再论各向异性介质转换波地震学,第一部分:理论     

Xiangyang Li  Jianxin Yuan British Geological Survey  West Mains Road  Edinburgh EH LA  UK. Formerly at British Geological Survey  now at PGS Inc.  Richmond Avenue  Suite  Houston  TX  USA. 《应用地球物理》2005,2(1)

我们业已研发了计算各向异性、非均质介质中P- SV转换波(C-波)的转换点和旅行时的新理论。据此 可以利用诸如相似性分析、迪克斯模型建模、克契 霍夫求和等常规方法来完成各向异性的处理和各向 异性处理,并使各向异性的处理成为可能。这里将 我们的新发展分作两部分来介绍。第一部分为理 论,第二部分为对速度分析和参数计算的应用。第 一部分理论包括转换点的计算和动校正的分析。  相似文献   

Converted-wave seismology in anisotropic media revisited,Part I: Basic theory     

Xiangyang Li  Jianxin Yuan 《应用地球物理》2005,2(1):26-40

We have developed new basic theories for calculating the conversion point and the travel time of the P-SV converted wave (C-wave) in anisotropic, inhomogeneous media. This enables the use of conventional procedures such as semblance analysis, Dix-type model building and Kirchhoff summation, to implement anisotropic processing, and makes anisotropic processing affordable. Here we present these new developments in two parts: basic theory and application to velocity analysis and parameter estimation. This part deals with the basic theory, including both conversion-point calculation and moveout analysis. Existing equations for calculating the PS-wave (C-wave) conversion point in layered media with vertical transverse isotropy (VTI) are strictly limited to offsets about half the reflector depth (an offset-depth ratio, xlz, of 0.5), and those for calculating the C-wave traveltimes are limited to offsets equal to the reflector depth (x/z=l.0). In contrast, the new equations for calculating the conversion-point extend into offsets about three-times the reflector depth (x/z=3.0), those for calculating the C-wave traveltimes extend into offsets twice the reflector depth (x/z=2.0). With the improved accuracy, the equations can help in C-wave data processing and parameter estimation in anisotropic, inhomogeneous media. This work is funded by the Edinburgh Anisotropy Project (EAP) of the British Geological Survey. First author: Xiangyang Li, Mr. Li is currently a professorial research seismologist (Grade 6) and technical director of the Edinburgh Anisotropy Project in the British Geological Survey. He also holds a honorary professorship in multicomponent seismology at the School of Geosciences, University of Edinburgh. He received his BSc(1982) in Geophysics from Changchun Geological Institute, China, an MSc (1984) in applied geophysics from East China Petroleum Institute (now known as the China University of Petroleum), and a PhD (1992) in seismology from the University of Edinburgh. During 1984–1987, he worked as a lecturer with the East China Petroleum Institute. Since 1991, he has been employed by the British Geological Survey. His research interests include seismic anisotropy and multicomponent seismology.  相似文献   

Seismic signature of a phreatic explosion: hydrofracturing damage at Karthala volcano, Grande Comore Island, Indian Ocean     

Cécile Savin  Jean-Robert Grasso  Patrick Bachelery 《Bulletin of Volcanology》2005,67(8):717-731

Karthala volcano is a basaltic shield volcano with an active hydrothermal system that forms the southern two-thirds of the Grande Comore Island, off the east coat of Africa, northwest of Madagascar. Since the start of volcano monitoring by the local volcano observatory in 1988, the July 11th, 1991 phreatic eruption was the first volcanic event seismically recorded on this volcano, and a rare example of a monitored basaltic shield. From 1991 to 1995 the VT locations, 0.5<M_l<4.3, show a crack shaped pattern (3 km long, 1 km wide) within the summit caldera extending at depth from –2 km to +2 km relative to sea level. This N-S elongated pattern coincides with the direction of the regional maximum horizontal stress as deduced from regional focal mechanism solutions. This brittle signature of the damage associated with the 1991 phreatic eruption is a typical pattern of the seismicity induced by controlled fluid injections such as those applied at geothermal fields, in oil and gas recovery, or for stress measurements. It suggests the 1991 phreatic eruption was driven by hydraulic fracturing induced by forced fluid flow. We propose that the extremely high LP and VT seismicity rates, relative to other effusive volcanoes, during the climax of the 1991 phreatic explosion, are due to the activation of the whole hydrothermal system, as roughly sized by the distribution of VT hypocenters. The seismicity rate in 1995 was still higher than the pre-eruption seismicity rate, and disagrees with the time pattern of thermo-elastic stress readjustment induced by single magma intrusions at basaltic volcanoes. We propose that it corresponds to the still ongoing relaxation of pressure heterogeneity within the hydrothermal system as suggested by the few LP events that still occurred in 1995.Editorial responsibility: H Shinohara  相似文献   

Interevent Time Distribution in Seismicity: A Theoretical Approach     

G. Molchan 《Pure and Applied Geophysics》2005,162(6-7):1135-1150

This paper presents an analysis of the distribution of the time τ between two consecutive events in a stationary point process. The study is motivated by the discovery of unified scaling laws for τ for the case of seismic events. We demonstrate that these laws cannot exist simultaneously in a seismogenic area. Under very natural assumptions we show that if, after rescaling to ensure Eτ =1, the interevent time has a universal distribution F, then F must be exponential. In other words, Corral’s unified scaling law cannot exist in the whole range of time. In the framework of a general cluster model we discuss the parameterization of an empirical unified law and the physical meaning of the parameters involved. An erratum to this article is available at .  相似文献   

Tectonic interpretation of aftershock relocations in eastern Papua New Guinea using teleseismic data and the arrival pattern method   总被引：1，自引：0，他引：1  

P. Tregoning  M. Sambridge  H. McQueen  S. Toulmin  T. Nicholson 《Geophysical Journal International》2005,160(3):1103-1111

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Comment on 'On sensitivity kernels for 'wave-equation' transmission tomography' by de Hoop and van der Hilst     

F. A. Dahlen  Guust Nolet 《Geophysical Journal International》2005,163(3):949-951

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Cenozoic bottom current sedimentation in the Cape basin, South Atlantic   总被引：1，自引：0，他引：1  

Etienne Wildeboer Schut  Gabriele Uenzelmann-Neben 《Geophysical Journal International》2005,161(2):325-333

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Linearized 2.5-dimensional parameter imaging inversion in anisotropic elastic media     

Stig-Kyrre Foss  Maarten V. de Hoop  Bjørn Ursin 《Geophysical Journal International》2005,161(3):722-738

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Adaptation of seismic skeletonization for other geoscience applications     

K. Vasudevan  D. Eaton  F. A. Cook 《Geophysical Journal International》2005,162(3):975-993

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A review on advances in seismology in Mexico after 30 years from the 1985 earthquake     

《Journal of South American Earth Sciences》2016

The 19 September 1985 (M_w8.1) earthquake, located on the Michoacán coast, Mexico, generated great damage in Mexico City, more than 300 km away from the epicentral area. Other important cities near the coast and in central Mexico also suffered severe damage. Thirty years after this important event, the National Autonomous University of Mexico (UNAM), the Centro de Investigación Científica y de Educación Superior de Ensenada, Baja California (CICESE) and other institutions organized a conference to discuss the scientific advances, particularly in seismology, that had taken place in Mexico since then.  相似文献