中小地震震源参数的求解及其相似关系

根据广东数字地震台网记录的区域性地震记录,利用遗传算法采用由"三段几何衰减模型"拟合得到的广东地区的衰减模型,得到广东地区Q值与频率的关系(Q(f)=454 8f0 37),由此衰减模型反演得到各台站的场地响应,最终得到72个中小地震的震源参数;并研究了广东地区震源参数的特征及其相似关系。这些地震的地震矩在1012N·m与1014N·m之间,求出与地方震震级之间的相似关系;该地区中小地震的应力降在0 02到3 2MPa之间,未显示与地震的规模(地震矩)有明显的依赖关系。     

宁夏地区中小地震震源参数的研究

利用宁夏及邻区的数字测震资料,选取2009年5月至2010年10月间的31个M2.7-ML4.9地震事件的波形记录,以Brune提出的震源谱为平方模型基础,通过消除观测谱中的几何扩散、非弹性衰减、场地响应、仪器响应等影响因素,得到这些地震的震源谱,根据Brune的圆盘震源模型计算并研究地震矩、矩震级、地震应力降、震源尺...     

Inversion of source parameters for moderate and small earthquakes in Beijing region

Introduction Beijing and the adjacent regions is a significant seismically active area and many geoscien- tists have studied to different extents the non-elastic attenuation and source parameters in the area. GAO et al (1986) and ZHUO et al (1990) studied the coda Q in the Beijing region by the method of dominant frequency and mechanical frequency division with the simulated data. With the con- tinuous construction of digital seismic station network, the digital data are more favorably used…     

甘肃地区震源参数的相关性研究

通过对甘肃数字地震台网2008年1月-2009年6月记录的ML 2.0-ML 6.0中小地震,S波观测谱中噪音、仪器、路径、场地等影响的逐一消除,利用遗传算法反演得到甘肃地区273条地震的震源谱,进而根据Brune的圆盘震源模型,计算地震矩、应力降、拐角频率、震源半径等震源参数,并研究甘肃地区震源参数的特征及相似关系....     

粤闽地区水化学地震前兆异常特征分析

研究了粤闽两省及其近海近年来2次强震以及6个中等地震水化学前兆资料,结果表明,中等地震与强震的水化学前兆异常在数量上有着显著的差异,中等地震震前以中短期及短临异常变化为主,而强震前则超过三分之一的水化学测项出现持续1～4年的长趋势异常变化。同时研究表明,单凭水化异常出现的集中程度对未来震中作出预测是无统计依据的。     

Source parameters of some large earthquakes in the eastern Mediterranean region based on an itertive maximum entropy technique

TeleseismicP-waves of some large earthquakes that occurred in the eastern Mediterranean region have been analysed by using an iterative maximum entropy technique in order to obtain the independent spectral parameters, the long-period spectral level ₀ and the corner frequencyf ₀ of the far-field displacement spectra.Based on these parameters, the seismic source parameters seismic momentM ₀, source dimensionr, fault lengthl, average displacement u, shear stress drop , radiated energyE _s and apparent stressn are calculated for the considered earthquakes by using Brune's and Madariaga's models.The striking feature of the source parameters obtained in this study is the low stress drop value which varies between 5 and 15 bars. If Madariaga's model had been used, higher stress drop values would have been obtained.The low stress drop earthquakes in the eastern Mediterranean region might be interpreted either by the possible presence of low strength material near the source or by the partial stress drop model.     

The focus parameters and their correlation from small earthquakes before and after the 1995 Douhe earthquake

IntroductionTheseismoIogymethodofearthquakepredictionissometimessimplycalled"predictingearthquakebyearthquake",thatis,animpendinglargeearthquakeispredictedonbasisofsomefeaturesofsmaIlearthquakesoccurredbeforeit.Forthispurpose,thecharactersoftemporaryspatiaIandmagnitudedistributionofsmalIearthquakesareintensiveIyinvestigated,whichareusuallycalIedasseismicitymethod.ThesuccessfuIpredictionofHaichengearthquakeinl975wasitSremarkabIeappIication.Besides,thepossibIechangesincharactersofseismicsou…     

Source parameters of four strong earthquakes in Bulgaria and Portugal at the beginning of the 20th century

Using original seismograph records and bulletin data we re-determined theorigin time, location, seismic moment (M₀) and magnitudes(M_S and M_w) for four earthquakes in the beginning of the20th century. These are two strong earthquakes April 4, 1904 nearKrupnik, Bulgaria (M_w = 6.8, M_S = 7.2 respectively), the April 231909 earthquake near Benavente, Portugal (M_S = 6.3), and the June14, 1913 earthquake near Gorna Orjahovitza, Bulgaria (M_S = 6.3).Twenty-nine traces from original records have been analysed, a largenumber of original station bulletins have been consulted and a consistentmethodology for analysing these early 20th century instrumentalinformation is presented.In spite of a thorough effort in re-assembling and quality control of theoriginal data, large inaccuracies remain in the improved instrumentalepicentre locations and origin times. The seismic moment estimates weobtained (2.3 10¹⁸ M₀ 3.9 10¹⁹Nm) are the first ever determined for these events. The magnitudeestimates (6.3 M_S 7.2 and 6.2 M_w 7.0) are robust and systematically lower than most of previousestimates for all earthquakes (Gutenberg and Richter, 1954; Christoskovand Grigorova, 1968; Karnik, 1969). For the largest Krupnik event ourestimates agree with those of Abe and Noguchi (1983b) and Pacheco andSykes (1992). The studied earthquakes all occur in moderately seismicactive regions, therefore our results may have significant consequences forhazard estimates in those regions.     

