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通过对紫坪铺水库数字遥测地震台网在汶川特大地震中的表现,分析通过特大地震洗礼的紫坪铺地震台网运行的经验和教训,提出遥测地震台网建设时观测仪器设备也应注意自身抗震的问题,并对今后地震台站观测仪器安装提出建议。 相似文献
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针对基于人工检测方法存在效率低、实时性差等问题，提出了一种空间通道注意力机制改进的Faster RCNN的砌体结构震损图片快速识别算法。基于湖北省应城M4.9级地震现场调查获取的砌体结构震害图片，制作砌体结构门窗洞口和震损类型的数据集；通过Mosaic方法对数据集进行数据增强后，构建空间通道注意力机制改进的Faster RCNN模型提取震害图片高级语义特征；使用湖北应城M4.9级地震砌体结构震害调查数据集对模型进行训练及验证并确定最终的模型超参；最后基于改进的Faster RCNN对砌体结构门窗洞口和震损类型进行快速检测。实验结果表明，该改进的算法可以有效的识别出门、窗、剥落、裂缝，其检测精确分别为：93.1%、97.6%、74.8%、62.3%。此外，单张震害照片检测时间为60 ms,为砌体结构震害快速检测提供了新的思路。 相似文献
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针对计算机断层成像稀疏重建过程中产生条状伪影的问题,本文提出一种基于对抗式残差密集深度神经网络的CT图像高精度稀疏重建方法.设计一种耦合残差连接、密集连接、注意力机制和对抗机制的UNet网络,以含条状伪影图像和高精度图像作为训练样本,通过大规模训练数据,对该网络进行训练,使其具有压制条状伪影的能力.首先,利用滤波反投影... 相似文献
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拟建中的某工程场址经工程地质勘探和基础开挖发现一规模较大的北西向断层。本文通过对该断层的地貌形态、断层面宏观结构、断层带内物质的显微构造分析以及第四纪地层的^14C测年，对该断层进行了活动性鉴定，并提出了工程设计应注意的问题。 相似文献
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本刊2013年第4期(35-41页)的《地震学百科知识(三)——地震学反演问题》一文,40页第6行中的"设A为n×m的实矩阵"应改为"设A为m×n的实矩阵",敬请读者注意。 相似文献
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针对南通地震台核旋观测的干扰，通过多种试验最终加以排除。这项工作表明，地震台站环境改造中要注意监测环境的保护，特别是铠装电缆的铺设要考虑到对磁、电观测的影响，并就如何进一步提高核旋的观测质量提出建议。 相似文献
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地震相识别技术是进行沉积环境分析与储层预测的有力工具.传统的人工地震相识别方法不仅工作量大,而且效率非常低.目前利用深度学习方法可以大幅度提高地震相识别的效率,但是受限于有限的数据集和网络提取特征能力,对样本数量少的地震相识别效果较差.针对上述问题,本文提出了基于改进U-Net的多属性地震相识别方法.首先通过弹性形变算法来扩增数据集,将经过属性选择后的多属性数据体作为输入数据,提高输入数据的数量和质量;其次通过引入注意力机制对网络提取的特征添加权重,提高U-Net网络提取特征的能力;并在损失函数中引入Dice指数,解决了样本不均衡问题.经过数值实验表明,基于改进U-Net模型可有效提高地震相预测准确率. 相似文献
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医学CT图像中含有的大量噪声以及肝脏肿瘤大小不均一、位置因人而异且与相邻器官较相似的组织密度等都造成肝脏肿瘤分割困难。现有传统全卷积神经网络（FCN）方法,通过为输入CT图像中每个像素分配类别标签来实现肝脏肿瘤分割,但在分割精度上仍会出现小目标漏检或目标边界分割模糊的问题。针对这些问题,本文提出一种瓶颈残差注意力机制U-net（BRA U-net）的肝脏肿瘤分割方法,通过引入瓶颈残差模块可在非常深的网络中大幅减少计算量的同时解决梯度消失问题,此外堆叠的注意力模块可以增大有效特征的比重。本文在公共MICCAI2017肝肿瘤分割数据集上测试了该框架,戴斯相似性系数值达到0.788,高于其他对比分割网络,并利用3D-IRCADb数据集来验证该方法的一般性,结果表明本文方法分割效果良好,能够为临床诊断提供可靠依据。 相似文献
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为能在搜救地震受困人员时，实时监测灾区情况，增强实时性及降低搜救误差，研究物联网技术在地震受困人员应急搜救中的应用，设计基于物联网的地震应急搜救系统，采用RFID识读器将采集的数据通过互联网传输至数据处理中心服务器上，再反馈至灾区信息处理子系统中的监测防御模块中，若出现异常情况则开启射频模块，命令现场报警装置响应报警应急搜救信号；通过蚁群算法获取最优搜救路线，及时搜救地震受困人员。实验结果表明，设计系统可有效搜救地震受困人员，且系统的吞吐率高达90%，搜救准确率均值高达97.6%，耗时均值仅为0.88 h，具有较高的搜救准确率和搜救效率。 相似文献
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It has been observed that post-critically reflected S-waves and multiples from the Moho discontinuity could play a relevant role on the ground motion due to medium to strong size earthquakes away from the source. Although some studies investigated the correlation between the Moho reflections amplitudes and the damage in the far field, little attention was given to the frequency content of these specific phases and their scaling with magnitude. The 2012 Emilia seismic sequence in northern Italy, recorded by velocimetric and accelerometric networks, is here exploited to investigate Moho reflections and multiples (SmSM). A single station method for group velocity-period estimation, based on the multiple filter technique, is applied to strong motion data to detect SmSM. Amplitude and frequency scaling with magnitude is defined for earthquakes from \(\hbox {Mw}=3.9\) to \(\hbox {Mw}=5.9\) . Finally, the ability of SmSM to affect the ground motion for a maximum credible earthquake within the Po plain is investigated by extrapolating observed engineering parameters. Data analysis shows that high amplitude SmSM can be recognized within the Po plain, and at the boundaries between the Po plain and the Alpine chain, at epicentral distances larger than 80 km, in the period range from 0.25 to 3 s and in the group velocity window from about 2.6 to 3.2 km/s. 5 % damped pseudo-spectral accelerations at different periods (0.3, 1.0 and 2.0 s), and Housner intensities, are obtained from data characterized by large amplitude SmSM. A scaling relationship for both pseudo-spectral accelerations and Housner intensities is found for the earthquakes of the 2012 Emilia seismic sequence. \(\hbox {I}_{\mathrm{MCS}}\) from VII to VIII is estimated, as a result of SmSM amplitude enhancement, at about 100 km for a maximum credible earthquake ( \(\hbox {Mw}=6.7\) ) in the Po plain, showing that moderate to high damage cloud be caused by these specific phases. 相似文献
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Irene Fischer 《Surveys in Geophysics》1975,2(1):3-54
