共查询到19条相似文献，搜索用时 125 毫秒
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本文选取华北地震区作为研究区域,尝试利用空间光滑活动模型进行地震危险性评估.首先对研究区域进行划分网格,依据地震构造和地震空间分布特征建立地震构造模型,确定构造区特征参数(b值、M0、Mu、断层方位角及M-L关系等).采用考虑了地震构造背景的椭圆光滑过程的地震活动参数模型,计算各网格点的地震发生率.并利用网格源的地震危险性概率评价方法,由不同输入地震目录通过综合加权得到该区域50年超越概率10％的加速度峰值区划结果.该方法充分体现了地震活动的空间非均一性,尤其适用于发震构造不甚清晰的中强地震可能造成的地震危险性,避免了常规潜在震源区的划分.且评价方法简单快捷,为地震区划以及重大工程地震安全性评价工作提供了新的技术方法. 相似文献
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本文对中国大陆东部102个中强潜在震源区内1500a以来5—6级地震的复发间隔进行了统计分析,得到了中强地震复发间隔不仅受潜源内断层活动性影响,还与发震构造是否交汇及邻区构造活动等因素有一定关系。中强地震复发间隔大致满足指数分布,通过给出的概率模型可以计算出研究区内各潜在震源区未来一定时间内的发震概率,为地震危险性分析提供一些基础资料。 相似文献
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在我国当前地震安全性评价中,普遍使用考虑地震活动时空不均匀性的概率地震危险性分析方法(CP-SHA),它规定以地震带为统计区域计算地震活动性参数b值和v4值。正在编制的中国地震动区划图(五代图)提出了针对潜在震源区进行三级划分原则:划分地震带、地震带上划分地震构造区、地震构造区内再划分潜在震源区。本文提出以地震构造区为统计区域回归统计方法计算b值和v4值,然后进行概率危险性分析计算,这样得到的结果可能更为合理。 相似文献
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根据华北地区的地震目录,建立了4个空间光滑的地震活动性模型,并以这些模型为空间分布函数,将华北地震区每个地震带的地震年发生率分配到空间格点中,计算这一地区的地震危险性．结果表明,采用仪器记录地震计算得到的地震活动性模型和地震危险性结果能够反映华北地区现今的地震活动水平和地震危险性水平,符合人们对现今华北地区地震危险性的认识;采用历史破坏性地震（Mge;4.7）计算的地震活动性模型和地震危险性结果,较好地反映了华北地区中强地震活动区的地震危险性水平;以地震应变计算地震活动率,并根据点椭圆模型和线椭圆模型计算得到的地震活动性模型,能够较好地反映大地震的活动水平和空间构造特征．将根据4个模型计算得到的50年超越概率10%峰值加速度（PGA）分布加权平均,得到综合的华北地区PGA分布,并将该PGA分布与根据《中国地震动参数区划图》中综合潜源方案计算得到的50年超越概率10%的PGA分布做了比较,发现二者无本质差别,均能反映华北地震区的地震危险性水平．当然,二者也具有一定的差异:前者计算得到的符合PGAge;100 cm/s2条件的区域面积明显要比后者的大,而符合PGAge;250 cm/s2条件的区域面积则比后者的要小. 这主要是由于潜在震源区类型和空间分布函数不同造成的． 相似文献
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前兆异常动态扫描与区域构造活动背景结合的研究--试建立华北地区构造活动性与地震危险性综合评估数字化图 总被引：2，自引：0，他引：2
为实现前兆异常空间扫描与构造活动背景的有机结合，本文提出：以近效十年2级以上地震的累计频次分布为依据，量化评估华北各构造区现今活动状态与基本活动水平，以近千年来的5级以上地震的年均发生率分布为依据量化评估断裂构造(带、段)的地震活动危险性，并将上述两项量化评估的数值分布图进行叠加，建立起标示华北地区现今构造活动与地震危险性的数字化图，以此作为前兆异常空间扫描的输入，从而增强前兆空间扫描图像中的构造活动信息及其异常演化特征，提高强震危险预测的能力。 相似文献
6.