祁连山中东段地区中小地震震源机制和区域应力场

利用哥伦比亚大学 GCMT 目录给出的祁连山中东段地区中强地震震源机制资料,研究较大区域（34°-41°N,100°-106°E）的应力场;利用该地区布设的中法微震数字监测台网多年监测资料和甘肃数字监测台网资料,使用 P 波和 S 波初动及振幅比联合反演方法,反演中小地震震源机制解和发震应力场。结果表明,地区构造应力大致为北东40°-45°水平向压应力;景泰地区主压应力方向约北东45°,绝大多数地震为走滑型。天祝-古浪地区有相当部分的逆断层地震分布,主压应力方向约60°,P 轴仰角在10°左右优势分布,大致为水平应力场。这与大区域构造应力场和断层实际分布基本一致。     

京西北延庆—怀来盆地的QSH值和小震震源参数的测定

用在一个地震台接上到的同一震源区内的较小地震的振幅谱去除大地震的振幅谱，求得较大地震震源同频趋势的斜率。利用Ｑ值在０．０００１－１００Ｈｚ之间几乎是常数是特性，用网格搜寻法对较大地震的振幅谱因衰减造成的损耗进行补偿，同时确定自震源对地震吧途径上的介持的品质因数、拐角频率和补偿后的频谱的零频极限。用这种方法，利用中－欧合作北京西北怀来数字地震台网的记录，确定了延庆－怀来盆地的品质因数ＱＳＨ值并测定了     

利用现代小地震分布研究1861年辽宁普兰店东6级地震的震中位置和发震构造

1861年7月19日发生在辽宁省普兰店东的6级地震在不同目录及研究中给出的震中位置有很大差异。总结以往对此次地震震中位置的研究,大致涉及4个不同地点。本文对分布在该区的现代小震进行重新定位,结果表明,小震活动在普兰店以东地区形成明显的北西向优势分布。综合分析1861年普兰店东6级地震的主要破裂方向为北西向,受北东向金州断裂北西向普兰店长海断裂的双重控制。     

利用重复地震观测粤闽交界地区地壳介质变化

利用粤闽两省数字化地震台网2007年6月～2010年5月的走时及波形记录对南澳地区ML≥1地震用双差法重新进行定位,根据定位结果挑选重复地震丛,并研究地震丛的P波走时经伪弯曲射线追踪技术及波形互相关校正后的走时差变化.经上述处理后,汕头台、潮州台记录的南澳地区地震的P波走时差在2008年6～8月间出现负异常,经与地震活动性及形变观测资料对比分析,认为该时段的负异常反映了区域地壳介质速度有所上升.     

Preliminary study of the straticulate structure of crust-mantle beneath east Guangdong and south Fujian Provinces of China

Using the 12 deep focus teleseismic P waveforms recorded by 6 short-period seismographs in east Guangdong and Fujian region of China as the observed data, synthetic P waveforms comparable to the observed ones are obtained by gradually adjusting the crust-mantle model and calculating the corresponding synthetic seismograms. The results suggest that the crust-mantle structure in this region is a vertically straticulate media structure consisting of 3 pairs of thin layers with a high- and low-velocity alternation. The crustal thickness tends to increase gradually from south to north, being 31.5 km in the south and 32.4 km in the north. Finally, the suggested model is tested using the explosive data of Yunfu, Guangdong Province. The theoretical travel-time of P waves agrees fairly well with the observed travel-time. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 172–179, 1992.     

闽粤赣交界区地震震源位置及速度结构研究

采用震源位置及速度结果的联合反演方法确定闽粤赣交界区(24°~26.5°N,114°~117.8°E)地震的震源位置以及震源区速度结构。结果显示:1闽粤赣交界区地震震源平均深度随震级增大而加深的特征明显,即地震震级越大,震源深度越深,但平均深度不超过15 km;越靠近沿海,地震震源深度有加深的趋势。2通过对河源地区、邵武-河源断裂带中段(寻乌-瑞金)区域、政和-大浦断裂带中段(漳平附近)区域以及闽粤近海区域地震剖面研究,发现地震多发生于高低速异常结合部位。     

