河北唐山地区中小地震震源参数的测定

采用谱分析的方法，利用首都圈数字遥测地震台网的观测资料，计算了唐山地区2002年ML2．0以上的58个中小地震的波谱，进而估算了地震矩、拐角频率、应力降、震源破裂半径，并讨论了它们之间的相互关系以及拐角频率和应力降的时间分布特征。分析表明，地震矩与震级、拐角频率与震级的关系密切，证实结果可信、稳定。     

云南中小地震矩震级的测定

利用云南省测震台网的数字地震波形资料,反演了2008年1月至2012年9月675个中小地震的震源波谱参数,并计算了这些地震的地震矩M0和矩震级Mw,最后利用回归分析方法得到了近震震级ML和Mw之间的关系式.     

河北省测震台网中小地震矩震级的测定

利用河北省测震台网的数字地震波形资料,反演了2008年12月至2010年4月62个中小地震的震源波谱参数,计算了这些地震的地震矩M0和矩震级Mw,利用正交回归分析方法得到了近震体波震级ML和Mw之间的关系式.     

一种计算中小地震地震矩的简易方法

从Ｂ．Ａ．Ｂｏｌｔ博士得到一个关系式出发，采用一种新的量值转换方法，能够较方便地求得各中小地震的地震矩；并且利用江苏地区的ＤＤ－１地震仪的模拟记录资料，得到了江苏及其邻近地区１．０≤ＭＬ≤４．０的中小地震的地震矩Ｍ０（单位为１０＾０７Ｎ·ｍ）与震级ＭＬ的统计关系式：ｌｏｇＭ０＝（１．７６±０．１１）ＭＬ＋（１５．５９±０．２８）。     

福建古田水口水库M_L4.8级地震序列震源参数研究

应用福建省区域数字地震台网观测记录到的古田水口水库ML4.8级地震序列的资料,在扣除地震记录数据中传播路径效应、台站场地响应和仪器响应后,采用Atkinson单地震、多台记录平均的反演方法计算震源参数,共计算了序列中的38个ML≥2.5级地震的震源参数。结果显示：地震矩与震级之间有较好的线性关系,统计关系式为logM0=1.08ML＋9.63;建立了用ML震级估算矩震级MW的公式MW=0.72ML＋0.387;其它的参数间虽有一定的相关性,但很难给出定量的关系。对地震序列应力降随时间发展的变化分析认为,在前震期水口水库区域存在应力加速积累的过程,有出现高应力降异常值的发生,临近主震时,应力降有所回调;最大余震后,应力降呈逐步衰减,未出现高异常值。     

云南姚安地震序列震源参数研究

2000年1月15日云南姚安发生5.9级和6.5级地震,利用布设在震中附近的6个流动数字地震台所记录的地震波资料,采用波谱分析和Brune理论的方法,得到姚安地震序列震源谱参数和震源参数。结果表明:地震序列的地震矩在108～1014N·m之间,应力降在0.005～10MPa之间,震源半径分布在50～660m之间,并得到地震矩M0和震级ML的关系为:lgM0=8.24+1.4ML。随着地震矩增大应力降增加,拐角频率反而减小;随震级的增大震源半径变大,但震源半径与应力降之间不存在明显的相关关系。     

浙江珊溪水库地震震源参数研究

利用浙江省区域数字地震台网记录的珊溪水库地震波资料,采用Brune(1970)模式,通过几何扩散校正、介质衰减校正、仪器校正等将速度记录谱归算为震源位移谱,使用遗传算法计算拐角频率及零频极限,进而计算震源半径、地震矩等小震震源参数,并系统分析了各种参数之间的关系。研究中使用发生于2002～2006年间ML2.0～4.6珊溪水库库区地震180个,分析结果为:地震矩范围为1011～1015N.m,震源破裂半径为74～727m,地震矩、拐角频率、矩震级及体波震级之间表现出一定的对数线性或半对数线性关系,并可分别表示为:lgM0=0.0061R 11.71,lgM0=1.11ML 10.11,MW=0.7447ML 0.7。地震应力降范围为0.08～4.95MPa,应力降与震源半径之间表现出一定的相关关系。     

姚安地震余震序列研究

将2000年姚安MS6.5地震的19个3.0≤ML<5.0余震的垂直分量在频率域内进行地震矩张量反演,对反演结果进行了讨论,并用最小二乘法回归了地震矩M0、矩震级MW和地方震震级ML之间的关系;根据对余震序列主压应力轴随时间的变化特点,分析了震区复杂的应力状态。     

