A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used ...A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibra- tion graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is dis- cussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P(Q)-S curve.展开更多
At a sampling rate of 100 samples per second,the YRY-4 four-gauge borehole strainmeters（FGBS） are capable of recording transient strains caused by seismic waves such as P and S waves or strain seismograms. At such a...At a sampling rate of 100 samples per second,the YRY-4 four-gauge borehole strainmeters（FGBS） are capable of recording transient strains caused by seismic waves such as P and S waves or strain seismograms. At such a high sampling rate, data from the YRY-4 strainmeters demonstrate fairly satisfactory self-consistency. The strain tensor seismograms demonstrate the senses of motion of P waves, that is, the type of seismic wave travels in the direction of the maximum normal strain change. The observed strain patterns of S waves significantly differ from those of P waves and should contain information about the source mechanism. Spectrum analysis shows that the strain seismograms are consistent with conventional broadband seismograms from the same site.展开更多
The present paper contributes in studying the phase velocities of P- and S-waves in a half space subjected to a compressive initial stress and gravity field. The density and acceleration due to gravity vary quadratica...The present paper contributes in studying the phase velocities of P- and S-waves in a half space subjected to a compressive initial stress and gravity field. The density and acceleration due to gravity vary quadratically along the depth. The dispersion equation is derived in a closed form. It is shown that the phase velocities depend not only on the initial stress, gravity, and direction of propagation but also on the inhomogeneity parameter associated with the density and acceleration due to gravity. Various particular cases are obtained, and the results match with the classical results. Numerical investigations on the phase velocities of P- and S-waves against the wave number are made for various sets of values of the material parameters, and the results are illustrated graphically. The graphical user interface model is developed to generalize the effect.展开更多
West Java in the western part of the Sunda Arc has a relatively high seismicity due to subduction activity and faults.In this study,double-difference tomography was used to obtain the 3D velocity tomograms of P and S ...West Java in the western part of the Sunda Arc has a relatively high seismicity due to subduction activity and faults.In this study,double-difference tomography was used to obtain the 3D velocity tomograms of P and S waves beneath the western part of Java.To infer the geometry of the structure beneath the study area,precise earthquake hypo・center determination was first performed before tomographic imaging.For this,earthquake waveform data were extracted from the regional Meteorological,Climatological,Geophysical Agency(BMKG)network of Indonesia from South Sumatra to Central Java.The P and S arrival times for about 1,000 events in the period April 2009 to July 2016 were selected,the key features being events of magnitude>3,azimuthal gap<210°and number of phases>8.A nonlinear method using the oct-tree sampling algorithm from the NonLinLoc program was employed to determine the earthquake hypocenters.The hypocenter locations were then relocated using double-difference tomography(tomoDD).A significant reduction of travel-time(root mean square basis)and a better clustering of earthquakes were achieved which correlated well with the geological structure in West Java.Double-difference tomography was found to give a clear velocity structure,especially beneath the volcanic arc area,i.e.,under Mt Anak Krakatau,Mt Salak and the mountains complex in the southern part of West Java.Low velocity anomalies for the P and S waves as well as the vp/vs ratio below the volcanoes indicated possible partial melting of the upper mantle which ascended from the subducted slab beneath the volcanic arc.展开更多
As most rocks are of an anisotropic nature, the measurement elastic modulus of anistropic rocks is of general interest. Nevertheless, uniaxial compression test is common method to measure the dynamic elastic constants...As most rocks are of an anisotropic nature, the measurement elastic modulus of anistropic rocks is of general interest. Nevertheless, uniaxial compression test is common method to measure the dynamic elastic constants of anisotropic rocks;the use of ultrasonic pulse test is attractive, because the test is non-destructive and easy to apply. This study aimed to demonstrate the influence of orientation of foliation planes of banded amphibolite rocks on the compressional (Vp), shear wave (Vs) velocities propagating and elastic modules using ultrasonic pulse test. The result showed that the planes of foliation have a major effect on the wave velocity, where the Vp and Vs were taken parallel to the foliation plane show higher values than those obtained in the other directions (β = 30。, 60。 and 90。). The preliminary conclusions are developed concerning that the elastic modulus is vary continuously as a function of cleavage orientation with respect to the direction of wave propagations, where Poisson’s ratio having the smallest relative change. The highest values of Young’s modulus and shear modulus are observed for foliation dip angles of 0? and the lowest values are for foliation dip angles of 90。. This indicates that the observed intrinsic anisotropy and the close relations of the directional dependent seismic anisotropy to the foliation planes are mainly a result of crystallographic preferred orientation of major minerals (e.g. horn- blende and elongated quarts grains).展开更多
