Joint inversion of P-wave velocity and Vp–Vs ratio: imaging the deep structure in NE Japan

A new inversion scheme is presented to obtain three-dimensional images of P-wave velocity（Vp） and P–S-wave velocity ratio（Vp/Vs） using P- and S-phase pairs, i.e., the same source–receiver pairs for the P- and S-wave arrival-time data. The S-wave velocity（Vs） was separately inverted using the S-phase arrival times. The earthquake hypocenters were simultaneously relocated in the joint inversion. The method considers the Vp/Vs anomaly as a model parameter in the inversion. The proposed method thus provides a more robust calculation of the Vp/Vs anomaly than the conventional method of dividing Vp by Vs. The method also takes into account the ray path difference between P- and S-waves, and hence yields a less biased Vp–Vs ratio than the method of inverting S–P-wave data for Vp and Vp/Vs anomalies under the assumption of identical P and S ray paths. The proposed method was used to image the crust and upper mantle in northeastern（NE） Japan taking advantage of a large number of high-quality arrival times of P- and S-wave source–receiver pairs. The inverted structures suggest that the subducting slab of the Pacific plate is an inclined zone of high-Vp and Vs anomalies with low Vp/Vs perturbation. The mantle wedge is characterized by low-Vp, low-Vs, and high-Vp/Vs anomalies at shallow depths beneath active volcanoes. These features are also observed at greater depths in the back-arc region. Although these features have been previously reported, the Vp/Vs anomaly pattern obtained in this study shows much less scatter and is much better correlated with the seismic velocity perturbation patterns than previous studies. The proposed method can be used, in conjunction with velocity anomaly patterns, to quantify thermal processes associated with plate subduction.

Phase velocity in 2D TTI media

We derive an expression for phase velocity in 2D tilted transverse isotropy （TTI） media. Snapshots of phase velocity in TTI and transverse isotropy （TI） model media are simulated and analyzed using the derived expression. In addition, the x-component character differences between the modeled phase velocities of the two media models are compared and analyzed.

Application of four-component dipole shear reflection imaging to interpret the geological structure around a deviated well

Acoustic reflection imaging in deep water wells is a new application scope for offshore hydrocarbon exploration.Two-dimensional(2 D)geological structure images can be obtained away from a one-dimensional(1 D)borehole using single-well acoustic reflection imaging.Based on the directivity of dipole source and four-component dipole data,one can achieve the azimuth detection and the three-dimensional(3 D)structural information around the wellbore can be obtained.We first perform matrix rotation on the field fourcomponent data.Then,a series of processing steps are applied to the rotated dipole data to obtain the reflector image.According to the above dipole shear-wave imaging principle,we used four-component cross-dipole logging data from a deviated well in the South China Sea to image geological structures within 50 m of a deviated well,which can delineate the structural configuration and determine its orientation.The configuration of near-borehole bedding boundaries and fault structures from shear-wave imaging results agrees with those from the Inline and Xline seismic profiles of the study area.In addition,the configuration and orientation of the fault structure images are consistent with regional stress maps and the results of the borehole stress anisotropy analysis.Furthermore,the dip azimuth of the bedding boundary images was determined using borehole wall resistivity data.Results of this study indicate that integrating borehole acoustic reflection with seismic imaging not only fills the gap between the two measurement scales but also accurately delineates geological structures in the borehole vicinity.

Application of joint elastic impedance inversion in the GD Oilfield

For the complicated reservoir description of the GD oilfield, P-wave and S-wave elastic impedance inversion was carried out using pre-stack seismic data to accurately identify the lithology of the reservoir. The joint inversion was performed using three or more partial stacks to overcome the singularity of post-stack seismic inversion that can not satisfy the requirements of complex reservoir description and to avoid the instability of the inversion result caused by low signal-noise ratio in the pre-stack gather. The basic theory of prestack elastic impedance inversion is briefly described in this paper and, using real data of the GD oilfield, the key steps of angle gather wavelet extraction, horizon calibration, S-wave velocity prediction, and elastic parameter extraction were analyzed and studied. The comprehensive interpretation of multiple elastic parameters determined from log analysis is a key to improving the effect ofprestack seismic inversion.

