东北地区地震活动的Rydelek-Sacks周期性检验和震级-周期谱研究

为检验中国东北地区地震活动可能存在的周期性特征和深、浅源地震在周期性活动上的相关性,利用Rydelek-Sacks检验方法和不同的地震目录,考虑了地震震级的选取对周期性特征识别可能存在的影响,并在震级-周期谱中进行了比较研究.对该地区1970-2009年ML≥4.5浅源地震、1920-2009年Ms≥5.0浅源地震和1...     

Study on the Criterion of the Correlation between Deformation Precursors and Earthquakes

The relationship between pre-seismic anomalous changes and earthquakes is one of the most basic information to comprehend the process of earthquake preparation and conduct earthquake prediction research. However, few researchers have carried out relevant investigations for a long time. In this paper, the distribution characteristics of deformation anomalies before the Wenchuan earthquake are analyzed, and the widespread distribution area is discussed. Based on previous studies, we improve the relationship between anomaly duration t and magnitude M by introducing distance D. The new model is characterized by lower magnitude fitting error, making it possible to establish the correlation between deformation precursors and earthquakes. The correlation standard between precursors and earthquakes here is defined as Niu''s criterion, which is applied to analyze and interpret the relationship between the short-term anomalies of Hongliuxia fault leveling and the Wenchuan and Jiuzhaigou earthquakes.     

基于POT模型的昆仑山地区地震统计特征分析

极值统计是研究较少发生但一旦发生即产生极大影响的随机事件的有效方法。本文以地震活动频繁的昆仑山地区作为研究区域,建立了基于广义帕累托分布的超阈值(POT)模型,并讨论了该地区若干地震活动性参数,包括强震震级分布、潜在震级上限、强震平均复发间隔、一定周期内的强震发震概率、一定时期内的重现水平和超定值重现震级。经统计分析得到：该地区震级阈值选定为 M_S5.5,超阈值期望震级为 M_S6.81,潜在震级上限高达 M_S9.08,M_S8.0 的平均复发间隔仅为 66.8 年,未来 3 年该地区发生 M_S5.5～M_S6.5 的概率在 80% 以上,百年重现水平即可达到历史最大震级MS8.1。     

Modelling of Strong Ground Motions from 1991 Uttarkashi,India, Earthquake Using a Hybrid Technique

We present a simple and efficient hybrid technique for simulating earthquake strong ground motion. This procedure is the combination of the techniques of envelope function (Midorikawa et al. Tectonophysics 218:287–295, 1993) and composite source model (Zeng et al. Geophys Res Lett 21:725–728, 1994). The first step of the technique is based on the construction of the envelope function of the large earthquake by superposition of envelope functions for smaller earthquakes. The smaller earthquakes (sub-events) of varying sizes are distributed randomly, instead of uniform distribution of same size sub-events, on the fault plane. The accelerogram of large event is then obtained by combining the envelope function with a band-limited white noise. The low-cut frequency of the band-limited white noise is chosen to correspond to the corner frequency for the target earthquake magnitude and the high-cut to the Boore’s f _max or a desired frequency for the simulation. Below the low-cut frequency, the fall-off slope is 2 in accordance with the ω² earthquake source model. The technique requires the parameters such as fault area, orientation of the fault, hypocenter, size of the sub-events, stress drop, rupture velocity, duration, source–site distance and attenuation parameter. The fidelity of the technique has been demonstrated by successful modeling of the 1991 Uttarkashi, Himalaya earthquake (Ms 7). The acceptable locations of the sub-events on the fault plane have been determined using a genetic algorithm. The main characteristics of the simulated accelerograms, comprised of the duration of strong ground shaking, peak ground acceleration and Fourier and response spectra, are, in general, in good agreement with those observed at most of the sites. At some of the sites the simulated accelerograms differ from observed ones by a factor of 2–3. The local site geology and topography may cause such a difference, as these effects have not been considered in the present technique. The advantage of the technique lies in the fact that detailed parameters such as velocity-Q structures and empirical Green’s functions are not required or the records of the actual time history from the past earthquakes are not available. This method may find its application in preparing a wide range of scenarios based on simulation. This provides information that is complementary to the information available in probabilistic hazard maps.     

