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近几十年来,震源的矩张量表示及其反演获得了巨大成功。在震源物理的研究中,地震矩张量作为一个二阶对称张量已被广泛接受并且得到了成功的应用,但非对称矩张量则鲜有提及。本文阐述了在震源理论中非对称矩张量在物理上的合理性及其重要性,指出断层厚度的地震效应需要用非对称矩张量来表示。 相似文献
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利用包括长周期体波、Rayleigh波和Love波在内的三分向波形记录,根据PREM模型应用自由振荡振型叠加方法计算理论地震图,反演1997年11月8日西藏玛尼Ms7.9地震的矩张量.获得的最佳双力偶的节面解为:NP1(走向343°,倾角76°,滑动角-177°),NP2(走向252°,倾角87°,滑动角-13°);地震矩为1.43×1020 Nm,Mw为7.4.其结果与哈佛大学的CMT解较一致.地震的发震断层面为北东东近东西方向,断层性质主要为左旋走滑断层,与地质背景、应力场特征相符合.研究使用的是适用于区域性地震的矩张量快速确定的方法,可以用来对区域性的地震活动给出准确而快速的监测. 相似文献
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2022年9月5日，在四川省甘孜州泸定县发生MS6.8地震.本研究收集区域台网震相数据、全球地震台网(GSN)、国际数字地震台网联盟(FDSN)与德国地学中心GEOFON台网的宽频带P波数据，利用双差定位、矩心矩张量解反演、有限断层波形反演和视震源时间函数分析等方法，分析了此次地震震源的基本特征.重定位结果显示，余震分布具有丛集性，3个地震丛分别集中在震中附近以及相距30 km左右的东南端和西北端，总体上西北端地震较浅，东南端地震较深.矩心矩张量反演表明，矩心位于29.55°N,102.14°E,深度16 km,释放地震矩1.0068×1019 N·m,相当于矩震级MW6.60,双力偶成分占88%,是一次近纯走滑的地震事件.结合余震分布可以断定，地震发生在走向163°、倾角77°(倾向西南),滑动角为-5°的断层面.有限断层反演显示，破裂区主要由两部分构成，破裂起始点及其周围是主要破裂区；另一破裂区位于其东南，总体表现为从西北向东南的单侧破裂，最大滑动量约1.4 m,位于起始破裂点附近.从矩心矩张量反演和有限断层反演得到... 相似文献
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本文在对称地震矩张量反演的基础上，进一步研究了非对称地震矩张量时间域反演的理论与方法，结果表明:非对称地震矩张量反演与对称地震矩张量反演类似，只需将对称地震矩张量反演方法略加改动，即增加3个待解参数，便可实现非对称地震矩张量反演.为了判断非对称地震矩张量反演相对于对称地震矩张量反演是否存在过度拟合，运用了AIC准则 (赤池信息准则).为了定量地描述地震矩张量之间的差异，引入了地震矩张量的矢量表示法.通过分析格林函数与地震矩张量各分量之间的关系，得出:在非对称地震矩张量反演时，若仅用垂直向地动位移数据，将无法区分Mxy与Myx这两个分量, 需要同时运用垂直向与水平向地动位移数据进行联合反演才能区分Mxy与Myx; 若采用不同的速度结构模型或不同的格林函数计算方法，则需重新评估地震矩张量各分量的分辨度问题.为检验非对称地震矩张量反演方法的可行性, 利用合成地震图进行了一系列数值试验.数值试验结果表明，在非对称地震矩张量反演中，有必要引入S波进行P波与S波联合反演以提高反演的准确性和判定断层面的能力. 相似文献
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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。 相似文献
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文中给出了根据地震释放的总地震矩求解平均应力场的方法,并使用加入随机误差的人工合成震源机制解数据和唐山余震区震源机制解数据对其进行检验。由检验结果可知,该方法可以应用于区域平均应力场的求解。使用的震源机制解资料越多,所得结果越稳定,且更接近真实的区域应力场。该方法的优点是: 用每个地震的震级作为权重,能够较好地反映出大小地震在应力场反演中的不同贡献; 并且在计算过程中不需要知道震源机制解2个节面中哪个节面为地震断层面。 相似文献
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Under the background of thrusting stress regime, a large number of strike-slip earthquakes occurred on the Miyaluo Fault during the Wenchuan earthquake sequence process, which is in the southern part of the Longmenshan Fault. In order to find the cause of their occurrence, stress tensors in subregions near the Miyaluo Fault are estimated. The result shows that in both north and south side of the Miyaluo Fault, the direction of principal compressive stress is nearly perpendicular to the Longmenshan Fault, and its dip is nearly horizontal, and the direction of tensile stress is nearly vertical. While in the Miyaluo fault zone, the direction of principal compressive stress is SWW-NEE, and its dip is nearly horizontal, the direction of principal tensile stress is NNW-SSE, also its dip is nearly horizontal. It is consistent with sinistral shear stress state in the Miyaluo fault zone. It was referred that the behavior of Miyaluo Fault during the Wenchuan earthquake sequence process was caused by tearing effect generated from unbalanced forces of two