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1.
为了更好地确定2017年8月8日九寨沟M_(S )7.0地震震源深度其发震机理,利用四川、甘肃和青海区域地震台网的观测波形数据,采用多种方法研究了此次地震的震源深度。首先,采用gCAP方法反演了九寨沟M_(S )7.0地震的震源机制解和矩心深度,结果显示,节面Ⅰ走向243°/倾角87°/滑动角-158°,节面Ⅱ走向151°/倾角68°/滑动角-3°,矩震级为M_(W )6.5,矩心深度为8 km;然后,采用ISOLA近震全波形方法反演了此次地震的震源机制解,反演结果与gCAP方法结果相差不大,矩心深度为7 km;最后,通过sPn震相与Pn震相之间的走时差测定此次地震初始破裂震源深度,结果显示深度约为12 km。研究表明,九寨沟M_(S )7.0地震的矩心深度为7—8 km,初始破裂深度约为12 km。 相似文献
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2015年3月14日在安徽阜阳地区发生了M_S4.3地震,随后发生3月23日M_s3.6余震.主震造成2人死亡13人受伤.房屋倒塌155间,受损1万多间.主震震级不大,而造成的灾害巨大.本文使用CAP方法反演了两次地震的震源机制解和震源深度,结果显示两次地震的震源机制解和深度一致.主震的机制解节面Ⅰ走向110°,倾角75°,滑动角—10°;节面Ⅱ走向202°,倾角80°,滑动角—164°;矩震级M_w4.3,余震矩震级M_w3.7,反演最佳深度均为3 km.最佳深度时波形拟合相关系数较高,表明反演结果是可靠的.使用sPn和sPL深度震相进一步分析了两次地震的震源深度.结果显示,选取的7个台站的sPn震相与Pn震相的平均到时差为1 s,对应的震源深度为3 km.震中距为36 km的利辛台的sPL震相与Pg震相到时差约为1.1 s,对应震源深度约3~4 km之间.两种深度震相分析的震源深度与CAP方法的结果一致,表明本文给出的阜阳地震震源深度为3 km左右基本是可靠的.本次地震造成较大灾害的原因很可能与地震震源较浅有关.阜阳地区地壳结构相对稳定,地质构造演化形成3 km厚的沉积层,本次地震可能是区域应力作用下发生在沉积层里的一次地震. 相似文献
3.
2016年7月31日广西苍梧发生的M_S5. 4地震是广西测震台网自建立以来所记录到的区域内最强地震。不同机构对于此次事件给出的震源深度结果相差较大,例如美国地质调查局(USGS)地震目录显示其深度为24. 5km,而全球矩心矩张量研究中心(Global CMT)测定的深度为15. 6km。为了进一步准确确定广西苍梧地震的震源深度,文中基于区域速度模型,首先利用走时残差全局搜索法初步得到此次地震震源深度及误差范围,然后使用CAP(Cut and Paste)方法反演苍梧地震震源机制,在此基础上,采用Rayleigh波振幅谱和s PL震相方法进一步约束了此次地震的震源深度。研究结果显示:利用走时残差全局搜索法获得的苍梧M_S5. 4地震震源深度及误差范围为(13±3) km,CAP方法反演的深度为10km,Rayleigh波振幅谱测定深度结果为9～10km,s PL震相测定深度结果为10km,最终确定广西苍梧M_S5. 4地震的震源深度约10km,这表明此次事件仍为发生于上地壳的地震。本文结果同时表明,USGS地震目录在研究区的震源深度精度有待提高。 相似文献
4.
本文用多种数字地震学方法研究了2012年7月20日江苏高邮Ms4.9级地震的震源机制解和震源深度.首先用CAP方法反演了江苏高邮Ms4.9级地震的震源机制解和震源深度,最佳解节面Ⅰ走向角为109°,倾角85°,滑动角18°;节面Ⅱ走向角17°,倾角72°,滑动角175°;矩震级Mw为4.82;优势震源深度为10 km.为验证研究结果的可靠性,我们一方面用Snoke方法反演了高邮地震的震源机制解,反演结果与CAP方法反演的结果相差不大;另一方面,使用近震深度震相到时差的测量和对远震波形拟合的方法进一步研究震源深度,结果均表明江苏高邮Ms4.9级地震的震源深度在9～10 km左右,与CAP方法的结果一致.多种方法研究结果的一致性可以充分说明本文研究结果比较可靠.结合前人地质资料的研究成果和本文对高邮地震震源机制解的研究,我们认为滁河断裂很可能是江苏高邮Ms4.9级地震的发震构造. 相似文献
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基于有限断层模型反演方法,利用区域宽频带数据反演了2022年1月青海门源MS6.9地震的震源破裂过程,并结合地质构造与地震重定位结果判断发震断层走向.综合反演结果表明:此次地震的发震断层走向为WNW向,主要以走滑为主;破裂主要发生在震源两侧,可能存在着双侧破裂,在震后2 s和9 s出现破裂极大值,最大错动量约为1.5 m,位于深度约6km处,发生明显破裂的深度约为16 km,地表破裂长度约20 km;此次地震释放的标量地震矩为1.23×1019N·m,相当于矩震级MW6.7,地震能量主要在前15 s释放;发震断层面的倾角为84.6°,接近于垂直,由于破裂范围较大,所以发生明显错动分布的地表投影也长达34 km. 相似文献
8.
