基于STFT和CNN的地震信号分类识别研究

地震信号分类——即信号震源类型的分类,尤其是天然地震和人工爆破的分类对于地震目录的清洗和强震实时预警等具有重要意义.本文首先对原始波形信号进行必要的预处理,然后对预处理后的信号进行分帧加窗,对窗内信号采用短时傅里叶变换,将原始波形信号从时域转换成时频域信号,生成时频谱图,每条波形生成一个时频图像;经过反复多次试验比较,将原尺寸时频谱图统一缩放为32×32像素大小的灰度图像,该灰度图像作为卷积神经网络(CNN)的输入,此时的分类效果和计算效率最优.采用以上方法对2010年至2016年发生在河北三河和北京通州等地区,震级为1.5 ～2.8级之间的54个天然地震事件的1674条波形和63个人工爆破事件的1509条波形,采用五折交叉验证法进行分类,得到的平均准确率为97.39％,与传统的支持向量机(SVM)方法和多层感知器(MLP)方法对比,分类准确率有大幅提升,与使用梅尔倒谱系数(MFCC)构建的CNN分类器方法对比,本文方法信噪比更低,分类准确率提高约1.5％.实验结果表明,采用短时傅里叶变换提取地震信号时频域特征,生成时频谱图,使用卷积神经网络对地震信号进行分类具有良好的分类效果.     

地震与火山电磁研究的国际学术交流与合作

国际地震与火山电磁研究工作组(EMSEV)于2001年在国际地磁学与高空物理学协会(IAGA)、国际地震学与地球内部物理学协会(IASPEI)及国际火山学与地球内部化学协会(IAVCEI)的大力支持下成立。自2001年起,EMSEV一直致力于地震与火山电磁研究的国际学术交流与合作,有力推进了地震与火山电磁研究。描述了EMSEV及其工作会议的概况,简要介绍了地震与火山电磁研究的国际学术交流与EMSEV的国际合作,讨论并展望了地震与火山电磁研究的前景。     

Tephra deposition on glaciers and ice sheets on Mars: Influence on ice survival, debris content and flow behavior

We examine the consequences of pyroclastic deposits being emplaced onto ice layers on Mars, both those in the polar caps and those forming glaciers on the flanks of some of the large shield volcanoes. We show that layers of pyroclasts greater than a few meters in thickness, whether emplaced cold (as fall deposits) or hot (as pyroclastic density current deposits) act almost exclusively to protect ice layers beneath them from sublimation, irrespective of whether they are emplaced at high or low elevations or high or low latitudes. Layers less than about 2 m thick, on the other hand, can cause significant ice loss by raising the surface temperature due to their low albedo and then transmitting that increased temperature to the underlying ice, especially on a diurnal time scale. This can have a significant bearing on the emplacement history of polar water ice and on the survival time of glacial ice on shield volcano flanks. A key factor in the latter case is the timing of the episodic volcanic activity relative to the cycles of climate change driven by Mars' obliquity and eccentricity variations.     

浅谈地震科技档案的归档管理

叙述了地震科技档案的重要性,针对当前地震科技档案归档工作中存在的制度不健全、档案原始件归档难等问题,提出了全面提高档案意识、领导重视、全员参与、及时归档等几点建议,以避免档案流失,做到资源共享,使科技档案更好地服务于防震减灾事业。     

地震科技发展战略之思考

防震减灾事业的长期可持续发展取决于地震科技进步,而制定好地震科技发展规划是推动地震科技进步的重要保障。本文建议了地震科技发展战略制定应考虑的5个原则,提出当前和今后一段时期地震科技发展战略的构想,从11个方面提出了“十一五”地震科技项目建议,同时,对其中地震预报科学实验场的选择提出了原则建议,进而从科学意义与必要性、已具备的条件、科学目标、监测与研究内容和运行机制与模式等5个方面论述了祁连山大震机理与预报科学实验场建设的可行性。     

Study on simulation of earth-fissures development and prediction based on GIS

Earth-fissure in Linfen city is dominated by many factors. Every factor is analyzed in detail and each coverage of them is established. After that, reciprocal relationship between them is determined by using AHP method. With the strong spatial-operation function of GIS, the advanced GIS models of earth-fissure simulation and multi-source forecast are built. On the basis of this, a satisfying prediction has provided extremely important science bases for the city future plans     

中外烈度表“人的感觉”和“器物的反应”对比研究

随着震害经验的积累以及人们对地震认识的深化,不断修改烈度标准,使烈度评定更加客观与科学是地震工程界一直所追求的.人的感觉和器物的反应都是评定一次地震时相应烈度的宏观标志,是烈度表的重要组成部分.鉴于此,本文简要介绍了中国历代地震烈度表(《新的中国地震烈度表》、《中国地震烈度表(1980)》、《中国地震烈度表( 1999...     

