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Relationship between Mesozoic Magmatism and Subduction in the Da Hinggan-Yanshan Area

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Acta Geologica Sinica(English Edition) 2001年第1期75卷 1-8页

作者： SHAO Ji'an LIU Futian CHEN Hui HAN Qingjun Peking University Beijing 100871 Institute of Geology and Geophysics Chinese Academy of SciencesBeijing 100101

High-resolution tomographic images of the belt crossing the Japan Trench-Changbai Mountains-Dong Ujimqin Qi are represented in this paper, revealing the shape of a subducted slab in the western Pacific region and characteristics of the lithospheric structures under the Changbai Mountains and the Da Hinggan Mountains. Studies of the spatial distribution, subduction time and the time-lag between the subduction and magmatism, combined with petrology and isotope geochemistry of the Late Mesozoic volcano-plutonic rocks from the Da Hinggan Mountains-Yanshan Mountains have further proved the independence of magmatic activities from the subduction of the Pacific plate. The Mesozoic tectono-thermal evolutionary history and structural characteristics of the lithosphere in the Da Hinggan Mountains and North China suggest that the formation and evolution of magma have probably a close relationship with the delamination and thinning of the continental lithosphere and the underplating resulting from the consequent upwelling of the asthenosphere. On the other hand, the large-scale strike-slip fault system, resulting from sinistral shearing of the Pacific plate relative to the Asian continent in the Mesozoic, is responsible for the formation and emplacement of magma on the continental margin. It was the intense crust-mantle interaction, together with structural deformation at the shallower levels that led to the large tectono-magmatic belt in the East Asian continental margin.

关键词： Da Hinggan-Yanshan Mountains volcanic-plutonic rock subduction tomographic image

tomographic inversion for microseismic source parameters in mining

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Applied Geophysics 2012年第3期9卷 341-348,362页

作者：缪华祥姜福兴宋雪娟杨淑华焦俊如北京科技大学中国石油勘探开发研究院 Repsol USA The WoodlandsTexas 77380USA

We propose a new method for inverting source function of microseismic event induced in mining. The observed data from microseismic monitoring during mining are represented by a wave equation in a spherical coordinate system and then the data are transformed from the time-space domain to the time-slowness domain based on tomographic principle, from whichwe can obtain the signals related to the source in the time-slowness domain. Through analyzing the relationship between the signal located at the maximum energy and the source function, we derive the tomographic equations to compute the source function from the signals and to calculate the effective radiated energy based on the source function. Moreover, we fit the real amplitude spectrum of the source function computed from the observed data into the co-2 model based on the least squares principle and determine the zero-frequency level spectrum and the corner frequency, finally, the source rupture radius of the event is calculated and The synthetic and field examples demonstrate that the proposed tomographic inversion methods are reliable and efficient

关键词： tomographic image microseismic event source function source spectrum the time-slowness domain

Automatically positioning microseismic sources in mining by the stereo tomographic method using full wavefields

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Applied Geophysics 2012年第2期9卷 168-176,234,235页

作者：缪华祥姜福兴宋雪娟宋建勇杨淑华焦俊如北京科技大学土木与环境工程学院中国石油勘探开发研究院地球物理研究所 Repsol USA The WoodlandTexas77380USA

For microseisimic monitoring it is difficult to determine wave modes and their propagation velocity. In this paper, we propose a new method for automatically inverting in real time the source characteristics of microseismic events in mine engineering without wave mode identification and velocities. Based on the wave equation in a spherical coordinate system, we derive a tomographic imaging equation and formulate a scanning parameter selection criterion by which the microseisimic event maximum energy and corresponding parameters can be determined. By determining the maximum energy positions inside a given risk district, we can indentify microseismic events inside or outside the risk districts. The synthetic and field examples demonstrate that the proposed tomographic imaging method can automatically position microseismic events by only knowing the risk district dimensions and range of velocities without identifying the wavefield modes and accurate velocities. Therefore, the new method utilizes the full wavefields to automatically monitor microseismic events.

关键词： microseismic full wavefields wavefield mode identification tomographic image source parameters automatic positioning