In the Qiongdongnan Basin, faults are well developed.Based on the drilling results, the traps controlled two or more faults are oil-rich. However, when only one fault cut through the sand body, there is no sign for hy...In the Qiongdongnan Basin, faults are well developed.Based on the drilling results, the traps controlled two or more faults are oil-rich. However, when only one fault cut through the sand body, there is no sign for hy-drocarbon accumulation in the sandstone. In terms of this phenomenon, the principle of reservoir-forming controlled by fault terrace is proposed, i.e., when the single fault activates, because of the incompressibility of pore water, the resistance of pore and the direction of buoyancy, it is impossible for hydrocarbon to ac-cumulate in sandstone. But when there are two or more faults, one of the faults acts as the spillway so the hydrocarbon could fill in the pore of sandstone through other faults. In total five gas bearing structures and four failure traps are considered, as examples to demonstrate our findings. According to this theory, it is well-advised that south steep slope zone of Baodao-Changchang Depression, south gentle slope zone of Lingshui Depression, north steep slope zone of Lingshui Depression, and north steep slope zone of Baodao Depression are the most favorable step-fault zones, which are the main exploration direction in next stage.展开更多
In the 1990s, several major earthquakes occurred throughout the world, with a common observation that near fault ground motion （NFGM） characteristics had a distinct impact on causing damage to civil engineering stru...In the 1990s, several major earthquakes occurred throughout the world, with a common observation that near fault ground motion （NFGM） characteristics had a distinct impact on causing damage to civil engineering structures that could not be predicted by using far field ground motions. Since then, seismic responses of structures under NFGMs have been extensively examined, with most of the studies focusing on structures with relatively short fundamental periods, where the traveling wave effect does not need to be considered. However, for long span bridges, especially arch bridges, the traveling wave （only time delay considered） effect may be very distinct and is therefore important. In this paper, the results from a case study on the seismic response of a steel arch bridge under selected NFGMs is presented by considering the traveling wave effect with variable apparent velocities. The effects of fling step and long period pulses of NFGMs on the seismic responses of the arch bridge are also discussed.展开更多
This paper presents a technique to reproduce compatible seismogran3s involving permanent displacen3ent effects at sites close to the fault source. A multi-objective evolutionary algorithm is used to minimize the diffe...This paper presents a technique to reproduce compatible seismogran3s involving permanent displacen3ent effects at sites close to the fault source. A multi-objective evolutionary algorithm is used to minimize the differences between the response spectra and multi-tapered power spectral delsilies corresponding to the recorded and simulated wavelbrms. The multi-taper method is used to reduce the spectral leakage that is inherent in the Fourier rams formed form ofwavelbrms, ieading to a reduction of variance in power spectral amplitudes, thus permitting the calibration of the two sets of data. The technique is implemented using the 1998-Fandoqa （lran） earthquake data and the results are compared with the actual observed data. Additionally, a comparison is made with a SAR interfcrometry study leading to fair agreement with the reported dislocation along the main fault. The simulation procedure and results are discussed and assessed concluding that, although the technique may be associated with uncertainties, it can still be used to reproduce wavelbnns at near source sites that include permanent dislocation, and can be used for seismic pertbrmance evaluation of structures in the region under study.展开更多
