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基于中国各构造区1900年以来的本尼奥夫应变累积释放序列,采用协整分析和因果关系检验方法研究表明,青藏高原与华北地区地震活动的应变释放存在着长期均衡关系;在某种程度上,青藏高原地区地震应变释放是华北地区应变释放发生变化的原因;青藏高原对华北地区地震应变释放的影响存在约20多年的滞后效应.本文结果对两个构造单元的地球动力学研究提供了统计学证据. 相似文献
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本文以青藏高原东南缘为研究区域,利用G-R震级能量经验公式和Benioff地震应变能释放曲线,对该区域内1500年以来的历史地震应变能释放进行了系统性的研究。文中给出了各断裂带和断块区的地震应变能释放周期表,及相应的地震危险性。分析发现研究区域地震应变能的释放具有东强西弱,南强北弱的特征,整体上各断层断块区的历史地震应变能释放符合准周期模式,某些断层和断块区上的地震周期具有某种程度上的同步现象。青藏高原东南缘现今处于大释放期中,地震的危险性不能忽视。局部结果显示,安宁河-则木河断裂带、小江断裂带的危险性很高,对于这些危险区要重点跟踪研究。今后仍需结合不同研究方法来提高地震危险性评估的可靠性。 相似文献
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Introduction At the juncture of Qinghai-Xizang, Ordos and Alxa blocks lies the Qinghai-Xizang plateau, an area with complicated topographic and morphologic features, strong tectonic activities and frequent earthquakes (many large-magnitude earthquakes have taken place), has become a focal area for geoscience study. Many geophysical and geological surveys have been carried out in and around the area, such as deep seismic sounding (DSS), gravimetry, magnetotelluric sounding, magnetic anomaly … 相似文献
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云南大理MS6.4地震和意大利拉奎拉（L'Aquila）MW6.3地震都因未能准确做出危险性预测给人民生命财产造成重大损失。哪些工作可能向政府和公众说明“哪里可能发生地震”、“最大量级多大”、“未来发震趋势如何”等问题都值得深入思考。本文根据天气预报思路,将地震活动按丛集性做分区处理,从各区M-t序列、3级地震活动性、2年来地震能量释放升级趋势、G-R关系等几方面分析了这两次地震主震发生前的地震活动特征,对比分析了它们之间的相似性。认为这两次地震的相似性有以下几点:①震源深度都比较浅。云南大理MS6.4地震震源深度8 km,意大利拉奎拉MW6.3地震震源深度8.8 km;②b值相近。云南大理MS6.4地震b=0.59,意大利拉奎拉MW6.3地震b=0.61。G-R关系外推震级相近,均为MGR6左右;③M-t图序列地震能量释放都呈升级趋势,地震活动也相似。平静打破后3级以上地震活跃,都出现震群现象,地震能量释放呈加速状态;④都属于前震-主震-余震型序列。意大利拉奎拉MW6.3地震主震前最大前震为MW5.2;云南大理MS6.4地震主震前最大前震为MS5.6,且前震震群特征明显。同时,本文讨论了按地震丛集性划分区域的合理性,认为按地震丛集性划分区域更容易把握区域地震活动的特点。这两次地震发生在不同区域,构造差异极大,属不同错动类型,用分区G-R关系和M-t序列分析,都得出较好的结果,再次说明了分区G-R关系和M-t序列分析对判断地震危险性的普适性特征,这为下一步产出“地震危险性云图”提供了依据。 相似文献
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A STUDY REVIEW ON CHARACTERISTICS OF SEISMIC ACTIVITY OF ACTIVE-TECTONIC BLOCK BOUNDARIES IN MAINLAND CHINA 
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下载免费PDF全文 More than 80 percent of strong earthquakes(M≥7.0)occur in active-tectonic block boundaries in mainland China, and 95 percent of strong earthquake disasters also occur in these boundaries. In recent years, all strong earthquakes(M≥7.0)happened in active-tectonic block boundaries. For instance, 8 strong earthquakes(M≥7.0)occurred on the eastern, western, southern and northern boundaries of the Bayan Har block since 1997. In order to carry out the earthquake prediction research better, especially for the long-term earthquake prediction, the active-tectonic block boundaries have gradually become the key research objects of seismo-geology, geophysics, geodesy and other disciplines. This paper reviews the research results related to seismic activities in mainland China, as well as the main existing recognitions and problems as follows: 1)Most studies on seismic activities in active-tectonic block boundaries still remain at the statistical analysis level at present. However, the analysis of their working foundations or actual working conditions can help investigate deeply the seismic activities in the active-tectonic block boundaries; 2)Seismic strain release rates are determined by tectonic movement rates in active-tectonic block boundaries. Analysis of relations between seismic strain release rates and tectonic movement rates in mainland China shows that the tectonic movement rates in active-tectonic block boundaries of the eastern region are relatively slow, and the seismic strain release rates are with the smaller values too; the tectonic movement rates in active-tectonic block boundaries of the western region reveal higher values, and their seismic strain rates are larger than that of the eastern region. Earthquake recurrence periods of all 26 active-tectonic block boundaries are presented, and the reciprocals of recurrence periods represent high and low frequency of seismic activities. The research results point out that the tectonic movement rates and the reciprocals of recurrence periods for most faults in active-tectonic block boundaries exhibit linear relations. But due to the complexities of fault systems in active tectonic block boundaries, several faults obviously deviate from the linear relationship, and the relations between average earthquake recurrence periods and tectonic movement rates show larger uncertainties. The major reason is attributed to the differences