The search for the Figure of the Earth is rooted in the age-old wonder about the world we live in. The ancient mythical notions have developed, under the tutelage of Greek systematic thought, into specific questions of the shape and size of the Earth. The history of these questions, now spanning more than two millenia, shows a continuous refinement in formulation, as each bona fide answer prompted refined measurements which, in turn, started a new round of problems. The change in concept of what one was looking for was, and still is, closely connected with the technical capability and its potential for further development. This change in concept is traced here from ancient times to the present throungh some of its milestones: Anaximander's partly invisible celestial sphere and Pythagoras' spherical Earth; Eratosthenes' exemplary combination of astronomy and land surveying for the dual purpose of determining the size of the spherical Earth and making a map of the habitable world; the identical dual purpose followed by the Académie Royale des Sciences in the 17th century, but on a more sophisticated technical level; the challenge to the spherical concept by Newton's gravitational theory and the absorption of that theory into a wider concept of the Figure of the Earth; the acknowledgment of the irregular geoid by Gauss, Bessel, and Helmert, and the changed significance of the ellipsoid; Heiskanen's and Vening Meinesz' ‘Basic Hypothesis of Geodesy’ concerning the hydrostatic equilibrium of the Earth, and O'Keefe's contradiction on the basis of satelite data; the dream of global surveys come true through satellite geodesy and the accompanying inclusion of the outer gravity field of the Earth into the concept of its Figure; and lastly, the present and projected capability of high precision measurement and the widening of the concept of the Figure of the Earth from 3-dimensional rigidity to 4-dimensional time-dependence. 相似文献
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The Soufrière volcano in Guadeloupe island delivered a phreatic eruption that commenced on July 8th, 1976 and lasted until March 1st, 1977. This eruption was similar to the 1797, 1798, 1809 and 1956 outbreaks. Phreatic activity ejected blocks derived from the fissure walls and fine pyroclasts produced by hydrothermal alteration of the old dome’s rocks. Field observations and measurements allowed the present authors to calculate the mass and energy transfer of steam and ashes: 107 tons of water (very low considering that on the mountain summit the annual precipitation is 10 tons m)2,106 m3 of ashes. The most important energy transfers was thermal: about 5 × 1020 ergs for each phreatic eruption. The total kinetic energy output was 2 × 1019 ergs for a total thermal energy output of 64 × 1020 ergs. The gases and fine pyroclasts did pollute the atmosphere, waters and soils and consequently affected the population living on the slopes of the volcano. 相似文献
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The 26 s peak in the ambient seismic noise spectrum is persistently excited and observed at stations globally. Using noise cross-correlation functions (NCFs), the location suggests that the source could be situated in the Gulf of Guinea and Fiji Basin. However, the Fiji Basin was proposed to be the mirror site (near antipode) of the Gulf of Guinea source instead of an independent source, assuming that the surface waves more efficiently propagate along the major-arc paths of oceanic movements. To investigate the propagation of the Rayleigh waves along continental and oceanic paths, we analyzed the surface wave data recorded from an earthquake near the Gulf of Guinea and found that Rayleigh waves travel along continental minor-arc paths more efficiently than along oceanic major-arc paths. We then located the source in the western Pacific Ocean from group velocities measured with earthquake data by using the travel time misfit in NCFs after calibration and concluded that the source is in the Vanuatu Islands. Moreover, the temporal variation of the 26 s microseismic peak observed in the western Pacific seismic stations is very different from that in stations near the Gulf of Guinea, which suggests that they are excited by independent sources. Therefore, the Vanuatu source should be an independent microseismic source. As it is close to volcanoes in the Vanuatu islands, the Pacific 26 s microseismic source might be excited by magmatic processes, which are also responsible for very-long-period volcanic tremors. 相似文献
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Alexei Gvishiani Renata Lukianova Anatoly Soloviev Andrei Khokhlov 《Surveys in Geophysics》2014,35(5):1123-1154
