共查询到20条相似文献，搜索用时 46 毫秒
1.
震源机制解,即对地震矩张量的推断,对于地震研究具有至关重要的意义.应变地震观测是张量观测,与摆式地震仪的位移矢量观测不同,可以为地震研究提供新的数据源.本文讨论用应变地震观测求解震源矩张量的基本原理.在距离震源足够远的地方,地震波可以看成平面波,其性质决定于震源矩张量.假设平面地震波的应变张量可以由震源矩张量通过坐标变换计算得到,就可以通过观测应变地震波求解震源机制.这个假设至少对于双力偶震源机制是成立的.由此可以证明,在理想的无限介质中,只要有两个以上不同地点的应变地震波观测,就可以解出震源矩张量.这为解决震源机制问题提供了新的方法.目前的地震矩张量求解方法需要两方面的条件:或者需要很多观测点(例如体波反演),或者需要长周期地震波资料(例如面波反演).这些方法只适用于分析比较大的地震.对于小震,因为通常其震中周围不会有足够多的摆式地震仪观测点观测到其地震波,而地震波周期又短,难以利用传统方法给出可靠的震源机制解,所以只需少数观测点就能求解震源矩张量的新方法特别有意义.用应变地震观测求解震源机制,可以给出更为精确的结果. 相似文献
2.
Moment tensors of eleven major earthquakes in the Tibetan Plateau and its surrounding region from 1966 to 1980 are estimated
by generalized inverse technique. The seismic source time function and focal depth are immediately determined in the inversion.
The results show that moment tensors of some events differ significantly from double couple, the deviation increases with
decreasing plunge angle of null axis. All these events occurred in the upper crust, much shallower than those reported so
far, for example, in NEIS Bulletin. Focal mechanism solution obtained from the moment tensors are consistent with the idea
that the Indian plate collides northwards with the Eurasian plate and that an eastward spreading exists in the crust of the
Tibetan Plateau. The stress drops for earthquakes of intraplate are systematically higher than those of earthquakes in suture
zone. The source process duration becomes longer with seismic moment, but for the same seismic moment, the process duration
for earthquakes in suture zone is about 1.4 times of those for intraplate event, these results suggest that the earthquakes
near suture zone may be of a special characteristics in source process differently from those in intraplate.
The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,14, 423 – 434, 1992. 相似文献
3.
A MS8.0 earthquake occurred in Wenchuan County, Sichuan Province, China, on May 12, 2008, and subsequently, numerous aftershocks followed. We obtained the moment tensor solutions and source time functions (STFs) for the Wenchuan earthquake and its seven larger aftershocks (MS5.0～6.0) by a new technique of moment tensor inversion using the broadband and long-period seismic waveform data from the Global Seismic Network (GSN). Firstly, the theoretical background and technical flow of the new technique was briefly introduced, and an aftershock of the Wenchuan earthquake sequence was employed to illustrate the real procedure for inverting the moment tensor; secondly, the moment tensor solutions and STFs of the eight events, including the main shock, were presented, and finally, the interpretation of the results was made. The agreement of our results with the GCMT results indicates the new approach is efficient and feasible. By using this approach, not only the moment tensor solution can be obtained but also the STF can be retrieved; the inverted STFs indicate that the source rupture process may be complicated even for the moderate earthquakes. The inverted focal mechanisms of the Wenchuan earthquake sequence show that the most of the aftershocks occurred in the main faults of the Longmenshan fault zone with predominantly thrustingwith minor right-lateral strike-slip component, but some of them may have occurred in the subfaults with strike-slip faulting in the vicinity of the main faults. 相似文献
4.
Moment tensor inversion of nine events in Iran using INSN data 总被引：1，自引：0，他引：1
Aref Bali Lashak Mehdi Zare Gholamreza Mortezanejad Shahrokh Pour Beyranvand 《Journal of Seismology》2010,14(4):751-760
In this research, moment tensor (MT) inversion procedure in frequency domain is applied to nine events in order to evaluate
the data efficiencies in computing source parameters of earthquakes in Iran. The events are recorded by Iranian National Seismological
Network (INSN) stations, currently comprising 22 broadband stations. For the purpose of this study, first, the inversion procedure
is applied to obtain source parameters. Then, the results obtained here are compared with those of Harvard global centroid
moment tensors (GCMT) in order to estimate their reliabilities. The results show reasonable consistencies with those of Harvard
GCMT within 0.075 uncertainties in logarithmic scalar moment or 0.05 in moment magnitude and 20° in Kagan angle for focal
angles. Furthermore, according to the present research, the calculated source parameters are not significantly sensitive to
the azimuthal gap. 相似文献
5.