existing in the results of the current earthquake recurrence studies. Furthermore, faults in active-tectonic boundaries exhibit complexities in many aspects, including different movement rates among various segments of the same fault and a certain active-tectonic block boundary contains some parallel faults with the same earthquake magnitude level. Consequently, complexities of these fault systems need to be further explored; 3)seismic activity processes in active-tectonic block boundaries present obvious regional characteristics. Active-tectonic block boundaries of the eastern mainland China except the western edge of Ordos block possess clustering features which indicate that due to the relatively low rate of crustal deformation in these areas, a long-time span is needed for fault stress-strain accumulation to show earthquake cluster activities. In addition, active-tectonic block boundaries in specific areas with low fault stress-strain accumulation rates also show seismic clustering properties, such as the clustering characteristics of strong seismic activities in Longmenshan fault zone, where a series of strong earthquakes have occurred successively, including the 2008 M8.0 Wenchuan, the 2013 M7.0 Lushan and the 2017 M7.0 Jiuzhaigou earthquakes. The north central regions of Qinghai-Tibet Plateau, regarded as the second-grade active-tectonic block boundaries, are the concentration areas of large-scale strike-slip faults in mainland China, and most of seismicity sequences show quasi-period features. Besides, most regions around the first-grade active-tectonic block boundary of Qinghai-Tibet Plateau display Poisson seismic processes. On one hand, it is still necessary to investigate the physical mechanisms and dynamics of regional structures, on the other hand, most of the active-tectonic block boundaries can be considered as fault systems. However, seismic activities involved in fault systems have the characteristic of in situ recurrence of strong earthquakes in main fault segments, the possibilities of cascading rupturing for adjacent fault segments, and space-time evolution characteristics of strong earthquakes in fault systems. 4)The dynamic environment of strong earthquakes in mainland China is characterized by “layering vertically and blocking horizontally”. With the progresses in the studies of geophysics, geochemistry, geodesy, seismology and geology, the physical models of different time/space scales have guiding significance for the interpretations of preparation and occurrence of continental strong earthquakes under the active-tectonic block frame. However, since the movement and deformation of the active-tectonic blocks contain not only the rigid motion and the horizontal differences of physical properties of crust-mantle medium are universal, there is still need for improving the understanding of the dynamic processes of continental strong earthquakes. So it is necessary to conduct in-depth studies on the physical mechanism of strong earthquake preparation process under the framework of active-tectonic block theory and establish various foundation models which are similar to seismic source physical models in California of the United States, and then provide technological scientific support for earthquake prevention and disaster mitigation. Through all kinds of studies of the physical mechanisms for space-time evolution of continental strong earthquakes, it can not only promote the transition of the study of seismic activities from statistics to physics, but also persistently push the development of active-tectonic block theory. 相似文献
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结合东南沿海地区的地质构造背景、地震活动特点,研究粤闽交界及其近海地区(N 22.80°~24.00°、E116.50°~118.00°)地震活动特征,结果表明此区域:1具备中强地震活动的构造背景;2现代小地震呈北东方向密集成带分布在南澎列岛附近,与北东向滨海断裂的方向一致;3 6级以上地震序列类型多属主余型;4 1971年有小震记录以来,一直存在背景性的ML2级左右地震活动;ML4级以上地震活动成丛分布特征明显;中等地震(ML4~5级)的发生与本区小震活动增强之间无明显关联;当出现年平均b值低于平均值、且较上一年b值下降幅度≥0.5时,可能预示本区进入ML4级地震活跃时段,东南沿海地震带在未来1~2年内可能有中强或以上地震发生;ML4.5级以上地震前,应变能释放曲线存在加速变化。 相似文献