京津冀地区位于华北地震区北部,区内受多组北北东向、北西西向断裂带的影响,构造活动强烈,地震活动水平较高.该区是我国城市密集、人口稠密、经济较发达地带,一旦发生中强地震,会严重影响着区域经济的发展和社会稳定,因此该区的地震活动性愈加值得关注和研究.本文收集了京津冀地区历史破坏性地震和1970年以来中小地震,分析了区域最小完整性震级时间、空间分布特征,基于古登堡-里克特G-R关系的震级-频度分布原理和泊松分布原理,统计分析了京津冀地区的地震活动性参数:a值、b值和V_4值,并定量地分析京津冀地区的地震时、空分布特征,探讨了京津冀地区的地震活动规律性、地震分布特征以及未来地震活动趋势.本文的研究结果可供京津冀地区地震活动性分析和地震危险性分析时参考. 相似文献
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中强地震活动区地震年平均发生率确定方法的比较 总被引：1，自引：0，他引：1
目前确定地震活动性参数的方法有2种,即潜在震源区划分法和格点空间光滑法.本文针对格点空间光滑法,重点介绍了高斯空间光滑法及其改进后的方法,并对比分析了这些方法的优缺点及适用性;然后以华中为研究区,分别采用高斯空间光滑法和潜在震源区法建立地震活动性模型计算地震年平均发生率,并利用概率地震危险性分析方法计算地震危险性,对比两种方法所得区划结果的差异并分析了引起差异的原因.结果表明:空间光滑法适用于中强地震活动区地震危险性或由背景地震引起的地震危险性的计算;潜在震源区划分法适用于考虑明确的发震构造的地震危险性.将2种方法相结合,综合考虑地震和已知构造信息是判断中强地震活动区地震危险性的可行方法. 相似文献
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本文利用34°N以南,105°E以东大陆东南地区中强地震和小震的震源机制解结果,分析了震源机制解与可能的中强震发震构造及潜源区方向的关系.华南及邻区地震震源机制解节面走向和主应力轴方位分布具有明显的优势方向,大部分M≥4.0地震震源机制解中一个节面走向与主要构造走向及大多数潜源区方向对应较好,多数小震的节面走向和主应力轴方位综合统计结果也能为潜源区方向的判定提供比较可靠的依据.同时通过对1996年南黄海Ms6.1地震和1997年福建龙岩-永安Ms5.2地震的震源机制解结果进行分析,并结合区域地质构造、地震活动以及地震的等震线长轴展布、余震分布等资料,探讨了这两个地区潜源区的划分. 相似文献
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新编制的地震动参数区划图采用了潜在震源区三级划分方案,以体现背景地震活动空间分布的不均匀性,并在地震构造区内归纳出统一的地震构造模型.本文根据西南地区潜在震源区三级划分的成果,分析了龙门山地震统计区内的龙门山和成都地震构造区的基本特征,历史地震活动强度及频度,主要活动构造的构造变形样式,建立了地震构造区的发震构造模型,确定了构造区的本底地震及划分构造源的地震构造标志.同时,提出了确定背景源空间分布函数的简单方法. 相似文献
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利用区域双差层析成像方法,基于2008年10月—2018年6月近震资料,对晋冀豫交界地区记录到的地震事件进行震源位置与P波、S波三维速度结构的联合反演。重新定位后,地震空间位置得到明显改善,浅部的速度结构与地形及沉积层厚度对应较好,研究区内控制性断裂和地震多分布在太行山隆起区的高、低速变化梯级带上。对比分析研究区内不同构造单元及同一构造单元不同深度的P、S波速度异常特征及其与中小地震和历史强震的分布关系,结合研究区内历史强震和现今中、小震分析发震构造及深部孕震环境,为该区未来强震危险区判定提供科学依据。 相似文献
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地震破裂区是地震时沿发震断裂带的同震错动面或破裂面在地表的垂直投影区域,指示了震源断层/破裂的位置与尺度。确定过去长期的强震/大地震破裂区是鉴别地震空区、研究与预测强震危险性的重要基础。对于现代强震,破裂区可运用多种现代技术方法确定,但对于历史强震,破裂区确定的方法需要探索与发展。以华北地区为例,研究利用烈度/等震线资料、结合地震构造与震区地表地质环境等信息确定历史强震破裂区的方法,并开展应用试验。结果表明:研究区现代地震破裂区延伸的烈度区间与极震区烈度、震区环境之间存在密切关系,基于这种关系建立了2条经验准则,可分别用于根据烈度分布确定华北2类震区环境(基岩区和厚层第四纪松散堆积覆盖区)历史强震破裂区的位置与延伸。文中还提出通过综合地震构造、现代小震/余震分布等信息,辅助确定历史强震破裂区横向宽度的思路与途径。作为应用试验,文中确定了5次历史地震的破裂区,结果表明本文发展的经验准则及相应方法适用于华北地区历史强震破裂区的确定。 相似文献
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—Measurements indicate that stress magnitudes in the crust are normally limited by the frictional equilibrium on pre-existing, optimally oriented faults. Fault zones where these limitations are frequently reached are referred to as seismic zones. Fault zones in the crust concentrate stresses because their material properties are different from those of the host rock. Most fault zones are spatially relatively stable structures, however the associated seismicity in these zones is quite variable in space and time. Here we propose that this variability is attributable to stress-concentration zones that migrate and expand through the fault zone. We suggest that following a large earthquake and the associated stress relaxation, shear stresses of a magnitude sufficient to produce earthquakes occur only in those small parts of the seismic zone that, because of material properties and boundary conditions, encourage concentration of shear stress. During the earthquake cycle, the conditions for seismogenic fault slip migrate from these stress-concentration regions throughout the entire seismic zone. Thus, while the stress-concentration regions continue to produce small slips and small earthquakes throughout the seismic cycle, the conditions for slip and earthquakes are gradually reached in larger parts of, and eventually the whole, seismogenic layer of the seismic zone. Prior to the propagation of an earthquake fracture that gives rise to a large earthquake, the stress conditions in the zone along the whole potential rupture plane must be essentially similar. This follows because if they were not, then, on entering crustal parts where the state of stress was unfavourable to this type of faulting, the fault propagation would be arrested. The proposed necessary homogenisation of the stress field in a seismic zone as a precursor to large earthquakes implies that by monitoring the state of stress in a seismic zone, its large earthquakes may possibly be forecasted. We test the model on data from Iceland and demonstrate that it broadly explains the historical, as well as the current, patterns of seismogenic faulting in the South Iceland Seismic Zone. 相似文献
