Seismic Interevent Time: A Spatial Scaling and Multifractality

The optimal scaling problem for the time t(L × L) between two successive events in a seismogenic cell of size L is considered. The quantity t(L × L) is defined for a random cell of a grid covering a seismic region G. We solve that problem in terms of a multifractal characteristic of epicenters in G known as the tau-function or generalized fractal dimensions; the solution depends on the type of cell randomization. Our theoretical deductions are corroborated by California seismicity with magnitude M ≥ 2. In other words, the population of waiting time distributions for L = 10–100 km provides positive information on the multifractal nature of seismicity, which impedes the population to be converted into a unified law by scaling. This study is a follow-up of our analysis of power/unified laws for seismicity (see Pure and Applied Geophysics 162 (2005), 1135 and GJI 162 (2005), 899).     

云南省3次地震的余震活动的折合能量-地震矩关系

折合能量或视应力如何随地震矩而变化，即折合能量一地震矩定标关系，是一个目前争议颇多的问题，需要更多的观测资料来参加讨论。本文利用2000年1月15日姚安5．9、6．5级地震，2001年10月27日永胜6．0级地震，2003年7月21日、10月16日大姚6．2、6．1级地震的余震序列的观测结果，讨论了这一问题。在估算能量时采用了Brune震源谱模型情况下的Andrews方法。结果表明，对这3次地震的余震序列来说，小于4级的地震活动的“折合能量”随地震矩而上升，而大于4级的地震数目虽不多，却呈现出折合能量不随地震矩而变化的特点。     

On the Prospect of Detecting the Process of Earthquake Preparation in the Spectrum of Seismic Noise: A Laboratory Experiment

The results of laboratory experiments aimed at studying the pattern of the transition process of a model fault into a metastable state are presented. The experiments are conducted on a slider model installed onto a long granite base wherein vibrations are excited. The idea of the experiments is that the mechanical properties of the fault change under the transition into the metastable state. These changes can be detected by the detailed examination of the parameters of microseismic noise. The conducted experiments show that, despite the low Q-factor of the block–fault mechanical system, the spectrum of the recorded oscillations definitely contains the harmonic components corresponding to the eigenmodes of this system. In the model with the interblock contact filled with quartz sand, the fundamental mode of the free oscillations alters most noticeably in the frequency band 1000–1200 Hz, where the clear effect of the spectral peak’s migration towards lower frequencies is observed as the contact approaches the moment of dynamic failure, and the approximately initial value is recovered after the sliding stops. The revealed effect gives hope that the changes in the stress–strain state of the fault zone at the final stage of earthquake preparation can be detected by analyzing the parameters of low-frequency seismic noise. The segment of the record during and after the passage of surface waves from remote earthquakes is perhaps amongst the most favorable for determining the characteristic values of the region under study. These oscillations with a period of a few dozen seconds have significant amplitudes and durations, which promotes the excitation of the resonant vibrations of the blocks.     

Correlation Between Local Slip Rate and Local High-frequency Seismic Radiation in an Earthquake Fault

For any earthquake, the slipping fault and the source of high-frequency seismic waves, by and large, coincide. On a more local scale, however, the areas of high seismic slip rate and of increased high-frequency radiation output (seismic luminosity) need not match. To study in some detail how slip rate and seismic luminosity are interrelated, a systematic study is performed that uses 251 records of teleseismic P waves from 23 intermediate-depth earthquakes of magnitude 6.8 and above. From a broadband trace we extract two time histories: (1) displacement and (2) 0.5–2.5 Hz band-passed and squared velocity, or ``HF power', and calculate correlation coefficient, ρ between the two. To reduce the bias related to formation of P coda, a special procedure is applied to data. We estimated the average value ρ = 0.52 (range of event averages 0.35 to 0.65) for the correlation coefficient between the radiated time histories for displacement and ``HF power', which is considerably below the ``ideal' value of unity. We argue that the same or even lower value characterizes the degree of slip rate - seismic luminosity correlation at the fault. Two factors may contribute to the revealed decorrelation: (1) random fluctuations of observed HF power (inevitable for a signal with a limited bandwidth), and (2) the genuine mismatch of slip rate and mean luminosity. We show that these factors, acting separately, would result in the ρ values equal to, correspondingly, 0.72 and 0.80. We also show that genuine decorrelation is statistically significant. We conclude that the observed values of ρ indicate genuine differences between the distributions of the slip rate and the seismic luminosity over the fault area. These results provide important constraints both for the accurate wide-band simulation of strong ground motion and for theoretical dynamic source models.     

Variable Tsunami Sources and Seismic Gaps in the Southernmost Kuril Trench: A Review

In the southernmost Kuril Trench, the tsunami source regions vary their along-trench extent even among earthquakes occurring within the same segment. Recent studies suggest that the tsunami source of the 1952 Tokachi-oki earthquake (M 8.1) differs from but partially overlaps with that of the 2003 Tokach-oki earthquake (M 8.0). Furthermore, the along-trench extent among the earthquakes seems to differ between deep and shallow portions of the subduction interface. A seismic gap has been recognized along the deep subduction interface between the sources of the 1952 and 1973 earthquakes. We propose that the gap is now larger, including both shallow to deep portions of the interface between the 1973 and 2003 earthquakes. Variability in spatial extent of large subduction earthquakes in both along-trench direction and trench-normal direction makes it difficult to forecast future earthquakes in the southernmost Kuril Trench.     

