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斜坡动力响应特征与斜坡形态密切相关,若入射地震波主频接近斜坡卓越频率就会放大斜坡动力响应,甚至造成斜坡失稳。汶川地震对远离震中的黄土地区造成了较为严重的破坏,局部场地震害和地震动放大效应显著。选取汶川地震典型黄土斜坡场地,利用地形台阵流动观测和数值模拟计算相结合的方法,系统开展强震动作用下黄土斜坡场地动力响应特征研究。结果表明:坡顶卓越频率最小,其PGA放大系数甚至达到坡底的1.98,这种现象可能与斜坡高差和入射波波长之比密切相关,比值0.2时坡顶放大效应达到最大。随斜坡坡度增加,放大效应增强,坡顶反应谱卓越周期放大系数可达5,说明斜坡地形对强震地面运动有显著影响。数值计算结果与实际强震观测基本吻合,其结果对黄土地区建设工程抗震设防具有重要的科学与实际意义。 相似文献
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地震作用下黄土场地对地震波不同分量的放大效应影响显著。针对黄土高原典型黄土场地在地震作用下的放大效应，设计并完成大型地震模拟振动台试验，通过输入不同强度的地震动荷载，研究黄土场地加速度（PGA）放大系数、傅里叶谱、加速度反应谱、H/V谱比与地震动强度和场地高度的变化规律，揭示地震波不同分量对黄土场地效应的影响。结果显示：黄土场地对地震波的水平分量具有明显的放大效应，对地震波垂直分量的放大效应影响较小；随着高程的增加，地震波水平分量PGA放大系数呈现非线性变化；随着地震动强度和高程的增加水平分量卓越频率的频段和幅值逐渐增加，卓越频率向低频偏移，放大倍数呈现出非线性特性。 相似文献
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新疆乌恰2次5.1级地震加速度记录特征对比分析 总被引：1，自引：0，他引：1
分析新疆乌恰两次5.1级地震4个强震台的强震动记录,第1次地震4个台记录卓越频率在4.25 Hz-13.59 Hz;第2次地震4个台记录卓越频率为2.45 Hz-3.61 Hz.从谱比曲线可以看出,2次地震在同一观测场地的场地效应基本相似,基岩台场地效应在高频部分有明显放大作用,土层场地在高频部分有明显的减小作用. 相似文献
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《地震研究》2020,(1)
准确的衰减特征及台站响应对于定量确定地震台网观测环境和分析其构造机制具有重要意义。选取2008—2017年辽宁数字地震台网地震波形资料,利用Lg波谱比与台站场地响应联合反演方法,获得了1～7 Hz Lg波三分向(UD,NS,EW)衰减关系,参与评估的32个台站的场地响应幅值曲线较为平滑,各频段衰减效应存在差异。大多数台站的场地效应幅值在1～8,少数台在低频或高频段上呈现放大效应,最大的幅值近16。结果表明:辽宁地区为低Q0(对应频率1 Hz)和低频率依赖性的构造活跃区,场地响应特征与浅层结构及地质构造有密切关系。不同场地类型的场地响应特征差异明显:井下场地类型的场地响应在低频段内(1～2 Hz)有明显的放大效应;地表较山洞场地类型的场地响应幅值在径向和垂向上都有抬升;相同场地类型中,场地响应放大效应在径向上比垂向上大的多,可能与台基岩性特征有关,而岩性差异对场地响应特征的影响不明显。 相似文献
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不规则地形和土层对地震动的影响较大,建(构)筑物选址及其抗震设防必须考虑地形和土层场地的放大效应,以避免或减轻其震害.利用自贡地形台阵记录的汶川地震(Ms8.0)的主震加速度时程,基于传统谱比法分别研究了地形和土层场地对地震动的放大效应.结果表明:(1)地形场地在低频的放大效应不明显,最大仅为1.24;在高频的放大效应较显著,在1~10 Hz频带,山顶的放大效应最大,EW、NS和UD地震动的最大放大效应分别为4.15、3.61和2.41,对应频率分别为5.72 Hz、6.46 Hz和7.44 Hz;在10~20 Hz频带,靠近山顶的山脊上某个地震动分量的放大效应最大,7#台站EW、5#台站NS和7#台站UD地震动的最大放大效应分别为9.10、5.56和2.52,对应频率分别为16.97 Hz、16.91 Hz和17.91 Hz.(2)地形场地的最大放大效应随高度有增加的趋势,且在0.1~10 Hz频带随高度增加的趋势更加明显.(3)土层场地水平向地震动在2 Hz以上开始明显放大,竖向地震动在4 Hz以上开始明显放大;EW、NS和UD地震动的最大放大效应分别为13.4、12.168和6.0,对应频率分别为6.94 Hz、7.55 Hz和10.8 Hz.(4)土层场地与地形场地的最大放大效应相比较,前者显著大于后者,对于水平向地震动,前者至少是后者的3倍以上;对于竖向地震动,前者至少是后者的2.5倍以上.(5)无论是地形场地还是土层场地,地震动的最大放大效应均有水平向大于竖向的特征. 相似文献
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利用乳山流动地震台网记录的2013年10月1日乳山M_L 3.8震群资料,基于Atkinson方法,计算得到该区Q值与频率f的关系:Q(f)=57.8 f ~(0.8562)。Moya方法仅依赖震源模型,计算绝对场地响应值,较能反映实际放大效应。采用该方法,计算14个流动地震台站场地响应,结果显示,场地响应在低频(1—2 Hz)放大作用不明显,而高频部分平均放大2—10倍,卓越频率3—10 Hz,且高频处场地响应衰减不明显。 相似文献
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基于汶川地震发生时自贡市西山公园地形影响台阵的加速度记录,利用双向反应谱比法分析了山脊地形对单自由度体系结构反应的放大效应,结果表明:(1)水平向结构反应在结构自振频率小于1Hz的低频段放大效应不明显;在1～ 10Hz频段山顶放大效应最大,最大值达3.25,对应频率为6.25Hz;在10 ～ 20Hz频段,各台站放大效应趋于平稳,靠近山顶的7号台站放大效应最明显,最大值为2.3,对应频率为16.7Hz.(2)结构反应的最大放大系数有随高度的增加而增大的趋势,且在1 ～ 10Hz频段这种趋势比较明显.(3)与其它场地效应估计方法相比较,该方法能够体现地形效应对结构反应的影响,从而更有利于研究建筑结构震害的分布. 相似文献
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利用2016年云南测震台网记录到的地脉动数据,运用H/V谱比法计算分析了47个测震台站在0.1～20.0Hz频段内的场地响应。选取2012～2016年期间云南测震台网记录到的ML≥2.5地震做单台震级偏差统计分析,挑出受场地放大作用而出现单台震级大于台网平均震级的台站做去场地放大校正,然后重新统计单台震级偏差情况。计算结果显示云南测震台网的台站受台基条件和所处位置等地质构造因素影响,均存在一定程度的场地放大作用,大部分台站场地响应的卓越频率为1～6Hz,放大倍数为2～4倍。受场地放大作用的影响,大姚、芒市等19个台站的单台ML震级大于台网平均震级。在去除场地放大作用后,台站单台震级与台网平均震级的偏差有所减小。 相似文献