In marine seismic exploration, ocean-bottom cable techniques accurately record the multicomponent seismic wavefield; however, the seismic wave propagation in fluid–solid media cannot be simulated by a single wave equ...In marine seismic exploration, ocean-bottom cable techniques accurately record the multicomponent seismic wavefield; however, the seismic wave propagation in fluid–solid media cannot be simulated by a single wave equation. In addition, when the seabed interface is irregular, traditional finite-difference schemes cannot simulate the seismic wave propagation across the irregular seabed interface. Therefore, an acoustic–elastic forward modeling and vector-based P-and S-wave separation method is proposed. In this method, we divide the fluid–solid elastic media with irregular interface into orthogonal grids and map the irregular interface in the Cartesian coordinates system into a horizontal interface in the curvilinear coordinates system of the computational domain using coordinates transformation. The acoustic and elastic wave equations in the curvilinear coordinates system are applied to the fluid and solid medium, respectively. At the irregular interface, the two equations are combined into an acoustic–elastic equation in the curvilinear coordinates system. We next introduce a full staggered-grid scheme to improve the stability of the numerical simulation. Thus, separate P-and S-wave equations in the curvilinear coordinates system are derived to realize the P-and S-wave separation method.展开更多
Joint PP–PS inversion offers better accuracy and resolution than conventional P-wave inversion. P-and S-wave elastic moduli determined through data inversions are key parameters for reservoir evaluation and fluid cha...Joint PP–PS inversion offers better accuracy and resolution than conventional P-wave inversion. P-and S-wave elastic moduli determined through data inversions are key parameters for reservoir evaluation and fluid characterization. In this paper, starting with the exact Zoeppritz equation that relates P-and S-wave moduli, a coefficient that describes the reflections of P-and converted waves is established. This method effectively avoids error introduced by approximations or indirect calculations, thus improving the accuracy of the inversion results. Considering that the inversion problem is ill-posed and that the forward operator is nonlinear, prior constraints on the model parameters and modified low-frequency constraints are also introduced to the objective function to make the problem more tractable. This modified objective function is solved over many iterations to continuously optimize the background values of the velocity ratio, which increases the stability of the inversion process. Tests of various models show that the method effectively improves the accuracy and stability of extracting P and S-wave moduli from underdetermined data. This method can be applied to provide inferences for reservoir exploration and fluid extraction.展开更多
From the near-field records of aftershock of Datong earthquakes in October 1989 and March 1991,an extra phase between P and S arrivals is found. High-precision epicenter location shows that some of these records are o...From the near-field records of aftershock of Datong earthquakes in October 1989 and March 1991,an extra phase between P and S arrivals is found. High-precision epicenter location shows that some of these records are obtained with the incidental angle less than the critical angle. This excludes the possibility that the extra wave phase is a refractive wave from ground surface. Particle motion analysis shows that the characteristic of the extra wave is similar to that of wave, so it is possible that the extra phase is an S to P convert wave from the bottom of sediment basin. Suppose a low velocity layer covers a high velocity basement. Successful simulation by the synthetic seismogram confirms that the extra phase is an S-P convert wave from the interface of the basin bottom. Modifying the depth of interface at each ray path to match the waveform, we obtain an interface distribution in space. In this way, a brief bottom image could be shown, and the Datong basin has a 'V' shaped bottom.展开更多
In this paper, based on the propagation theorics of seismic waves in anisotropic medium and in cracked two-phase medium, the constitutive relations and dynamic equations of the propagation of seismic waves in Cracked ...In this paper, based on the propagation theorics of seismic waves in anisotropic medium and in cracked two-phase medium, the constitutive relations and dynamic equations of the propagation of seismic waves in Cracked twophase anisotropic medium with fourfold rotation symmetry have been derived, and the preliminary theoretical analysis have been made for plane wave as an example.展开更多
