Dependence of the energy released during earthquake on ambient shear stress   总被引：1，自引：0，他引：1  

Pei-Shan Chen  Seweryn J. Duda 《地震学报(英文版)》1993,6(3):593-600

Starting with dislocation model, using the result of the fracture mechanics: the slip displacement at the crack tip is proportional to the length of the crack and the applied ambient shear stressτ ₀ ² , we consider the dislocation in the earthquake to be the slip displacement at the crack tip and have obtained the analysis expresses of displacement and velocity pulse for the circular crack and have calculated the seismic wave energy radiated by earthquake. The seismic wave energyE ∞M ₀ τ ₀ ² f(v) _r , i. e.E is proportional to the seismic momentM ₀ and the square of the ambient shear stressτ ₀ ² and increases with the rupture velocityv _r . In frequency domain, integrating the square of source velocity spectrum derived from our the scaling law model, we have also obtained the seismic wave energyE released by earthquake and earthquake radiated effficiencyη.E ∞M ₀ τ ₀ ² also. If takingτ ₀ = 10.0 MPa, E=4.79M ₀. This result is consistent with the estimate by Vassiliou and Kanamori (1982). Theη=5.26%. The distribution of the seismic wave energy is that most of the energy contains in the frequency range between the first corner frequencyf _c1 and thirdf _c3, amount to 92.3% the energy in the rangef<f _c1 is about 3.85% and 3.85% whenf>f _c3. Thef _c3 is about 8Hz forM ⩾ 6, thus most of radiated energy is below 2Hz. This phenomenon had been verified by Vassiliou Kanamori. Previous results show the energy radiated by earthquake to be strongly dependent on ambient shear stress. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 146–152, 1993. This work was supported by the Deutsche Forschungsgemeinschaft, Bonn, F. R. Germany. The support is grateful acknowledged. The authors are also grateful to Professor Klussmann and Mr. Hasthoff for their lots of help.  相似文献   

Foreword     

Seweryn J. Duda 《Tectonophysics》1982,84(1):VII-VIII

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A statistical study of earthquake occurrence     

James A. Powell  Seweryn J. Duda 《Pure and Applied Geophysics》1975,113(1):447-460

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Discussion of the Features of Synthetic Amplitude-Distance Curves of Teleseismic P Waves for Global Earth Models     

Janský  J.  Kvasnička  M.  Duda  S.J. 《Studia Geophysica et Geodaetica》1997,41(2):130-148

The reason why the synthetic amplitude distance curves of P-waves for models IASP91 and PREM, observed for shallow sources up to epicentral distance of 28°, oscillate is illustrated by means of synthetic seismograms. Furthermore the position of the beginning of the diffraction of the P-wave at the CMB, depending on the prevailing signal period, is discussed in connection with the extension of Fresnel volumes.  相似文献   

Spectral P-wave magnitudes, Aki's ω-square model and source parameters of earthquakes     

Dipankar Sarkar  Seweryn J. Duda   《Tectonophysics》1985,118(3-4)

The earthquake magnitude is a quantity sampling the spectrum of the far-field radiation.With a suit of properly defined magnitudes in a sufficiently broad range of frequencies, the radiated spectrum can be restored and analyzed.A method is proposed for the extraction of stress drop, fault length and seismic moment from magnitudes on a routine basis. Thereby, the theoretical spectrum as predicted by the ω-square model of Aki is utilized.In applying the method to earthquakes which occurred in several parts of Asia over a time-span of 3 years, it is shown that in most cases earthquakes in a given region are characterized by the same stress drop, varying however from region to region. In one region a change of the stress drop with time is found, eventually indicating a change in the state of stress in the particular region during the time interval investigated.  相似文献   

Internal solitons in the northeastern south China Sea. Part I: sources and deep water propagation   总被引：11，自引：0，他引：11  

Ramp  S.R. Tswen Yung Tang Duda  T.F. Lynch  J.F. Liu  A.K. Ching-Sang Chiu Bahr  F.L. Hyoung-Rok Kim Yang  Y.-J. 《Oceanic Engineering, IEEE Journal of》2004,29(4):1157-1181

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P. E. Hart  R. O. Duda  M. T. Einaudi 《Mathematical Geology》1978,10(5):589-610

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Till kinematics in the Stargard drumlin field,NW Poland constrained by microstructural proxies     

Piotr Hermanowski  Jan A. Piotrowski  Piotr Duda 《第四纪科学杂志》2020,35(7):920-934

Deciphering the relationships between streamlined subglacial landforms and deposits therein helps to constrain the dynamics of past ice sheets. Here we present microstructural analyses of till from the largest drumlin field in the North European Lowland generated by a major palaeo-ice stream of the Scandinavian Ice Sheet. Data derived from thin sections and X-ray microtomography (μCT) reveal multiple microstructures including microshears, circular structures, grain stacks and crushed grains. Long axes of micro-clasts measured in thin sections are directionally clustered and have low, down-ice-oriented dip angles. Some samples reveal subordinate clustering oriented at high angles to the main direction. The μCT data show low clustering strengths of clasts and no systematic fabric pattern in the entire set of samples. There is no correspondence between the clast orientations and the directions of drumlin long axes, suggesting that the till is antecedent in relation to the drumlin-shaping process. The observations indicate spatially and temporally variable, shallow-seated brittle and ductile deformation controlled by porewater pressure fluctuations and generated time-transgressively parallel to till accretion. Consistently with previous studies, the data suggest that the Stargard drumlins are erosional remnants of a pre-existing terrain shaped by material removal from the inter-drumlin areas.  相似文献   

Acoustic mode coupling by nonlinear internal wave packets in a shelfbreak front area     

Duda  T.F. 《Oceanic Engineering, IEEE Journal of》2004,29(1):118-125

A computational case study of coupled-mode 400-Hz acoustic propagation over the distance 27 km on the continental shelf is presented. The mode coupling reported here is caused by lateral gradients of sound-speed within packets of nonlinear internal waves, often referred to as solitary wave packets. In a waveguide having unequal attenuation of modes, directional exchange of energy between low- and high-loss modes, via mode coupling, can become time dependent by the movement of waves and can cause temporally variable loss of acoustic energy into the bottom. Here, that bottom interaction effect is shown to be sensitive to stratification conditions, which determine waveguide properties and, in turn, determine modal attenuation coefficients. In particular, time-dependent energy loss due to the presence of moving internal wave packets is compared for waveguides with and without a frontal feature similar to that found at the shelfbreak south of New England. The mean and variability of acoustic energy level 27 km distant from a source are shown to be altered in a first order way by the presence of the frontal feature. The effects of the front are also shown to be functions of source depth.  相似文献   

Validation of genetic algorithm-based optimal sampling for ocean data assimilation     

Kevin D. Heaney  Pierre F. J. Lermusiaux  Timothy F. Duda  Patrick J. Haley 《Ocean Dynamics》2016,66(10):1209-1229

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