In the previous work of the present study,moment tensors of 11 major earthquakes in the Qinghai-Xizang Plateau and its surrounding region from 1966 to 1980 are estimated by generalized inversion technique.The seismic source time function and focal depth are immediately determined in the inversion.The results indicated that all earthquakes investigated here are shallow events within the upper crust.The purpose of this paper is to present a summary of the distribution of focal depths of earthquakes in and near the Qinghai-Xizang Plateau from the above result,combining the focal depths of 78 significant earthquakes from 1964 to 1986,which are relocated individually by other authors,as well as to discuss its tectonic implication. 相似文献
6.
A MS8.0 earthquake occurred in Wenchuan County, Sichuan Province, China, on May 12, 2008, and subsequently, numerous aftershocks followed. We obtained the moment tensor solutions and source time functions (STFs) for the Wenchuan earthquake and its seven larger aftershocks (MS5.0~6.0) by a new technique of moment tensor inversion using the broadband and long-period seismic waveform data from the Global Seismic Network (GSN). Firstly, the theoretical background and technical flow of the new technique was briefly introduced, and an aftershock of the Wenchuan earthquake sequence was employed to illustrate the real procedure for inverting the moment tensor; secondly, the moment tensor solutions and STFs of the eight events, including the main shock, were presented, and finally, the interpretation of the results was made. The agreement of our results with the GCMT results indicates the new approach is efficient and feasible. By using this approach, not only the moment tensor solution can be obtained but also the STF can be retrieved; the inverted STFs indicate that the source rupture process may be com-plicated even for the moderate earthquakes. The inverted focal mechanisms of the Wenchuan earthquake sequence show that the most of the aftershocks occurred in the main faults of the Longmenshan fault zone with predomi-nantly thrustingwith minor right-lateral strike-slip component, but some of them may have occurred in the sub-faults with strike-slip faulting in the vicinity of the main faults. 相似文献
7.
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
8.
Moment tensor inversion of near-source broadband data 总被引：1，自引：0，他引：1
Ｍｏｍｅｎｔ ｔｅｎｓｏｒ ｉｎｖｅｒｓｉｏｎ ｏｆ ｎｅａｒ－ｓｏｕｒｃｅ ｂｒｏａｄｂａｎｄ ｄａｔａ（吴忠良）（陈运泰（倪江川）（王培德）（王鸣）Ｍｏｍｅｎｔｔｅｎｓｏｒｉｎｖｅｒｓｉｏｎｏｆｎｅａｒ－ｓｏｕｒｃｅｂｒｏａｄｂａｎｄｄａｔａ￥Ｚ... 相似文献
9.
The main goal of this study is to provide moment tensor solutions for small and moderate earthquakes of the 2009 L’Aquila seismic sequence (central Italy). The analysis was performed by using data coming from the permanent Italian seismic network run by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) and the “Cut And Paste” (CAP) method based on broadband waveform inversion. Focal mechanisms, source depths and moment magnitudes are determined through a grid search technique. By allowing time shifts between synthetics and observed data the CAP method reduces dependence of the solution on the assumed velocity model and on earthquake location. We computed seismic moment tensors for 312 earthquakes having local magnitude in the range between 2.7 and 5.9. The CAP method has made possible to considerably expand the database of focal mechanisms from waveform analysis in the lowest magnitude range (i.e. in the neighborhood of magnitude 3) without overlooking the reliability of results. The obtained focal mechanisms generally show NW–SE striking focal planes in agreement with mapped faults in the region. Comparisons with the already published solutions and with seismological and geological information available allowed us to proper interpret the moment tensor solutions in the frame of the seismic sequence evolution and also to furnish additional information about less energetic seismic phases. Focal data were inverted to obtain the seismogenic stress in the study area. Results are compatible with the major tectonic domain. We also obtained a relation between moment and local magnitude suitable for the area and for the available magnitude range. 相似文献
10.