In order to understand the site soil response of the Xiangtang borehole seismic array under real strong ground motion, reveal the site response, verify the technique of borehole exploration, and improve the precision ...In order to understand the site soil response of the Xiangtang borehole seismic array under real strong ground motion, reveal the site response, verify the technique of borehole exploration, and improve the precision of in-situ test and laboratory test, this paper presents a new approach, which is composed of two methods. One is the layered site seismic response method, whose layer transform matrix is always real. The other is a global-local optimization technique, which uses genetic algorithm （GA）-simplex method. An inversion of multi-component waveforms of P, SV and SH wave is carried out simultaneously. By inverting the records of three moderate and small earthquakes obtained from the Xiangtang borehole array （2^#） site, the soil dynamic characteristic parameters, including P velocity, damping ratio and frequency-dependent coefficient b, which has not been given in previous literatures, are calculated. The results show that the soil S wave velocity of the Xiangtang 2^# borehole is generally greater than that obtained from the 1994 in-situ test, and is close to the velocity of the 3^# borehole, which is more than 200 m away from the 2^# borehole. Meanwhile, perceptible soil nonlinear behavior under peak ground motion of about 60×10^-2 m/s^2 is detected by the inversion analysis. The presented method can be used for studying the soil response of other borehole array sites.展开更多
We analyzed digital seismogram data of 5668 earthquakes that occurred in Yunnan region between July of 1999 and December of 2003. Among the 22 seismic stations, six ones, namely Baoshan, Yongsheng, Lijiang, Heqing, Yi...We analyzed digital seismogram data of 5668 earthquakes that occurred in Yunnan region between July of 1999 and December of 2003. Among the 22 seismic stations, six ones, namely Baoshan, Yongsheng, Lijiang, Heqing, Yimen, and Luquan, were selected and their attenuations of P and S waves were measured by using the extended coda-normalization method. The six stations were classified into three regions according to their location, that is, Baoshan area, Yongsheng-Lijiang-Heqing (YLH) area and Luquan-Yimen (LY) area. The values of QS-1 and QP-1 are expressed as QS-1=0.00867 f-0.86, QP-1=0.01155 f-0.93, QS-1=0.01824 f-0.92, QP-1=0.02288 f-0.92, and QS-1=0.01647 f-0.91, QP-1=0.02826 f-0.97 in Baoshan, YLH, LY areas respectively. The attenuation of YLH, LY are closer to each other, however, Baoshan area is apparently lower. Comparing attenuation in the three areas with other areas of the world using the same method, it is suggested that the attenuations of P and S waves in YLH and LY areas are close to Kanto of Japan, but much higher than southeast of South Korea. The QS-1 and QP-1 in Baoshan area are slightly higher than southeastern South Korea. Furthermore, the results indicate that our QS-1 in Yunnan area is close to others by analyzing the coda attenuation.展开更多
We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersi...We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersion data. Thickness and S\|wave velocity of each sub layer are taken from Love wave dispersion data, then P\|wave velocity structure was deduced using Rayleigh wave dispersion data. Densities of sub layers were estimated by the empirical relationships between seismic velocity and rock density. Having S\| and P\|wave velocities, v p/ v s ratio is calculated for each sub layer. Six sub layers in crust of Tibetan Plateau has been identified, which are 0～8km, 8～30km, 30～40km, 40～62km, 62～68km and 68～75km respectively. The S\|wave velocity structure of the Plateau is 3 13, 3 32, 3 15, 3 92, 3 45 and 3 87 km/s for each sub layer; and P\|wave velocities are 6 00, 6 10, 5 72, 6 35, 6 78 and 6 64km/s respectively v p/ v s ratios in sub layers are 1 92, 1 84, 1 82, 1 62, 1 96 and 1 72; and corresponding Poisson ratios are 0 31, 0 29, 0 28, 0 19, 0 32 and 0 24. Our result on Poisson ratios of Tibetan crust was supported by seismic waveform modelling by Rodgers and Schwartz (1998).展开更多
文摘A new method of detecting the vertical bearing capacity for single-pile with high strain is discussed in this paper. A heavy hammer or a small type of rocket is used to strike the pile top and the detectors are used to record vibra- tion graphs. An expression of higher degree of strain (deformation force) is introduced. It is testified theoretically that the displacement, velocity and acceleration cannot be obtained by simple integral acceleration and differential velocity when long displacement and high strain exist, namely when the pile phase generates a whole slip relative to the soil body. That is to say that there are non-linear relations between them. It is educed accordingly that the force P and displacement S are calculated from the amplitude of wave train and (dynamic) P-S curve is drew so as to determine the yield points. Further, a method of determining the vertical bearing capacity for single-pile is dis- cussed. A static load test is utilized to check the result of dynamic test and determine the correlative constants of dynamic-static P(Q)-S curve.
