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运用经验格林函数法模拟了2008年5月12日汶川8.0级大地震的近场强地面运动.拟合过程中,首先参考其他学者反演结果给出的滑动量分布的特征,确定强震动生成区的大致范围;然后利用Somerville等(1999)提出的地震矩与凹凸体面积间的经验关系式确定强震动生成区(SMGA)细小划分的初值,继而利用遗传优化算法确定以上两者的最优值及其他震源参数.数值模拟波形同实际地震观测记录在时间域和频率域分别进行了比较,结果显示,在所选取的18个观测台中,多数台站的数值模拟结果同实际观测结果符合得很好,特别是大于1 Hz的高频部分.我们发现断层面上有5个强震动生成区,其中两个的位置与其他学者反演的滑动量集中分布区相一致,但强震动生成区规模和上升时间比Somerville等(1999)获得的定标率外延的估计值要小. 相似文献
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利用中小震作为经验格林函数,选取0.2~2.0 Hz频段的强震数据进行波形反演,获得了2021年福岛县冲地震的破裂过程。结果表明:该地震的破裂主要集中在断层面距离震源约25 km的区域内,沿震源向东北延伸约5 km,向西南延伸约20 km;在该区域内,识别出两个滑动量集中的区域,均分布在距离震源约15 km西南侧,主要滑动量集中区域最大滑动量约3.2 m,深度基本与震源一致;次要滑动量集中区域略比主要滑动量集中区域浅约18 km。该震源模型对应矩震级Mw7.3,破裂速度为2.4 km/s。通过选择不同的中小震组合进行波形反演,结果对该震源模型特性无显著影响,揭示了该震源模型的稳健性;基于该震源模型合成反演分析中未使用的强震观测台站强震动,获得的合成波形与观测波形有很好的相关性,充分证明了该震源模型时空特征的可靠性。 相似文献
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二维频率空间域的数值模拟方法具有以下的优势:多炮模拟时,计算成本比时间域方法低;无累计误差;在地震反演中处理多震源模拟时,只需要有限的几个频率就可以得到好的反演结果.差分离散化形成的稀疏系数矩阵,需要求解一个巨大规模的线性方程组,最大瓶颈是需要海量的计算机内存,导致计算量庞大.本文在前人研究的基础上,采用嵌套剖分网格排序法,极大限度减少对计算机内存的需求,从而减少了计算量.针对弹性波数值模拟的特征,提出二维频率空间域弹性波多炮模拟的快速计算流程.数值模拟试验证明使用嵌套剖分排序法的弹性波多炮数值模拟比压缩存储法具有节省存储量、计算效率高等优势,为后续的二维频率空间域弹性波全波形反演奠定了很好的基础. 相似文献
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由于震中附近强震台分布不均,文中联合使用近场2个国家强震动观测台网的强震台和7个云南地震预警台网烈度台的强震记录,采用经验格林函数法构建了特性化震源模型,并利用此模型对近场强震动进行了模拟。结果表明：烈度台的记录可与强震台的记录联合,共同作为强震动模拟的对象,但应注意区分二者的有效频带;在0.20～30.0Hz频带,在53YBX台处的NS分量上,模拟结果的伪加速度反应谱较好地再现了0.1s处的峰值,在EW分量上,合成的速度波形虽然幅值较低,但较好地再现了速度脉冲波段;在53DLY台处的合成波形较好地再现了约2s的长周期地震动;在0.50～30.0Hz频带,合成波形和反应谱与信噪比较高的烈度台的记录较为一致。文中确定的用于模拟强震动的特性化震源模型由一个强震动生成域构成,其面积和相应的短周期范围内加速度震源谱的水平段幅值与地震矩的关系均遵循经验标度律。 相似文献
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基于近台强震波形数据可快速且稳定地反演地震破裂过程.利用国家地震烈度速报与预警工程实施过程中青海地区新建和改建的强震动观测台站的波形数据,基于迭代反褶积和叠加法(IDS)对2022年1月8日青海门源MS6.9地震的震源破裂过程进行了反演.反演结果显示:破裂为自初始破裂点向ESE向扩展的单侧破裂,持续时间约为14 s(主要集中在2—8 s),最大滑动量为3.6 m,破裂长度约为20 km.破裂在纵向上自深部向浅部扩展,这与现场调查的地表破裂吻合.余震序列空间分布展示出显著的分段特征,预示了破裂区复杂的构造. 相似文献
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《国际地震动态》2019,(11)
正十五期间,我国累计部署约2 000个强震动台站,台站分布密度增加,观测技术得到很大发展。我国即将实施"国家地震预警与烈度速报工程"建设,建成后台网台间距将达到20—40 km,资料能够快速获取。但强震动数据在滑动分布反演方面尚未应用于地震应急和灾害评估中。强震动数据大量应用于实时或者近实时地震动预测系统中,在实时场地放大系数研究方面,现有研究大多利用标量值来表征场地放大系数,缺少实时校正依赖于频率的场地放大系数的研究,期望通过研究改进实现在地震应急与地震动预测中发挥重要作用。本文围绕强震动数据深入应用于断层滑动分布反演和地震动预测方面,主要研究了快速基线校正获取可靠永久位移的方法、利用近场位移进行快速滑动分布反演、实时校正依赖于频率的场地放大系数3个方面的内容。论文主要取得了以下认识和成果:(1)分析了强震动记录基线漂移的原因,总结了国内外提出的基线校正方法,针对现有基线校正方法自动化程度低,难以快速获取近场位移的问题,改进和完善了自动基线校正方法,形成了针对国内外多种强震动仪器记录数据进行快速处理获取永久位移的能力,并利用改进的基线校正方法对不同强震动台网的强震动数据进行处理,并与附近GPS台站记录的位移对比,验证了计算结果的可靠性。研究显示改进的方法能够获得近场专业强震动仪记录到的强震动记录的永久位移,同时也检测到P-alert台网近场永久位移偏离严重,显示大地震发生时MEMS传感器记录强震动数据可能难以恢复可靠近场永久位移。(2)总结了均匀半空间和水平成层半空间的同震位错理论和反演理论及方法。利用台湾CWB和NCREE强震动台网记录到的近场永久位移数据、GPS数据、 Sentinel-1A和ALOS-2In SAR数据基于单断层模型和双断层模型分别反演与联合反演得到了美浓地震滑动分布结果,对比分析不同模型下反演结果,显示本次地震单一发震断层模型结果更加合理。