基于深度学习的地震震级分类

为了探索地震加速度时程记录的震级信息,训练卷积神经网络基于地震震级大小对地震记录进行分类,将K-NET和KiK-net中将近12万个地震记录作为样本,对其进行信息筛选和归一化,之后将地震加速度时程记录用作输入,训练卷积神经网络模型以M5.5为分类界限来区分大震和小震。结果显示,在训练集中基于该模型的分类准确率为93.6％,在测试集中的准确率为92.3％,具有良好的分类效果,这表明大震记录与小震记录之间存在一些根本的区别,即可通过地震动加速度时程记录获取一定的震级信息。      

中国大陆特征地震震级分布规律

根据特征地震的震级分布符合正态分布的基本假设,对特征地震的震级分布规律进行定量化研究.考虑到原地复发型大地震的震级数据稀少,提出利用大地震的同震位移转换得到震级数据,再对不同观测点所得到的震级数据进行归一化处理,使所有归一化震级数据均服从均值为0的同分布,进而可以统计得到反映特征地震震级变异性的标准差σ.最后基于广泛搜集的中国大陆54个特征地震的同震位移,利用本文给出的统计方法得到一个通用的标准差σ=0.08,为进一步研究特征地震的发生概率模型提供了重要依据.      

湖南地震视应变与地震的对应关系分析

利用湖南省地震台网记录到的资料,研究了1970年以来湖南地区五次ML≥4.0级地震的地震视应变场的分布和时空演化特征.ML≥4.0以下的地震视应变与震级相关性较小,ML≥4.0以上地震的视应变值随震级增加呈非线形快速增大,说明:湖南地区地震视应变的时空演变与地震具有较好的对应关系.     

Characteristics of Energy Accumulation and Release of Seismogenic Tectonics and Seismic Risk Analysis in Some Areas in the Tianshan Mountains, Xinjiang1

INTRODUCTIONHowtocombinethestudyofseismogenictectonicswithearthquakepredictionisanurgentscientificdifficulty .Thereexistbiggapsbetweenstudymethodsandcurrentknowledgeonseismogenitectonics ,earthquakeprediction ,seismogenesisandthephysicsofearthquakeoccurre…     

Sensitivity analysis of the parameters of earthquake recurrence time power law scaling

The stability of the power law scaling of earthquake recurrence time distribution in a given space–time window is investigated, taking into account the magnitude of completeness and the effective starting time of aftershock sequences in earthquake catalogs from Southern California and Japan. A new method is introduced for sampling at different distances from a network of target events. This method allows the recurrence times to be sampled many times on the same area. Two power laws with unknown exponents are assumed to govern short- and long-recurrence-time ranges. This assumption is developed analytically and shown to imply simple correlation between these power laws. In practice, the results show that this correlation structure is not satisfied for short magnitude cutoffs (m _c = 2.5, 3.5, 4.5), and hence the recurrence time distribution departs from the power law scaling. The scaling parameters obtained from the stack of the distributions corresponding to different magnitude thresholds are quite different for different regions of study. It is also found that significantly different scaling parameters adjust the distribution for different magnitude thresholds. In particular, the power law exponents decrease when the magnitude cutoff increases, resulting in a slower decrease of the recurrence time distribution, especially for short time ranges. For example, in the case of Japan, the exponent p₂ of the power law scaling at large recurrence times follows roughly the relation: , where m _c is the magnitude cutoff. In case of Southern California, it is shown that Weibull distribution provides a better alternative fit to the data for moderate and large time scales.     

