乌恰地震加速度记录特征研究

研究了1985年乌恰余震取得的加速度记录,从地质及地球物理的角度探讨一些加速度异常点。分析了记录的峰值加速度与震害及场地烈度的对应关系。对比了竖向和水平向加速度、速度反应谱及谱与震级的变化特征。     

云南地区地面峰值加速度衰减规律

根据云南地区的实测强震加速度资料，采用回归分析法研究了云南地区的地面水平、垂直峰值加速度衰减规律。共选取云南地区加速度记录240条，进行了加速度衰减规律的统计，并把得到的结果与前人的结果进行比较分析，提出更适合云南地区地震地质特征的加速度衰减规律。     

澜沧-耿马强震地面运动特征研究

本文利用澜沧-耿马地震中记录到的强震加速度数据,对地面运动加速度峰值和反应谱进行了统计分析。文中研究了震级、震中距、地震方位和场地条件等各种因素对加速度峰值和反应谱形状的影响,提出了适用于本地区的地震加速度峰值和反应谱值的哀减公式并和过去的一些研究结果进行了对。比文中证明了地面运动加速度矢量峰值的衰减与烈度等震线或主发震断层走向的对应关系。     

高聚物防渗墙土质堤坝地震加速度响应的动力离心试验研究

为研究高聚物防渗墙土质堤坝地震加速度反应规律,采用El Centro波,在0.05 g、0.1 g、0.2 g和0.4 g工况下进行了高聚物防渗墙土质堤坝和传统刚性防渗墙—混凝土防渗墙土质堤坝的离心机振动台的对比试验。试验采用非等应力离心模型,利用加速度传感器测量了坝体不同位置的加速度时程响应。结果表明:高聚物防渗墙土质堤坝峰值加速度随输入地震动增加而增加,随坝高增加而增加,最大峰值加速度在坝顶上;高聚物防渗墙土质堤坝最大峰值加速度随输入地震动的增大呈线性增加趋势,而最大峰值加速度放大系数随输入地震动增大而减小;从模型试验的角度来看,在同等水平地震作用下,混凝土防渗墙土质堤坝抗地震加速度反应能力好于高聚物防渗墙土质堤坝,但在强震下混凝土防渗墙体发生了破坏,这一点可由附近土体加速度突增判断。     

航空重力测量中载体运动加速度的确定

航空重力测量是使用重力仪、GPS及其他传感器测定地球重力场的一种新型技术，其基本原理是利用重力仪测定包括重力加速度、载体运动加速度以及其他一些加速度在内的总加速度，从观测值中减去利用GPS确定的载体运动加速度，再加上一些改正，得到了重力加速度. 本文推导了确定载体运动加速度的直接解算法的公式，利用某次航空重力测量数据，分别在静态、动态两种情况下，分析了确定载体运动加速度精度. 结果表明：在静态、60s的平滑间隔条件下，载体加速度的确定精度是0.4—0.9mGal；在动态、90s的平滑间隔条件下，整个飞行测段载体运动加速度的确定精度是1—3mGal.     

汶川8.0级地震强震动加速度记录的初步分析

本文对国家强震动台网中心收集的2008年5月12目14时28分04秒汶川8．0级地震中获取的420组三分量加速度记录进行了处理和初步分析。在分析前对原始加速度记录进行整理、转换数据格式、零线校正、录入原数据,形成标准格式的未校正加速度数据;在这次地震中布设在龙门山断裂带及其周围地区有50多个台站获得了大于100 Gal的加速度记录,有46组三分量加速度记录的断层距小于100km,使中国大陆近断层区域所获得的强震动加速度记录的数量成倍增加。本文依据这批数据对汶川大地震强震动特性进行了初步分析,给出了此次地震断层附近地区的PGA衰减规律,并利用此规律模拟断层附近的加速度峰值,绘制了PGA分布图;给出了汶川地震断层附近的加速度反应谱、上盘效应、速度大脉冲效应等地震动特征,这些特征可作为抗震设计规范修订的依据及灾区重建时参考;最后展望了这批强震动加速度记录的应用前景。     

场地条件对地表峰值加速度的放大效应分析

在研究西安地区大量钻孔资料的基础上,构造了44个不同等效剪切波速和覆盖层厚度场地条件下的典型场地剖面,利用一维等效线性化地震反应分析方法,计算了不同场地在3种不同强度的地震动输入下的地面峰值加速度,分析了地震动峰值加速度放大系数ks随场地类别、等效剪切波速Vse、覆盖层厚度H和输入地震动强度ar的变化特征,指出了按场地类别对地震动峰值加速度调整存在的问题。分析结果表明,加速度放大系数随等效剪切波速、覆盖层厚度及基岩输入地震动强度的增大而减小;等效剪切波速对加速度放大系数的影响大于覆盖层厚度的影响,随着输入地震动强度的增大,覆盖层厚度对加速度放大系数的影响成份有逐渐加大的趋势;覆盖层厚度对加速度放大系数的影响程度随着等效剪切波速的增大而逐渐减弱;加速度放大系数与场地等效剪切波速和覆盖层厚度之间具有较高的拟合度的统计回归关系。由此提出了直接用场地等效剪切波速和覆盖层厚度对地震动峰值加速度进行调整的新途径。最后,就地震动峰值加速度随场地条件的调整方法,提出了有待进一步研究的问题。     