1995年陡河地震前后小震震源参数及其相互关系

在震源谱的多台多震尾波解法的基础上,应用Brune震源模型,求解1995年10月6日陡河ML5.9地震前后在其周围发生的48次小地震的震源因子和震源波谱,进而估算了地震矩、拐角频率和应力降,并讨论了它们之间的相互关系和在陡河地震前后随时间的变化．结果表明:小震震源因子表现出相当大的稳定性,震源因子的峰值频率和随频率的变化形态都很相似．发现震前一年左右曾多次出现应力降较高的事件．需要指出的是,考虑到应力降由地震矩和拐角频率计算得到以及地震矩和拐角频率的相关关系,实际上,这里的高应力降指的是拐角频率高于正常值的情形．      

传统地震目录中增加矩震级及震源机制解的必要性分析

本文梳理了我国地震目录的产出现状,对于我国近几年应急机构和区域台网产出的震源机制解、矩震级进行了比较研究。结果表明:中国地震局地球物理研究所和地震预测研究所对于国内陆地地区6级以上地震的地震矩张量解的产出率为100%,5级以上地震的地震矩张量解产出率为81%。这两个研究所给出的3种矩张量结果和GCMT给出的矩张量结果较为一致,类型统计一致率分别达到71%、86%和66%,其中P、T轴空间夹角优势分布在15°左右。产出的矩震级和GCMT解得到的矩震级相差不大,偏差在0.1以内的比率分别为46%、86%和71%,偏差在0.3以内的比率分别为85%、100%和97%。结果表明对于我国内陆地区的5级以上地震,这两个研究所产出率较高、结果较为一致。而由各台网据震源参数得出的5级左右地震的矩震级和GCMT求解的矩震级比较起来明显偏小。由此探讨了在传统地震目录中增加震源机制解及矩震级的必要性。     

地震的震级

简要介绍了地方性震级Mi、体波震级mb、面波震级Ms和矩震级Mw的定义及其测定方法,分析了它们的优点和缺点,并对震级饱和效应及其产生的原因作了介绍和解释。文章指出,矩震级是一个表征地震绝对大小的量,它与地震震源的物理过程直接关联,不会饱和;与传统上使用的其他震级标度相比,矩震级具有明显的优点,是当今国际地震学界推荐优先使用的震级标度。     

1996年5月3日包头西Ms=6.4地震的矩张量解

利用ＣＤＳＮ及ＧＤＳＮ数字化Ｐ波波形资料,用遗传算法反演１９９６年包头西ＭＳ＝６．４地震的地震矩张量解。结果表明该地震矩张量解以双力偶成分为主,是断层面接近南北走向的左旋走滑错动,断裂面走向与大震后５天内余震的分布带走向基本一致。压应力轴与张应力转接近水平,前者近北西西走向,后者近北北东走向。     

Global shear stress pattern in main seismic active belts

ＧｌｏｂａｌｓｈｅａｒｓｔｒｅｓｐａｔｅｒｎｉｎｍａｉｎｓｅｉｓｍｉｃａｃｔｉｖｅｂｅｌｔｓＬＥＩＸＩＡＯ（肖磊）ＰＥＩ－ＳＨＡＮＣＨＥＮ（陈培善）ＩｎｓｔｉｔｕｔｅｏｆＧｅｏｐｈｙｓｉｃｓ，ＳｔａｔｅＳｅｉｓｍｏｌｏｇｉｃａｌＢｕｒｅａｕ，Ｂｅｉ...     

2009年4月6日意大利拉奎拉(L＇Aquila)地震快速矩张量解.

