板块边界及板块内部地震火山活动区的地震层析成像研究

IOCAS-IR > 海洋地质与环境重点实验室

	板块边界及板块内部地震火山活动区的地震层析成像研究
	陈传绪
学位类型	博士
导师	吴时国 ; 赵大鹏
	2015-05-18
学位授予单位	中国科学院大学
学位授予地点	北京
学位专业	海洋地质与地球物理
关键词	速度层析成像衰减层析成像多道地震板块边界板间地震周期性震颤和滑动板内地震长白山板内火山
摘要	地震和火山活动是地球物质能量循环的重要环节，也是人类所需面对的主要自然灾害，对这两大地球基本过程的研究具有重要的科学和灾害预警意义。本论文应用地震学成像方法（天然地震速度和衰减层析成像，人工地震偏移成像）研究对比了马尼拉俯冲带、卡斯卡迪亚俯冲带、日本北海道地区俯冲带、太平洋板块深俯冲系统以及美国新马德里板内地震带等地震火山活跃区域。主要取得了以下的主要研究成果和发现：1）整合马尼拉俯冲带地区的21条多道地震剖面和6条OBS剖面的观测结果，揭示了马尼拉海沟北段输入板块在地壳属性、基底埋深、沉积物厚度等方面的差异。对比发现，输入板块的性质差异和该地区的地震活动性差异存在空间关联，这一结果有助于对该俯冲带孕震能力的评估; 2）获取了美国西海岸卡斯卡迪亚俯冲带地区的三维速度结构。结果表明，该俯冲带板块交界处的速度结构以及断层行为均存在分段分布特征。输入板块年龄的分段特征使得发生在俯冲系统中的板块脱水、蛇纹石化过程存在差异，进而引起了板块边界处含水程度的差异，导致板块交界断层处摩擦性质的变化，最终导致了断层行为（ETS，以及地震）的分段特征; 3）获取了日本北海道地区的三维P波和S波速度结构以及P波和S波的衰减结构。结果清晰地表明，和岛弧火山相关的高温地幔上升流表现为低波速、高衰减特征，俯冲的太平洋板块表现为高波速、低衰减特征。在北海道地区的火山弧缺口下，地幔楔的深度和结构明显变化，揭示出该地区岩浆活动明显低于两侧的原因；4）获取了美国中部新马德里板内地震带深部的三维速度结构，结果显示，在新马德里地震带下岩石圈地幔150-250 km深度处存在明显的低速异常体。该异常体代表了岩石圈地幔中的薄弱带，使得该地震带区别于其周围的板内区域。这一结果为解释板内地震成因提供了新的视角；5）获取了东北亚地区的太平洋板块深俯冲系统的三维速度结构，结果清晰地表明，长白山板内火山下的高温低波速异常发源于太平洋滞留板块之上的大地幔楔内，长白山火山的起源与滞留板块的脱水及大地幔楔内的热上升流密切相关。
其他摘要	Earthquakes and volcanic eruptions are two main geological processes which transfer energy and materials through the Earth systems, and they are also the most serious natrual hazards on Earth. In this work, we used seismological methods, including seismic velocity and attenuation tomography, and multi-channel seismic data migration imaging, to study seismic structure of the seismogenic and volcanic zones in several interplate and intraplate regions including the Manila, Cascadia, South-Kuril and Northeast Asia subduction zones, as well as the New Madrid intraplate seismic zone. Our main findings are summarized as follows. 1) We studied the detailed seismic structure of the incoming plate along the northern Manila trench by integrating 21 multi-channel seismic lines and 6 OBS profiles. The seismic imaging revealed crustal heterogeneities, crustal thickness, sediment thickness and basement depth of the incoming plate. The segmentation of the incoming plate correlates well with the deformation pattern of the accretionary wedges and seismically active regions, implying that pre-existing heterogeneities inherited from the rifting process of the continental margin may have an important effect on carving seafloor morphology and seismicity at the precollision zone. 2) We investigated the detailed crustal and upper-mantle structure of the Cascadia subduction zone by conducting tomographic inversions using a starting velocity model which includes the high-velocity subducting Juan de Fuca slab as a priori information. The lateral velocity variations revealed by our tomographic images indicate different degrees of slab dehydration and forearc mantle serpentinization. The segmentation in episodic tremor and slip (ETS) is also spatially coincident with the velocity heterogeneities, suggesting that the ETS occurrence and recurrence interval are controlled by fluid activity in and around the mantle wedge corner. 3) We obtained detailed 3-D velocity and attenuation tomography of the crust and upper mantle beneath Hokkaido, Japan. Low-velocity and high-attenuation anomalies are revealed beneath active arc volcanoes, which reflect arc volcanism caused by a combination of slab dehydration and hot upwelling flow in the mantle wedge. However, such anomalies are absent beneath the volcanic gap area in southern Hokkaido, indicating weak or none flux melting at the arc-arc collision zone. 4) We determine a 3-D P-wave velocity model of the crust and upper mantle of the New Madrid Seismic Zone. Our results show that, beneath this intraplate seismic zone, a significant low-velocity (low-V) zone exists in the upper mantle down to 200 km depth. This low-V zone may have relatively low shear strength and act as a viscously weak zone embedded in the lithosphere, being apt to concentrate tectonic stress and transfer stress to the seismogenic faults in the upper crust, leading to the large intraplate earthquakes in the New Madrid Seismic Zone 5) We obtained an updated P-wave tomography of the Pacific subduction zone under Northeast Asia, targeting at the mantle transition zone beneath the vicinity of the Changbai volcano. Our result shows that a focused mantle upwelling originates from the hinge of the stagnant slab beneath the Changbai volcano. The origin and localized concentration of the asthenospheric upwelling may result from a combined effect of deep dehydration of hydrous minerals, additional fluids released through deep earthquakes and stronger mantle circulation near the hinge of the stagnant Pacific slab.
学科领域	海洋地质与环境
语种	中文
文献类型	学位论文
条目标识符	http://ir.qdio.ac.cn/handle/337002/23275
专题	海洋地质与环境重点实验室
作者单位	中科院海洋研究所
第一作者单位	中国科学院海洋研究所
推荐引用方式 GB/T 7714	陈传绪. 板块边界及板块内部地震火山活动区的地震层析成像研究[D]. 北京. 中国科学院大学,2015.

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