用强震记录检验深厚土层小应变下一维等效线性化土层地震反应

本文以强震记录为基础,通过土层地震反应计算得到了地表加速度与加速度反应谱,对比研究了由强震记录得到的地表加速度以及由地表加速度得到的与土层地震反应相同阻尼下的加速度反应谱.结果表明:在高频段与中频段,用一维等效线性化计算得到的土层地震反应加速度值与反应谱值比地表实测得到的加速度记录值与加速度反应谱值偏低;但在低频段,计...     

MEMS型加速度传感器在超高层建筑振动监测中的性能对比测试

为开展MEMS型加速度传感器在超高层建筑振动监测应用中的性能对比测试,选取4种不同类型MEMS型加速度传感器与G1B型力平衡式加速度传感器,将其安装在地王大厦相同测点,对MEMS型、G1B型加速度传感器记录的结构环境振动数据进行时程、频谱和模态频率对比分析,并对其记录的结构地震响应进行时域及频域对比。研究结果表明,不同类型MEMS型加速度传感器仪器噪声均大于G1B型加速度传感器,其中MEMS-I型加速度传感器噪声水平相对较小,与G1B型加速度传感器模态频率识别结果及地震响应监测数据吻合较好,验证了MEMS-I型加速度传感器可较准确地记录到结构强振动响应,适用于超高层建筑日常结构振动监测。     

强地面运动加速度峰值三向比值统计分析

水平向加速度峰值比为两条水平向加速度峰值的较大值与较小值的比值;竖向与水平向加速度峰值比为竖向加速度峰值与两条水平向加速度峰值的较小值的比值。以2 129次破坏性地震的156 783组地震动加速度记录为基础,研究水平向、竖向与水平向加速度峰值比值的统计分布特征,对加速度记录按照震中距、震级和震源深度进行分类统计分析。统计分析结果表明：水平向加速度峰值比总体平均值为0.83,水平向加速度峰值比≤0.85的累积概率为63%;竖向与水平向加速度峰值比总体呈现极值Ⅱ型分布特征,竖向与水平向加速度峰值比总体平均值为0.44,竖向与水平向加速度峰值比≤0.65的累积概率为92%。水平向加速度峰值比随震中距的增大而增大,竖向与水平向加速度峰值比随震中距的增大而减小。竖向与水平向加速度峰值比随着震级的增大而增大;在大震(7相似文献   

强震观测网、高灵敏度地震观测网、地中强震观测网、宽频带地震观测网

阪神·淡路大震灾后 ,日本着手对原有的地震观测体制作彻底改革 ,多项全国性配置地震计的计划同时开始启动。地震引起的地面晃动的程度不尽相同 ,无感微小地震引发的晃动仅有 0 .0 0 1 μm,频率为1 0 Hz;巨大地震引起的地面晃动的幅度高达 2～ 3 m,周期也有几十秒。虽说都称之为地震计 ,但由于地震动的振幅和频率涉及的范围太大 ,所以应针对观测对象选用不同类型的地震计。下面介绍不同类型的观测网。1　强震观测网 ( K- NET)无论大地有多大的晃动都能将其准确记录下来的地震计称之为强震计。它构造坚实 ,信号明确 ,通常设置在地表 ,对了…     

Age, geology, geophysics, and geochemistry of Mahukona Volcano, Hawai`i

The size, shape, and magmatic history of the most recently discovered shield volcano in the Hawaiian Islands, Mahukona, have been controversial. Mahukona corresponds to what was thought to be a gap in the paired sequence (Loa and Kea trends) of younger Hawaiian volcanoes (<4?Ma). Here, we present the results of marine expeditions to Mahukona where new bathymetry, sidescan sonar, gravity data, and lava samples were collected to address these controversies. Modeling of bathymetric and gravity data indicate that Mahukona is one of the smallest Hawaiian volcanoes (～6,000?km³) and that its magmatic system was not focused in a long-lived central reservoir like most other Hawaiian volcanoes. This lack of a long-lived magmatic reservoir is reflected by the absence of a central residual gravity high and the random distribution of cones on Mahukona Volcano. Our reconstructed subsidence history for Mahukona suggests it grew to at least ～270?m below sea level but probably did not form an island. New ⁴⁰Ar–³⁹Ar plateau ages range from 350 to 654?ka providing temporal constraints for Mahukona’s post-shield and shield stages of volcanism, which ended prematurely. Mahukona post-shield lavas have high ³He/⁴He ratios (16–21?Ra), which have not been observed in post-shield lavas from other Hawaiian volcanoes. Lava compositions range widely at Mahukona, including Pb isotopic values that straddle the boundary between Kea and Loa sequences of volcanoes. The compositional diversity of Mahukona lavas may be related to its relatively small size (less extensive melting) and the absence of a central magma reservoir where magmas would have been homogenized.     