研究显示地震以倾滑为主,主要滑动破裂集中在9—15 km之间,并没有延伸到地表,破裂主要发生在震中西北区域,近地表最大滑动量为0.95 m,最终矩震级为6.29,平均应力降为1.21 MPa,最大应力降为6.31 MPa。(3)利用日本F-net测震数据基于考虑震源时间函数效应的矩张量反演方法反演得到了熊本主震的震源机制解。利用日本K-net和Kik-net强震动台网记录的近场永久位移、ALOS-2In SAR数据、Geonet位移数据分别建立单一断层和分段式断层模型进行滑动分布单独反演与联合反演研究,显示分段式断层模型结果更加合理,滑动分布主要在震中东北方10—30 km间,同时震中附近具有较大的滑动量,破裂延伸到地表,分段1断层模型平均滑动量为2.19 m,最大滑动量6.00 m,平均应力降19.66 MPa,最大应力降90.75 MPa。分段2断层模型平均滑动量约1.48 m,最大滑动量为4.00 m,平均应力降为15.72 MPa,最大应力降为116.62 MPa,矩震级为7.04,破裂过程在阿苏火山西南段结束。基于K-net和Kik-net快速获取的永久位移反演滑动分布结果和基于Geonet GPS位移数据、Sentinel-1A In SAR形变数据反演得到滑动分布结果都比较一致而且可靠,研究显示大震后利用高密度强震动台网后快速获取滑动分布用于震后应急响应和灾害评估是切实可行的。(4)系统总结了国内外场地放大系数校正研究现状,显示利用标量数值来校正场地放大系数的方法不能产生依赖于频率的放大系数,因此,研究实时校正依赖于频率的场地放大系数,设计因果递归无限脉冲响应滤波器(IIR)来建模场地放大系数,完成了软件实现。收集了Kiknet IBRH10与IBRH19两个台站208次地震的强震动记录,利用谱比法得到了井下台站和地面台站之间的相对场地放大系数,设计IIR滤波器对井下观测数据滤波模拟得到了自由地表地震动。利用谱比法计算IBRH10和IBRH19两个台站间的相对谱比,设计因果递归滤波器实现场地放大系数,模拟得到了IBRH10台的加速度时程和傅里叶谱。统计分析所有观测数据和模拟数据的仪器地震烈度,发现预测准确程度有较大提高。本方法很好的改进了加速度时程和仪器地震烈度的预测。为场地放大系数的实时校正提供了一种比较准确的计算方法。(5)以熊本地震为例,基于联合反演滑动分布结果,利用随机有限断层方法模拟得到了熊本地震KMMH12台站与KMMH13台站的基岩加速度时程,提出将IIR方法引入到随机有限断层地震动模拟。通过熊本地震两个台站从井下到地表的模拟和自由地表台站之间的模拟,均取得了较好的模拟结果,验证了方法的有效性。将相关工作结合起来,对更加准确的预测地震动场有重要的支持作用。 相似文献
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利用自动经验基线校正方法,分析日本2008年岩手-宫城内陆Mw6.9地震震中周围密集强震动观测台网资料,快速解算出了同震位移场分布,并据此反演了震源滑动模型.经与GPS结果比较,两种不同方法给出的同震位移幅值、方向和总体分布特征较为接近.基于相同断层面参数反演的震源模型空间展布形态、主要滑动范围、平均和最大滑动量、滑动方向以及由模型计算的矩震级等均吻合较好,从而验证了方法的可行性.讨论了自动经验基线校正方法尚存在的问题和不足,为今后利用强震资料快速解算Mw6-7级及以上地震的同震位移场并反演震源滑动分布提供参考. 相似文献
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2013年7月22日,在甘肃岷县漳县交界处发生MS6.6地震,地震震中位置靠近临潭—宕昌断裂.本文通过构建有限断层模型,利用国家强震动台网中心提供的12条强地面运动三分量资料,通过波形反演方法来研究这次地震的震源破裂过程.结果显示这次地震是发生在甘东南地区岷县—宕昌断裂带东段附近的一次MW6.1级逆冲兼具左旋走滑破裂事件,最大滑动量约为80cm.发震断层走向及滑动性质与岷县—宕昌断裂吻合,推断本次地震与东昆仑断裂向北的扩展和推挤密切相关,是岷县—宕昌断裂进一步活动的结果. 相似文献
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基于甘肃文县获得的汶川地震强余震记录分析和FLAC3D软件模拟场地地震反应的方法研究了地形条件对地震动的影响.首先结合文县流动地震台强余震记录,分析了文县山包场地的地震动分布特征;其次对该山包进行了地形测量、地震勘探和土样采取,根据实测资料建立了FLAC3D三维场地数值模型,采用实际基岩记录输入,研究了山包不同部位地震动的分布特征.研究表明:数值计算与观测的结果在一定频段范围内有较好一致性;其时域峰值加速度放大比接近,反应谱谱比结果放大趋势一致,1 ～10Hz的地震动放大最明显;FLAC3D软件能够有效地模拟三维场地的地震反应. 相似文献
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对有限断层地震波能量辐射的估算通常采用断层面上子源能量的逐点求和方法。基于Brune圆盘模型,Anderson推导出有限断层地震波能量辐射S波的求解公式,即 ,其中 为断层面上地震矩, 为剪切模量, 和 分别为动态应力降和静态应力降,并指出在复合震源模型强地面运动预测应用中 以满足能量守恒。Rivera和Kanamori则从能量辐射表象定理出发,给出了有限断层中辐射能量的积分表达式,明确地指出了逐点求和所存在的问题。依据该积分表达式,本文推导出了复合源模型中新的辐射能完整的求解方法,指出Anderson方法实为断层面上点源辐射能量的简单叠加求和,后者则充分考虑了断层面上任一点在任一时刻能量传播过程中受到的断层面上所有位移破裂路径的交互影响。以1976年唐山7.6地震为例,应用上述方法分别计算了有限断层模型的辐射能量及近场强地面运动,如质点运动加速度,速度。结果表明如果模型参数满足 时,由本文给出的求解方法计算所得到的地震波辐射能已远远超出实际的辐射能量值,直接导致了对近场强地面运动参数如质点速度、加速度等的过高估算。因此,Zeng等和Anderson工作的局限性是非常明显的:地震矩守恒以及非物理的 无法准确地预测近场地面运动。未来工作中,对于有限断层模型的建立,在地震矩守恒这一约束条件的基础上,远场和近场能量解（或视应力）将可作为另一个重要的约束条件,为强地面运动的模拟提供一个更为恰当的求解方案。 相似文献
