The recently built China Digital Seismic Network consists of the China National Digital Seismic Network （CNDSN）, 31 regional seismic networks and several small aperture arrays with more than 1 000 stations including...The recently built China Digital Seismic Network consists of the China National Digital Seismic Network （CNDSN）, 31 regional seismic networks and several small aperture arrays with more than 1 000 stations including 850＋ broadband stations. It forms a gigantic seismic array that provides an unprecedented opportunity to study the Earth＇s deep interior besides its routine task of seismic monitoring. Many modern seismic studies rely on rotation of vertical and horizontal components in order to separate different types of seismic waves. Knowledge of the orientations of the two horizontal components thus is important to perform a correction rotation. We analyzed particle motions of teleseismic P waves recorded by the network and used them to estimate the northcomponent azimuth of each station. An SNR-weighted-multi-event method was introduced to obtain component azimuths that best explain the P-wave particle motions of all the events recorded at a station. The method provides robust estimates including a measurement error calculated from background noise levels. We found that about one third of the stations have some sort of problems, including misorientation of the two horizontal components, mislabeling and polarity reversal in one or more components. These problems need to be taken into account for any rotation based seismic studies.展开更多
High-resolution seismic models of sediment basins are critical inputs for earthquake ground motion prediction and petroleum resource exploration.In this study we employed a newly developed technique that utilizes the ...High-resolution seismic models of sediment basins are critical inputs for earthquake ground motion prediction and petroleum resource exploration.In this study we employed a newly developed technique that utilizes the frequency-dependent nonlinear P-wave particle motion to estimate sedimentary structure beneath the Bohai Bay basin.A recent study suggests that the delay of the P wave on the horizontal component relative the vertical component and its variations over frequency are caused by interference of the direct P wave with waves generated at the sediment base.The frequency-dependent delay time can be used to constrain sediment thickness and seismic velocity beneath recording stations.We measured the particle motions of teleseismic P waves recorded by 249 broadband stations of the North China Array,which covers the western Bohai Bay basin and its surrounding areas.We found that the P waves of 90 stations inside the Bohai Bay basin and other local basins within the Taihang and Yanshan mountain ranges exhibit significant frequency-dependent nonlinear particle motions,and used the particle motion data to invert the sediment thickness(Z0)and surface S-wave velocity(β0).The estimated sediment thickness inside the Bohai Bay Basin varies from 1.02 km to 3.72 km,with an average of 3.20 km,which roughly agrees with previous active source studies.展开更多
We study the reduction of peak velocity on the ground surface of a soil valley caused by loss of wave energy by large nonlinear strains and strain localization inside the valley,for excitation by a half-sine P-wave pu...We study the reduction of peak velocity on the ground surface of a soil valley caused by loss of wave energy by large nonlinear strains and strain localization inside the valley,for excitation by a half-sine P-wave pulse.This study is a follow up to our previous study of out of plane response for excitation by an SH-pulse.In this paper,we consider the in-plane response,and assume that the soil material does not support tension,but the normal stress at a point in the soil can be compression(negative)or zero.A point in the soil with zero stress behaves as a stress-free point,it does not transmit normal stress and appears as a crack point.Because of this,along with the nonlinear response associated with compression and shear,the in-plane response in this study is more complex than that of the out-of-plane SH response.We study the interplay of two opposing effects:(i)jump in impedance from a higher value(half-space)to a lower value(valley),which amplifies the linear motions at the free surface of the valley,and(ii)the occurrence of nonlinear zones in the valley,which reduce the motion at the valley surface.展开更多