2023年12月18日甘肃积石山发生M_(S)6.2地震,该地震造成了严重的地质灾害,属国内近些年来6级以上地震所罕见.基于多阶段定位方法对2023年积石山M_(S)6.2地震序列进行了重定位,根据gCAP(generalized Cut And Paste)方法反演了序列中M_(S)...2023年12月18日甘肃积石山发生M_(S)6.2地震,该地震造成了严重的地质灾害,属国内近些年来6级以上地震所罕见.基于多阶段定位方法对2023年积石山M_(S)6.2地震序列进行了重定位,根据gCAP(generalized Cut And Paste)方法反演了序列中M_(S)≥3.0以上地震的震源机制及矩心深度,并对震源机制节面进行聚类分析,获取了地震序列的主要断层面形状,计算了积石山地震序列震源区的构造应力场,研究了其应力场与震源机制节面及断层面的关系,最后结合地质构造、地壳形变等资料综合探讨和推测了积石山地震序列可能的发震构造.结果显示:(1)重定位结果表明,积石山M_(S)6.2地震序列震中区的长轴主要沿着拉脊山北缘断裂南段呈NNW向的优势展布,整个序列长约15km、宽约6km,北端、南端各分别止于大河家镇南侧及积石山县西侧,且存在显著的丛集分区特征,主要划分为大河家镇到刘集乡之间的北段余震稀疏区,以及刘集乡到积石山县西侧之间的南段余震密集区,其中南段余震密集区呈现为NW-SE向的分支和NNW-SSE向的分支,且两个分支形成了NW端分叉且SE端汇聚的分布特征,大部分余震主要集中在NW-SE向分支而积石山M_(S)6.2主震位于NNW-SSE向分支的NE侧.整个序列的平均震源深度约为11.4km,大多数地震主要集中在9~14km深度范围,其中主震的初始破裂深度为13.6km.震源深度剖面清晰勾勒出地震序列的主要发震断层面倾向为NE向,积石山M_(S)6.2主震则位于倾向NE的断层面底端,余震基本位于M_(S)6.2主震的上方,大体呈现为单侧破裂的特征.(2)gCAP波形反演表明,积石山M_(S)6.2主震震源机制节面I的走向/倾角/滑动角为304°/55°/65°,节面II的走向/倾角/滑动角为163°/42°/121°,P轴方位51°和其倾伏角7°,矩心深度10km,矩震级M_(W)5.95.主震及M_(S)3.0以上余震的震源机制主要表现以逆冲为主且略带少量的走滑分量,震源机制的P轴主要呈现近NE-SW向的水平挤压,矩心深度介于9~12km之间,平均矩心深度10.7km.(3)震源机制节面聚类分析得出两簇聚类中心节面,其中NE倾向的聚类中心节面走向311°及倾角43°,其形状和重定位的深度剖面大体一致.震源区应力场反演结果显示,积石山震源区的最优压应力轴走向、倾伏角分别为57°和15°,表明积石山震源区应力场表现为NE向的近水平挤压,并以逆冲为主的应力状态.通过将其反演得到的应力场投影到积石山地震序列震源机制节面及其聚类中心节面,发现积石山应力体系在这些震源机制节面和聚类中心节面上均更容易产生逆冲破裂的地震事件.(4)结合已有区域地质构造、地壳形变等研究,综合分析认为积石山M_(S)6.2地震序列的发震构造和拉脊山北缘主断裂南段(积石山东缘断裂)与其至少两条走向略不同的反冲断层组成的“y”型冲断构造所在的复杂逆冲推覆环境有关,其中积石山M_(S)6.2主震位于NNW-SSE走向、SW倾向拉脊山北缘主断裂南段与其NW-SE走向、NNW-SSE走向及NE倾向的次级反冲断层形成的背冲式构造“y”形汇合部位,并在拉脊山北缘主断裂南段上的反冲断层上发生了相对密集的积石山余震序列.展开更多
基金The Key Projects in the National Science &Technology Pillar Program during the Twelfth Five-year Plan Period under contract No.2011ZX05025-002-05
文摘In the Qiongdongnan Basin, faults are well developed.Based on the drilling results, the traps controlled two or more faults are oil-rich. However, when only one fault cut through the sand body, there is no sign for hy-drocarbon accumulation in the sandstone. In terms of this phenomenon, the principle of reservoir-forming controlled by fault terrace is proposed, i.e., when the single fault activates, because of the incompressibility of pore water, the resistance of pore and the direction of buoyancy, it is impossible for hydrocarbon to ac-cumulate in sandstone. But when there are two or more faults, one of the faults acts as the spillway so the hydrocarbon could fill in the pore of sandstone through other faults. In total five gas bearing structures and four failure traps are considered, as examples to demonstrate our findings. According to this theory, it is well-advised that south steep slope zone of Baodao-Changchang Depression, south gentle slope zone of Lingshui Depression, north steep slope zone of Lingshui Depression, and north steep slope zone of Baodao Depression are the most favorable step-fault zones, which are the main exploration direction in next stage.
基金Federal Highway Administration(FHWA) Under Grant No.DTFH41-98900094
文摘In the 1990s, several major earthquakes occurred throughout the world, with a common observation that near fault ground motion （NFGM） characteristics had a distinct impact on causing damage to civil engineering structures that could not be predicted by using far field ground motions. Since then, seismic responses of structures under NFGMs have been extensively examined, with most of the studies focusing on structures with relatively short fundamental periods, where the traveling wave effect does not need to be considered. However, for long span bridges, especially arch bridges, the traveling wave （only time delay considered） effect may be very distinct and is therefore important. In this paper, the results from a case study on the seismic response of a steel arch bridge under selected NFGMs is presented by considering the traveling wave effect with variable apparent velocities. The effects of fling step and long period pulses of NFGMs on the seismic responses of the arch bridge are also discussed.