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利用高分辨光学影像获取的同震水平位移场资料联合远场波形数据反演获得了2013年巴基斯坦俾路支MW7.7地震的震源过程模型.结果显示这是发生在具有弧形铲状几何形态的Hoshab断层上的一次左旋走滑为主要运动特征的强烈地震事件.推断这种具有罕见运动模式的强烈地震是斜向应力场与特殊的断层几何形态共同作用的结果.研究工作中采用大数据量均匀分布的同震位移资料参与反演计算,结果表明这种以完整图像的形式使用位移场资料的方式可以克服资料可能存在的系统误差获得可信的结果. 相似文献
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It gradually becomes a common work using large seismic wave data to obtain source parameters, such as seismic moment, break radius, stress drop, with completingof digital seismic network in China (Hough, et al, 1999; Bindi, et al, 2001). These parameters are useful on earthquake prediction and seismic hazard analysis.Although the computation methods of source parameters are simple in principle and the many research works have been done, it is not easy to obtain the parameters accurately. There are two factors affecting the stability of computation results. The first one is the effect of spread path and site respond on signal. According to the research results, there are different geometrical spreading coefficients on different epicenter distance. The better method is to introduce trilinear geometrical spreading model (Atkinson, Mereu, 1992; Atkinson, Boore, 1995; WONG, et al, 2002). In addition, traditional site respond is estimated by comparing with rock station, such as linear inversion method (Andrews, 1982), but the comparative estimation will introduce some errors when selecting different stations. Some recent research results show that site respond is not flat for rock station (Moya, et al, 2000; ZHANG,. et al, 2001; JIN, et al, 2000; Dutta, et al, 2001). The second factor is to obtain low-frequency level and corner frequency fromdisplacement spectrum. Because the source spectrum model is nonlinear function,these values are obtained by eye. The subjectivity is strong. The small change of corner frequency will affect significantly the result of stress drop. 相似文献
14.
采用Wu等(2004)提出的地震强度测定方法,应用近场速度波形记录,测定地震参数M_(ew),实现了川滇地区中强地震(M_W≥5.7)强度近实时快速测定。M_(ew)是一个与矩震级M_W对接的地震参数,与传统的应用振幅测定震级的方法相比,不会存在震级饱和问题,与全球矩心矩张量(GCMT)的矩震级M_W具有较好的一致性。该方法解决了应用近场波形资料和矩张量反演方法求取大地震矩震级比较困难的问题,可为区域中强地震速报提供近实时矩震级提供参考,从而提高地震速报的时效性和准确性,同时为强震加速度数据的应用奠定基础。 相似文献
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《Geofísica Internacional》2014,53(2):211-220
We apply a single-step, finite-fault analysis procedure to derive a coseismic slip model for the large MW 7.4 Ometepec-Pinotepa Nacional, Mexico earthquake of 20 March 2012, using teleseismic P waveforms recorded by the Global Seismographic Network. The inversion is conducted in near-realtime using source parameters available from the USGS/NEIC and the Global Centroid Moment Tensor (gCMT) project. The fault orientation and slip angle are obtained from the gCMT mechanism assuming that the fault coincides with the shallow-dipping nodal plane. The fault dimensions and maximum rise time are based on the magnitude reported for