Borehole radar velocity inversion using cokriging and cosimulation

A new radar velocity tomography method is presented based on slowness covariance modeling and cokriging of the slowness field using only measured travel time data. The proposed approach is compared to the classical LSQR algorithm using various synthetic models and a real data set. In each case, the proposed method provides comparable to or better results than LSQR. One advantage of this approach is that it is self-regularized and requires less a priori information. The covariance model also allows stochastic imaging of slowness fields by geostatistical simulations. Stable characteristics and uncertain features of the inverted models can then be easily identified.     

从剖面的视觉效果谈海上地震资料处理

视觉效果是地震资料处理质量的重要评判标准之一，本文从信号处理、聚焦质量和信噪比等三个方面对影响地震资料处理视觉效果的几个侧面进行了探讨。好的信号处理体现在剖面的子波周期数少且旁瓣幅度小，同时频率丰富、频率成分之间能量关系协调。好的聚焦质量相当于获得了地层的特写图像，其关键是合适的成像方法和对应的速度分析质量，文中探讨了速度分析的基本原则。提高信噪比的同时，要保证成像的可靠性，其关键是在噪声衰减过程中把握有效信号和噪声的平衡关系，注重去噪的针对性。     

Observation of shear zone development in ring-shear apparatus with a transparent shear box

Using a new ring-shear apparatus with a transparent shear box and video image analysis system, drained and undrained speed-controlled tests were conducted on coarse-grained silica sands to study the shear-zone formation process in granular materials. Velocity distribution profiles of grains under shear at various stages in the ring shear tests were observed through processing the video image by the Particle Image Velocimetry (PIV) program. Shear-zone thickness and type of shear mode (slide-like or flow-like) during shear were observed. Before reaching peak strength in low-speed and drained condition test, a comparatively major part of the sample in the upper shear box showed a velocity distribution profile of structural deformation and dilatancy behavior. After peak strength, the velocity profile changed into a slide-like mode and thereafter showed almost no change. In higher speed tests with drained and undrained conditions, an almost slide-like mode was observed, compared to low-speed test. Apparent shear-zone thicknesses of high-speed tests are thinner than low-speed tests. Unexpectedly, almost no difference was observed in the shear-zone thickness and mode of shear (slide or flow-like) between drained and undrained tests. This study was conducted as part of the International Programme on Landslides (IPL) M101 “Areal prediction of earthquake and rain induced rapid and long-traveling flow phenomena (APERITIF)” of the International Consortium on Landslides (ICL). These results will contribute to understanding the mechanism of shear-zone development in granular materials as a basic knowledge for disaster risk mitigation of rapid long run-out landslides.     

Microzonation of Zeytinburnu region with respect to soil amplification: A case study

A microzonation study is performed as a part of the Zeytinburnu Pilot Project within the framework of the Earthquake Master Plan for Istanbul to determine the effects of local soil conditions on the earthquake forces that will act on structures. For this purpose, detailed geological and geotechnical studies are conducted at the site, a geological map which demonstrates the local geological features of the site is prepared, and the site is classified with respect to the dynamic behaviour based on the data gathered from the soil borings. In order to investigate the effects of local soil conditions on the dynamic behaviour, site response analyses are performed with the computer code EERA by utilizing the findings of field and laboratory investigations. The behaviour of the region during a probable earthquake is investigated through one dimensional response analyses and microzonation maps are prepared with respect to ground shaking intensity in accordance with the new microzonation manual [Ansal, A., Laue, J., Buchheister, J., Erdik, M., Springman, S., Studer, J., and Koksal, D., 2004. “Site characterization and site amplification for a seismic microzonation study in Turkey” 11th Int. Conference on Soil Dynamics and Earthquake Engineering and 3rd Earthquake Geotechnical Engineering, San Francisco; Studer, J. and Ansal, A., 2004. Belediyeler için Sismik Mikrobölgeleme El Kitabı, Araştırma Raporu, Afet İşleri Genel Müdürlüğü, Bayındırlık ve İskan Bakanlığı, Afet Risk Yönetimi Dünya Enstitüsü].     

