共查询到20条相似文献，搜索用时 328 毫秒
1.
根据震前小震活动、ｂ值、η值、Ｎ值、“地震窗”的月频度、孕震地震条带、缺震曲线值，并利用地震学方法提取大震前兆信息的测震学参数：波速比值、振幅比值、尾波持续时间比值等地震活动性参数的变化，研究了武定６．５级地震前地震活动的特征。 相似文献
2.
3.
近年来,国内学者强调对于复杂和超限结构需进行中震性能设计,即在小震弹性设计后进行中震下的承载力复核及调整,然而中震设计能否提高结构整体抗震性能仍存在争议.为探究中震设计与小震设计方法的差异,本文依据现行规范,以设防烈度、结构高度和场地类别为变化参数,建立了48个典型RC剪力墙模型,并分别以"小震"、"高规中震"、"广东... 相似文献
4.
5.
本文依据赤峰南部台网的实测资料,论述了该地小震活动与唐山大震及强余震的呼应关系。突出体现了小震活动的“窗口效应”,并从小震活动规律探索其与地质构造的内在联系,试图为监测京津唐地区的大震提供依据和线索。 相似文献
6.
本文对1970年以来西宁盆地及邻近区域的中小震目录运用分时段累计频度、b值曲线、时间窗滑移等方法,对其监测能力的逐年变化情况进行了分析研究,并给出了不同时段的最小完整震级和最小可能完整性震级随时间变化的曲线.结果表明,本研究区域的地震监测能力逐年提高,由最初的ML2.3提升到目前的ML1.5.同时表明,在数次周边1000 km范围内的7级以上大震前,本区域的ML2~3明显增多,这一现象表明西宁盆地及邻近区域的小震活动特征具有一定的前兆指示意义.空间b值表明:西宁盆地内部一直处于较高b值的状态,而其外围尤其是北部区域处于低b值状态,值得持续关注. 相似文献
7.
8.
2008年2—4月,位于汶川大震初始破裂点的紫坪铺水库附近发生了一系列的小震活动,它们与汶川地震和紫坪铺水库小震的关系值得研究。本文采用CAP方法,反演了紫坪铺水库7个专用数字地震台站的数据,得到震级大于ML 1.0的28个震源机制解。结果表明:有19个地震事件集中在紫坪铺水库东南方向的都江堰附近,最大地震为逆冲型,发震机制为逆冲型带走滑分量,少量带正断层分量;从深度剖面看,地震震源深度主要集中分布在地下13km附近区域,都江堰震群丛集在前山断裂带上,其它地震散布在中央断裂带上;发震最大主压应力方向随时间的变化具有从最大主压应力方向变化比较大到趋向一致的演化过程。这些现象说明龙门山断裂带在都江堰附近存在1个凸凹体,形成应力集中点,引发都江堰震群活动,由此迫使龙门山断裂带前山断裂发生逆冲性活动,从而加剧了龙门山断裂带中央断裂的活动,在一定程度上加速了汶川地震的发生。 相似文献
9.
10.
对国内外45 例地震预测预报震例的相关资料与文献进行查证与整理,总结、分析了震例中采用的中长期预测方法、短临前兆异常以及预报结果。研究表明,对地震发生的时间、地点和震级三要素均明确预测的概率较低,且仅为三要素的粗略预测,准确预测地震目前尚难做到。中国在地震预测过程中更注重对短临前兆异常的观测,在震前小震活动异常、地下水化学组分、地下水状态、地磁、地电、地倾斜、地应力应变、电磁波异常、前震平静等前兆预测方法中,根据震前小震活动异常作出临震预测的成功率较高,可作为预测某些类型大震的重要参考指标之一;国外震例大多是对地震进行中长期预测,在中长期预测结果的基础上采取以“防”为主的防震减灾策略,长期预测的理论和方法比中国丰富。 相似文献
11.