基金supported by the Special Fund for Earthquake Research in the Public Interest(No.201108009)
文摘At a sampling rate of 100 samples per second,the YRY-4 four-gauge borehole strainmeters（FGBS） are capable of recording transient strains caused by seismic waves such as P and S waves or strain seismograms. At such a high sampling rate, data from the YRY-4 strainmeters demonstrate fairly satisfactory self-consistency. The strain tensor seismograms demonstrate the senses of motion of P waves, that is, the type of seismic wave travels in the direction of the maximum normal strain change. The observed strain patterns of S waves significantly differ from those of P waves and should contain information about the source mechanism. Spectrum analysis shows that the strain seismograms are consistent with conventional broadband seismograms from the same site.
基金supported by the Research Fellow of Indian School of Mines in Dhanbad (No. 2010DR0016)
文摘The present paper contributes in studying the phase velocities of P- and S-waves in a half space subjected to a compressive initial stress and gravity field. The density and acceleration due to gravity vary quadratically along the depth. The dispersion equation is derived in a closed form. It is shown that the phase velocities depend not only on the initial stress, gravity, and direction of propagation but also on the inhomogeneity parameter associated with the density and acceleration due to gravity. Various particular cases are obtained, and the results match with the classical results. Numerical investigations on the phase velocities of P- and S-waves against the wave number are made for various sets of values of the material parameters, and the results are illustrated graphically. The graphical user interface model is developed to generalize the effect.
基金the Directorate General of Resources for Science Technologythe Higher Education of the Republic of Indonesia for granting a PMDSU scholarship to SR
文摘West Java in the western part of the Sunda Arc has a relatively high seismicity due to subduction activity and faults.In this study,double-difference tomography was used to obtain the 3D velocity tomograms of P and S waves beneath the western part of Java.To infer the geometry of the structure beneath the study area,precise earthquake hypo・center determination was first performed before tomographic imaging.For this,earthquake waveform data were extracted from the regional Meteorological,Climatological,Geophysical Agency(BMKG)network of Indonesia from South Sumatra to Central Java.The P and S arrival times for about 1,000 events in the period April 2009 to July 2016 were selected,the key features being events of magnitude>3,azimuthal gap<210°and number of phases>8.A nonlinear method using the oct-tree sampling algorithm from the NonLinLoc program was employed to determine the earthquake hypocenters.The hypocenter locations were then relocated using double-difference tomography(tomoDD).A significant reduction of travel-time(root mean square basis)and a better clustering of earthquakes were achieved which correlated well with the geological structure in West Java.Double-difference tomography was found to give a clear velocity structure,especially beneath the volcanic arc area,i.e.,under Mt Anak Krakatau,Mt Salak and the mountains complex in the southern part of West Java.Low velocity anomalies for the P and S waves as well as the vp/vs ratio below the volcanoes indicated possible partial melting of the upper mantle which ascended from the subducted slab beneath the volcanic arc.