the event. Teleseismic data from the USGS/NEIC Continuous Waveform Buffer database are used in the inversion with record start times set to the P-wave arrivals used to compute the earthquake hypocenter. The inversion is stabilized by requiring a smooth transition of slip across the fault while minimizing the seismic moment. These constraints are applied using a smoothing weight that is estimated from the inverse problem, allowing the recovery of the least-complicated rupture history in a single step. Inversion of the deconvolved, ground-displacement waveforms reveals a simple, circular rupture similar in extent to the source identified by the USGS/NEIC using body-and surface-wave data, indicating that the teleseismic P waves can provide a first-order source model for the event in near-realtime. Additional inversions conducted using velocity records identify a more-detailed rupture model characterized by an elliptical 2500 km2 source region extending updip and downdip from the hypocenter. This elliptical source preserves the orientation and overall dimensions of a dual-source slip model obtained recently by other investigators using local strong motions and global seismic waveforms. The results indicate that velocity waveforms could provide additional details of the earthquake rupture in near-realtime, finite-fault inversions using teleseismic P waves. 相似文献
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D. Hidayat B. Voight C. Langston A. Ratdomopurbo C. Ebeling 《Journal of Volcanology and Geothermal Research》2000,100(1-4)
Multiphase (MP) and low frequency (LF) earthquakes with spectral peak amplitudes at 3–4 and 1 Hz, respectively, are two common types of shallow volcanic earthquakes previously recognized at Merapi Volcano. Their mechanisms are poorly understood but MPs have been temporally associated with lava dome growth. We conducted a seismic experiment in January–February 1998, using four broadband seismographs to investigate the nature of seismic activity associated with dome growth. During our experiment, Merapi experienced mild dome growth with low-level seismic activity. We compare our data to that recorded on a local short-period (SP) network, with the following preliminary results.MP and LF events as recorded and classified on the short-period network instruments were recognized on the broadband network. Frequency spectrograms revealed similar patterns in the near summit region at widely separated broadband stations. Higher frequency spectra than previously recognized were identified for both MP and LF events, and were strongly attenuated as a function of radial distance from the source. Thus the spectral characteristics of these events as recorded on far-field stations are not fully indicative of the source processes. In particular, many events classified as LF-type appear