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The determination of the coefficient of viscosity of eruptive products gives useful elements to the knowledge of possible variations of composition and physical conditions of the magmas. 相似文献
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As is known, the secular deceleration of the Earth's diurnal rotation is explained mainly by the tidal friction in the ocean. Below we consider this mechanism in some detail, taking into account also elastic deformations of the mantle under the action of ocean loading and the interaction between the tide-generating body, ocean tidal wave, liquid outer core, and solid inner core. It is shown that elastic displacements of the core-mantle boundary under the action of ocean loading are of about the same amplitude and phase as the elastic loading displacements of the Earth's outer surface. As a result, side by side with the mechanism of secular deceleration of diurnal rotation of the mantle, there are also (1) the opposite mechanism of secular acceleration of diurnal rotation of the outer liquid core and of the solid inner core and (2) the mechanism of excitation of differential rotation in the liquid core. Taking these effects into account, we compare theoretical and modern observed data on the eastward drift of the solid inner core. It is shown that the best agreement may be obtained if the turbulent viscosity of the liquid core is about 2 × 10
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Poise 相似文献
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The nutations of the planets Mars andEarth are investigated and compared. Alarge number of interior structureparameters are involved in the nutationcomputations. The comparison between the observations and the computationsprovides several constraints on these parmeters andtherefore allows a better understanding of the physics of the interior of theplanet. For the Earth, the high precision of the observations of the nutationshas led to a very good determination of interior properties of the planet. ForMars, observations of nutations are not yet available, and we review how theamplitude of the Martian nutations depends on the hypotheses consideredfor its interior. Although Mars is very similar to the Earth, its interior is not well known;for example, we don't knowif its core is liquid or solid. Only if the core is liquid,the Free Core Nutation (FCN) normal mode exists and can alter the nutationswhich are close to the resonance. From the observed geoids, it is known thatboth planets are not in hydrostatic equilibrium. The departure is larger forMars than for the Earth, and consequently, the implication of considering a convective mantle instead of a mantle in hydrostatic equilibrium described byClairaut's equation for the initial equilibrium state of the planet is largeron the Martian nutations than on the Earth nutations. The consequences of theuncertainty in the core dimensions are also examined and shown to be of a veryhigh influence for Mars if the core is liquid, due to the potential changes inthe FCN resonance. The influence of the presence of an inner core, which isknown to exist for the Earth, could be more important for Mars than for theEarth if the inner core is large. Due to the presence of Tharsis on Mars, thetriaxiality of this planet has, additionally, larger effects than on Earth. 相似文献