最大熵原理在地震时间间隔和震级分布中的应用

基于最大熵原理,得到地震时间间隔和地震震级的概率分布函数。根据时间间隔分布,得到地震发震概率,当概率上升达到警界值时,可对云南5级以上中强地震做出预测。6个月以内中短期预测对应率为91％;3个月以内,短临期预测对应率为73％。根据震级分布,得到用最大熵原理求出的地震理论发生次数,理论发震次数与实际较为接近。用最大熵原理求出了云南不同地区不同震级档次5级以上中强地震的复发周期。分析认为,云南7级以上大震危险性在逐步逼近,西部危险性高于东部。     

基于谱元法数值模拟研究地震判定准则

本文以宁夏区域地震台网为例,分析了波形互相关法在判定重复地震中可能存在的问题并讨论了相应的处理方法,通过构建三维非均匀体模型并利用谱元法数值模拟地震波的传播,统计了不同台站观测到的地震对波形互相关系数的分布,进一步研究了互相关系数与非均匀体性质及震源机制解之间的关系。结果表明:针对宁夏区域地震台网,利用波形互相关法判定重复地震比地震定位方法更有效;互相关系数在不同台站的取值与震源附近三维非均匀体强度和直达波与尾波的振幅比有关,对于相同的震源间距,较弱震源、较弱非均匀体或者较强振幅的直达波均会导致波形互相关系数变高,因此应选取更高的互相关系数阀值来判定重复地震。宁夏区域地震台网平均台间距为30—50 km,通过选取直达波较弱的台站或只截取尾波窗口计算互相关系数并设定较高的阀值,利用波形互相关法可有效地判定M_L1.0—3.0重复地震,进而为重复地震的监测与研究提供依据。      

Multiasperity fault model and the nature of short-period subsources

We suggest to consider the breaking of an asperity,i.e., a small contact patch between fault walls, as a typical subsource producing an elementary short-period radiation pulse from a source of a large earthquake. Based on the results ofDas andKostrov we propose formulas to describe amplitudes and spectra of acceleration for a multiasperity fault/source model. The stress drop over an asperity is determined in several ways; the estimates agree to give the average value of several hundred bar. Theoretical acceleration spectral shapes for the case of similar asperities agree with the observed ones, they reproduce such features as lower-frequencyf ¹ slope, peak, and high-frequency cutoff. The statistical stress-drop distribution over the population of asperities, and also the related distribution of peak accelerations are discussed. There distributions are found to be the power-law ones with exponent near to 2. This means that acceleration peaks are formed normally by breaking of individual asperities. We consider small earthquakes as produced by breaking of single asperities, this idea explains the observed correlation between the upper cutoff frequency of acceleration spectrum and the typical characteristic frequency of small earthquakes.     

极值理论在福建沿海地区地震预测中的研究与应用

利用陈培善等人对极值理论修改后的极值分布函数模型对1971年1月-2012年9月福建沿海地区的地震资料进行统计分析,单位时间内最小与最大地震的确定分别考虑相关区域内台网的监控能力以及删除余震后的实际情况.根据修正后的极值理论统计计算出该地区地震的复发周期及截至2015年12月可能发生的相应地震的次数与发震概率,并对有关结果进行映震能力分析,为今后福建沿海地区地震趋势分析提供可遵循的理论依据.     

Recurrence of Large Earthquakes: Bayesian Inference from Catalogs in the Presence of Magnitude Uncertainties

We present a Bayesian method that allows continuous updating the aperiodicity of the recurrence time distribution of large earthquakes based on a catalog with magnitudes above a completeness threshold. The approach uses a recently proposed renewal model for seismicity and allows the inclusion of magnitude uncertainties in a straightforward manner. Errors accounting for grouped magnitudes and random errors are studied and discussed. The results indicate that a stable and realistic value of the aperiodicity can be predicted in an early state of seismicity evolution, even though only a small number of large earthquakes has occurred to date. Furthermore, we demonstrate that magnitude uncertainties can drastically influence the results and can therefore not be neglected. We show how to correct for the bias caused by magnitude errors. For the region of Parkfield we find that the aperiodicity, or the coefficient of variation, is clearly higher than in studies which are solely based on the large earthquakes.     

中国海域及邻区地震时间分布特征研究

地震时间分布特征研究是进行地震预测和地震危险性分析的重要基础.以中国海域统一地震目录为基础资料,以指数分布模型、伽马分布模型、威布尔分布模型、对数正态分布模型以及布朗过程时间分布(BPT)模型为目标模型,采用极大似然法估算模型参数.根据赤池信息准则(AIC)、贝叶斯信息准则(BIC)以及K-S检验结果确定能够描述海域地...     