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发震构造特性是潜在震源区划分及其地震年发生率确定的重要依据。潜在震源区除了反映“未来具有发生破坏性地震的地区”的内涵外,还应反映高震级档地震具有相似复发特征的涵义。由于在地震活动性参数统计单元内,有一些具有不同本底地震的活动构造块体,为更好地反映地震活动的空间不均匀性,考虑潜在震源区的三级划分是有必要的。通过分析潜在震源区内高震级档地震的复发特征,计算预测时段内潜在震源区的高震级档地震的发震概率,采用预测时段内概率等效转换获得地震年平均发生率的方法,有助于在中国地震危险性分析框架内考虑潜在震源区的强震复发特性。另外,文中还对潜在震源区内特征地震次级震级档频度不足的特性和发震构造上强震非均匀性在地震危险性分析中的应用问题进行了探讨 相似文献
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云南活动性断裂带的结构变异与孕震体构造的空间关系 总被引：2，自引：1，他引：1
中国的强震主要发生在一些板内大型走滑断裂带上,地震的破裂基本上是以走滑型破裂为特征。在这些活动性的走滑断裂带上形成的孕震体构造与该走滑断裂结构在空间的变化有关,并且表现出几种主要的变异形式。结合西南地区地震构造的实例,本文剖析了这几种结构变异形式,阐明了孕震体构造存在的空间机制。本文从地震与构造丛集相关及其所具有的分维特征入手,展开了对孕震区断裂结构变异特征的识别和孕震体空间机制的探讨,表述了一条活动性大断裂必须由若干次级断裂和无数中小断裂的空间组合,才能形成孕震体的必要条件。 相似文献
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Crustal velocity,density structure,and seismogenic environment in the southern segment of the North-South Seismic Belt,China 
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下载免费PDF全文 The southern segment of the North-South Seismic Belt in China is a critical region for earthquake preparedness and risk reduction efforts. However, limited by the low density of seismic stations and the use of single-parameter physical structural models, the deep tectonic features and seismogenic environment in this area remain controversial. Thus, a comprehensive analysis based on high-resolution crustal structures and multiple physical parameters is required. In this study, we applied the ambient noise tomography method to obtain the three-dimensional (3D) crustal S-wave velocity structure using continuous waveform data from 112 permanent stations and 350 densely distributed temporary stations in the southern segment of the North-South Seismic Belt. Then, we obtained the high-resolution 3D density structure through wavenumber-domain 3D gravity imaging constrained by the velocity structure. The low-velocity and low-density anomalies in the upper crust of the study area were mainly distributed in the Sichuan Basin and around Dali and Simao, while the high-velocity and high-density anomalies were primarily distributed in the Panxi region, corresponding to the surface geological features. Two prominent low-velocity and low-density anomalies were observed in the middle and lower crust: one to the west of the Songpan-Garzê block and Sichuan-Yunnan diamond-shaped block, and the other near the Anninghe-Xiaojiang fault. Combined with the spatial distribution of seismic events in the study area, we found that previous earthquakes predominantly occurred in the transition zones between high and low anomaly regions and in the low-velocity and low-density zones in the upper crust. In contrast, moderate-to-strong earthquakes mainly occurred within the transition zones between high and low anomaly regions and close to the high-velocity and high-density regions, often with low-velocity and low-density layers below their hypocenters. Fluids play a critical role in the seismogenic process by reducing fault strength and destabilizing the stress state, which may be a triggering factor for earthquakes in the study area. Additionally, the upwelling of molten materials from the mantle may lead to energy accumulation and stress concentration, providing an important seismogenic background for moderate-to-strong earthquakes in this area. 相似文献
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R. B. S. Yadav Yusuf Bayrak J. N. Tripathi S. Chopra A. P. Singh Erdem Bayrak 《Pure and Applied Geophysics》2012,169(9):1619-1639