The Yecheng,Xinjiang, China,earthquake of February 14, 1980

In this study, we have checked the location and focal depth of the Yecheng earthquake (m _b = 6.0, maximum intensity VII) of February 14, 1980. The result shows that this is an intermediate event with a focal depth of 90 km. The microepicenter is located at 36. 4°N, 76, 9°E, while the macroepicenter is at 37.3°N, 76.9°E, 90 km to the north of the microepicenter. This is the first destructive intermediate event in China which led to a damage as severe as of intensity VII. The focal mechanism of the event is determined to be of thrust type. Combined with the analysis of seismological and geological data in surrounding area, the possible relation between the event and plate movement has been discussed. The result in this paper indicates that in some particular place, the destructive effect of intermediate event should be considered in seismic hazard assessment.     

Sun, climate, hunger, and mass migration

Paleoclimatic studies indicate four epochs of global cooling during the last 4 000 years, i. e. during the few centuries before and after 2000 BC, 800 BC, 400 AD, and 1 600 AD; the quasiperiodicity corresponds to cyclic variation of solar activity. Global temperature changes influenced regional precipitation patterns: Northern Europe was wetter while the middle- and low-latitude lands were more arid during colder epochs. Both sets of cold climatical conditions were unfavorable for agricultural production. Historical records show that large demographic movements in history took place because of crop failures and mass starvation, rather than escaping from war zones. The “wandering” of the Germanic tribes during the first two or three centuries of the Christian Era is one example. Whereas the accelerated release of carbon dioxide from the burning of fossil fuels is ultimately to cause global warming, historical evidence indicates, however, that global warming has been on the whole a blessing to mankind. Global cooling, on the other hand, has curtailed agricultural production and has led to famines and mass migrations of people. Perhaps the most important task at the present is not so much computer-modelling of greenhouse effect on global climate, but water-management and agricultural researches to insure food-supply for an everincreasing world population.     

Physical properties,vitrinite reflectance,and microstructure of coal,Taiyuan Formation,Qinshui Basin,China

In this study, we experimentally established the relationship between physical properties, vitrinite reflectance, and microstructure of coal, Taiyuan Formation, Qinshui Basin, China using representative coal samples collected from three different mines via the rock mechanics testing system (MTS). We analyzed the organic macerals, vitrinite reflectance, and microstructure of 11 coal samples using petrography and scanning electron microscopy (SEM). The experimental results suggest that (1) the elastic parameters can be described by linear equations, (2) both P-and S-wave velocities display anisotropy, (3) the anisotropy negatively correlates with vitrinite reflectance, and (4) the acoustic velocities and Young’s modulus are negatively correlated with the volume of micropores. The derived empirical equations can be used in the forward modeling and seismic inversion of physical properties of coal for improving the coal-bed methane (CBM) reservoir characterization.     

Spatial distribution,source apportionment,and associated risks of trace metals (As,Pb, Cr,Cd, and Hg) from a subtropical river,Gomti, Bangladesh

Sediment samples from the Gomti River basin were investigated to determine and evaluate trace metal concentrations,their biological effect,and potential ecological and human health risks for adults and children.The mean concentrations of trace metals were organized in the descending order of mercury(Hg)(0.08 mg/kg)>chromium(Cr)(0.06 mg/kg)>lead(Pb)(0.05 mg/kg)>arsenic(As)(0.02 mg/kg)>cadmium(Cd)(0.01 mg/kg).The current study illustrated that metals were attributed to the area from natural sources and different anthropogenic sources especially from industries.However,the concentration levels were lower than the sediment quality guidelines(SQGs)based on the effect-range classifications of threshold effect concentration(TEC)and probable effect concentration(PEC).Therefore,the concentration of the elements showed no adverse biological effects on aquatic organisms.The evaluated potential ecological risk index also revealed the low toxicity to the aquatic environment.Moreover,the applied sediment quality indices,geo-accumulation index(Igeo),contamination factor(CF),and contamination severity index(CSI)suggested that the contamination levels of the elements were in the acceptable range,and the contamination had not notably impacted on the sediment quality.The risk index(HI)concerning age groups was significantly less than the threshold limit of 1 indicating that the contamination had no non-carcinogenic risk effect.The total carcinogenic risk(TCR)was less than a risk value of 1×10⁴.Hence,the current study suggests that immediate remediation is not required due to an absence of alarming conditions in the study area.Proper monitoring of the attribution of the metal elements should be done for the betterment of human and environmental health。     

山西高平地震

阐述了发生在山西高平的地震和对高平有影响的地震，分析了高平市的地震灾害，通过分析得出高平地震与晋获断裂带活动有关的结论。