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为研究陕西地区地磁短周期变化特征,1996年9月从陕西南部石泉至甘肃宁县布设临时测线一条,在测线上进行地磁短周期变化三分量同步观测．在3 min至2 h周期范围内,统计计算了各测点各周期成分的地磁垂直转换函数、水平转换函数及谱成分关系．在数据处理中参考应用了随机数据理论,取得了较好效果．分析指出,该区地磁短周期变化受武功、乾陵之间地下近东西向异常感应电流集中的区域性影响及测点附近局部感应电流影响．其主要分布特征为,垂直分量变化在武功和乾陵之间存在一反向轴,频率响应显示出转换函数在周期约20 min时有最大值． 相似文献
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涡度相关测定中平均周期参数的确定及其影响分析 总被引：4，自引：1，他引：4
应用涡度相关技术估算地-气界面的水、热和CO2交换量的研究越来越普遍.为了获得真实可靠的地表通量数据,在实际应用过程中必须根据每个观测点不同的下垫面条件,对观测数据进行相应的订正,并通过对观测数据的分析来确定相关的技术参数.利用禹城、长白山两个观测站的10Hz原始涡度相关数据,以不同的平均周期(从1~720min)对数据进行了重新计算,并将重新计算的结果与30min平均周期的通量值进行了比较,分析选取不同平均周期参数得到的通量值之间的差异.其中重点分析了在禹城小麦地获取的15d连续观测数据.结果表明:(ⅰ)在禹城,当平均周期取值范围在10~60min变化时,相对30min平均周期的通量值改变小于2%;当平均周期作短于10min变化时,通量的计算结果随平均周期的缩短而明显地降低(最大相对误差为?12%);当平均周期作大于120min变化时,通量的计算结果变得不稳定(最大相对误差为±10%以上).(ⅱ)禹城小麦地通量的计算表明,10min平均周期对研究通量日变化比较好,30min平均周期比较适合于通量的长期观测研究.(ⅲ)提出了一种可以确定涡度相关测定中平均周期参数范围的归一化比值方法.通过对农田和森林不同类型下垫面观测数据的对比分析表明:高大的森林下垫面比相对矮小的作物下垫面在一定范围内增加平均周期长度时有增 相似文献
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本文以巴彦岱1号井静水位为研究对象，分别应用别尔采夫滤波、小波分析与相关分析等方法，研究巴彦岱1号井静水位周期变化主要影响因素。分析结果表明，巴彦岱1号井静水位在日波、半日波频段主要受固体潮的影响；气压影响频段可能为64—256min、32—2048h（1—2个月周期的月波）2个频段，年周期变化与气温变化具有较强的线性相关性。 相似文献
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利用中国南极长城站1986年2月4日和6日00－13 h(UT)F的分钟值、国内10个地磁台H，D，Z磁照图的每分钟采样值和由H及Z算出的F分钟值，采用最大熵谱分析和带通滤波处理，得出以下初步结果:① 在T=10－90 min内，日照半球均有明显的太阳耀斑的地磁效应(sfe)．其中，以周期为15，20，25和30 min的谱较为明显，而30－35 min的谱最显著，其同期X-射线谱为10 min和15 min；② 经过谱分析和滤波处理，地处西半球的南极长城站周围为10－70 min的sfe亦可辨认，但最大振幅对应的周期与日照半球不同．本文的这一结果进一步证实了在黑夜半球也可观测到sfe现象；③ 两次sfe的日下点均在兰州附近，相应的电流密度约为24 A/km．而sfe的过渡带为地理纬度=22－24N附近．该带内H-钩扰的sfe几乎不能辨认． 相似文献
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本文利用北半球的超级双极光雷达网数据，考察了一次行星际磁场南向突变时高纬电离层对流的响应特征，着重分析了响应的时间尺度. 对所研究的事件，行星际磁场南北分量在1.5 min内从+7 nT突变到-8 nT，而在突变前后约40 min内都保持相对稳定. 结果表明，电离层对流的初始响应发生在磁正午附近，相对于行星际磁场突变到达磁层顶的时间有大约3 min的滞后；响应与磁地方时有明显依赖关系，离磁正午越远，响应的滞后时间越长，晨昏两侧的对流响应比磁正午滞后约6 min，磁午夜的对流响应比磁正午滞后约12 min；对流重新趋于稳定的时间与磁地方时没有明显的依赖关系，该时间尺度约为10～14 min. 相似文献
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应用相关性分析和小波分析方法，研究气压、水位与榆树沟分量应变之间的关系及影响机制，结果表明：(1)水位是榆树沟分量应变长周期变化的主要影响因素，尤其对分量应变EW、NE向影响较显著，表现为中高度线性负相关；2016—2018年EW向相位滞后水位约1 d, NE向相位滞后水位约8 d; 2019—2021年EW向相位滞后水位约4 d, NE向相位滞后水位约7 d;(2)气压是分量应变短周期变化的主要影响因素，EW、NW向对其响应更为灵敏，表现为中高度线性负相关；EW向与气压不存在相位滞后，NW向相位滞后气压约55 min;(3)小波分析结果显示，气压对EW分量影响的显著频段为26～28 min、210～215 min,对NW分量影响的显著频段为26～28 min、211～214 min。 相似文献
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利用连续小波变换对全天山地区1790年1月至1997年12月的地震活动情况进行分析和研究。结果表明，全天山地震活动即存在约11O年的大震活跃周期和50年左右的地震活动幕，也存在与太阳黑子活动相关的周期，并且这些周期是随时间变化的。与此同时，新疆南、北天山等地震带1893年以来也普遍存在相对比较稳定的11年和50年左右地震活动周期，只是在不同年份有较大的波动。连续小波变换揭示了新疆地震活动周期的时变性。根据新疆大震活动的11年左右周期可推测2006～2007年左右新疆地区有可能再次发生7级左右大地震，2002～2005年之间地震活动相对偏弱，Ms≥4．7级中强震次数偏少，活动强度为5级和6级地震。 相似文献
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Horizontal ground deformation measurements were made repeatedly with an electronic distance meter near the Puu Oo eruption site approximately perpendicular to Kilauea's east rift zone (ERZ) before and after eruptive episodes 22–42. Line lengths gradually extended during repose periods and rapidly contracted about the same amount following eruptions. The repeated extension and contraction of the measured lines are best explained by the elastic response of the country rock to the addition and subsequent eruption of magma from a local reservoir. The deformation patterns are modeled to constrain the geometry and location of the local reservoir near Puu Oo. The observed deformation is consistent with deformation patterns that would be produced by the expansion of a shallow, steeply dipping dike just uprift of Puu Oo striking parallel to the trend of the ERZ. The modeled dike is centered about 800 m uprift of Puu Oo. Its top is at a depth of 0.4 km, its bottom at about 2.9 km, and the length is about 1.6 km; the dike strikes N65° E and dips at about 87°SE. The model indicates that the dike expanded by 