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
11.
We treat the problem of the non-uniqueness of the moment tensor inversion for shallow earthquakes from long period surface
wave data. We give an existence condition for double couples radiating the same long period surface waves as the deviatoric
moment tensor obtained by such inversion. We describe the family of such double couples and show that they may provide better
estimates of double couple mechanisms than the traditional “best double-couple” solution. We demonstrate the results of application
to four large shallow earthquakes with different source signatures. 相似文献
12.
分析矿震破裂机制及微震的时空分布能够为矿区灾害评估提供更多的有效信息.本研究基于密集台阵观测对2019年11月12日辽宁抚顺2.4级矿震开展震源参数研究,震源机制解显示地震破裂包含明显的非双力偶分量,表现为体积压缩的塌陷机制,且震源深度较浅,最佳拟合矩心深度为0.6 km.同时,对11月3日—25日记录的连续地震波形开展微震扫描,新检测出324个微震事件(-0.5~2.0级),定位结果显示在M 2.4矿震发生前M>1.0级事件显著增多,且在矿震位置存在近南北向的微震条带分布,微震序列随时间向深部迁移(约1.5 km),暗示存在断层活化迹象.结合震源破裂机制,我们认为此次事件与矿区塌陷破裂密切相关,同时伴随先存断裂的剪切滑动.本研究表明,基于密集台阵观测的地震矩张量反演和微震检测研究,对判定矿震类型及防范矿区灾害具有重要的研究意义. 相似文献
13.
利用地震台网宽频带地震记录计算福建中等强度地震的震源机制解 总被引：2，自引：0，他引：2
2007—2009年福建及邻近地区共发生4级以上地震10次。 这些频繁发生的中等强度地震, 给当地居民的生活带来了不小的影响, 因而有必要加强对这些地震的分析研究。 本文利用BSL开发的矩张量反演程序TDMT_INVC, 使用福建数字地震台网宽频带台站地震波形记录, 对2007—2009年福建地区发生的4次ML>4.2地震的震源机制解进行反演, 并对反演得到的震源机制解进行分析; 在反演过程中, 利用波形拟合方法确定这4次地震的震源深度。 相似文献
14.
15.
Lane R. Johnson 《Pure and Applied Geophysics》2014,171(8):1641-1668
At The Geysers geothermal reservoir in northern California, evidence strongly suggests that activities associated with production of electric power cause an increase in the number of small earthquakes. First-degree dynamic moment tensors are used to investigate the relationship between induced earthquakes and injection of water into a well as part of a controlled experiment in the northwest Geysers. The estimation of dynamic moment tensors in the complex shallow crust at The Geysers is challenging, so the method is described in detail with particular attention given to the uncertainty in the results. For seismic events in the moment magnitude range of 0.9–2.8, spectral moduli of dynamic moment tensors are reliably recovered in the frequency range of 1–100 Hz, but uncertainty in the associated spectral phases limits their use to a few simple results. A number of different static moment tensors are investigated, with the preferred one obtained from parameters of a model fitted to the spectral modulus of the dynamic moment tensor. Moment tensors estimated for a group of 20 earthquakes exhibit a range of source mechanisms, with over half having significant isotropic parts of either positive or negative sign. Corner frequencies of the isotropic part of the moment tensor are about 40 % larger than the average of the deviatoric moment tensor. Some spatial patterns are present in source mechanisms, with earthquakes closely related in space tending to have similar mechanisms, but at the same time, some nearby earthquakes have very different mechanisms. Tensional axes of displacement in the source regions are primarily horizontal, while the pressure axes range from near horizontal to vertical. Injection of water into the well in the center of the study area clearly causes an increase in the number of earthquakes per day, but an effect upon source mechanisms is not evident. 相似文献
16.