2009年4月6日1点32分42秒协调世界时（UTC）,在意大利中部地区发生了MW6.4地震．作者利用矩张量快速反演技术,通过反演全球台网的宽频带P波波形得到了这次地震的矩张量解,并判断走向132deg;、倾角53deg;、滑动角——103deg;的节面是地震发生的断层面．      

FOCAL MECHANISM OF THE AUGUST 8, M7.0 SICHUAN JIUZHAIGOU AND AUGUST 9, M6.6 XINJIANG JINGHE EARTHQUAKES OF 2017

The W-phase is a long period phase arriving between the P and S wave phases of a seismic source, theoretically representing the total near-and far-field long-period wave-field. Recent study suggests that the reliable source properties of earthquake with magnitude greater than ~M_W4.5 can be rapidly inverted by using the W-phase waveform data. With the advantage of W-phase, most of major earthquake research institutes in the world have adopted the W-phase based inversion method to routinely assess focal mechanism of earthquake, such as the USGS and GFZ. In this study, the focal mechanism of the August 8, 2017 M7.0 Sichuan Jiuzhaigou and August 9, 2017 M6.6 Xinjiang Jinghe earthquakes were investigated by W-phase moment tensor inversion technique using global seismic event waveform recordings provided by Incorporated Research Institutions for Seismology, Data Management Center. To get reliable focal mechanism, we strictly select raw waveform data and carry out inversion in stages. At first, we discard waveform without correct instrument information. Then we carry out an initial inversion using selected waveform data to get primary results. Using the preliminary results as input, we carry out grid-search based inversion to find the final optimal source parameters. The inverted results indicate that the August 8, M7.0 Sichuan Jiuzhaigou shock resulted from rupturing on a NW-trending normal fault with majority of strike-slip movement. The parameters of two nodal planes are strike 152.7°, dip 61.4°, rake -4.8° and strike 245.0°, dip 85.8°, rake -151.3° respectively, and focal depth is 14.0km. The August 9, Xinjiang Jinghe M6.6 shock resulted from rupturing on a south-dipping thrust fault with left-lateral strike-slip. The parameters of two nodal planes are strike 100.6°, dip 27.5°, rake 114.1° and strike 259.3°, dip 65.1°, rake 78.0°, and the focal depth is 16.0km. The direction of two nodal planes is consistent with regional seismotectonic background.     

Relationships between moment magnitude and fault parameters: theoretical and semi-empirical relationships

Fault parameters are important in earthquake hazard analysis. In this paper, theoretical relationships between moment magnitude and fault parameters including subsurface rupture length, downdip rupture width, rupture area, and average slip over the fault surface are deduced based on seismological theory. These theoretical relationships are further simplified by applying similarity conditions and an unique form is established. Then, combining thc simplified theoretical relationships between moment magnitude and fault parameters with seismic source data selected in this study, a practical semi-empirical relationship is established. The seismic source data selected is also to used to derive empirical relationships between moment magnitude and fault parameters by the ordinary least square regression method. Comparisons between semi-empirical relationships and empirical relationships show that the former depict distribution trends of data better than the latter. It is also observed that downdip rupture widths of strike slip faults are saturated when moment magnitude is more than 7.0, but downdip rupture widths of dip slip faults are not saturated in the moment magnitude ranges of this study.     

2002年3月31日台湾M 7.5地震概述

2002年3月31日在台湾以东沿海附近发生里氏7.5级地震，造成生命和财产的较严重损失。文章概述了这次地震的情况，包括震源参数、震源机制解、破坏、伤亡和发震背景。     

Quick moment tensor solution for 6 April 2009, L'Aquila,Italy, earthquake

A M_W6.4 earthquake occurred in L'Aquila, central Italy at 1:32:42 (UTC), April 6, 2009. We quickly obtained the moment tensor solution of the earthquake by inverting the P waveforms of broadband recordings from the global seismographic network (GSN) stations using the quick technique of moment tensor inversion, and further inferred that the nodal plane of strike 132°, dip 53° and rake ?103° is the seismogenic fault.     

Moment tensor inversion of explosive long period events recorded on Arenal volcano,Costa Rica,constrained by synthetic tests

In order to constrain the moment tensor solution of an explosive seismic event recorded on Arenal volcano, Costa Rica, we perform tests using synthetic data. These data are generated using a 3D model including the topography of the volcano and the best estimation of the velocity model available for Arenal. Solutions for (i) the moment tensor components, and (ii) the moment tensor plus single forces, are analyzed. When noisy data and mislocated sources are used in the inversion, spurious single forces are easily generated in the solution for the moment tensor components plus single forces. Forces also appear when the inversion is performed using an explosive event recorded on Arenal in 2005. Synthetic tests indicate that these forces might be spurious. However the mechanism is correctly retrieved by the inversion in both solutions. The ability to recover the explosive mechanism for the 2005 event combined with the interpretative aids from the synthetics tests will enable us to invert for the large variation in events observed on Arenal.