祁连山地震带地震短期综合预报方案研究

在多年地震预报研究和实践工作的基础上，系统研究了祁连山地震带地震活动短期阶段具有共性特征的地震活动增强、群体前兆异常演化、重点前兆和重点地震活动现象等，总结、提炼出了区域短期综合预报方案。     

新生地震构造带的研究——地震地质研究新开拓的一项工作

地震构造带是地震地质研究最重要的内容之一.几十年来,许多研究者对我国所有已知的地震构造带进行了大量的调查研究,但这些都是老(先存)断层带新活动而导致地震的构造带.笔者通过多年的研究发现,还存在新构造时期(N-Q)才产生的断层带或地震构造带.揭示出唐山-河间-磁县、庙西北-黄河口和腾冲-耿马-澜沧等几条新生地震构造带.由...     

大震前地震活动平静现象一种可能的机制:断层的蠕滑-匀阻化

许多大地震前地震活动存在明显的平静现象,由于其普遍性,地震平静现象被认为是具有物理意义的地震前兆并被作为地震预报的重要依据.关于大震前地震平静现象的物理机制,国内外学者从不同角度进行了研究,其中包括用破裂强度的双峰式分布、扩容硬化、震前滑动造成的应力松弛、震源体内外介质性质的差异和相互作用等机制解释强震孕育过程中短期地震活动的平静现象.尽管在一些模型中把岩石力学实验结果作为证据之一,但来自与地震活动最相似的岩石变形声发射的实验证据并不多.因为以往大量的实验结果表明,在恒定的加载条件下(等位移速率、等应力速率等),岩石破坏失稳前声发射活动多表现为加速特征,尽管一些岩石破坏前声发射活动加速现象不明显,但也难以观测到平静现象.然而,在我们开展的一系列断层结构和介质不同的中尺度标本的声发射实验中,一些标本破坏失稳前声发射活动表现出明显的相对平静现象,据此我们对大地震前地震活动平静现象的物理机制进行了讨论.     

不同标度震级关系和台基影响问题探讨

利用近年中国数字地震台网观测报告中的中国及邻区地震目录资料,取能够同时计算面波震级MS和近震震级ML的地震,拟合出2种震级之间的关系,发现与过去使用30余年的换算公式存在系统差别。考虑现代化地震数字观测系统有动态范围大、频带宽、台站多、覆盖区域广、测定精度高的特点,由此拟合的关系应当更可靠。考虑不同误差因素统计面波震级MS和近震震级ML的关系表明,2种震级之间换算和不换算的差别并不大,因此建议MS和ML震级之间不换算为宜。分析地震台站的场地响应发现:一些基岩台的放大因子在1附近,场地响应不随频率变化;处于沉积土层的台站,放大因子在低频段大于1,高频段小于1;还有一些台站在某个频段范围大于1,或者小于1。另外,沉积土层台站的单台震级和台网平均震级差也随周期增大,呈现由负到正的增长趋势。看来并不存在固定的台站校正系数,因此不能把台站校正作为提高震级测定精度的方法。     

基于《中国震例》的地震空区和地震条带统计特征

基于《中国震例》(1970—2013年), 系统清理了246次M≥5.0震例前的地震活动图像异常, 并结合区域差异进行地震空区和地震条带的统计特征研究。 结果显示: ① 在246次震例中, 震前出现地震空区、 地震条带的震例数分别为105次、 51次, 占震例总数的42.7%和20.7%; ② 随着主震震级的增大, 地震空区和地震条带出现的比例逐渐增大, 尤其是7级以上地震, 震前出现地震空区的震例数占同类震例总数的83.3%, 出现地震条带的震例数占同类震例总数的66.7%, 可见地震空区和地震条带可能是7级以上强震的重要异常判据; ③ 针对整个中国大陆及近海, 地震空区和地震条带的持续时间、 展布尺度、 起始震级与主震震级存在一定线性关系, 相关系数能够通过95%置信水平的阈值检验; ④ 各主要构造分区的统计结果差异较大, 青藏高原北部除地震空区持续时间外, 其余地震空区和地震条带参数与主震震级之间的线性关系均通过阈值检验, 南北带中南段和华北地区有个别参数通过检验, 天山地区所有参数均未通过检验。     

盈江2011年Ms5.8与2008年Ms5.9地震的震害差异及原因

介绍盈江2011年Ms5.8与2008年Ms5.9地震震害调查的房屋破坏比的确定方法,揭示了Ms5.8地震的各种震害特征,并将两次地震的震害差异做了对比.分析造成Ms5.8地震各种破坏重于Ms5.9地震的原因,提出了震区恢复重建与规划发展的建议、建(构)筑物在选址、施工、抗震设防方面的注意事项和各类建(构)筑物加强抗震...     