Haruka Tsunetaka 《地球表面变化过程与地形》2021,46(14):2984-2998
The intensity of rainfall events with potential to cause landslides has varying temporal characteristics. In this study, the time at which the 72-h accumulated rainfall reached its maximum was used to standardize the period of rainfall measurement. The proposed standardization of the rainfall period was used in conjunction with the return level of rainfall intensity, obtained from intensity–duration–frequency curves, to investigate rainfall intensity anomalies associated with 10 hazardous rainfall events that triggered numerous landslides at the regional scale in Japan. These landslides included shallow landslides in volcanic and non-volcanic areas, as well as deep-seated landslides. The rainfall events that triggered the shallow landslides were divided into two types: downpours that repeatedly reached close to the 100-year return level within approximately 3–4 h, and accumulated rainfall that reached close to 200–400 mm over longer time intervals but within 72 h. Lithological differences seemed unrelated to the differences between the two types of shallow-landslide-triggering rainfall; however, precipitation >1000 mm was necessary to trigger deep-seated landslides. Although the characteristics of the hyetographs differed markedly among the landslide-triggering rainfall events, all the landslides could have been triggered when the mean rainfall intensity reached the 100-year rainfall level during the standardized period. Thus, the landslide trigger can be evaluated indirectly based on the increase in the return level of the mean rainfall intensity, which could provide a means for estimating the time of landslide occurrence. 相似文献
12.
A model‐based method is proposed for improving upon existing threshold relationships which define the rainfall conditions for triggering shallow landslides but do not allow the magnitude of landsliding (i.e. the number of landslides) to be determined. The SHETRAN catchment‐scale shallow landslide model is used to quantify the magnitude of landsliding as a function of rainfall return period, for focus sites of 180 and 45 km2 in the Italian Southern Alps and the central Spanish Pyrenees. Rainfall events with intensities of different return period are generated for a range of durations (1‐day to 5‐day) and applied to the model to give the number of landslides triggered and the resulting sediment yield for each event. For a given event duration, simulated numbers of landslides become progressively less sensitive to return period as return period increases. Similarly, for an event of given return period, landslide magnitude becomes less sensitive to event duration as duration increases. The temporal distribution of rainfall within an event is shown to have a significant impact on the number of landslides and the timing of their occurrence. The contribution of shallow landsliding to catchment sediment yield is similarly quantified as a function of the rainfall characteristics. Rainfall intensity–duration curves are presented which define different levels of landsliding magnitude and which advance our predictive capability beyond, but are generally consistent with, published threshold curves. The magnitude curves are relevant to the development of guidelines for landslide hazard assessment and forecasting. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
13.
由于不同时期各观测系统所用震级标度、仪器性能和测量方法的不同,各种中国地震目录中所列震级值常不一致。本文在收集和整理1900——1948年间,中国地震的仪器观测资料的基础上,采用统一的震级标度修定震级,以期给出该时期的均一震级目录。为此,采用古登堡-里克特1945年面波震级公式和1956年体波震级公式,作为基本震级标度,并将1962年的莫斯科-布拉格公式用于较短周期面波的面波震级测定,以作补充。统计表明,在这段时期内,两者之间是比较一致的。 根据这种标度,重新核算了《全球地震活动性及有关现象》一书的手稿资料,并用所有能收集到的台站振幅、周期资料计算了震级;建立了徐家汇台的量规函数和应用观测到P波的最大距离估计震级的计算公式;统计出各种震级目录中的震级值对古登堡-里克特震级标度的归算关系。从而得到了1900——1948年间中国地震的修订震级。文中列出6.5级以上的中国地震目录。 修订后的震级与国内外已有目录的统计对比结果表明,修订后的震级与阿部的全球大震目录中我国地震的震级相近,而与1983年编《中国地震目录》(未计入直接引用徐明同震级的部分)所列震级平均偏差虽小,但离散较大。 本文根据修订后的震级目录,探讨了《全球地震活动性及有关现象》一书中震级的含意,结果与盖勒-金森的结 相似文献
14.