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Geomagnetism and Aeronomy - The magnetic evolution of the active region of the Sun at the level of the photosphere has been studied. Magnetic synoptic maps of the 2007 Kitt Peak Observatory were... 相似文献
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Studia Geophysica et Geodaetica - 相似文献
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地震激励下处于深水中的桥墩和周围水体的相互作用将对桥梁结构的动力响应产生较大影响。首先对地震作用下水-桥墩的相互作用理论做了概括,给出了动水压力对桥墩的作用效应及各自的适用范围;对主要的三种考虑流固耦合效应的分析方法做了对比,探讨了地震作用下影响水-结构相互作用的主要因素,并对今后的研究提出了建议。 相似文献
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Josef Vykutil 《Studia Geophysica et Geodaetica》1968,12(2):217-220
Резюме Дается вывод формул для вычислений длины хорды, длины и азимутов нормаляных сечений и длины геодезической линии эллипсоида.
Применяются тригонометрические функции данных величин и постоянные принятого ргфгргнц-эллипсоида, что является целесообразным
при использовании вычислителQjных машин, особенно автоматов. Рабочие формулы рекомендуются в форме (8–11).
Dedicated to Professor František Fiala on His 85th Birthday
Address: Veveři 95, Brno. 相似文献
Dedicated to Professor František Fiala on His 85th Birthday
Address: Veveři 95, Brno. 相似文献
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V. E. Pavlov T. Yu. Tolmacheva R. V. Veselovskiy A. V. Latyshev A. M. Fetisova I. V. Bigun 《Izvestiya Physics of the Solid Earth》2017,53(5):702-713
Until recently, the existing data prevented the geophysicists from accurately dating the Bysy-Yuryakh stratum, which outcrops in the middle reach of the Kotuy River, constraining the time of its formation to a wide interval from the end of the Late Cambrian to the beginning of the Silurian. The obtained paleomagnetic data unambiguously correlate the Bysy-Yuryakh stratum to the Nyaian regional stage and constrain its formation, at least a considerable part of it, by the Tremadocian. This result perfectly agrees with the data on the Bysy-Yuryakh conodonts studied in this work and yields a spectacular example of the successful application of paleomagnetic studies in solving important tasks of stratigraphy and, correspondingly, petroleum geology. Within the Bysy-Yuryakh stratum, we revealed a large normal-polarity interval corresponding to the long (>1 Ma) period when the geomagnetic reversals were absent. This result, in combination with the data for the Tremadocian and Middle–Upper Cambrian sequences of the other regions, indicates that (1) the rate of occurrence of the geomagnetic reversals on the eve of the Ordovician Moyero superchron of reversed polarity was at most one reversal per Ma; (2) the superchron does not switch on instantaneously but is preceded by a certain gradual change in the operation conditions of the dynamo mechanism which, inter alia, manifests itself by the reduction of the frequency of geomagnetic reversals with the approach of the superchron. This finding supports the views according to which a process preparing the establishment of the superchrons takes place at the core–mantle boundary. 相似文献