雨水触发地震及其对喀斯特地质的依赖

最近报道的因3次独立的暴雨引发的雨水触发地震都发生在喀斯特地质区域。本人在该文中讨论了在强降雨直接侵入喀斯特地区以后喀斯特水文地质是怎样通过水流通道控制雨水触发地震的。这种通道导致水头大量增加,更重要的是,它极大地增加了作用于地下孔弹性介质的垂直应力。快速加载于孔弹性介质的载荷,通过以一种观测到的向水库注水类似的方式,增加深部孔隙压力,从而诱发地震。采用简单的一维孔弹性介质模型可以看到,深部流体压力的激增是边界处压力阶跃的实质性的一部分,接下来是与典型的线性扩散问题相关的随时间变化的孔隙压力的增加。这些结果含有对触发地震所必需的流体压力变化的暗示,并导致以下尚待检验的假设：明显的雨水触发地震将只发生在喀斯特地区。     

中国大陆背景噪声成像研究及应用前景

对长时间序列的背景地震噪声进行互相关计算可以得到台站间的经验格林函数,这种方法不依赖天然地震及人工震源,仅利用台站记录的背景噪声就能得到地下结构,该方法可以更为便捷地获得地震活动性较低地区的地下构造.随着背景噪声层析成像技术的发展应用,该方法会进一步提高地壳上地幔速度模型的分辨率.本文综述了背景噪声成像技术及其在中国大...     

Transporting capacity of overland flow on plane and on irregular beds

In this paper the transporting capacity of thin flows, in the laminar and transitional flow regime, is studied. Experiments were carried out on irregular as well as on plane beds, using two totally different set-ups. The results of these two types of experiment were convergent. In both cases, sediment concentration was clearly related to grain shear velocity and unit stream power, expressed as the product of mean velocity and slope (Yang, 1973). The data agreed with those of Kramer and Meyer (1969). For a sandy bed, the unit stream power relationship was able to predict reasonably well the sediment concentrations measured on a mulched surface. For laminar and transitional flows, both the unit stream power and the shear velocity are related in the same way to slope and unit discharge. The unit stream power is a parameter which in particular can be very easily measured and might therefore become useful in obtaining a quick estimate of the transporting capacity of a thin flow. However, before a sediment transport equation for thin flows can be developed, more information is needed about the influence of the flow regime and grain size and density.     

Raindrop impact and water flow on the vegetative surfaces of trees and the effects on stemflow and throughfall generation

The physical processes of raindrop impact and water flow on the leaves and branches of selected tropical tree species were examined under laboratory conditions using simulated rainfall. Inclined branches were found to be particularly efficient in detaining impacting water droplets. This efficiency in raindrop detention increases linearly as a function of branch inclination on branches that are initially dry. On branches that have been thoroughly wetted, this increase in raindrop detention with branch inclination is best expressed as a logarithmic function. At branch inclinations of 60° above the horizontal, the quantity of branchflow was found to be > 80 per cent of the total quantity of impacting rainfall, indicating that < 20 per cent was lost to rainsplash. The strong positive relationship between branchflow and branch inclination explains why trees with large projected areas of steeply inclined upthrust branches have significant quantities of intercepted water draining from their branches and trunks under heavy rainfall conditions. This drainage from the woody frame of trees influences surficial processes by generating both stemflow and large throughfall droplets.     

场地划分中存在的问题及建议

针对现行建筑抗震设计规范中场地分类方法面临的场地分类物理含义不明确,各类场地的界限容易引起设计地震动参数发散等问题进行了探讨并给出解决建议。针对场地分类物理含义不明确的问题,在现行场地分类方法的基础上,根据场地覆盖层厚度和等效剪切波速,对场地进行分层次分类:第一层次与现行的分类相一致,以场地基本周期为基础,根据覆盖层厚度进行分类;第二层次在第一层次分类基础上进一步考虑场地软硬程度,根据等效剪切波速进行亚分类。根据目前对厚软场地地震灾害及地震动特性的研究,并结合大量长周期建筑结构的经济建设发展现状,对场地分类进行了扩展,由原来的四大类扩展到五大类,同时明确各分类界限,尤其是Ⅱ,Ⅲ和Ⅳ类场地的界限由原来的开放式进行有限化,有效地避免了由场地分类导致的设计地震动参数发散的问题。      

Note on Coriolis-Stokes force and energy

In this study, we consider the origin of the Coriolis-Stokes (CS) force in the wave-averaged momentum and energy equations and make a short analysis of possible energy input to the ocean circulation (i.e., Eulerian mean velocity) from the CS force. Essentially, we find that the CS force appears naturally when considering vertically integrated quantities and that the CS force will not provide any energy input into the system for this case. However, by including the “Hasselmann force”, we show some inconsistencies regarding the vertical structure of the CS force in the Eulerian framework and find that there is a distinct vertical structure of the energy input and that the net input strongly depends on whether the wave zone is included in the analysis or not. We therefore question the introduction of the “Hasselmann force” into the system of equations, as the CS force appears naturally in the vertically integrated equations or when Lagrangian vertical coordinates are used.     