An overview of the geomagnetic observations made in the northern part of Russia is presented from a historical perspective. Several stations were deployed on the territory of the former Soviet Union during the International Geophysical Year, 1957–1958, with the active participation and guidance of the Interagency Geophysical Committee which is inherited by the Geophysical Center of the Russian Academy of Sciences (GC RAS). In the 1990s, the majority of these stations, especially those in the remoter regions, were closed. Nowadays, the geomagnetic network, including the observatories of the INTERMAGNET program, has been restored. Examples of high-latitude geomagnetic variations in the Russian longitudinal sector are shown, and maps and trends of the secular variation over the territory of Russia presented. Particular attention is paid to the automated processing of data and to the analysis methods used. To process the growing amount of high-resolution geomagnetic data, sophisticated mathematical methods based on the fuzzy logic approach and new discrete mathematical analysis algorithms have been developed. The formal methods and algorithms for recognizing both artificial and natural disturbances in the magnetograms are described. 相似文献
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We apply a newly developed numerical method to improve the Moho geometry by the implementation of gravity data. This method utilizes expressions for the gravimetric forward and inverse modeling derived in a frequency domain. Methods for a spectral analysis and synthesis of the gravity field and crust density structures are applied in the gravimetric forward modeling of the consolidated crust-stripped gravity disturbances, which have a maximum correlation with the (a priori) Moho model. These gravity disturbances are obtained from the Earth’s gravity disturbances after applying the topographic and stripping gravity corrections of major known anomalous crust density structures; in the absence of a global mantle model, mantle density heterogeneities are disregarded. The isostatic scheme applied is based on a complete compensation of the crust relative to the upper mantle density. The functional relation is established between the (unknown) Moho depths and the complete crust-stripped isostatic gravity disturbances, which according to the adopted isostatic scheme have (theoretically) a minimum correlation with the Moho geometry. The system of observation equations, which describes the relation between spherical functions of the isostatic gravity field and the Moho geometry, is defined by means of a linearized Fredholm integral equation of the first kind. The Moho depths are determined based on solving the gravimetric inverse problem. The regularization is applied to stabilize the ill-posed solution. This numerical procedure is utilized to determine the Moho depths globally. The gravimetric result is presented and compared with the seismic Moho model. Our gravimetric result has a relatively good agreement with the CRUST2.0 Moho model by means of the RMS of differences (of 3.5 km). However, the gravimetric solution has a systematic bias. We explain this bias between the gravimetric and seismic Moho models by the unmodelled mantle heterogeneities and uncertainties in the CRUST2.0 global crustal model. 相似文献
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Claire L. Schelske Hans Züllig Mary Boucherle 《Aquatic Sciences - Research Across Boundaries》1987,49(1):42-50
Biogenic silica concentrations were determined from core samples of laminated sediments collected from Lake Zürich and Lake St. Moritz and used to calculate rates of biogenic silica sedimentation. In Lake Zürich biogenic silica sedimentation increased from 65 g SiO2·?2·yr?1 in 1894 to nearly 900 g SiO2·m?2·yr?1 in 1896 and in Lake St. Moritz biogenic silica sedimentation increased about 6-fold during the 1930s. Both periods of increased biogenic silica flux followed increased loadings of domestic sewage to the lakes. In Lake Zürich the period of increased flux only lasted for a few years whereas in Lake St. Moritz high fluxes were maintained to the top of the core. In Lake Zürich increased production and sedimentation of diatoms could be maintained only until the silca reservoir in the water mass was depleted whereas in Lake St. Moritz (0.10 year residence time and a mean depth of 25 m) diatom production and sedimentation was maintained at a high level by rapid replenishment of silica from tributary inputs. Although historical patterns of biogenic silica sedimentation differed for the two lakes, it is hypothesized that increased biogenic silica deposition in both lakes occurred because diatom production was stimulated by phosphorus enrichment of the water mass and that the silica biogeochemistry of both lakes was affected as a result. 相似文献