The maximum likelihood estimation method is applied to study the geographical distribution of earthquake hazard parameters and seismicity in 28 seismogenic source zones of NW Himalaya and the adjoining regions. For this purpose, we have prepared a reliable, homogeneous and complete earthquake catalogue during the period 1500–2010. The technique used here allows the data to contain either historical or instrumental era or even a combination of the both. In this study, the earthquake hazard parameters, which include maximum regional magnitude (M max), mean seismic activity rate (λ), the parameter b (or β?=?b/log e) of Gutenberg–Richter (G–R) frequency-magnitude relationship, the return periods of earthquakes with a certain threshold magnitude along with their probabilities of occurrences have been calculated using only instrumental earthquake data during the period 1900–2010. The uncertainties in magnitude have been also taken into consideration during the calculation of hazard parameters. The earthquake hazard in the whole NW Himalaya region has been calculated in 28 seismogenic source zones delineated on the basis of seismicity level, tectonics and focal mechanism. The annual probability of exceedance of earthquake (activity rate) of certain magnitude is also calculated for all seismogenic source zones. The obtained earthquake hazard parameters were geographically distributed in all 28 seismogenic source zones to analyze the spatial variation of localized seismicity parameters. It is observed that seismic hazard level is high in Quetta-Kirthar-Sulaiman region in Pakistan, Hindukush-Pamir Himalaya region and Uttarkashi-Chamoli region in Himalayan Frontal Thrust belt. The source zones that are expected to have maximum regional magnitude (M max) of more than 8.0 are Quetta, southern Pamir, Caucasus and Kashmir-Himanchal Pradesh which have experienced such magnitude of earthquakes in the past. It is observed that seismic hazard level varies spatially from one zone to another which suggests that the examined regions have high crustal heterogeneity and seismotectonic complexity. 相似文献
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为了理解地震的发生和地壳结构不均匀性的关系，利用南加州地震台网的固定台和临时台所记录的2863个兰德斯余震和区域地震，共计107401个P波和19624个S波高质量的到时数据，采用地震层析成像方法得到了兰德斯地震区P波和S波的精细的三维速度结构和泊松比分布．结果显示，地震的发生和分布与地壳结构的横向不均匀性有密切的关系．总体上看，兰德斯地震区余震成丛分布，并被低速块体截断，其中4级以上地震大多分布于P波高、低速异常过渡区域或偏向高速块体一侧，这可能是因为高速区多属地壳脆性介质，易于造成应力集中，导致地震；反之，低速度区则可能代表破碎程度较高、富含流体或温度较高区域，因而更倾向于产生无震变形．基于兰德斯地震区强震震源位置、地震区P波、S波速度异常与泊松比分布推断，兰德斯地震区可能有流体存在．地壳流体易使地壳岩石弱化，从而引发大地震． 相似文献
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Imene Meriem Benbakhti Said Maouche Djelloul Belhai Assia Harbi Jean-François Ritz Ghilles Rabai Ahmed Rezouk Fawzi Doumaz 《Journal of Seismology》2018,22(6):1549-1561
In this work, we reappraise the seismogenic potential of the geologic structures in the western Tell Atlas of Algeria, considered active host to moderate to low magnitude earthquakes. The direct identification of active faults is generally a difficult task in northern Algeria. The active tectonics in the Oran Plio-Quaternary age basin (Northwestern Algeria) is analyzed and characterized through a morpho-structural study combining topographic, geomorphologic, geological, and neotectonic data. Folds and fault scarps affecting Quaternary deposits show that the region is affected by compressional deformation still active nowadays, as shown by the recorded seismic activity. Our new observations enable a better understanding of the present seismotectonic context of the Oran region, particularly with regard to the magnitude and source of the 1790 Oran damaging event. The obtained result helps to shed some light on the elusive active tectonics characterizing this coastal area, and to assess regional seismic hazard, particularly in coastal zones where large seismogenic areas straddle the onshore–offshore zones. 相似文献