Planform-asymmetry and backwater effects on river-cutoff kinematics and clustering

River bends occasionally meander to the point of cutoff, whereby a river shortcuts itself and isolates a portion of its course. This fundamental process fingerprints a river's long-term planform geometry, its stratigraphic record, and biogeochemical fluxes in the floodplain. Although meander cutoffs are common in fast-migrating channels, timelapse imagery of the Earth surface typically does not offer a long enough baseline for statistically robust analyses of these processes. We seek to bridge this gap by quantifying cutoff kinematics along the Humboldt River (Nevada) – a stream that, from 1994 to 2019, hosted an exceptionally high number of cutoffs (specifically, 174 of the chute type and 53 of the neck type). A coincidence between major floods and cutoff incidence is first suggestive of hydrographic modulation. Moreover, not just higher sinuosity but also upstream planform skewness is associated with higher cutoff incidence and channel widening for a sub-population of chute cutoffs. We propose a conceptual model to explain our results in terms of channel-flow structure and then examine the distances between adjacent cutoffs to understand the mechanisms governing their clustering. We find that both local and nonlocal perturbations together trigger the clustering of new cutoffs, over distances capped by the backwater length and over yearly to decadal timescales. Our research suggests that planform geometry and backwater controls might sway the occurrence of cutoff clusters – both local and nonlocal – thereby offering new testable hypotheses to explore the evolution of meandering-river landscapes that have significant implications for river engineering and stratigraphic modelling. © 2020 John Wiley & Sons, Ltd.     

浅谈地震科技档案的归档

地震科技档案以其独有的专业性、多样性、成套性和现实性为特征,它凝结着科技人员的心血和智慧,具有极珍贵的保存和开发利用价值,对指导地震科学研究起着举足轻重的作用.地震科学所表现出的探索性,地震观测项目的多样性,防震减灾涉及社会领域的广泛性,尤其以高科技为先导,地震科技现代化不断发展的新形势,决定了做好地震科技档案工作的重要意义.     

基于建筑物与POI数据的人口空间化研究

人口数据是地震灾害人员伤亡评估的基础,准确的人口空间分布信息对提高应急灾情评估的准确度和开展高效的应急决策具有重要意义。本文结合建筑物空间分布、POI(兴趣点)、路网与人口统计等数据,基于Spearman相关分析以及多元线性回归分析方法,构建人口空间化模型,实现了人口统计数据基于规则格网的更为精确的可视化表达。结果表明:(1)建筑物空间分布能较好地反映人口的宏观分布特征,但是对于人口分布细节特征的刻画,则是以POI数据来反映人口的微观分布特征效果更为理想;(2)受区域经济发展影响,人口分布具有明显的空间差异,由城镇向乡村区域递减的趋势明显,中心城区、周边城镇、偏远乡镇之间的人口密度差异巨大。基于建筑物与POI数据的人口模拟值与实际值的偏差较小,数据精度符合实际情况,可为灾情研判提供可靠的基础数据。     

Controls on the stability and inclinations of hillslopes formed on hard rock

In identifying controls on rock slope form a distinction is made between: (1) rock slopes with joints which dip steeply out of a cliff and hence are subject to mass failure of the rock mass above a critical joint; and (2) rock slopes with inclinations which are either in equilibrium with the mass strength of their rocks, or have profiles which will develop towards strength equilibrium as cross joints open. In the first class of slope, stability results not just from the basic frictional resistance of the rock but also from the frictional roughness along the critical joint and from the normal stress acting across that joint. Stability may be reduced by weathering and loss of strength of the joint wall rock. As a result of normal stress variations with depth, induced by overburdens, high cliffs which are not undercut have a concave profile. The second group of slopes includes those with inclinations controlled at the scale of individual joint blocks, buttressed slopes and those on unjointed rock masses. Buttressed and unjointed rock masses develop towards a condition of mass strength equilibrium as cross joints open. Strength equilibrium slopes may be recognized by application of a rock mass strength classification proposed for geomorphic purposes. Eleven propositions are formulated which identify controls on rock slope development and some consequences of these controls.     

地震前兆与短临预报探索

针对地震短临预报面临的科学问题,分析研究了地震前兆(近场前兆、远场前兆和大尺度动态前兆)预报地震的物理基础;总结了地震短临前兆时空演化特征和同步耦合现象。高空技术在地震前兆观测中的应用将有利于短临预报实践与探索。     

Observation and research on ULF and VLF seismo－electromagnetic radiation

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On-site and off-site material preparation pavement approaches on particle emission and associated health impacts on workers

Stochastic Environmental Research and Risk Assessment - The resurfacing of urban road networks is a prevalent practice for extending their life and therefore shares an important contribution to the...