目的:分析心电图P波参数对高血压心房颤动(Atrial fibrillation,AF)患者消融术后复发的预测价值。方法:回顾性分析2023年1月至2024年10月我院首次接受消融术的87例高血压AF患者资料,参考术后12 m内是否复发分复发组(21例)和非复发组(66...目的:分析心电图P波参数对高血压心房颤动(Atrial fibrillation,AF)患者消融术后复发的预测价值。方法:回顾性分析2023年1月至2024年10月我院首次接受消融术的87例高血压AF患者资料,参考术后12 m内是否复发分复发组(21例)和非复发组(66例),比较两组P波终末电势(P-wave terminal force in lead V1,PtfV1)、P波离散度(P-wave dispersion,Pd)、P波变异(P-wave variation,Pv)及最大P波时限(Maximum P-wave duration,Pmax),分析上述指标与术后复发的关系及预测价值。结果:与非复发组对比,复发组Pd、Pv、Pmax均更高(P<0.05),但对比两组PtfV1,差异无统计学意义(P>0.05);多因素Logistic回归分析显示,Pd、Pv、Pmax与高血压AF患者术后复发显著相关(P<0.05);绘制受试者工作特征曲线结果显示,Pd、Pv、Pmax三者联合预测高血压AF患者复发的曲线下面积为0.840,均高于单一指标预测(P<0.05)。结论:Pd、Pv、Pmax三者联合在高血压AF患者术后复发中预测价值较高。展开更多
Based on arbitrarily wide-angle wave equations,a reverse-time propagation scheme is developed by substituting the partial derivatives of depth and time with central differences. The partial derivative of horizontal di...Based on arbitrarily wide-angle wave equations,a reverse-time propagation scheme is developed by substituting the partial derivatives of depth and time with central differences. The partial derivative of horizontal direction is replaced with high order difference. The imaging condition is computed by solving the eikonal equations. On the basis of above techniques,a prestack reverse-time depth migration algorithm is developed. The processing exam-ples of synthetic data show that the method can remove unwanted internal reflections and decrease the migration noise. The method also has the advantage of fidelity and is applicable of dip angle reflector imaging.展开更多
Using over 3 500 first P arrival times recorded by nine digital seismic stations from Hainan Digital Seismic Net-work during 1999～2005,a 3-D P-wave velocity model of the crust under Hainan Island and adjacent regions...Using over 3 500 first P arrival times recorded by nine digital seismic stations from Hainan Digital Seismic Net-work during 1999～2005,a 3-D P-wave velocity model of the crust under Hainan Island and adjacent regions has been determined. The results show that the pattern of velocity anomalies in the shallower upper crust is somewhat associated with the surface geological tectonics in the region. A relative low-velocity anomaly appears north of the Wangwu-Wenjiao fault zone and a relative high-velocity anomaly appears south of the Wangwu-Wenjiao fault zone,corresponding to the depressed areas in north Hainan Island,where many volcanoes are frequently active and geothermal values are relatively higher,and the uplifted and stable regions in central and south of the Hainan Is-land. In the middle and lower crust velocities are relatively lower in east Hainan than those in west Hainan,possi-bly suggesting the existence of the upwelling of hot materials from the mantle in east Hainan. The pattern of veloc-ity anomalies also indicates that NW faults,i.e.,the Puqian-Qinglan fault,may be shallower,while the E-W Wangwu-Wenjiao fault may be deeper,which perhaps extends down to Moho depth or deeper.展开更多
An analytical solution for scattering of plane P waves by circular-arc layered alluvial valleys was derived by Fourier-Bessel series expansion technique, and the solution was utilized to analyze the effects of alluvia...An analytical solution for scattering of plane P waves by circular-arc layered alluvial valleys was derived by Fourier-Bessel series expansion technique, and the solution was utilized to analyze the effects of alluvial sequence and their relative stiffness on the scattering of incident waves.展开更多
目的探讨心电图P波参数与脑白质病变(white matter lesions,WMLs)严重程度之间的关联,为WMLs的预防和治疗提供科学依据。方法选取289例符合入组标准的WMLs住院患者作为研究对象,其均接受常规12导联心电图和头颅磁共振成像检查。根据Faze...目的探讨心电图P波参数与脑白质病变(white matter lesions,WMLs)严重程度之间的关联,为WMLs的预防和治疗提供科学依据。方法选取289例符合入组标准的WMLs住院患者作为研究对象,其均接受常规12导联心电图和头颅磁共振成像检查。根据Fazekas量表评分将这些患者分为无-轻度组(158例)和中-重度组(131例)。收集两组患者的临床资料、既往病史、心电图P波参数[包括P波时限、P波电轴、V_(1)导联P波终末电势(terminal force of P-wave in lead V_(1),PTFV_(1))],以及血脂等数据,并进行比较分析。采用Logistic回归模型分析影响WMLs的独立危险因素。结果中-重度组患者的年龄、有高血压或糖尿病病史者占比及PTFV_(1)>4000μV·ms者占比均明显高于无-轻度组,且差异均有统计学意义(均P<0.01)。多变量Logistic回归分析表明,年龄增长、高血压、糖尿病以及PTFV_(1)>4000μV·ms均为WMLs的独立危险因素。结论无创心电图指标PTFV_(1)经济便捷、易于获取,可用于评估心房异常,对WMLs的防治具有一定的应用价值。展开更多
Wave reflection and refraction in layered media is a topic closely related to seismology,acoustics,geophysics and earthquake engineering.Analytical solutions for wave reflection and refraction coefficients in multi-la...Wave reflection and refraction in layered media is a topic closely related to seismology,acoustics,geophysics and earthquake engineering.Analytical solutions for wave reflection and refraction coefficients in multi-layered media subjected to P wave incidence from the elastic half-space are derived in terms of displacement potentials.The system is composed of ideal fluid,porous medium,and underlying elastic solid.By numerical examples,the effects of porous medium and the incident wave angle on the dynamic pressures of ideal fluid are analyzed.The results show that the existence of the porous medium,especially in the partially saturated case,may significantly affect the dynamic pressures of the overlying fluid.展开更多