Shear-wave Splitting of Aftershocks of the M_S 5.7 Jiujiang-Ruichang Earthquake

Shear wave splitting is studied based on the digital waveforms of three seismic stations DJS, SZD and WUJ, which were set up after the Jiujiang-Ruichang MS5.7 earthquake of November 26, 2005 around the epicenter area. The result shows that the time delays of slow shear waves of the DJS station, which is not far from the epicenter and where the distribution of faults is complex near the station, are relatively larger and the polarization directions of fast shear waves are not concentrated; the predominant polarization direction of fast shear waves of WUJ station, with single fault distributed nearby, has a difference of 35° to the strike of the fault and is inconsistent with the direction of regional principal compressive stress. The predominant polarization direction of fast shear waves of SZD station with no faults nearby is in accordance with regional principal compressive stress. There is no obvious regular relationshipship between the delay time and the focal depth.

Semi-active Control with Variable Damper for Pier-Beam Transversal Vibration

In this paper, the method of semi-active control with variable damper is presented to deal with the relatively poor transversal seismic condition of bridge. Based on the LQR control algorithm the control effectiveness for transverse vibration of pier-beam structure of bridge are discussed. Taking the structure as a multiple-degree of freedom system, the calculating model of structure-variable damper system is set up and the differential equation is derived, combined with practical example the control system is simulated and studied by various semi-active control algorithms and passive strategy with MATLAB. The results show that the semi-active control with variable damper can decrease the transverse vibration effectively and the control effect is obvious.

Study of Crustal Thickness and Poisson Ratio of Hebei and Its Adjacent Areas by Teleseismic Receiver Function

We collected waveforms of a teleseismic event which occurred from January 2007 to October 2011 from 174 broadband seismic stations deployed in Hebei and its adjacent areas. Using the H-k stacking method,the average thickness and Poisson's ratio of the crust are acquired. In order to obtain reliable receiver functions, the broadband seismograms of 488 teleseismic earthquakes occurring in the epicentral distance range from 30° to 90° with magnitudes larger than Mb6. 0 are collected. The results show that crustal thickness have conspicuous lateral heterogeneity and have good correlation to the regional geological tectonic features. Poisson ratio's value is equated with the global models estimates which fluctuate at about 0. 25. Crustal thickness has positive correlation to the topography and the Taihang Mountains form the transition zone of thick and thin crustal thickness. There is an obvious difference in crustal thickness beneath the north and south of the Shanxi earthquake zone and the Poisson ratio of Datong,Ningwu and Anze basins is greater than 0. 3. The crustal thickness beneath the Zhang-Bo( Zhangjiakou-Bohai Sea)earthquake zone decreases from west to north and its Poisson ratio shows conspicuous lateral heterogeneity. The thin crust and low Poisson ratio in the Huabei( North China)basin may correlate with the delamination of the North China craton.

Method of forecasting seismic energy induced by longwall exploitation based on changes in ground subsidence

A method of forecasting total seismic energy induced by longwall exploitation, based on changes in ground subsidence, is presented in the form of a linear regression model with one with one independent variable. In the method, ground subsidence is described with a cross-section area of a subsidence trough Pw along a line of observations in the direction of an advancing longwall front, approximately along the axis of the longwall area. Total seismic energy is determined on the basis of seismic energy data of tremors induced by exploitation. The presentation consists of a detailed method and evaluation of its predictive ability for the area of longwall exploitation within the region of one of the coal mines in the Upper Silesian Coal Basin. This method can be used for forecasting the total seismic energy released by tremors within the area directly connected with the exploitation, in which the seismic activity induced by this exploitation occurs. The estimation of the parameters of the determined model should each time be carried out with investigations of the correctness of the model. The method cannot be applied when the number of recorded phenomena is small and when there is insufficient data to make it possible to calculate the index Pw.

On Shear Wave Splitting in the Zhangjiakou-Bohai Sea Seismic Belt

The Zhangjiakou-Bohai Sea seismic belt is an important seismic zone in North China. The direction of principal compressive stress is near EW in this region. According to digital seismic data from the Capital Region from September 2005 to September 2010,and using the SAM method,the spatial distribution of the crust anisotropy characteristics are studied and discussed in the middle-eastern part of the Zhangjiakou-Bohai Sea seismic belt. The principal polarization direction,which is near EW direction,is obvious in the middleeastern Zhangjiakou-Bohai Sea seismic belt. The spatial distribution of polarization direction crossing the Zhangjiakou-Bohai Sea seismic belt shows that there is little difference among the Yanshan uplift area,inside of the seismic zone and North China basin,and the principal polarization direction is near EW.

