基于深度学习的倾斜摄影建筑物表面损毁信息提取

建筑物受损信息是地震受灾程度评估的基础,针对传统建筑物表面信息识别人工成本高、效率低等问题,受深度学习提取建筑物影像的启发,提出利用无人机倾斜摄影模型与深度学习相结合的方法提取震后建筑物表面破损信息。以2019年长宁6.0级地震为例,选用双河镇震后倾斜摄影模型切片图为数据源,对比分析面向对象分类方法、VGG-16模型和DeeplabV3+模型对建筑物表面损毁信息的提取结果。分析结果表明,针对建筑物表面破损信息的提取,尤其是细小裂缝的提取,语义分割网络DeeplabV3+模型具有较强的优势(准确率96.93%、召回率96.85%、总体精度96.89%),可实现建筑物表面破损信息的有效提取,具有较强的应用价值。     

陕西地震监测台网恢复重建与通讯网络改造

陕西地震监测台网震后恢复重建项目实施过程中,通过优化台网布局和增加台网密度,新建GNSS连续观测系统,提高了地震监测能力;采用的通讯网络新架构以及OSPF路由协议,不仅提升了监测网络通讯系统的可靠性,而且取得降低通讯费用的显著成效.     

新疆巴楚和塔什库尔干地震台下方地壳结构研究

Using the teleseismic waveform data recorded by the seismic station Bachu( hereafter referred to as station BCH) i n the Tarim Basin and the seismic station Taxkorgan(h ereafter referred to as station TAG) i n the west Kunlun Mountains for years,we applied the receiver function H-κ stacking method to study the crustal structure beneath stations BCH and TAG. The results showed that there are obvious differences in the crustal thickness beneath stations BCH and TAG,and the regional crustal thickness and terrain have a very good corresponding relationship. There are high crustal average V P/ V S values beneath the two stations. The crustal thickness is 44 km,and the crustal average wave velocity ratio is 1. 849 beneath station BCH. There is a sharp discontinuity in the middle of the crust beneath station BCH at a depth of 21 km. There is a low average P wave velocity and low V P/ V S from the surface to the discontinuity beneath station BCH.The depth of the discontinuity is consistent with the lower interface of the focal depth from accurate location in the Jiashi earthquake source area adjacent to station BCH; and may be the crustal brittle-ductile conversion boundary. The crustal thickness is 69 km,and the crustal average wave velocity ratio is 1. 847 beneath station TAG,a thicker crust and high V P/ V S may indicate that materials in the lower crustal are prone to plastic flow,which is responsible for the thickening of the crust.     

Comparison of daily and sub-daily SWAT models for daily streamflow simulation in the Upper Huai River Basin of China

Despite the significant role of precipitation in the hydrological cycle, few studies have been conducted to evaluate the impacts of the temporal resolution of rainfall inputs on the performance of SWAT (soil and water assessment tool) models in large-sized river basins. In this study, both daily and hourly rainfall observations at 28 rainfall stations were used as inputs to SWAT for daily streamflow simulation in the Upper Huai River Basin. Study results have demonstrated that the SWAT model with hourly rainfall inputs performed better than the model with daily rainfall inputs in daily streamflow simulation, primarily due to its better capability of simulating peak flows during the flood season. The sub-daily SWAT model estimated that 58 % of streamflow was contributed by baseflow compared to 34 % estimated by the daily model. Using the future daily and 3-h precipitation projections under the RCP (Representative Concentration Pathways) 4.5 scenario as inputs, the sub-daily SWAT model predicted a larger amount of monthly maximum daily flow during the wet years than the daily model. The differences between the daily and sub-daily SWAT model simulation results indicated that temporal rainfall resolution could have much impact on the simulation of hydrological process, streamflow, and consequently pollutant transport by SWAT models. There is an imperative need for more studies to examine the effects of temporal rainfall resolution on the simulation of hydrological and water pollutant transport processes by SWAT in river basins of different environmental conditions.     

An isotope study of the accumulation mechanisms of high-sulfur gas from the Sichuan Basin,southwestern China

The mechanism of hydrogen sulfide (H₂S) generation plays a key role in the exploration and development of marine high-sulfur natural gas, of which the major targets are the composition and isotope characteristics of sulfur-containing compounds. Hydrocarbon source rocks, reservoir rocks, natural gases and water-soluble gases from Sichuan Basin have been analyzed with an online method for the content of H₂S and isotopic composition of different sulfur-containing compounds. The results of comparative analysis show that the sulfur-containing compounds in the source rocks are mainly formed by bacterial sulfate reduction (BSR), and the sulfur compounds in natural gas, water and reservoir are mainly formed by thermal sulfate reduction (TSR). Moreover, it has been shown that the isotopically reversion for methane and ethane in high sulfur content gas is caused by TSR. The sulfur isotopic composition of H₂S in natural gas is inherited from the gypsum or brine of the same or adjacent layer, indicating that the generation and accumulation of H₂S have the characteristics of either a self-generated source or a near-source.     