An analytical solution for scattering of plane P waves by a semi-cylindrical hill was derived by using the wave function expansion method, and convergence of the solution and accuracy of truncation were verified. The ...An analytical solution for scattering of plane P waves by a semi-cylindrical hill was derived by using the wave function expansion method, and convergence of the solution and accuracy of truncation were verified. The effect of incident frequency and incident angle on the surface motion of the hill was discussed, and it was shown that a hill greatly amplifies incident plane P waves, and maximum horizontal displacement amplitudes appear mostly at the inclined incidence of waves, which are located at the half-space; and maximum vertical displacement amplitudes emerge mostly at the vertical incidence of waves, which are situated at the hill.展开更多
A type of specific fractured hydrocarbon reservoir, a shale fractured reservoir, exists in the Shengli oilfield. Due to very small porosity of this type, low sensitivity to the variation of petrochemical property para...A type of specific fractured hydrocarbon reservoir, a shale fractured reservoir, exists in the Shengli oilfield. Due to very small porosity of this type, low sensitivity to the variation of petrochemical property parameters, and strong anisotropy, it is very difficult to explore for them. So far, there is no set of mature methods for recognition of direction, distribution, and density of the fractures by an integrated analysis of geologic, geophysical, well log, drilling data, and etc. This paper presents a new method for acoustic impedance variation with azimuth （IPVA）, based on existing fracture detection methods. Seismic acquisition, processing, and recognition techniques were developed for detecting directional vertical fractures using multi-azimuth P wave data in combination with the seismic and geological features of shale fractures in the Luojia area. The IPVA research is carried out for recognizing the distribution, strike, and density of fractures based on the study of velocity variation with azimuth （VVA） and amplitude variation with azimuth （AVA） for full azimuth P wave data at different CMP positions. Through practical application in the Luojia area, primary results have been obtained which verifies that the IPVA method provides good potential for quantitative detection of parallel, high angle, shale fractures.展开更多
The effect of seawater on vertical ground motions is studied via a theoretical method and then actual offshore ground motion records are analyzed using a statistical method. A theoretical analysis of the effect of sea...The effect of seawater on vertical ground motions is studied via a theoretical method and then actual offshore ground motion records are analyzed using a statistical method. A theoretical analysis of the effect of seawater on incident plane P and SV waves at ocean bottom indicate that on one hand, the affected frequency range of vertical ground motions is prominent due to P wave resonance in the water layer if the impedance ratio between the seawater and the underlying medium is large, but it is greatly suppressed if the impedance ratio is small; on the other hand, for the ocean bottom interface model selected herein, vertical ground motions consisting of mostly P waves are more easily affected by seawater than those dominated by SV waves. The statistical analysis of engineering parameters of offshore ground motion records indicate that:(1) Under the infl uence of softer surface soil at the seafl oor, both horizontal and vertical spectral accelerations of offshore motions are exaggerated at long period components, which leads to the peak spectral values moving to a longer period.(2) The spectral ratios(V/H) of offshore ground motions are much smaller than onshore ground motions near the P wave resonant frequencies in the water layer; and as the period becomes larger, the effect of seawater becomes smaller, which leads to a similar V/H at intermediate periods(near 2 s). These results are consistent with the conclusions of Boore and Smith(1999), but the V/H of offshore motion may be smaller than the onshore ground motions at longer periods(more than 5 s).展开更多
基金supported by NSF grant EAR-063566(F.N.)National Natural Science Foundation of China grant 40774042(J.L.)
