheric storms and geomagnetic storms,geomantic storm intensity dependence and time duration of ionospheric storms are analyzed in detail.Analysis results indicate that the types of ionospheric storms vary in different phases of a solar cycle.CIR-driven positive and positive-negative storms are more likely to occur in the declining phase of the solar cycle,while negative phase storms more in solar maximum and negative-positive storms mainly in solar minimum.CME-driven positive storms and negative storms mostly occur in solar maximum.There is no remarkable seasonal difference for the occurrence of different types of ionospheric storms except the positive-negative storms most likely to occur in summer.The time delays between geomagnetic disturbances and the start time of ionospheric storms are-6to 6hours in general,but CIR-driven ionopsheric storms involve in a wider range with a time delay of-12 to 24hours and CME-driven storms is delayed from-6to6 hours.Moreover,for CIR-driven ionospheric storms,positive and negative storms mostly occur in main phase of magnetic storms,positive-negative storms mostly in initial and main phase,and negative-positive storms mainly in initial phase.For CME-driven storms,positive,negative and positive-negative storms basically occur in main phase.Our investigation also demonstrates certain correlation between the types of ionospheric storms and the AE maximum indices.Ionopsheric negative storms often occur in stronger geomagnetic activity,with the AE maximum intensity between 800 to 1200nT while positive-negative storms tend to occur with AE maximum intensity higher than 400 nT.Compared to CIR driven storms,AE maximum value during CME driven storms is higher.The duration of CIR-driven storms is longer(1to 6days)than that of CME-driven storms(1to 4days).The ionosphere response to interplanetary conditions contribute to the study the ionospheric disturbance.Statistical anal","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"58 1","pages":"2250-2262"},"PeriodicalIF":1.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71079399","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 plate convergent belt in the eastern South China Sea (SCS) is an important window for studying the tectonic evolution of the SCS and the Philippine Sea (PhS) since late-Miocene. We studied the plate interactions of this area since the late-Miocene based on block kinematics, morphology of the subducted SCS slab and focal mechanism solutions (FMS). At the late stage of the late-Miocene, the westward motion of the PhS plate was first impeded by its collision with the Palawan micro continental plate in the south, and then by the collision of the Luzon arc with the South China continental margin in the north. Consequently, the middle part between the two collision zones became a passage where westward movement of the PhS plate continued relatively smoothly. Because of these two impediments, the rate of westward motion increased northwards to its maximum in the northern Luzon and then decreased northwards, leading to the westward migration of the Manila trench. The subducted SCS slab, however, did not roll back accordingly due to the SE-directed mantle flow. As a result, the subducted slab suffered strong push and slightly reverse bending of the subducted slab occurred in the contact face between PhS and SCS lithosphere. According to this model, morphology of the Manila trench was shaped by the differential westward motion rates from south to north of the northern Luzon, and the width of the subducted slab played little role. Furthermore, the double arc in the north Luzon arc was also induced by a differential westward moving velocity along the arc. A shear zone whose location coincides with the east arc might have facilitated its formation.
{"title":"Present-Day Crustal Movement and Focal Mechanism Solutions, and Plate Interaction Since Late-Miocene in the Eastern South China Sea","authors":"Sun Jinlong, Cao Jing-he, Xu Hui-long","doi":"10.1002/CJG2.20160","DOIUrl":"https://doi.org/10.1002/CJG2.20160","url":null,"abstract":"The plate convergent belt in the eastern South China Sea (SCS) is an important window for studying the tectonic evolution of the SCS and the Philippine Sea (PhS) since late-Miocene. We studied the plate interactions of this area since the late-Miocene based on block kinematics, morphology of the subducted SCS slab and focal mechanism solutions (FMS). At the late stage of the late-Miocene, the westward motion of the PhS plate was first impeded by its collision with the Palawan micro continental plate in the south, and then by the collision of the Luzon arc with the South China continental margin in the north. Consequently, the middle part between the two collision zones became a passage where westward movement of the PhS plate continued relatively smoothly. Because of these two impediments, the rate of westward motion increased northwards to its maximum in the northern Luzon and then decreased northwards, leading to the westward migration of the Manila trench. The subducted SCS slab, however, did not roll back accordingly due to the SE-directed mantle flow. As a result, the subducted slab suffered strong push and slightly reverse bending of the subducted slab occurred in the contact face between PhS and SCS lithosphere. According to this model, morphology of the Manila trench was shaped by the differential westward motion rates from south to north of the northern Luzon, and the width of the subducted slab played little role. Furthermore, the double arc in the north Luzon arc was also induced by a differential westward moving velocity along the arc. A shear zone whose location coincides with the east arc might have facilitated its formation.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"58 1","pages":"123-134"},"PeriodicalIF":1.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://sci-hub-pdf.com/10.1002/CJG2.20160","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"51221144","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}