文摘As most rocks are of an anisotropic nature, the measurement elastic modulus of anistropic rocks is of general interest. Nevertheless, uniaxial compression test is common method to measure the dynamic elastic constants of anisotropic rocks;the use of ultrasonic pulse test is attractive, because the test is non-destructive and easy to apply. This study aimed to demonstrate the influence of orientation of foliation planes of banded amphibolite rocks on the compressional (Vp), shear wave (Vs) velocities propagating and elastic modules using ultrasonic pulse test. The result showed that the planes of foliation have a major effect on the wave velocity, where the Vp and Vs were taken parallel to the foliation plane show higher values than those obtained in the other directions (β = 30。, 60。 and 90。). The preliminary conclusions are developed concerning that the elastic modulus is vary continuously as a function of cleavage orientation with respect to the direction of wave propagations, where Poisson’s ratio having the smallest relative change. The highest values of Young’s modulus and shear modulus are observed for foliation dip angles of 0? and the lowest values are for foliation dip angles of 90。. This indicates that the observed intrinsic anisotropy and the close relations of the directional dependent seismic anisotropy to the foliation planes are mainly a result of crystallographic preferred orientation of major minerals (e.g. horn- blende and elongated quarts grains).
基金financially supported by the Natural Science Foundation of China(No.41774133)the Open Funds of SINOPEC Key Laboratory of Geophysics(No.wtyjy-wx2017-01-04)National Science and Technology Major Project of the Ministry of Science and Technology of China(No.2016ZX05024-003-011)
文摘In marine seismic exploration, ocean-bottom cable techniques accurately record the multicomponent seismic wavefield; however, the seismic wave propagation in fluid–solid media cannot be simulated by a single wave equation. In addition, when the seabed interface is irregular, traditional finite-difference schemes cannot simulate the seismic wave propagation across the irregular seabed interface. Therefore, an acoustic–elastic forward modeling and vector-based P-and S-wave separation method is proposed. In this method, we divide the fluid–solid elastic media with irregular interface into orthogonal grids and map the irregular interface in the Cartesian coordinates system into a horizontal interface in the curvilinear coordinates system of the computational domain using coordinates transformation. The acoustic and elastic wave equations in the curvilinear coordinates system are applied to the fluid and solid medium, respectively. At the irregular interface, the two equations are combined into an acoustic–elastic equation in the curvilinear coordinates system. We next introduce a full staggered-grid scheme to improve the stability of the numerical simulation. Thus, separate P-and S-wave equations in the curvilinear coordinates system are derived to realize the P-and S-wave separation method.
基金supported by the National Science and Technology Major Project(No.2016ZX05047-002-001)
文摘Joint PP–PS inversion offers better accuracy and resolution than conventional P-wave inversion. P-and S-wave elastic moduli determined through data inversions are key parameters for reservoir evaluation and fluid characterization. In this paper, starting with the exact Zoeppritz equation that relates P-and S-wave moduli, a coefficient that describes the reflections of P-and converted waves is established. This method effectively avoids error introduced by approximations or indirect calculations, thus improving the accuracy of the inversion results. Considering that the inversion problem is ill-posed and that the forward operator is nonlinear, prior constraints on the model parameters and modified low-frequency constraints are also introduced to the objective function to make the problem more tractable. This modified objective function is solved over many iterations to continuously optimize the background values of the velocity ratio, which increases the stability of the inversion process. Tests of various models show that the method effectively improves the accuracy and stability of extracting P and S-wave moduli from underdetermined data. This method can be applied to provide inferences for reservoir exploration and fluid extraction.
基金State Key Basic Research Development and Programming Project (95-13-05-02) the Federal Institute for Geosciences and Natural Resources, Germany.
文摘From the near-field records of aftershock of Datong earthquakes in October 1989 and March 1991,an extra phase between P and S arrivals is found. High-precision epicenter location shows that some of these records are obtained with the incidental angle less than the critical angle. This excludes the possibility that the extra wave phase is a refractive wave from ground surface. Particle motion analysis shows that the characteristic of the extra wave is similar to that of wave, so it is possible that the extra phase is an S to P convert wave from the bottom of sediment basin. Suppose a low velocity layer covers a high velocity basement. Successful simulation by the synthetic seismogram confirms that the extra phase is an S-P convert wave from the interface of the basin bottom. Modifying the depth of interface at each ray path to match the waveform, we obtain an interface distribution in space. In this way, a brief bottom image could be shown, and the Datong basin has a 'V' shaped bottom.
文摘In this paper, based on the propagation theorics of seismic waves in anisotropic medium and in cracked two-phase medium, the constitutive relations and dynamic equations of the propagation of seismic waves in Cracked twophase anisotropic medium with fourfold rotation symmetry have been derived, and the preliminary theoretical analysis have been made for plane wave as an example.