11 cm during repose periods, for an average volumetric expansion of nearly 500 000 m3. The volume of magma added to the dike during repose periods was variable but correlates positively with the volume of erupted lava of the subsequent eruption and represents about 8% of the new lava extruded. Dike geometry and expansion values are used to estimate the pressure increase near the eruption site due to the accumulation of magma during repose periods. On average, vent pressures increased by about 0.38 MPa during the repose periods, one-third of the pressure increase at the summit. The model indicates that the dikelike body below Puu Oo grew in volume from 3 million cubic meters (Mm3) to about 10–12 Mm3 during the series of eruptions. The width of this body was probably about 2.5–3.0 m. No net long-term deformation was detected along the measured deformation lines. 相似文献
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J. H. Wood 《地震工程与结构动力学》1976,4(4):349-377
A study has been made of the response, during the San Fernando earthquake 9 February 1971, of the nine-storey steel frame Building 180, located at the California Institute of Technology, Jet Propulsion Laboratory, Pasadena. The analysis throws light on the actual dynamical properties of the building during the earthquake, and also demonstrates that it is possible, when the ground motion is specified, to make accurate predictions of building motions during moderate earthquakes by using a linear viscously damped model. Methods of evaluating the lower mode periods and damping ratios from the earthquake records are described and the values obtained are compared with results from dynamic testing before and after the earthquake and with the periods computed from computer models of the building. Although no structural damage occurred and computed stresses in the steel frame were less than yield stresses, the periods measured by an ambient vibration test after the earthquake were of the order of 10 per cent higher than the pre-earthquake values. The maximum periods during the earthquake were found to be about 30 per cent higher than the post-earthquake periods. 相似文献
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Harsh K. Gupta Douglas C. Nyman Mark Landisman 《Earth and Planetary Science Letters》1977,34(1):51-55
Shield-like upper mantle velocity structure has been inferred to exist below the Indo-Gangetic Plains from a study of mantle Rayleigh and Love wave group and phase velocities for periods extending to 200 seconds. The investigations have been carried out for the path between the World Wide Standard Seismic Network Stations at Chiengmai (CHG), Thailand, and New Delhi (NDI), India, for an earthquake with its epicenter in the New Hebrides Islands. Application of improved frequency time analysis has permitted measurement of regional surface wave dispersion for periods extending to several minutes; previous results for this region were for periods no greater than about one minute. 相似文献
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A. Alfaro L. G. Pujades X. Goula T. Susagna M. Navarro J. Sanchez J. A. Canas 《Pure and Applied Geophysics》2001,158(12):2499-2511
—?In order to evaluate soil effects in the urban area of Barcelona, the Nakamura's technique has been used to estimate the predominant periods of soils. Noise measurements for 195 sites were performed using a strong motion accelerograph and a velocimeter. In this work, the resulting preliminary map of predominant periods is presented. The obtained predominant periods are coherent with the geological and geotechnical features of the area. The analysis of the information has allowed the distinctions among several types of soil and underlying materials. A predominant period of about 0.06?s is evaluated for sites located over outcrop Paleozoic rock in the Tibidabo-Collserola Mountains. For sites consisting of material named tricycle, that is the most extensive and also the most heterogeneous zone, predominant period range from 0.10?s up to 2.0?s depending on the thickness of the surface materials and the kind and thickness of the underlying materials. In the Besós river two zones are observed: the riverside with periods between 0.50?s and 0.83?s and a second area with periods between 1.0 and 2.1?s. In the Llobregat river delta the obtained periods are quite homogeneous with values around 0.72?s. Other predominant periods are found in some tertiary rock outcrop. 相似文献