sides of the fault. To understand the rupture mode of the aftershocks in subregions as described above, the total seismic moment tensors are estimated by adding the corresponding component separately of the seismic moment tensor of aftershocks in each region. The result shows the similar trend of total seismic moment tensor components in the north and south side of the Miyaluo Fault(indicating the consistency of rupture mode in the north and south side of the Miyaluo Fault), and most seismic moment tensor components in the south side is higher than that in the north side, especially the compression component perpendicular to Longmenshan Fault and expansion component in the vertical direction. It indicates that thrusting component in the southeast direction in the south side is greater than that in the north side, and the thrusting difference causes the sinistral tearing effect of the Miyaluo Fault. We also find that the sinistral tearing component of the Miyaluo Fault is the same order of magnitude with the thrusting difference of its two sides, which indicates that the tearing effect of Miyaluo Fault can be completely explained by thrusting difference of its two sides. According to the analysis, we put forward the dynamic model of the Miyaluo Fault, which can explain the above phenomenon. 相似文献
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Generally the decomposition of a seismic moment tensor is not unique. However, to favorably view the characteristics of a certain seismic source, one must decompose a seismic moment tensor into parts according to assumptions about the properties of the seismic source. Different from natural earthquakes in which the shear dislocation component plays a predominant role in the source process, and the seismic moment tensor can be separated into an isotropic component, a double couple, and a compensated linear vector dipole (CLVD), underground nuclear explosions have three major components in their source process, i.e., the explosion, the tensional spalling, and the tectonic strain release associated with the explosion. In such a situation the conventional moment tensor decomposition for earthquakes is not convenient to estimate the yield of the explosion and to characterize the tectonic strain release. In this paper, an alternative decomposition scheme is proposed to deal with the moment tensor of underground nuclear explosions, which might benefit the approach to study the tectonic strain release induced by underground nuclear detonations. 相似文献
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Ambiguous Moment Tensors and Radiation Patterns in Anisotropic Media with Applications to the Modeling of Earthquake Mechanisms in W-Bohemia 总被引：3，自引：0，他引：3