Influence of Fluctuating Groundwater Table on Volatile Organic Chemical Emission Flux at a Dissolved Chlorinated-Solvent Plume Site

Groundwater elevation fluctuation has been recognized as one mechanism causing temporal indoor air volatile organic chemical (VOC) impacts in vapor intrusion risk assessment guidance. For dissolved VOC sources, groundwater table fluctuation shortens/lengthens the transport pathway, and delivers dissolved contaminants to soils that are alternating between water saturated and variably saturated conditions, thereby enhancing volatilization potential. To date, this mechanism has not been assessed with field data, but enhanced VOC emission flux has been observed in lab-scale and modeling studies. This work evaluates the impact of groundwater elevation changes on VOC emission flux from a dissolved VOC plume into a house, supplemented with modeling results for cyclic groundwater elevation changes. Indoor air concentrations, air exchange rates, and depth to groundwater (DTW) were collected at the study house during an 86-d constant building underpressurization test. These data were used to calculate changes in trichloroethylene (TCE) emission flux to indoor air, during a period when DTW varied daily and seasonally from about 3.1 to 3.4 m below the building foundation (BF). Overall, TCE flux to indoor air varied by about 50% of the average, without any clear correlation to changes in DTW or its change rate. To complement the field study, TCE surface emission fluxes were simulated using a one-dimensional model (HYDRUS 1D) for conditions similar to the field site. Simulation results showed time-averaged surface TCE fluxes for cyclic water-table elevations were greater than for stationary water-table conditions at an equivalent time-averaged water-table position. The magnitudes of temporal TCE emission flux changes were generally less than 50% of the time-averaged flux, consistent with the field site observations. Simulation results also suggested that TCE emission flux changes due to groundwater fluctuation are likely to be significant at sites with shallow groundwater (e.g., < 0.5 m BF) and permeable soil types (e.g., sand).     

Elastic one-return boundary element method and hybrid elastic thin-slab propagator for strong-contrast media with sharp boundaries

In this paper, we developed the theory and algorithm of an elastic one-way boundary element method(BEM) and a corresponding hybrid elastic thin-slab propagator for earth media with sharp boundaries between strong contrast media. This approach can takes the advantage of accurate boundary condition of BEM and completely overcomes the weak contrast limitation of the perturbationtheory based one-way operator approach. The one-way BEM is a smooth boundary approximation, which avoids huge matrix operations in exact full BEM. In addition, the one-way BEM can model the primary-only transmitted and reflected waves and therefore is a valuable tool in elastic imaging and inversion. Through numerical tests for some simple models,we proved the validity and efficiency of the proposed method.     

青海地区盐渍土分布规律及其独特工程特性探讨

针对青海一些地区盐渍土当硫酸钠含量小于1%时也会产生盐胀,而超氯盐渍土却不会产生溶陷的事实,进行了较为深入细致的论证和研究。以数据、事实为依据,得出了与现行理论及规范有较大出入的论断。     

龙门山及其邻区的地壳厚度和泊松比

根据龙门山及其周边地区(26°～35°N,98°～109°E)的132个台站的宽频带远震记录,使用H-k叠加方法计算地壳厚度和波速比.结果表明该区域的地壳厚度总体变化是:从东向西增加,东部的最小厚度为37.8km,西部的最大厚度是68.1 km,其中横跨龙门山断裂带的地壳厚度变化最大,从东南的41.5km增加到西北的52.5km.根据Airy均衡理论,用台站的高程和观测地壳厚度数据求得最小二乘意义下的壳幔密度差为0.649g/cm3,平均地壳厚度为37.9km.龙门山及其邻近地区基本上处于均衡状态.松潘-甘孜地体北部和西秦岭造山带具有低泊松比(v<0.26),扬子地台的西南部具有低一中泊松比(v<0.27),松潘-甘孜地体南部、三江褶皱带和四川盆地具有中一高泊松比(0.26≤P≤0.29).该地区的泊松比空间分布不支持青藏高原东部广泛分布的下地壳流的假说.龙门山断裂带南段及其附近地区的高泊松比(v≥0.30)可以看成是地壳具有较高的铁镁质组分和/或存在部分熔融.该地区下地壳可能是处于富含流体和温度较高的部分熔融状态.松潘-甘孜块体南部的上地壳物质向东运动,受刚性强度较大的扬子地台的阻挡,导致沿龙门山断裂带产生应变积累.当断层被地壳流体弱化,积累的应变能量快速释放,产生汶川Ms8.0地震.     

塔里木北部地区三叠系储层溶蚀作用机理

塔里木北部地区三叠系储层在成岩演化过程中曾经历两期溶蚀作用，深埋成岩环境的晚期溶蚀较早期近地表－浅埋成岩环境溶蚀要剧烈得多，溶蚀作用的最大特点是铝硅酸盐矿物较碳酸盐矿物剧烈。溶蚀作用发生的机理是由于三叠系储层处于８０～１２０℃热窗、成岩流体富含低分子量羧酸、碱度由低分子量羧酸控制，铝硅酸盐和碳酸盐矿物均处于去稳定状态。溶蚀作用的发育程度受控于储层砂体的沉积和岩石学特征以及早期成岩发育程度。