文摘The recently built China Digital Seismic Network consists of the China National Digital Seismic Network （CNDSN）, 31 regional seismic networks and several small aperture arrays with more than 1 000 stations including 850＋ broadband stations. It forms a gigantic seismic array that provides an unprecedented opportunity to study the Earth＇s deep interior besides its routine task of seismic monitoring. Many modern seismic studies rely on rotation of vertical and horizontal components in order to separate different types of seismic waves. Knowledge of the orientations of the two horizontal components thus is important to perform a correction rotation. We analyzed particle motions of teleseismic P waves recorded by the network and used them to estimate the northcomponent azimuth of each station. An SNR-weighted-multi-event method was introduced to obtain component azimuths that best explain the P-wave particle motions of all the events recorded at a station. The method provides robust estimates including a measurement error calculated from background noise levels. We found that about one third of the stations have some sort of problems, including misorientation of the two horizontal components, mislabeling and polarity reversal in one or more components. These problems need to be taken into account for any rotation based seismic studies.
文摘High-resolution seismic models of sediment basins are critical inputs for earthquake ground motion prediction and petroleum resource exploration.In this study we employed a newly developed technique that utilizes the frequency-dependent nonlinear P-wave particle motion to estimate sedimentary structure beneath the Bohai Bay basin.A recent study suggests that the delay of the P wave on the horizontal component relative the vertical component and its variations over frequency are caused by interference of the direct P wave with waves generated at the sediment base.The frequency-dependent delay time can be used to constrain sediment thickness and seismic velocity beneath recording stations.We measured the particle motions of teleseismic P waves recorded by 249 broadband stations of the North China Array,which covers the western Bohai Bay basin and its surrounding areas.We found that the P waves of 90 stations inside the Bohai Bay basin and other local basins within the Taihang and Yanshan mountain ranges exhibit significant frequency-dependent nonlinear particle motions,and used the particle motion data to invert the sediment thickness(Z0)and surface S-wave velocity(β0).The estimated sediment thickness inside the Bohai Bay Basin varies from 1.02 km to 3.72 km,with an average of 3.20 km,which roughly agrees with previous active source studies.
文摘We study the reduction of peak velocity on the ground surface of a soil valley caused by loss of wave energy by large nonlinear strains and strain localization inside the valley,for excitation by a half-sine P-wave pulse.This study is a follow up to our previous study of out of plane response for excitation by an SH-pulse.In this paper,we consider the in-plane response,and assume that the soil material does not support tension,but the normal stress at a point in the soil can be compression(negative)or zero.A point in the soil with zero stress behaves as a stress-free point,it does not transmit normal stress and appears as a crack point.Because of this,along with the nonlinear response associated with compression and shear,the in-plane response in this study is more complex than that of the out-of-plane SH response.We study the interplay of two opposing effects:(i)jump in impedance from a higher value(half-space)to a lower value(valley),which amplifies the linear motions at the free surface of the valley,and(ii)the occurrence of nonlinear zones in the valley,which reduce the motion at the valley surface.