甘改—玉树断裂带的近代地震与未来地震趋势估计

通过对甘改－玉树断裂带上近代地震的震级，震中位置和地震地表破裂的空间展布特征的研究，采用Ｎｉｓｈｅｎｋｏ和Ｂｕｌａｎｄ发展的“特征地震复发时间通用分布”概率模型，即“ＮＢ”模型，对甘孜玉树断裂带各段落未来５０ａ内强震趋势进行了估计。     

An automatic scheme for baseline correction of strong-motion records in coseismic deformation determination

Coseismic deformation can be determined from strong-motion records of large earthquakes. Iwan et al. (Bull Seismol Soc Am 75:1225–1246, 1985) showed that baseline corrections are often required to obtain reliable coseismic deformation because baseline offsets lead to unrealistic permanent displacements. Boore (Bull Seismol Soc Am 91:1199–1211, 2001) demonstrated that different choices of time points for baseline correction can yield realistically looking displacements, but with variable amplitudes. The baseline correction procedure of Wu and Wu (J Seismol 11:159–170, 2007) improved upon Iwan et al. (Bull Seismol Soc Am 75:1225–1246, 1985) and achieved stable results. However, their time points for baseline correction were chosen by a recursive process with an artificial criterion. In this study, we follow the procedure of Wu and Wu (J Seismol 11:159–170, 2007) but use the ratio of energy distribution in accelerograms as the criterion to determine the time points of baseline correction automatically, thus avoiding the manual choice of time points and speeding up the estimation of coseismic deformation. We use the 1999 Chi-Chi earthquake in central Taiwan and the 2003 Chengkung and 2006 Taitung earthquakes in eastern Taiwan to illustrate this new approach. Comparison between the results from this and previous studies shows that our new procedure is suitable for quick and reliable determination of coseismic deformation from strong-motion records.     

内蒙古地区地方性震级的量规函数研究

选取2008年1月~2015年11月内蒙古测震台网81个台站所记录的6342次地震事件,基于震级残差统计方法,计算了81个台站单台震级与台网平均震级的偏差、平均偏差和标准偏差。分析认为,BHS等6个台站震级偏差较大的原因可能是台站场地响应放大、台基风化等。台基校正前、后单台震级平均偏差值ΔMLi随震中距的变化曲线显示,曲线形态基本未有大的改变,台基校正后较之前震级平均偏差绝对值降低0.01,表明台基对地方性震级偏差的影响不大。同时,进行了81个台站的台基校正获得了内蒙古新量规函数,结果表明,全国量规函数除了震中距为0~120km时适合于内蒙古地区以外,其余情况下均偏高,不符合内蒙古地区的特征。因此,本文修定了全国量规函数,得到了校正后的内蒙古地区量规函数。     

Earthquakes: Recurrence and Interoccurrence Times

The purpose of this paper is to discuss the statistical distributions of recurrence times of earthquakes. Recurrence times are the time intervals between successive earthquakes at a specified location on a specified fault. Although a number of statistical distributions have been proposed for recurrence times, we argue in favor of the Weibull distribution. The Weibull distribution is the only distribution that has a scale-invariant hazard function. We consider three sets of characteristic earthquakes on the San Andreas fault: (1) The Parkfield earthquakes, (2) the sequence of earthquakes identified by paleoseismic studies at the Wrightwood site, and (3) an example of a sequence of micro-repeating earthquakes at a site near San Juan Bautista. In each case we make a comparison with the applicable Weibull distribution. The number of earthquakes in each of these sequences is too small to make definitive conclusions. To overcome this difficulty we consider a sequence of earthquakes obtained from a one million year “Virtual California” simulation of San Andreas earthquakes. Very good agreement with a Weibull distribution is found. We also obtain recurrence statistics for two other model studies. The first is a modified forest-fire model and the second is a slider-block model. In both cases good agreements with Weibull distributions are obtained. Our conclusion is that the Weibull distribution is the preferred distribution for estimating the risk of future earthquakes on the San Andreas fault and elsewhere.