to have much high frequency energy near the source. This aspect of these so-called LF earthquakes, and their association with very-long-period (VLP) pulses, suggests that many events identified in the far-field as LF events are in actuality a variety of the MP event and involve similar source processes. Broadband records indicated that simple large-amplitude VLP pulses were embedded in MP and LF wavetrains. From event to event these pulses were similar in their waveforms and had periods of 4 s. VLP events embedded in LF and MP earthquakes were located using particle motions. The epicenters were clustered in a central region of the dome complex, and preliminary source depths were within about 100 m of the dome surface, suggesting a source region deep within the dome or the uppermost conduit. A similar source location was established by study of MP high-frequency onsets. Our broadband data suggests that we have recorded both elastic seismic waves and a simple embedded pulse that is interpreted to represent a surface tilt at the seismometer site. The inferred tilt indicates an inflation and subsequent deflation, possibly caused by a gas pressure pulse or episodic shallow magma transport with stick-slip movement of the conduit wall. 相似文献
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—?The aim of our study consists of analyzing potentially non-double-couple seismic events recorded at regional distances. In order to define the nature of the seismic source, a moment tensor inversion is carried out as this method is general enough not to initially constrain the source mechanism. In this paper we present an application to a seismic event induced by a mine collapse which occurred near the town of Halle in Germany. Because of its induced nature, many parameters such as the location and geometry of this seismic source are known. This information allows us to test the influence of inadequate propagation modeling on the moment tensor obtained from the inversion. Green's functions have been computed with the reflectivity method in a flat layered medium, using the European model EurID (Du et? al., 1998; Dufumier et al., 1997). From the inversion of P-wave seismograms recorded by the German Regional Seismic Network will, we obtained a source time function which can be decomposed into two subevents. The first one has a large isotropic part and a deviatoric mechanism with near vertical nodal planes. No volume change is observed for the second subevent, but a deviatoric component opposite of the first one. The addition of S-waves does not change the results of the inversion which are stable. Surface waves were not used because of their poor dispersion curves. Based on the moment tensor obtained from these inversions, the physical process at the source is compatible with a large cavity collapse. 相似文献