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Based on the digital seismic waveform data observed from regional and reservoir seismic networks,the seismicity and source parameters in the Zipingpu reservoir area from January 1,2000 to May 11,2008 before the Wenchuan MS8.0 earthquake are studied. The analysis shows a continuous activity of small earthquakes before the Wenchuan MS8. 0 earthquake. The level of seismic activity was from ML2.0 to ML3.0 in recent years. The impoundment of Zipingpu reservoir started in September 2005 and the obvious increment of seismic activities occurred in February 2008,but according to the analysis of the longer time series,the frequency and intensity of seismic activities do not exceed its range,which means it is still a fluctuation of regional seismic activities or tectonic activity. At the same time,we also studied the spatio-temporal distribution and the change of apparent stress difference in the source region before the great earthquake,and the results show that the apparent stress values of small earthquakes are generally higher than fitted values of apparent stress in the reservoir area in the nearly three months before the Wenchuan MS8.0 earthquake. It can be seen from the spatial distribution of apparent stress difference,that the epicenter of the earthquake is located at a low stress distribution area,and the relatively high apparent stress difference is at the east of the epicenter. Apparent stress increment occurred in local areas. 相似文献
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The variations in the intensity of the global seismic process during the 20th and beginning of the 21st centuries are analyzed. It is established that the evolution of the global seismic process is marked by a trend of a certain quasi-periodicity in the release of seismic energy. The analysis of the lithospheric seismicity during 113 years has shown that this time interval accommodated three periods of seismic activation separated by two periods of relative seismic quiescence. The global seismicity of the Earth is strongly dominated by the contributions of the earthquakes in the Pacific seismic belt. A considerable effect is also provided by the northeastern margin of the Indian Ocean. The horizontal displacements of the lithospheric plates are probably responsible for the accumulation of stresses in the potential sources of the earthquakes at the interplate contacts and in the orogenic areas inside the continents. The revealed clustering of the earthquakes with M ≥ 8.3 in the narrow time intervals is probably due to the fact that the strongest seismic event that occurs at the beginning of each activation is a trigger which simultaneously causes the relaxation of a few dozen mature potential sources within 10–15 years. This interval of seismic activation is followed by a relatively quiet period of 30–35 years, when the energy for the next activation is accumulated in a series of high-magnitude sources. 相似文献
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The results of laboratory experiments on biaxially compressed physical models of a seismic source are presented, discussed and interpreted in terms of nonlinear dynamics; the relation is shown between the degree of seismic pulse coherency (expressed through the amplitude frequency spectra development) and energy (or magnitude) in a series of model experiments. It has been ascertained that the degree of radiated waves coherency plays a more important role concerning the seismic energy release than the size (radius) of the seismic source.The relations among individual source parameters obtained in the laboratory were tested by the analysis of three series of seismograms of aftershocks which followed the 1988 Spitak earthquake (two series) and the 1975 Oroville earthquake (one series). The fundamental effect observed in the laboratory, i.e., the growth of pulse coherency with increasing stress concentration in the focal region (reflected in growing earthquake magnitude), was clearly manifested in all three earthquake aftershock series.Due to derivation by a comparison of the above results, obtained on the basis of nonlinear dynamics with the classical source models by Brune, Madariaga and others, it seems to be namely the self-organizing of the structure itself caused by the increasing stress field in the seismic source, which can answer the question concerning the degree of energy cumulation in the earthquake focus at a given moment. 相似文献
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通过对1966年以来的华北地区地震活动期强震前的前性兆系列研究,得出华北地区在现今活动期内有统一的地壳应力场作用的结论。 相似文献
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长江下游—南黄海地震带位于华北地震区东南部, 带内地震主要受长江下游和南黄海海域内一系列断裂的控制, 以中强地震活动为主, 是地震活动较强的地区。 本文充分利用该带最新的区域地震台网资料, 历史地震复核资料以及地震构造等资料, 统计和计算了b值、 V4和中小地震能量密度值, 探讨了带内b值空间分布与历史强震、 中小地震能量密度值空间分布的关系, 进一步研究了长江下游—南黄海地震带的地震活动性特征。 通过本文的研究, 获得了长江下游—南黄海地震带的地震活动性参数, 为概率危险性分析提供计算参数; 探讨了该带未来百年地震发展趋势, 初步判定了该带潜在地震危险区, 为地震活动中长期预测提供参考依据和方法; 研究结果对地震区划、 工程场地地震安全性评价、 地震活动中长期预测均有重要意义。 相似文献