{"title":"A method for processing GNSS data from regional reference networks to enable single-frequency PPP-RTK","authors":"Baocheng Zhang, D. Odijk","doi":"10.6038/CJG20150709","DOIUrl":"https://doi.org/10.6038/CJG20150709","url":null,"abstract":"","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"71 1","pages":"2306-2319"},"PeriodicalIF":1.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71079426","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. Xia, Lingli Gao, Yudi Pan, Chao Shen, Xiaofei Yin
Multi channel Analysis of Surface Waves (MASW) analyzes high-frequency Rayleigh waves to determine near-surface shear (S)-wave velocities. This method is getting increasingly attention in the near-surface geophysics and geotechnique community in the past 20 years because of its non-invasive, non-destructive, efficient, and low-cost advantages. They are viewed by near-surface geophysics community as one of most promise techniques in the future. We introduce some research results about propagation and applications of high-frequency surface waves proposed by near-surface geophysical research group at China University of Geosciences (Wuhan) in recent years. Non-geometric wave exists uniquely in near-surface materials, especially in unconsolidated sediments. It is valuable for a quick and accurate estimation of S-wave velocity of the surface layer. Our study shows that non-geometric waves are leaky waves and they are dispersive. Leaky surface wave could cause misidentification when treating the leaky-wave energy as fundamental or higher modes Rayleigh wave. Such misidentification will result in wrong inversion results. By obtaining Rayleigh-wave Green's function after separating fundamental- and higher-mode Rayleigh waves, we verify the feasibility of virtual source method in Rayleigh-wave survey, which could tremendously decreases the cost of field works. Compared to Rayleigh waves, a fewer parameters are involved in Multichannel Analysis of Love Waves (MALW), which makes Love-wave dispersion curves simpler than Rayleigh waves. As a result, inversion of Love waves is more stable and the degree of non-uniqueness is reduced. Images of Love-wave energy are usually sharper and of higher resolution than those from Rayleigh waves. This make picking Love-wave phase velocities much easier and more accurate. Analysis on relationship between surface-wave wavelength and penetrating depth by using Jacobian matrix shows that: as for fundamental mode with the same wavelength, Rayleigh wave can see 1.3~1.4 times deeper than Love waves, however, their penetrating depths are similar for higher modes. We also make some attempts on time-domain Love-wave waveform inversion. We divide the subsurface model into different sizes of blocks according to resolution of Love waves. We remove the source effect by deconvolution, and achieve an appropriate subsurface S-wave velocity model via updating S-wave velocity of each block to fit observed waveforms. This method does not need horizontal-layered-model assumption, and can be applied to any kind of 2D media.
{"title":"New findings in high-frequency surface wave method","authors":"J. Xia, Lingli Gao, Yudi Pan, Chao Shen, Xiaofei Yin","doi":"10.6038/CJG20150801","DOIUrl":"https://doi.org/10.6038/CJG20150801","url":null,"abstract":"Multi channel Analysis of Surface Waves (MASW) analyzes high-frequency Rayleigh waves to determine near-surface shear (S)-wave velocities. This method is getting increasingly attention in the near-surface geophysics and geotechnique community in the past 20 years because of its non-invasive, non-destructive, efficient, and low-cost advantages. They are viewed by near-surface geophysics community as one of most promise techniques in the future. We introduce some research results about propagation and applications of high-frequency surface waves proposed by near-surface geophysical research group at China University of Geosciences (Wuhan) in recent years. Non-geometric wave exists uniquely in near-surface materials, especially in unconsolidated sediments. It is valuable for a quick and accurate estimation of S-wave velocity of the surface layer. Our study shows that non-geometric waves are leaky waves and they are dispersive. Leaky surface wave could cause misidentification when treating the leaky-wave energy as fundamental or higher modes Rayleigh wave. Such misidentification will result in wrong inversion results. By obtaining Rayleigh-wave Green's function after separating fundamental- and higher-mode Rayleigh waves, we verify the feasibility of virtual source method in Rayleigh-wave survey, which could tremendously decreases the cost of field works. Compared to Rayleigh waves, a fewer parameters are involved in Multichannel Analysis of Love Waves (MALW), which makes Love-wave dispersion curves simpler than Rayleigh waves. As a result, inversion of Love waves is more stable and the degree of non-uniqueness is reduced. Images of Love-wave energy are usually sharper and of higher resolution than those from Rayleigh waves. This make picking Love-wave phase velocities much easier and more accurate. Analysis on relationship between surface-wave wavelength and penetrating depth by using Jacobian matrix shows that: as for fundamental mode with the same wavelength, Rayleigh wave can see 1.3~1.4 times deeper than Love waves, however, their penetrating depths are similar for higher modes. We also make some attempts on time-domain Love-wave waveform inversion. We divide the subsurface model into different sizes of blocks according to resolution of Love waves. We remove the source effect by deconvolution, and achieve an appropriate subsurface S-wave velocity model via updating S-wave velocity of each block to fit observed waveforms. This method does not need horizontal-layered-model assumption, and can be applied to any kind of 2D media.","PeriodicalId":55257,"journal":{"name":"地球物理学报","volume":"58 1","pages":"2591"},"PeriodicalIF":1.4,"publicationDate":"2015-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"71079495","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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