Anisotropic material properties are usually neglected during inversions for source parameters of earthquakes. In general anisotropic media, however, moment tensors for pure-shear sources can exhibit significant non-double-couple components. Such effects may be erroneously interpreted as an indication for volumetric changes at the source. Here we investigate effects of anisotropy on seismic moment tensors and radiation patterns for pure-shear and tensile-type sources. Anisotropy can significantly influence the interpretation of the source mechanisms. For example, the orientation of the slip within the fault plane may affect the total seismic moment. Also, moment tensors due to pure-shear and tensile faulting can have similar characteristics depending on the orientation of the elastic tensor. Furthermore, the tensile nature of an earthquake can be obscured by near-source anisotropic properties. As an application, we consider effects of inhomogeneous anisotropic properties on the seismic moment tensor and the radiation patterns of a selected type of micro-earthquakes observed in W-Bohemia. The combined effects of near-source and along-path anisotropy cause characteristic amplitude distortions of the P, S1 and S2 waves. However, the modeling suggests that neither homogeneous nor inhomogeneous anisotropic properties alone can explain the observed large non-double-couple components.The results also indicate that a correct analysis of the source mechanism, in principle, is achievable by application of anisotropic moment tensor inversion. 相似文献
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Based on Generalized Seismic Ray Theory (Helmberger, 1968), a new quickly linear inversion method from the data of seismic
waveform to seismic moment tensor and source mechanism for domestic earthquake is studied in this paper. Six moderately strong
earthquakes which occurred in Chinese mainland in the past few years are studied. The seismic source parameters of these earthquakes,
seismic moment tensors, scalar seismic moments, fault plane solutions and source time functionsetc, are obtained.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 261–268, 1993. 相似文献
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利用单台数字地震记录反演天祝—古浪5.4级地震矩张量 总被引：2，自引：0，他引：2
利用单台３分向数字化记录反演了１９９６年６月１日甘肃天祝－古浪５．４级地震的矩张量,并对所得结果与用Ｐ波被动符合的结果进行了比较。结果表明,二具有很好的一致性。结合谝地震的震源机制和震源区的断层的构造情况,认为该地震是在ＮＥ－ＳＷ的压应力作用下,近ＥＷ向的源原西断层天祝－古浪段左旋破裂错动的结果。由于我们得出的结果只是利用了记录波形的最初几个波形,因此它基本反映了该地震的初始破裂错动情况。 相似文献
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2013年吉林前郭MS5.8震群为爆发性震群，目前余震活动仍然在持续.基于吉林、辽宁、黑龙江、内蒙古四省地震台网记录的前郭震群波形资料，利用波形信噪比、震源类型、台站及速度模型组合的指标选择最佳的反演方案，应用矩张量的三种反演模式，对序列中5个MS≥5.0地震进行矩张量反演研究，获得了全矩张量、偏矩张量和纯双力偶的矩张量.使用F-test对地震的三种模式的矩张量反演结果进行显著性检验来确定最佳反演模式.结果显示，5个地震的最优矩张量解均为全矩张量模式反演获得的结果，其双力偶分量仅有20%~65%，矩心深度位于地下3~4 km处，地震在Hudson震源类型图上的投影远离双力偶震源类型区域.这些结果表明，震源类型并非典型的构造地震，推断前郭地震可能是与人类活动有关的诱发地震. 相似文献
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三峡库区湖北秭归与巴东交界地区2013年以来发生5次M S4.0以上地震.本文基于湖北、重庆等省属13个测震台站宽频带波形数据,采用kiwi软件包和rapidinv12程序反演了这些地震的全矩张量解,结果显示所有地震双力偶解均为走滑兼逆断性质,两个节面走向、倾角、滑动角与P、T轴走向和倾俯角的一致性均较好,主压应力P轴NWW走向,倾角近水平,主张应力T轴NNE走向.与三峡库区现今构造应力场比较,这5次地震主压应力P轴与主张应力T轴的平均方向与其大体一致,并且节面1平均走向也与附近主要断裂:高桥断裂和周家山—牛口断裂走向大体一致,反映了这些地震受到区域现今构造应力环境的控制与影响.通过对地震矩张量的ISO+DC+CLVD分解显示,所有地震的ISO成分均低于10%,纯双力偶DC成分偏少而CLVD成分较多,主要与震源区地下浅层介质复杂的各向异性、多重剪切错动或液态下拉张错动有关.结合震源区局部特殊的岩层岩性结构和水文地质环境,分析认为库水长时期的侵蚀溶蚀与加卸荷载作用,有利于引起局部岩层强度降低,在特殊水位时段将触发岩层失稳而滑动破裂,这5次地震中CLVD成分较多正是这一复杂过程的重要体现. 相似文献