使用芦山地震序列2013年4月20日至5月20日一个月的地震震相数据和MS4.0以上地震的波形数据, 通过双差定位方法得到了3398个地震的精定位结果, 利用时间域全波形反演方法得到17个地震的矩张量解。 综合分析地震双差定位结果和芦山地震序列中强地震震源机制解, 发现芦山地震发震构造由主震断层和次级反冲断层组成, 主震断层为一走向北东、 倾向北西、 倾角约为45°的高角度逆冲断层, 次级反冲断层与主震断层走向相同, 倾向相反, 两条断层均未出露地表。 主震和余震震源机制解均为逆冲型, 几乎没有走滑分量。 震源区主压应力方位为北西向, 与发震断层走向近乎垂直。 相似文献
17.
D. A. Safonov T. V. Nagornykh A. V. Konovalov A. A. Stepnov 《Journal of Volcanology and Seismology》2017,11(3):225-234
We report determinations of the focal mechanisms for Sakhalin earthquakes during 2006 through 2015 by two different methods: the polarity of first motions using the FOCMEC program and the inversion of waveforms using the ISOLA program. We show that the resulting moment tensor solutions fairly well fit the tectonic crustal stresses for Sakhalin as determined by previous workers. We have examined the component of the moment tensor that involves a linear dipole. This is at its maximum in areas of active mud volcanism and industrial activities in oil-and-gas fields. 相似文献
18.
19.
青藏高原地震的震源深度及其构造意义 总被引：16，自引：4，他引：16
在本研究的前一项工作中，根据ＷＷＳＳＮ的长周期无震体波记录，采用广义反演技术，确定了１９６６年至１９８０年期间发生在西藏高原及其周围地区的１１个主要地壳地震和地震矩张量，同时得到了震源时间函数和震源深度。所分析的地震具有较浅的震源深度，且均分布于上部地壳范围内，本文根据上述结果，结合其它逐个测定的１９６４年至１９８６年发生在青藏高原的７８个中强地震的震源深度的结果，讨论了青藏高原地震的震源深度分布 相似文献
20.
Heidi Houston Helen Anderson Susan L. Beck Jiajun Zhang Susan Schwartz 《Pure and Applied Geophysics》1993,140(2):331-364
To evaluate the tectonic significance of the October 20, 1986 Kermadec earthquake (M
w
=7.7), we performed a comprehensive analysis of source parameters using surface waves, body waves, and relocated aftershocks. Amplitude and phase spectra from up to 93 Rayleigh waves were inverted for centroid time, depth, and moment tensor in a two-step algorithm. In some of the inversions, the time function was parameterized to include information from the body-wave time function. The resulting source parameters were stable with respect to variations in the velocity and attenuation models assumed, the parameterization of the time function, and the set of Rayleigh waves included. The surface wave focal mechanism derived (=275°, =61°, =156°) is an oblique-compressional mechanism that is not easy to interpret in terms of subduction tectonics. A seismic moment of 4.5×1020 N-m, a centroid depth of 45±5 km, and a centroid time of 13±3 s were obtained. Directivity was not resolvable from the surface waves. The short source duration is in significant contrast to many large earthquakes.We performed a simultaneous inversion ofP andSH body waves for focal mechanism and time function. The focal mechanism agreed roughly with the surface wave mechanism. Multiple focal mechanisms remain a possibility, but could not be resolved. The body waves indicate a short duration of slip (15 to 20 s), with secondary moment release 60s later. Seismically radiated energy was computed from the body-wave source spectrum. The stress drop computed from the seismic energy is about 30 bars. Sixty aftershocks that occurred within three months of the mainshock were relocated using the method of Joint Hypocentral Determination (JHD). Most of the aftershocks have underthrusting focal mechanisms and appear to represent triggered slip on the main thrust interface. The depth, relatively high stress drop, short duration of slip, and paucity of true aftershocks are consistent with intraplate faulting within the downgoing plate. Although it is not clear on which nodal plane slip occurred, several factors favor the roughly E-W trending plane. The event occurred near a major segmentation in the downgoing plate at depth, near a bend in the trench, and near a right-lateral offset of the volcanic are by 80 km along an E-W direction. Also, all events in the region from 1977 to 1991 with CMT focal mechanisms similar to that of the Mainshock occurred near the mainshock epicenter, rather than forming an elongate zone parallel to the trench as did the aftershock activity. We interpret this event as part of the process of segmentation or tearing of the subducting slab. This segmentation appears to be related to the subduction of the Louisville Ridge, which may act as an obstacle to subduction through its buoyancy. 相似文献