基金Joint Seismological Science Foundation of China (604036 and 105034)
文摘In order to understand the site soil response of the Xiangtang borehole seismic array under real strong ground motion, reveal the site response, verify the technique of borehole exploration, and improve the precision of in-situ test and laboratory test, this paper presents a new approach, which is composed of two methods. One is the layered site seismic response method, whose layer transform matrix is always real. The other is a global-local optimization technique, which uses genetic algorithm （GA）-simplex method. An inversion of multi-component waveforms of P, SV and SH wave is carried out simultaneously. By inverting the records of three moderate and small earthquakes obtained from the Xiangtang borehole array （2^#） site, the soil dynamic characteristic parameters, including P velocity, damping ratio and frequency-dependent coefficient b, which has not been given in previous literatures, are calculated. The results show that the soil S wave velocity of the Xiangtang 2^# borehole is generally greater than that obtained from the 1994 in-situ test, and is close to the velocity of the 3^# borehole, which is more than 200 m away from the 2^# borehole. Meanwhile, perceptible soil nonlinear behavior under peak ground motion of about 60×10^-2 m/s^2 is detected by the inversion analysis. The presented method can be used for studying the soil response of other borehole array sites.
基金The specialized fund for pre-study of national key basic study (2002CCD01700)national key project of science and technology from China Ministry of Science and Technology during the 10th Five-year Plan (2004BA601B01-04-03)
文摘We analyzed digital seismogram data of 5668 earthquakes that occurred in Yunnan region between July of 1999 and December of 2003. Among the 22 seismic stations, six ones, namely Baoshan, Yongsheng, Lijiang, Heqing, Yimen, and Luquan, were selected and their attenuations of P and S waves were measured by using the extended coda-normalization method. The six stations were classified into three regions according to their location, that is, Baoshan area, Yongsheng-Lijiang-Heqing (YLH) area and Luquan-Yimen (LY) area. The values of QS-1 and QP-1 are expressed as QS-1=0.00867 f-0.86, QP-1=0.01155 f-0.93, QS-1=0.01824 f-0.92, QP-1=0.02288 f-0.92, and QS-1=0.01647 f-0.91, QP-1=0.02826 f-0.97 in Baoshan, YLH, LY areas respectively. The attenuation of YLH, LY are closer to each other, however, Baoshan area is apparently lower. Comparing attenuation in the three areas with other areas of the world using the same method, it is suggested that the attenuations of P and S waves in YLH and LY areas are close to Kanto of Japan, but much higher than southeast of South Korea. The QS-1 and QP-1 in Baoshan area are slightly higher than southeastern South Korea. Furthermore, the results indicate that our QS-1 in Yunnan area is close to others by analyzing the coda attenuation.
文摘We estimated crustal v p/ v s ratio of Tibetan Plateau by combined inversion of Love and Rayleigh wave dispersion data. It is developed by us that the joint inversion methods using both Love and Rayleigh wave dispersion data. Thickness and S\|wave velocity of each sub layer are taken from Love wave dispersion data, then P\|wave velocity structure was deduced using Rayleigh wave dispersion data. Densities of sub layers were estimated by the empirical relationships between seismic velocity and rock density. Having S\| and P\|wave velocities, v p/ v s ratio is calculated for each sub layer. Six sub layers in crust of Tibetan Plateau has been identified, which are 0～8km, 8～30km, 30～40km, 40～62km, 62～68km and 68～75km respectively. The S\|wave velocity structure of the Plateau is 3 13, 3 32, 3 15, 3 92, 3 45 and 3 87 km/s for each sub layer; and P\|wave velocities are 6 00, 6 10, 5 72, 6 35, 6 78 and 6 64km/s respectively v p/ v s ratios in sub layers are 1 92, 1 84, 1 82, 1 62, 1 96 and 1 72; and corresponding Poisson ratios are 0 31, 0 29, 0 28, 0 19, 0 32 and 0 24. Our result on Poisson ratios of Tibetan crust was supported by seismic waveform modelling by Rodgers and Schwartz (1998).