文摘目的:分析心电图P波参数对高血压心房颤动(Atrial fibrillation,AF)患者消融术后复发的预测价值。方法:回顾性分析2023年1月至2024年10月我院首次接受消融术的87例高血压AF患者资料,参考术后12 m内是否复发分复发组(21例)和非复发组(66例),比较两组P波终末电势(P-wave terminal force in lead V1,PtfV1)、P波离散度(P-wave dispersion,Pd)、P波变异(P-wave variation,Pv)及最大P波时限(Maximum P-wave duration,Pmax),分析上述指标与术后复发的关系及预测价值。结果:与非复发组对比,复发组Pd、Pv、Pmax均更高(P<0.05),但对比两组PtfV1,差异无统计学意义(P>0.05);多因素Logistic回归分析显示,Pd、Pv、Pmax与高血压AF患者术后复发显著相关(P<0.05);绘制受试者工作特征曲线结果显示,Pd、Pv、Pmax三者联合预测高血压AF患者复发的曲线下面积为0.840,均高于单一指标预测(P<0.05)。结论:Pd、Pv、Pmax三者联合在高血压AF患者术后复发中预测价值较高。
文摘Based on arbitrarily wide-angle wave equations,a reverse-time propagation scheme is developed by substituting the partial derivatives of depth and time with central differences. The partial derivative of horizontal direction is replaced with high order difference. The imaging condition is computed by solving the eikonal equations. On the basis of above techniques,a prestack reverse-time depth migration algorithm is developed. The processing exam-ples of synthetic data show that the method can remove unwanted internal reflections and decrease the migration noise. The method also has the advantage of fidelity and is applicable of dip angle reflector imaging.
基金The special project of Detection of Haikou City Earthquake Active Faults from the Tenth Five-year Plan of China Earthquake Administration (0106512)Joint Seismological Science Foundation of China (105086)CAS Key Laboratory of Marginal Sea Geology (MSGL0503).
文摘Using over 3 500 first P arrival times recorded by nine digital seismic stations from Hainan Digital Seismic Net-work during 1999～2005,a 3-D P-wave velocity model of the crust under Hainan Island and adjacent regions has been determined. The results show that the pattern of velocity anomalies in the shallower upper crust is somewhat associated with the surface geological tectonics in the region. A relative low-velocity anomaly appears north of the Wangwu-Wenjiao fault zone and a relative high-velocity anomaly appears south of the Wangwu-Wenjiao fault zone,corresponding to the depressed areas in north Hainan Island,where many volcanoes are frequently active and geothermal values are relatively higher,and the uplifted and stable regions in central and south of the Hainan Is-land. In the middle and lower crust velocities are relatively lower in east Hainan than those in west Hainan,possi-bly suggesting the existence of the upwelling of hot materials from the mantle in east Hainan. The pattern of veloc-ity anomalies also indicates that NW faults,i.e.,the Puqian-Qinglan fault,may be shallower,while the E-W Wangwu-Wenjiao fault may be deeper,which perhaps extends down to Moho depth or deeper.
基金Key Project Process Mechanism and Prediction of Geological Hazards (2001CB711005-1-3) and State Key Basic Research Project Mechanism and Prediction of Continental Earthquakes (G1998040702). sponsored by the Ministry of Science and Techno
基金State Natural Science Foundation of China (No.59878032).
文摘An analytical solution for scattering of plane P waves by circular-arc layered alluvial valleys was derived by Fourier-Bessel series expansion technique, and the solution was utilized to analyze the effects of alluvial sequence and their relative stiffness on the scattering of incident waves.
文摘目的探讨心电图P波参数与脑白质病变(white matter lesions,WMLs)严重程度之间的关联,为WMLs的预防和治疗提供科学依据。方法选取289例符合入组标准的WMLs住院患者作为研究对象,其均接受常规12导联心电图和头颅磁共振成像检查。根据Fazekas量表评分将这些患者分为无-轻度组(158例)和中-重度组(131例)。收集两组患者的临床资料、既往病史、心电图P波参数[包括P波时限、P波电轴、V_(1)导联P波终末电势(terminal force of P-wave in lead V_(1),PTFV_(1))],以及血脂等数据,并进行比较分析。采用Logistic回归模型分析影响WMLs的独立危险因素。结果中-重度组患者的年龄、有高血压或糖尿病病史者占比及PTFV_(1)>4000μV·ms者占比均明显高于无-轻度组,且差异均有统计学意义(均P<0.01)。多变量Logistic回归分析表明,年龄增长、高血压、糖尿病以及PTFV_(1)>4000μV·ms均为WMLs的独立危险因素。结论无创心电图指标PTFV_(1)经济便捷、易于获取,可用于评估心房异常,对WMLs的防治具有一定的应用价值。
基金National Natural Science Foundation of China Under Grant No.50309005National Key Basic Research and Development Program Under Grant No.2002CB412709
文摘Wave reflection and refraction in layered media is a topic closely related to seismology,acoustics,geophysics and earthquake engineering.Analytical solutions for wave reflection and refraction coefficients in multi-layered media subjected to P wave incidence from the elastic half-space are derived in terms of displacement potentials.The system is composed of ideal fluid,porous medium,and underlying elastic solid.By numerical examples,the effects of porous medium and the incident wave angle on the dynamic pressures of ideal fluid are analyzed.The results show that the existence of the porous medium,especially in the partially saturated case,may significantly affect the dynamic pressures of the overlying fluid.