文摘This paper presents a technique to reproduce compatible seismogran3s involving permanent displacen3ent effects at sites close to the fault source. A multi-objective evolutionary algorithm is used to minimize the differences between the response spectra and multi-tapered power spectral delsilies corresponding to the recorded and simulated wavelbrms. The multi-taper method is used to reduce the spectral leakage that is inherent in the Fourier rams formed form ofwavelbrms, ieading to a reduction of variance in power spectral amplitudes, thus permitting the calibration of the two sets of data. The technique is implemented using the 1998-Fandoqa （lran） earthquake data and the results are compared with the actual observed data. Additionally, a comparison is made with a SAR interfcrometry study leading to fair agreement with the reported dislocation along the main fault. The simulation procedure and results are discussed and assessed concluding that, although the technique may be associated with uncertainties, it can still be used to reproduce wavelbnns at near source sites that include permanent dislocation, and can be used for seismic pertbrmance evaluation of structures in the region under study.
文摘2023年12月18日甘肃积石山发生M_(S)6.2地震,该地震造成了严重的地质灾害,属国内近些年来6级以上地震所罕见.基于多阶段定位方法对2023年积石山M_(S)6.2地震序列进行了重定位,根据gCAP(generalized Cut And Paste)方法反演了序列中M_(S)≥3.0以上地震的震源机制及矩心深度,并对震源机制节面进行聚类分析,获取了地震序列的主要断层面形状,计算了积石山地震序列震源区的构造应力场,研究了其应力场与震源机制节面及断层面的关系,最后结合地质构造、地壳形变等资料综合探讨和推测了积石山地震序列可能的发震构造.结果显示:(1)重定位结果表明,积石山M_(S)6.2地震序列震中区的长轴主要沿着拉脊山北缘断裂南段呈NNW向的优势展布,整个序列长约15km、宽约6km,北端、南端各分别止于大河家镇南侧及积石山县西侧,且存在显著的丛集分区特征,主要划分为大河家镇到刘集乡之间的北段余震稀疏区,以及刘集乡到积石山县西侧之间的南段余震密集区,其中南段余震密集区呈现为NW-SE向的分支和NNW-SSE向的分支,且两个分支形成了NW端分叉且SE端汇聚的分布特征,大部分余震主要集中在NW-SE向分支而积石山M_(S)6.2主震位于NNW-SSE向分支的NE侧.整个序列的平均震源深度约为11.4km,大多数地震主要集中在9~14km深度范围,其中主震的初始破裂深度为13.6km.震源深度剖面清晰勾勒出地震序列的主要发震断层面倾向为NE向,积石山M_(S)6.2主震则位于倾向NE的断层面底端,余震基本位于M_(S)6.2主震的上方,大体呈现为单侧破裂的特征.(2)gCAP波形反演表明,积石山M_(S)6.2主震震源机制节面I的走向/倾角/滑动角为304°/55°/65°,节面II的走向/倾角/滑动角为163°/42°/121°,P轴方位51°和其倾伏角7°,矩心深度10km,矩震级M_(W)5.95.主震及M_(S)3.0以上余震的震源机制主要表现以逆冲为主且略带少量的走滑分量,震源机制的P轴主要呈现近NE-SW向的水平挤压,矩心深度介于9~12km之间,平均矩心深度10.7km.(3)震源机制节面聚类分析得出两簇聚类中心节面,其中NE倾向的聚类中心节面走向311°及倾角43°,其形状和重定位的深度剖面大体一致.震源区应力场反演结果显示,积石山震源区的最优压应力轴走向、倾伏角分别为57°和15°,表明积石山震源区应力场表现为NE向的近水平挤压,并以逆冲为主的应力状态.通过将其反演得到的应力场投影到积石山地震序列震源机制节面及其聚类中心节面,发现积石山应力体系在这些震源机制节面和聚类中心节面上均更容易产生逆冲破裂的地震事件.(4)结合已有区域地质构造、地壳形变等研究,综合分析认为积石山M_(S)6.2地震序列的发震构造和拉脊山北缘主断裂南段(积石山东缘断裂)与其至少两条走向略不同的反冲断层组成的“y”型冲断构造所在的复杂逆冲推覆环境有关,其中积石山M_(S)6.2主震位于NNW-SSE走向、SW倾向拉脊山北缘主断裂南段与其NW-SE走向、NNW-SSE走向及NE倾向的次级反冲断层形成的背冲式构造“y”形汇合部位,并在拉脊山北缘主断裂南段上的反冲断层上发生了相对密集的积石山余震序列.