Inclusion of P–Δ effect in displacement‐based seismic design of steel moment resisting frames

A procedure for treating the P– Δ effect in the direct displacement‐based seismic design of regular steel moment resisting frames with ideal elastoplastic material behaviour is proposed. A simple formula for the yield displacement amplification factor as a function of ductility and the stability coefficient is derived on the basis of the seismic response of an inelastic single degree‐of‐freedom system taking into account the P– Δ effect. Extensive parametric seismic inelastic analyses of plane moment resisting steel frames result in a simple formula for the dynamic stability coefficient as a function of the number of stories of a frame and the column to beam stiffness ratio. Thus, the P– Δ effect can be easily taken into account in a direct displacement‐based seismic design through the stability coefficient and the yield displacement amplification factor. A simple design example serves to illustrate the application of the proposed method and demonstrate its merits. Copyright © 2007 John Wiley & Sons, Ltd.     

北极放大的时空变化特征及其与北极涛动的联系

The Arctic near-surface air temperatures are increasing more than twice as fast as the global average–a feature known as Arctic amplification(AA).A modified AA index is constructed in this paper to emphasize the contrast of warming rate between polar and mid-latitude regions,as well as the spatial and temporal characteristics of AA and their influence on atmospheric circulation over the Northern Hemisphere.Results show that AA has a pronounced annual cycle.The positive or negative phase activities are the strongest in autumn and winter,the weakest in summer.After experiencing a remarkable decadal shift from negative to positive phase in the early global warming hiatus period,the AA has entered into a state of being enlarged continuously,and the decadal regime shift of AA in about 2002 is affected mainly by decadal shift in autumn.In terms of spatial distribution,AA has maximum warming near the surface in almost all seasons except in summer.Poleward of 20°N,AA in autumn has a significant influence on the atmospheric circulation in the following winter.The reason may be that the autumn AA increases the amplitude of planetary waves,slows the wave speeds and weakens upper-level zonal winds through the thermal wind relation,thus influencing surface air temperature in the following winter.The AA correlates to negative phase of the Arctic oscillation(AO) and leads AO by 0–3 months within the period 1979–2002.However,weaker relationship between them is indistinctive after the decadal shift of AA.     

弹性层状半空间中凸起地形对入射平面SH波的放大作用

对Wolf理论进行拓展,使之可解决凸起地形对波的散射问题,进而利用间接边界元法,求解了弹性层状半空间中凸起地形对入射平面SH波的放大作用问题。本文模型的显著特点之一是考虑了层状半空间的动力特性以及层状半空间和凸起地形的阻尼;特点之二是计算精度高。文中以基岩上单一土层中半圆凸起地形对入射平面SH波的放大作用为例进行了数值计算分析。研究表明,基岩上单一土层中凸起地形对入射平面SH波放大作用和均匀半空间中凸起地形有着本质的差别;土层动力特性不仅影响凸起地形地表位移的幅值,还会影响地表位移的频谱;阻尼会显著降低凸起地形对高频波的放大作用。     

川滇地区中小震重新定位与速度结构的联合反演研究

通过震源与速度结构联合反演, 利用2000年4月至2006年3月云南和四川区域地震台网给出的P波初至走时资料, 确定了川滇地区的三维速度结构, 同时获得了川滇地区6642次中小地震的重新定位结果。 结果表明: ① 川滇地区地震震源平均深度随震级增大而加深的特征明显, 地震震级越大, 震源深度越深, 但震源下界不超过25 km; ② 在瑞丽-龙陵、 丽江-小金河以及龙门山等断裂带以西地区, 震源深度偏浅, 大多在15 km以上, 15 km深度以下地震稀少; ③ 川滇地区中小地震分布具有与强震相同的地壳深部介质背景, 震源大多分布于正、 负异常过渡区的速度相对较高一侧, 而其下方主要为低速异常分布。     

弱度比在裂隙含流体检测中的应用

裂隙中的流体检测对油气田勘探和开发有重要意义.裂隙弱度比受裂隙中流体的影响,而弱度比对速度比特别敏感,本文对弱度比与速度比的关系进行了研究,给出了弱度比与转换波速度比和时间比的表达式,并将此应用到WJT气田的裂隙含气检测中.实际资料的应用表明,用弱度比检测裂隙中的流体是可能的,弱度比剖面可作为裂隙含流体检测的基本剖面之一.     

Changes in polar amplification in response to increasing warming in CMIP6

由于全球变暖,极地地区的气候经历了明显的变暖放大.在本项研究中,我们根据CMIP6模式的三种变暖情景(SSP1-2,6,SSP2-4.5和SSP5-8.5)下,极地放大变化对各个反馈机制(包括普朗克,温度递减率,云,水蒸气,反照率反馈,CO2强迫,海洋热吸收和大气热传输)的响应进行了分析.结果表明,通过用“辐射核”方法...