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Building period formulas in seismic design code are evaluated with over 800 apparent building periods from 191 building stations and 67 earthquake events. The evaluation is carried out with the formulas in ASCE 7‐05 for steel and RC moment‐resisting frames, shear wall buildings, braced frames, and other structural types. Qualitative comparison of measured periods and periods calculated from the code formulas shows that the formula for steel moment‐resisting frames generally predicts well the lower bound of the measured periods for all building heights. But the differences between the periods from code formula and measured periods of low‐ to‐medium rise buildings are relatively high. In addition, the periods of essential buildings designed with the importance factor are about 40% shorter than the periods of non‐essential buildings. The code formula for RC moment‐resisting frames describes well the lower bound of measured periods. The formula for braced frames accurately predicts the lower bound periods of low‐to‐medium rise buildings. The formula for shear wall buildings overestimates periods for all building heights. For buildings that are classified as other structural types, the measured building periods can be much shorter than the periods calculated with the code formula. Based on these observations, it is suggested to use Cr factor of 0.015 for shear walls and other structural types. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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太湖定振波的初步研究 总被引：1，自引：0，他引：1
初步分析研究了太湖定振波的变化规律,结果表明:(1)东、西太湖有各自的振动周期,东太湖变化范围在181—292min,平均为243min;西太湖在120—540min,平均为400min。(2)观测到的最大振幅(1/2波高)为120—130mm。(3)用差分法对定振波的特征值进行了近似估算,其周期误差为20min。(4)定振波引起的湖流相当大,当振幅为100mm时,最大流速可达±20cm/s。(5)定振波振幅的突变与气压场、风场和降水分布不均匀并在短期内发生突变有关。 相似文献
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福建省数字化形变资料的异常分析 总被引：1，自引：0，他引：1
为了提取中短期地震前兆信息,对福建省2006～2008年数字化形变观测整点值资料进行了二进小波多分辨率分析,结果表明：小波分析结果的细节部分dn主要包含周期为2n-2a＋1小时的信号,而近似部分‰包含所有周期大于2n＋1小时的信号;在此期间,福建省及其邻近地区的中强地震发生前,多数形变观测台站或测项同步接收到了周期大约为21～43d幅度较大的异常信号,这些信号可能是地震前兆。 相似文献
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The mathematical methods of direct spectral analysis were employed for the database that was drawn from the monitoring of well # 30 during 2004 in order to obtain the amplitude-frequency function of steam-water mixture pressure in the Verkhne-Mutnovskii hydrothermal system (the depth at which pressure was measured was 950 m, the time interval between measurements was 2 min, resulting in a total of about 250000 determinations). We identified large-scale and small-scale types of pressure variability. The large-scale variability reflects the low-frequency component of the variation and is seen as macro-fluctuations involving considerable (as large as 2 bars), sudden or gradual pressure changes. The small-scale variability consists of both irregular and regular oscillations. Medium-frequency and high-frequency components can be identified in the latter variability. The medium-frequency component consists of gradual fluctuations with periods of about 20 min (a frequency of 0.00083 Hz), with the maximum pressure changes between measurements being 0.7 bars. The high-frequency component consists of sudden pressure changes (drops, rises, or spikes), as well as of fluctuations with periods below 5 min. 相似文献