对于在Rayleigh波勘探中经常提取到的多模式频散曲线，如何在理论上对其特征进行描述是一个很有意义的问题. 本文根据Rayeigh波频散方程中传递矩阵具有的高频近似特征，提出了传递矩阵的高频近似分解公式，据此导出了频散方程的高频近似分解公式，并在此基础上，定义了Rayleigh波的4种基本模式(R模、S模、R型周期模和S型周期模). 根据频散方程具有的周期性特征，给出了周期模频散曲线之间的平均间隔近似公式，以及在任意频率和相速度段内频散方程根的数目（即多模式的激发数目）的预测公式. 在这些结果的基础上，本文最后提出了频散方程数值搜根的一种新方法. 相似文献
15.
Nurulkamal Masseran Muhammad Aslam Mohd Safari 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(3):545-559
The occurrences of extreme pollution events have serious effects on human health, environmental ecosystems, and the national economy. To gain a better understanding of this issue, risk assessments on the behavior of these events must be effectively designed to anticipate the likelihood of their occurrence. In this study, we propose using the intensity–duration–frequency (IDF) technique to describe the relationship of pollution intensity (i) to its duration (d) and return period (T). As a case study, we used data from the city of Klang, Malaysia. The construction of IDF curves involves a process of determining a partial duration series of an extreme pollution event. Based on PDS data, a generalized Pareto distribution (GPD) is used to represent its probabilistic behaviors. The estimated return period and IDF curves for pollution intensities corresponding to various return periods are determined based on the fitted GPD model. The results reveal that pollution intensities in Klang tend to increase with increases in the length of time between return periods. Although the IDF curves show different magnitudes for different return periods, all the curves show similar increasing trends. In fact, longer return periods are associated with higher estimates of pollution intensity. Based on the study results, we can conclude that the IDF approach provides a good basis for decision-makers to evaluate the expected risk of future extreme pollution events. 相似文献
16.
砌体结构抗震抗剪强度分析 总被引：9，自引：0，他引：9
进行了墙体抗剪强度理论和公式的研究。将主拉强度理论与剪摩强理论相结合,形成了一种新和强度理论,即拉摩强度理论。根据该理论,导出了墙体抗剪强度公式。给出了公式系数的确定方法,并确定了砖墙体的公式系数。将本文建议的砖墙体抗剪强度公式与抗震和砌体规范采用的抗剪强度公式进行了比较,比较结果表明：抗震规范公式值较小;砌体规范公式值较在,本文公式值介于两者中间。 相似文献
17.
18.
The possibility of determining local horizontal inhomogeneities of the shear and bulk moduli from data on amplitudes and phases of tidal tilts and strains is considered. Simple analytical formulas determining the sought effects are derived by the perturbation method, and their numerical estimates are determined for the simplest 2-D models. It is shown that relative variations in the shear and bulk moduli affect not only the amplitudes and phases of variations in tidal parameters but also the shape of curves of tidal amplitude anomalies versus the horizontal coordinate. Given adequate spatial resolution, this can significantly facilitate the elastic moduli inversion from tidal data. 相似文献
19.
工程结构抗震设防标准的决策分析 总被引：16，自引：4，他引：12
提出了工程结构抗震设防标准的决策方法,该决策方法以结构初始造价分析和地震损失分析为基础。建立了结构初始造价与设计烈度的关系,并提出了地震损失的估计方法。使用该决策方法导出了最佳设计烈度和重现周期的解析表达式,从而得出了对抗震设计具有重要意义的结论。 相似文献
20.
根据峰值加速度、速度、位移对构造环境剪应力场和地震矩的依赖关系,导出了直接计算矩震级的公式．用北京怀来小台网（速度记录）、唐山强震观测台网（加速度记录）和北京地区台网（速度记录）的地震记录资料,检验了这些公式的可用性．结果表明,利用加速度或速度记录测定的矩震级与常规方法（根据位移谱高度）测定的矩震级十分接近．证明了这些公式的正确性,从而拓宽了用于测定震级的资料类型,即不仅限于位移记录,速度和加速度记录都可用于测定震级． 相似文献