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两个原因使我们必须开展深部探测.一是寻找深部资源,二是更好地理解形成和控制陆内成矿的深部动力学过程,预测新的矿集区.在深部探测专项、国家自然科学基金和地质调查项目资助下,作者在长江中下游成矿带及邻区开展了系统的多尺度、综合地球物理探测.包括:成矿带尺度的宽频地震探测及"廊带式"综合探测,矿集区尺度的骨干剖面探测和三维建模,矿田尺度的三维探测与反演模拟.探测结果在三个层次取得了一系列新认识和新发现,完善了相关探测方法技术.主要包括:揭示了成矿带岩石圈结构、深部过程及对成岩、成矿的控制,提出了成矿带形成的动力学模型,诠释了在狭窄的成矿带内形成大规模金属堆积的深部因素;揭示了典型矿集区地壳三维结构、组成和断裂分布,建立了矿集区三维结构模型和区域成矿模式,推断了主要控矿岩体、地层的空间展布,预测了新的找矿靶区;开展了"玢岩型"、斑岩型和热液型多金属矿床综合地球物理探测试验,总结了勘查模式,预测了深边部找矿靶区;提出了硬岩区反射地震数据采集设计、激发到接收的有效措施,探索了地震弱信号提取、噪声压制、静校正和偏移等处理新技术、新方法;提出了强电磁干扰区电磁去噪的数字形态滤波等技术,完善了二/三维带地形和考虑各向异性情况的电磁正反演技术. 相似文献
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7级以上的强震并不是在一片空白上突然发生的,而是在一种间歇性的地震活动背景下发生的,研究这种背景地震活动的规律,为判定一个活动期的强震的潜在震源区提供信息。本文通过对华北历史上记录到的18次7级以上强震的震前史和震后史的研究,提出了华北地区强震背景地震活动的四条规律:①强震前多有6级以上的背景地震发生;②并且多有信息地震发生;③短时间近距离的两个强震之间可能出现缓震现象;④强震具有一定的减震作用。文中根据这四条规律,对华北地区1501——1730年的强震潜在震源区做了判别分析。 相似文献
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为了解2013年11月23日吉林前郭MS5.8和2018年5月28日吉林松原MS5.7地震震源区的地壳速度结构及其孕震环境,本研究收集了东北地区CEA固定台站、NECESSArray流动台站和五大连池WAVESArrary流动台站的连续波形数据,使用背景噪声成像方法,获得了前郭地震和松原地震震源区地壳S波速度结构.结果显示,这两个地震主要发生在相对高波速异常区,而震源区下方存在明显低波速异常,且该低速层呈北北东走向,并有向北延展的趋势.结果表明,震源区相对高波速异常区易于积累能量孕育地震,而震源区下方的低波速异常可能代表了流体作用.这种流体作用会降低断层面有效正应力从而触发地震.这种流体作用可能和太平洋板块深俯冲至我国东北地区（包括前郭地震和松原地震震源区）下方的地幔转换内形成"大地幔楔"结构与动力学密切相关.在"大地幔楔"结构中,由于地幔转换带中滞留板块脱水作用和地幔角流作用,容易形成热湿物质上涌,进而导致松辽盆地中北部岩石圈物质拆沉、地幔流体入侵至中下地壳、然后作用于断裂带,从而导致了两个震源区中强度地震的发生. 相似文献
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Emilio Rodríguez-Escudero José J. Martínez-Díaz José A. Álvarez-Gómez Juan M. Insua-Arévalo Ramón Capote del Villar 《Bulletin of Earthquake Engineering》2014,12(5):1831-1854
In this work we analyze the tectonic setting of the recent damaging seismic series occurred in the Internal Zones of the eastern Betic Cordillera (SE Spain) and surrounding areas, the tectonic region where took place the 11th May 2011 Mw 5.2 Lorca earthquake. We revisit and make a synthesis of the seven largest and damaging seismic series occurred from 1984 to 2011. We analyze their seismotectonic setting, and their geological sources under the light of recent advances in the knowledge on active faults, neotectonics, seismotectonics and stress regime, with special attention focused on the Lorca Earthquake. These seismic series are characterized by two types of focal mechanisms, produced mainly by two sets of active faults, NNW–SSE to NNE–SSW small (no larger than 20–30 km) extensional faults with some strike slip component, and E–W to NE–SW large strike slip faults (more than 50 km long) with some compressional component (oblique slip faults). The normal fault earthquakes related to the smaller faults are dominant in the interior of large crustal tectonic blocks that are bounded by the large E–W to NE–SW strike-slip faults. The strike slip earthquakes are associated to the reactivation of segments or intersegment regions of the large E–W to NE–SW faults bounding those crustal tectonic blocks. Most of the seismic series studied in this work can be interpreted as part of the background seismicity that occurs within the crustal blocks that are strained under a transpressional regime driven by the major strike slip shear corridors bounding the blocks. The seismotectonic analysis and the phenomenology of the studied series indicate that it is usual the occurrence of damaging compound earthquakes of M \(\sim \) 5.0 associated with triggering processes driven by coseismic stress transfer. These processes mainly occur in the seismic series generated by NNW–SSE to NNE–SSW faults. These mechanical interaction processes may induce a higher frequency of occurrence of this kind of earthquakes than considered in traditional probabilistic seismic hazard assessments and it should be taken into account in future seismic hazard assessments. 相似文献