基金National Natural Science Foundation of China Under Grant No.50378063Excellent Young Teacher Program of Ministry of Education
文摘An analytical solution for scattering of plane P waves by a semi-cylindrical hill was derived by using the wave function expansion method, and convergence of the solution and accuracy of truncation were verified. The effect of incident frequency and incident angle on the surface motion of the hill was discussed, and it was shown that a hill greatly amplifies incident plane P waves, and maximum horizontal displacement amplitudes appear mostly at the inclined incidence of waves, which are located at the half-space; and maximum vertical displacement amplitudes emerge mostly at the vertical incidence of waves, which are situated at the hill.
文摘A type of specific fractured hydrocarbon reservoir, a shale fractured reservoir, exists in the Shengli oilfield. Due to very small porosity of this type, low sensitivity to the variation of petrochemical property parameters, and strong anisotropy, it is very difficult to explore for them. So far, there is no set of mature methods for recognition of direction, distribution, and density of the fractures by an integrated analysis of geologic, geophysical, well log, drilling data, and etc. This paper presents a new method for acoustic impedance variation with azimuth （IPVA）, based on existing fracture detection methods. Seismic acquisition, processing, and recognition techniques were developed for detecting directional vertical fractures using multi-azimuth P wave data in combination with the seismic and geological features of shale fractures in the Luojia area. The IPVA research is carried out for recognizing the distribution, strike, and density of fractures based on the study of velocity variation with azimuth （VVA） and amplitude variation with azimuth （AVA） for full azimuth P wave data at different CMP positions. Through practical application in the Luojia area, primary results have been obtained which verifies that the IPVA method provides good potential for quantitative detection of parallel, high angle, shale fractures.
基金the 973 Program under Grant No.2011CB013601Basic Science Research Foundation of IEM,CEA under Grant No.2011B02+1 种基金National Natural Science Foundation of China under Grant No.51238012,9121530113,50938006International Science&Technology Cooperation Program of China under Grant No.2012DFA70810
文摘The effect of seawater on vertical ground motions is studied via a theoretical method and then actual offshore ground motion records are analyzed using a statistical method. A theoretical analysis of the effect of seawater on incident plane P and SV waves at ocean bottom indicate that on one hand, the affected frequency range of vertical ground motions is prominent due to P wave resonance in the water layer if the impedance ratio between the seawater and the underlying medium is large, but it is greatly suppressed if the impedance ratio is small; on the other hand, for the ocean bottom interface model selected herein, vertical ground motions consisting of mostly P waves are more easily affected by seawater than those dominated by SV waves. The statistical analysis of engineering parameters of offshore ground motion records indicate that:(1) Under the infl uence of softer surface soil at the seafl oor, both horizontal and vertical spectral accelerations of offshore motions are exaggerated at long period components, which leads to the peak spectral values moving to a longer period.(2) The spectral ratios(V/H) of offshore ground motions are much smaller than onshore ground motions near the P wave resonant frequencies in the water layer; and as the period becomes larger, the effect of seawater becomes smaller, which leads to a similar V/H at intermediate periods(near 2 s). These results are consistent with the conclusions of Boore and Smith(1999), but the V/H of offshore motion may be smaller than the onshore ground motions at longer periods(more than 5 s).