利用sPL震相测定福建顺昌地区地震震源深度

选用福建数字地震台网宽频带记录,利用sPL震相测定顺昌地区2007年至2017年间ML≥3.5地震的震源深度。基于地震的震源机制解,结合本地区的速度模型,利用频率-波数法(F-K方法),先计算出相应震中距上不同深度的格林函数,再进一步得到sPL震相在不同深度上的理论波形;根据sPL震相的特点,选用震中距30~50km范围的宽频带台站记录,经过去仪器响应、滤波、旋转至传播路径后,将其和理论波形进行比对,找出波形最为相似的对应深度。结果显示顺昌地区地震深度为7km左右。     

中国大陆主要地震活动区中小地震震源参数研究

本文利用中国大陆几个主要地震活动区近几年积累的大量ML≥3.0数字地震观测记录,在分别反演得到13个不同构造研究区域的介质衰减模型、348个台站的场地效应的基础上,自0.1~20 Hz的SH观测波形数据中逐步消除了仪器、噪声、几何扩散、传播路径的介质衰减、台站场地效应等影响后,恢复了2573次3.0≤ML≤6.0地震的震源谱,采用ω平方震源模型拟合震源谱后,利用Brune的圆盘模型计算了它们的震源参数,并讨论了中国大陆中小地震的震源特征,比较了中国大陆不同地区的应力降释放水平,综合讨论了地震应力降与震源深度、机制解类型、地震大小等各种因素的关系.研究表明,中国大陆中小地震释放的应力降在0.1~20 MPa之间,绝大多数在10 MPa以下.新疆天山中东段地区、青藏块体东北缘及龙门山断裂带东北缘是高应力降地震集中的区域,表明这里的断层受到相对较强的构造剪应力作用.中小地震释放的应力降随着震级的增大而增大,应力降Δσ∝M03.14,不遵循常数应力降模型.在深度20 km以内,中小地震释放的应力降对深度的依赖不显著,但在20 km以上深度显示出随深度增大而增大的现象.中小地震释放的应力降没有表现出与震源机制类型的相关性.本研究实现了震源参数的准实时计算,丰富了大陆块体内部地震震源定标率关系研究的样本.可以预见,随着中小地震数据的大量产出和积累,这些震源参数的时空分布特征研究将会为地震预测预报研究提供有实际物理意义的依据,得到的介质衰减模型及场地效应等也将对台网日常震级ML测定所需的量规函数、台站校正值的研究提供重要参考.     

Inversion of source parameters and attenuation of the Tangshan aftershocks

Source parameters and characteristics of regional attenuation of Tangshan aftershocks are studied by using digital records of Tangshan aftershocks. An inversion method of P wave spectra to reduce influence on the ambiguity in the estimates of parameters by the usual spectrum analysis method is developed. By testing with digital simulation data and applying to actual data, it is confirmed that the method is usable. Source parameters of the Tangshan Luanxian area are obtained by using records of 35 earthquakes at 5 stations.Q values of P wave and high frequency decay rate γ of source spectrum at 5 stations are obtained. TheQ values range from 408 to 847, and the mean value is 520; whiley ranges from 1.54 to 3.22, and the mean value is 2.41. In the studies of spectra of the micro-earthquakes in the Luanxian area, that stress drop increases with increasing earthquake moment is found. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 430–441, 1991.     

关中陕南地区一些小地震震源参数和环境剪应力的研究

对2001年9月～2002年6月间发生在关中陕南地区42次小地震,利用数字地震记录资料,进行了波谱分析和震源参数的测定,并分析了环境剪应力分布特征。结果显示关中陕南地区环境剪应力处于较低水平,应力值3.3×105～32.2×105Pa之间,西部12×105～32×105Pa略高于东部8×105～17×105Pa,中部最低。西部有两个应力值较高区,一个是宝鸡、眉县、凤翔附近区域较高值区,应力值20×105～32×105Pa,另一个是留坝、凤县附近区域较高值区,应力值20×105～37×105Pa之间。东部的较高值区是高陵、耀县、三原附近地区,应力值在16×105～18×105Pa之间,该区域曾发生1998年1月5日泾阳MS4.8级地震。     

赣粤闽交界及邻区近年中强地震加卸载响应比特征研究

以地震应变能作为响应因子,研究了1997至2007年赣粤闽交界及邻区4．0级（ML≥4．0）以上中强地震临震前的加卸载响应比（Y值）的基本变化特征,研究结果表明,80％以上的地震在临震前Y值呈现出高值异常形态。因而它可以作为此地区地震预测的一种手段。     

福建及沿海地区地震活动力源探讨

综合地震震源机制解和地壳形变观测资料的研究, 求得福建及其沿海地区现代震源应力场, 认为这与台湾地区、 台湾海峡应力场相互衔接, 主压应力轴优势方位为NW-SE向, 力轴仰角较小, 应力场近于水平挤压, 形变场反映近期福建沿海亦受北西方向, 接近与海岸垂直的挤压力。 进一步分析该区域内的断裂构造特征和地震活动强度由东至西逐渐减弱的规律, 认为菲律宾海板块与欧亚板块的相互作用力不仅是台湾强震力源所在, 而且其影响向西扩展, 福建及其沿海地区地震活动主要力源仍然是来自这两大板块的相互作用力。