High accuracy NMO correction and application for VTI media

It is difficult for normal moveout(NMO)correction of shallow long offset of vertical transversely isotropic medium,as seismic event after conventional NMO correction experienced strong stretching and distortion due to interleaving of signal.Even using higher order non-hyperbolic NMO correction,it still cannot get the right results.This paper aims to improve the accuracy of NMO correction.Based on the analysis of conventional NMO correction method and previous optimization move-out equation,we use longitudinal optimization method to correct seismic event.The results of the theoretical model and the real data show that our method can completely remove NMO stretching and greatly improve correction accuracy.

Research on ray tracing in VTI medium based on different models

The study on seismic anisotropy is one of the difficult problems in the field of geophysics nowadays.As a method of ray theory,the seismic anisotropy ray tracing is an important means to study the anisotropic seismic wave propagation. The traditional ray tracing system formulated in terms of elastic parameters in the anisotropy is more complicated than that in the isotropic case. Considering the difficulty,a kind of ray tracing system formulated in terms of phase velocity and group velocity is introduced. The new method is similar to the expressions for isotropic media,and avoids the trouble of determining the eigenvalue vector at each time. Besides the ray tracing numerical simulation of different models of vertical transversely isotropic( VTI) medium is carried out,in order to verify the accuracy and applicability of the method and further study the characteristics of wave field propagation in different VTI mediums. The study is certainly valuable in reference for later processing of the anisotropic seismic data.

Variations of shear wave splitting in the 2013 Lushan Ms7.0 earthquake region

In this paper, variations of shear wave splitting in the 2013 Lushan Ms7.0 earthquake sequence were studied. By analyzing shear wave particle motion of local events in the shear wave window, the fast polarization directions and the delay time between fast and slow shear waves were derived from seismic recordings at eight stations on the southern segment of the Longmenshan fault zone. In the study region, the fast polarization directions show partition characteristics from south to north. And the systematic changes of the time delays between two split shear waves were also observed. As for spatial distribution, the NE fast polarization directions are consistent with the Longmenshan fault strike in the south of focal region, whereas the NW fast direction is parallel to the direction of regional principal compressive stress in the north of focal region. Stations BAX and TQU are respectively located on the Central and Front-range faults, and because of the direct influence of these faults, the fast directions at both stations show particularity. In time domain, after the main shock, the delay times at stations increased rapidly, and decreased after a period of time. Shear-wave splitting was caused mostly by stress-aligned microcracks in rock below the stations. The results demonstrate changes of local stress field during the main shock and the aftershocks. The stress on the Lushan Ms7.0 earthquake region increased after the main shock, with the stress release caused by the aftershocks and the stress reduced in the late stage.

The Goos-Hnchen shift of wide-angle seismic reflection wave

The partial derivative equations of Zoeppritz equations are established and the derivatives of each matrix entry with respect to wave vectors are derived in this paper.By solving the partial derivative equations we obtained the partial derivatives of seismic wave reflection coefficients with respect to wave vectors,and computed the Goos-Hnchen shift for reflected P-and VS-waves.By plotting the curves of Goos-Hnchen shift,we gained some new insight into the lateral shift of seismic reflection wave.The lateral shifts are very large for glancing wave or the wave of the incidence angle near the critical angle,meaning that the seismic wave propagates a long distance along the reflection interface before returning to the first medium.For the reflection waves of incidence angles away from the critical angle,the lateral shift is in the same order of magnitude as the wavelength.The lateral shift varies significantly with different reflection interfaces.For example,the reflected P-wave has a negative shift at the reflection interface between mudstone and sandstone.The reflected VS-wave has a large lateral shift at or near the critical angle.The lateral shift of the reflected VS-wave tends to be zero when the incidence angle approaches 90°.These observations suggest that Goos-Hnchen effect has a great influence on the reflection wave of wide-angles.The correction for the error caused by Goos-Hnchen effect,therefore,should be made before seismic data processing,such as the depth migration and the normal-moveout correction.With the theoretical foundation established in this paper,we can further study the correction of Goos-Hnchen effect for the reflection wave of large incidence angle.