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To consider the influence of aftershocks in engineering design, the correlations between main shocks and aftershocks should be examined, and an aftershock simulation method with main shock ground motions needs to be developed. In this study, the data on the sequences of main shock-aftershock ground motions and other related parameters were collected. Using these data, correlations between the magnitude, frequency, duration and energy of the main shock-aftershock ground motions were investigated. The results showed that the magnitude of the aftershock can be larger than that of the main shock. The shapes of the Fourier amplitude spectra of main shocks and aftershocks were similar; however, the predominant frequency and high-frequency components of the aftershock tended to be larger. Considering the magnitude difference between the main shock and the aftershock, the correlation of durations was explored. Additionally, a new concept, the duration ratio, was defined to describe the concentration of seismic energy release, and main shock energy was strongly positively correlated with the energy attenuated during the main shock-aftershock sequence. Finally, based on these results regarding correlation, an aftershock synthesis using recorded main shock ground motions was constructed with the trigonometric series method for seismic design, and some examples are given to analyze the rationality of this synthetic method.
相似文献19.
Alpine headwaters in subarctic regions are particularly sensitive to climate change, yet there is little information on stream thermal regimes in these areas and how they might respond to global warming. In this paper, we characterize and compare the hydrological and thermal regimes of two subarctic headwater alpine streams within an empirical framework. The streams investigated are located within two adjacent catchments with similar geology, size, elevation and landscape, Granger Creek (GC) and Buckbrush Creek (BB), which are part of the Wolf Creek Research Basin in the Yukon Territory, Canada. Hydrometeorological and high-resolution stream temperature data were collected throughout summer 2016. Both sites exhibited a flow regime typical of cold alpine headwater catchments influenced by frozen ground and permafrost. Comparatively, GC was characterized by a flashier response with more extreme flows, than BB. In both sites, stream temperature was highly variable and very responsive to short-term changes in climatic conditions. On average, stream temperature in BB was slightly higher than in GC (respectively 5.8 and 5.7°C), but less variable (average difference between 75th and 25th quantiles of 1.6 and 2.0°C). Regression analysis between mean daily air and stream temperature suggested that a greater relative (to stream flow) groundwater contribution in BB could more effectively buffer atmospheric fluctuations. Heat fluxes were derived and utilized to assess their relative contribution to the energy balance. Overall, non-advective fluxes followed a daily pattern highly correlated to short-wave radiation. G1enerally, solar radiation and latent heat were respectively the most important heat source and sink, while air–water interface processes were major factors driving nighttime stream temperature fluctuations. 相似文献
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The rapid release of strain energy is an important phenomenon leading to seismic events or rock failures during the excavation of deep rock.Through theoretical analysis of strain energy adjustment during blasting and mechanical excavation,and the interpretation of measured seismicity in the Jin-Ping Ⅱ Hydropower Station in China,this paper describes the characteristics of energy partition and induced seismicity corresponding to different energy release rates.The theoretical analysis indicates that part of the strain energy will be drastically released accompanied by violent crushing and fragmentation of rock under blast load,and this process will result in seismic events in addition to blasting vibration.The intensity of the seismicity induced by transient strain energy release highly depends on the unloading rate of in-situ stress.For mechanical excavation,the strain energy,which is mainly dissipated in the deformation of surrounding rock,releases smoothly,and almost no seismic events are produced in this gradual process.Field test reveals that the seismic energy transformed from the rock strain energy under high stress condition is roughly equal to that coming from explosive energy,and the two kinds of vibrations superimpose together to form the total blasting excavation-induced seismicity.In addition,the most intense seismicity is induced by the cut blasting delay; this delay contributes 50% of the total seismic energy released in a blast event.For mechanical excavation,the seismic energy of induced vibration(mainly the low intensity acoustic emission events or mechanical loading impacts),which accounts only for 1.5‰ of that caused by in-situ stress transient releasing,can be ignored in assessing the dynamic response of surrounding rock. 相似文献