2022年6月1日四川芦山6.1级地震应急产品及震源参数初步分析

北京时间2022年6月1日17时0分四川雅安市芦山县(30.37°N,102.94°E)发生6.1级地震,中国地震台网中心于震后3min发布自动速报结果、震后9min发布正式速报结果,同时联合多家单位启动地震应急产品产出工作,共产出震源参数、历史地震、地震构造、震源机制、余震精定位、推测烈度和震源破裂过程等9类应急产品。结果显示,本次地震发生在龙门山断裂带,位于青藏高原巴颜喀拉地块、岷山构造带、川滇构造带的交汇处;震源机制解表明该地震为一次逆冲型事件;余震精定位结果显示余震展布呈近NE向,与震中区域断裂走向基本一致;烈度速报推测极震区烈度达Ⅸ度,区域面积约2km²,Ⅷ度及以上区域总面积约197km²,涉及四镇一乡。     

Rupture process and aftershock focal mechanisms of the 2022 M6.8 Luding earthquake in Sichuan

According to the China Earthquake Networks Center, a strong earthquake of M6.8 occurred in Luding County, Ganzi Tibetan Autonomous Prefecture, Sichuan Province, China (102.08°E, 29.59°N), on September 5, 2022, with a focal depth of 16 km. Rapid determination of the source parameters of the earthquake sequence is vital for post-earthquake rescue, disaster assessment, and scientific research. Near-field seismic observations play a key role in the fast and reliable determination of earthquake source parameters. The numerous broadband seismic stations and strong-motion stations recently deployed by the National Earthquake Intensity Rapid Report and Early Warning project have provided valuable real-time near-field observation data. Using these near-field observations and conventional mid- and far-field seismic waveform records, we obtained the focal mechanism solutions of the mainshock and M ≥ 3.0 aftershocks through the waveform fitting method. We were further able to rapidly invert the rupture process of the mainshock. Based on the evaluation of the focal mechanism solution of the mainshock and the regional tectonic setting, we speculate that the Xianshuihe fault formed the seismogenic structure of the M6.8 strong earthquake. The aftershocks formed three spatially separated clusters with distinctly different focal mechanisms, reflecting the segmented nature of the Xianshuihe fault. As more high-frequency information has been applied in this study, the absolute location of the fault rupture is better constrained by the near-field strong-motion data. The rupture process of the mainshock correlates well with the spatial distribution of aftershocks, i.e., aftershock activities were relatively weak in the maximum slip area, and strong aftershock activities were distributed in the peripheral regions.     

高频地质雷达与混凝土护壁层无损测厚

本文在系统研究地质雷达探测技术和混凝土护壁层结构及其地球物理特征的基础上,探讨了应用地质雷达探测技术实现混凝土护壁层层厚无损检测的可行性及其工作方法、技术,并通过实测案例显示了直观、可靠、精确的效果,进一步证实了方法的可靠性。     

夏季印度洋海温偶极子对冬季东亚高空急流的影响研究

基于1979—2019年ERA5、NCEP/NCAR再分析资料及多套海温资料,分析夏季印度洋偶极子模态对东亚高空急流的影响,并对热力动力机制展开探讨。结果表明,当夏季印度洋偶极子为正(负)位相,即夏季印度洋西部出现暖(冷)异常,东部出现冷(暖)异常时,冬季的东亚副热带急流增强(减弱),极锋急流强度减弱(增强)。伴随着印度洋偶极子位于正位相,增强(减弱)的经向温度梯度,加强(减少)的低层大气斜压性和较强(较弱)的瞬变涡动动能,易导致冬季的副热带急流增强(极锋急流减弱)。进一步利用多元线性回归方法定量区分热力和动力因子的相对贡献,夏季印度洋偶极子主要通过热力作用影响两支急流。比较两个动力因子发现,极锋急流的减弱主要以大气斜压性为主,而副热带急流的加强则以涡动动能为主。     

Numerical and Laboratory Analysis of Relaxation Tests for Determining Time-Dependent Properties of Rock

Roof falls in coal mines may occur within a few months to a few years after excavation. In this paper, we proposed the use of relaxation tests as a substitute for time-dependent tests. The relation between creep behavior and relaxation behavior was numerically investigated and demonstrates that the material assigned with creep model can show relaxation behavior. Then the relaxation model was developed by modifying the Burgers creep model. Numerical simulation of a relaxation test on a simulated rock model in 3DEC yielded results that were similar to theoretical prediction. A relaxation test was performed on two groups of specimens under varying load conditions. Results from the laboratory tests validated the approach of using relaxation test to determine time-dependent properties. Finally, time-dependent properties were investigated by performing relaxation tests at different stages of a complete stress–strain curve. The relaxation test during strain-softening was unsuccessful; however, the relaxation behavior at residual stage in post-failure region was more significant than that in pre-failure region and the sudden drop in stress indicated there was strength deterioration due to the accumulation of viscous strain.     

三维城市建模中的建筑墙面纹理快速获取

阐述了建筑墙面纹理快速重建需要解决的问题和实现策略,并从实用、经济的角度出发,对纹理影像数据源的选择、获取方式,纹理快速提取系统的构建以及重建过程中影像方位元素获取、轮廓线影像匹配关键算法的实现等各方面进行了具体探讨,最后以数码相机拍摄的近景影像和直升机机载视频序列影像作为纹理数据源分别设计和实现了两个软件系统,进行了快速重建实验,并取得了较好的纹理重建效率和效果。     

二维地电影像——一种高分辨率岩性预测技术

在吸收传统的电阻率法勘探技术精华和方法理论的基础上,应用二维的观点和数字模拟重构技术,论述了二维地电影像系统的理论、方法、技术,并通过实测案例展示了该技术在研究工程与环境地质调查问题中的优势及可性行。     

Multi-timescale variation of East Asian winter monsoon intensity and its relation with sea surface temperature during last millennium based on ECHO-G simulation

Based on the simulation results derived from ECHO-G global coupled climate model, several East Asian winter monsoon (EAWM) indices are compared in order to choose the most suitable one for signaling the intensity of winter monsoon in the last millennium. The index I_shi, which is defined with normalized sea level pressure difference between sea and land in mid and low latitudes, is selected to describe the winter monsoon intensity variation owing to its better capability for reflecting the variation of winter monsoon subsystems, such as the continental high pressure, Aleutian low, East Asian major trough, westerly jet stream, and surface air temperature than the other indices examined. Wavelet analysis on index I_shi shows that the EAWM intensity is characterized by multi-timescale variation with inter-annual, decadal, inter-decadal and inter-centennial oscillations on the background of a slight descending trend. Correlation analysis between the EAWM index and sea surface temperature (SST) at various timescales reveals that the SST in mid-latitudes might provide the background of the EAWM strength changes above decadal timescales, and a negative-feedback process lasting for about two years is found between the EAWM intensity and the SST in the eastern equatorial Pacific. According to the correlation, the El Nino occurrence in the second-half of the year leads to weaker EAWM than normal in the following winter and the weakened EAWM corresponds to lower SST in eastern equatorial Pacific after about half a year, which will then strengthen the EAWM intensity in the next winter. It is a stable feedback process and its mechanism is discussed.