Topology optimization of supporting structure for seismic response reduction of an arch

A flexible supporting structure that reduces seismic response of an arch is proposed. Topology and cross-sectional areas of the supporting structure modeled as a truss structure are optimized through two steps of static and dynamic optimization problems. In the first step, a flexible supporting structure that has diagonal displacement at the top under horizontal load is obtained by solving static optimization problems. Then, in the second step, the cross-sectional area of the flexible member is optimized to minimize the seismic response acceleration of the arch evaluated by the complete quadratic combination(CQC) method. Time-history seismic response analysis is carried out to show that the response in the normal direction of the roof successfully decreases due to flexibility of the supporting structure; in addition, installing passive energy dissipation devices into the flexible supporting structure is very effective in reducing the tangential response of the arch.

Fiber Optic 3-Component Seismometer

An all-metal 3-component optical fiber seismometer was proposed and experimentally demonstrated. The theoretical analysis was given based on the electro-mechanical theory. Calibration results showed that the axis sensitivity was about 41 dB （re： 0dB=1rad/g） with a fluctuation ＋2dB in the frequency bandwidth of 5 Hz - 400 Hz. A transverse sensitivity of about -40 dB was achieved. The fluctuation of the acceleration sensitivity for the three accelerometers in the seismometer was within ±2.5 dB. The minimum phase demodulation detection accuracy of the phase-generated cartier （PGC） was 10-Srad/√Hz, and the minimum detectable acceleration was calculated to be 90 ng/√Hz.

Effect of hydration on the elasticity of mantle minerals and its geophysical implications

Recent studies have shown that major nominally anhydrous minerals in the Earth's mantle, such as olivine, pyroxene and garnet, can incorporate considerable amounts of water as structurally bound hydroxyl. Even a small amount of water is present in mantle minerals, it can strongly affect a number of physical properties, including density, sound velocity, melting temperature, and electrical conductivities. The presence of water can also influence the dynamic behavior, lead to lateral velocity heterogeneities, and affect the material circulation of the Earth's deep interior. In particular, seismic studies have reported the existence of low-velocity zones in various locations of the Earth's upper mantle and transition zone, which has been expected to be associated with the presence of water in the region. In the past two decades, the effect of water on the elasticity and sound velocities of minerals at relevant pressure-temperature(P-T) conditions of the Earth's mantle attracted extensive interests. Combining the high P-T experimental and theoretical mineralogical results with seismic observations provides crucial constraints on the distribution of water in the Earth's mantle. In this study, we summarize recent experimental and theoretical mineral physics results on how water affects the elasticity and sound velocity of nominally anhydrous minerals in the Earth's mantle, which aims to provide new insights into the effect of hydration on the density and velocity profile of the Earth's mantle, which are of particular importance in understanding of water distribution in the region.

Static mechanics analysis of no bumping no vibration welding structure with double-inclined surface for high-speed & heavy-load CWR

It is known from our former theoretical analysis that the single-inclined welding surface which is inclined towards the transverse direction of the rail can only eliminate vertical bumping, and the single-inclined welding surface which is inclined towards the vertical direction of the rail can only eliminate lateral vibration. In this paper, we put forward a welding structure of double-inclined welding surface to eliminate the vertical bumping and lateral vibration at the same time, and analyze the stress state of continuous welded rail (CWR) by combining geometrical azimuth. Furthermore, the increase of bearing capacity of CWR with the double-inclined welding surface is theoretically analyzed.

如何提高私营工商业营业额营业税统计的及时性

私营工商业营业额营业税统计工作,是税务统计工作中较大而版税版税复杂的一项.一九五三年税制修订后,由于纳税环节的改变,有了各种计税与不计税的营业额,统计表的指示增多,再加以改按工商八大部分行业统计,工作更形复杂.在通去指示简单的情况下,约需一、五○○左右工作日,尚不能及时提出,而且牵扯外勤专责干部的力量,使他们每月总要抽出很多暗阴忙于进行统计,