超大功率振动源在首都圈地区地震监测预报中的应用研究

俄罗斯科学家西伯利亚分院研制了几种型号的超大功率振动源，其特点是功率大，信号传播距离远，探测深度大。目前，我国首都圈地区已建成由100多个子台组成的数字化地震台网。文章介绍了俄罗斯超大功率振动源及其在我国首都圈地区地震监测预报中的应用研究。     

中国大陆强震轮回活动的计算机模型研究

通过对中国大陆7级以上强震的研究发现,地震活动呈现为时间上轮回和空间上迁移的动态图像。为探索这种图像的物理本质,本文应用非线性动力学模型来模拟在统一构造应力场作用下含有多个活动地震带的地震构造块体的地震活动。文中用若干列并联排列的基本元件(由Maxwell体和刚性滑块组成)来模拟地震活动带,并用耦合元件来模拟地震活动带之间和带内各段之间的相互耦合作用。本文的研究结果有助于理解强震的轮回活动以及高潮中成组强震间的相互影响特征。     

亚洲国家地震生命损失的标度律及中长期预测研究

研究了亚洲11个重要地震国家或地区(阿富汗, 巴基斯坦, 菲律宾, 日本, 伊朗, 印度, 印尼, 中国大陆, 中国华北地区, 中国南北带)近代地震造成人员死亡率的自相似指数标度律, 并将其应用于泊松模型中, 预测2025年前亚洲重要地震国家发生地震生命损失千人、 万人和十万人以上巨灾事件的概率。 其中, 中国大陆华北地区、 日本和印尼发生万人以上死亡的巨灾概率可能较高。     

山东乳山震群遗漏地震检测及震源区活动特征分析

对震群活动特征的深入研究可以为区域地震危险性分析和地震活动趋势判断提供有效的依据,但受台网布局和震群位置的影响,地震目录中往往会遗漏一些地震,而地震目录的完整性将会影响震群活动特征分析的可靠性.因此,本文利用基于GPU加速的模板匹配方法对山东乳山震群2014年5月至2015年6月期间固定台站和流动台阵记录的连续波形进行...     

云南台网区域自动地震速报及人工速报定位偏差

选取2009年7月1日至2017年12月31日云南地震台网区域自动地震速报及人工地震速报定位结果,对比全国统一编目结果,对定位偏差进行分析,结果显示:①自动速报用时不受台站分布的影响,但漏报地震较多;人工速报用时与台站分布有密切的关系,台站分布均匀合理地区地震速报用时明显减少;②对于震中位置的确定,1类地震基本在规定范围内,但2、3类地震区域自动速报存在较大问题,人工速报虽有改善但仍需进一步优化;③区域自动速报系统对于M≥4.5地震震级的确定偏差较大,人工速报基本不存在问题;④震源深度偏差基本都在规定范围内,偏差超过规定范围的地震基本分布在台站稀少、分布不合理地区,人工速报对于结果的改善没有明显效果。最后分析了漏报和误报情况,为云南台网地震速报的提高提供一定的参考。     

四川汶川8．0级地震前后中国大陆西部地震活动特征及震后趋势分析

通过对汶川8．0级地震前后中国大陆地震活动特征的分析,探讨了汶川8．0级地震的地震活动背景．重新划分了中国大陆7级以上地震的活动周期,并根据汶川地震发生的构造背景分析了汶川地震对中国大陆活动趋势的影响和西部大三角与中国大陆强震活动趋势的关系。分析结果表明：在未来1-3年中国大陆特别是西部强震活动仍然处于活跃状态,有可能再次发生7级以上地震。     

Evaluation of Porosity and Saturation Degree by Laboratory Joint Measurements of Velocity and Resistivity: A Model Improvement

—This paper illustrates the laboratory procedures and experiments carried out on samples with different lithologies and reconstructed samples in order to test and implement an electroseismic model (Carrara et al., 1994) which allows the evaluation of porosity and the saturation degree of rocks. The testing was conducted by comparing porosity (Φ) and saturation degree (S _w ?) values, obtained from measured resistivity (ρ) and elastic wave velocity (V _P ?) by means of appropriate formulations, with the values of Φ and S _w previously calculated by geotechnics and employed as standards. The experimental results have led to a good definition of the model to be proposed as an application method in the field of hydrogeology.     

施甸5.9级地震场地与震害的关系

施甸5．9级地震震源浅导致了其震害偏重，而特殊的场地条件则导致许多烈度异常区（点）的产生。概述了施甸县历史地震的情况，介绍了旋甸5．9级地震震区自然根貌和场地特征，以近百年现场调查点资料为基础，将影响震害的四种主要因素，按其对震害影响程度的轻重分类，分析了该次地震的震害分布特征与异常区的场地特征，结果表明，在影响震害的诸多场地因素中，以地基土特性的影响最重。