利用双差定位方法对西藏比如MS6.1地震序列141次ML≥2.0地震进行重新定位,采用CAP波形反演方法获得主震的震源机制解,并运用最小空间旋转角方法比较不同机构发布的震源机制解的差异。重新定位后主震震中位置为(31.924°N,92.824°E),靠近余震区中心,震源深度为12.8 km;余震分布沿NE向展布,长约18 km。沿NE向深度剖面结果显示,在主震右上方存在5 km×10 km的近椭圆形地震破裂空区。主震的震源机制解为正断兼走滑型,最佳矩心深度为9.3 km,矩震级为5.98。结合重新定位后余震分布、主震与历史地震震源机制解及地质构造背景等分析,认为具有左旋运动性质的安多南缘断裂可能是该次地震序列的主要发震构造。 相似文献
9.
2018年9月12日19时6分,陕西省汉中市宁强县发生5.3级地震,不同机构给出的震源深度结果相差较大。为进一步确定宁强5.3级地震的震源深度,基于区域速度模型,首先利用CAP方法反演得到该地震的震源机制解,然后采用瑞利面波振幅谱和CAP深度误差函数联合反演,进一步测定了此次地震的矩心深度。结果显示:CAP方法得到的陕西宁强5.3级地震矩心深度约为12km,瑞利面波振幅谱测定的矩心深度为13km,结合引入的误差函数联合反演,最终确定陕西宁强5.3级地震的矩心深度为13km左右,表明此次地震仍属于发生于上地壳的地震。 相似文献
10.
本文介绍了2019年4月7日北京海淀M2.9及4月14日北京怀柔M3.0地震的基本参数速报情况,并利用区域台网波形数据,采用全波形反演方法ISOLA获得了这两次地震的最佳双力偶解。反演结果显示:M2.9地震的节面Ⅰ走向29°,倾角70°,滑动角?149°,节面Ⅱ走向288°,倾角61°,滑动角?22°;矩心深度14 km,矩震级MW=3.4。M3.0地震的节面Ⅰ走向93°,倾角84°,滑动角?30°,节面Ⅱ走向186°,倾角60°,滑动角173°;矩心深度16 km,矩震级MW=3.4。震源机制反演结果表明,两次地震均为走滑型为主的地震,其与震源区域附近历史地震震源机制解具有相同性质。 相似文献
11.
基于数十年来已有的研究进展,提出了一种地方和区域地震震源机制反演技术——广义极性振幅技术（GPAT）,并通过一系列数值实验检验了这种技术的可行性和抗干扰能力.首先,从地震波场概念出发,利用P波初动极性与广义震相振幅构建矢量,建立反演系统,并给出求解技术;然后,考虑影响反演结果的各种因素,包括台站布局、台站数目、随机噪声、震中位置误差、震源深度误差和速度模型误差,分别进行了单一因素影响测试;最后,同时考虑各种因素进行了综合测试.实验结果表明,GPAT是可行的,具有良好的抗干扰能力.需要强调的是,在众多影响因素中,速度模型误差对反演结果的影响最大. 相似文献
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小微震事件的震源机制是区域应力场及诸多地球动力学研究的基础资料。陕西地区为多个地震带的交汇区,近些年积累了丰富的小微震波形资料。运用新近发展的适用于求解小微震震源机制的广义极性振幅技术(GPAT),结合陕西2015地壳速度模型,求解陕西测震台网2011年4月至2015年12月间记录的121次ML1.5~3.5事件的震源机制。反演结果表明:(1)以上事件的震源机制大部分为走滑及正断类型,其比例占64.5%;逆断型机制占22.3%。(2)反演震源机制得到的震源深度与定位深度具有良好的一致性;矩震级与近震震级间存在差别,且这种差别随事件的变小而增大。(3)对比渭河断陷带相关研究成果,验证了该区域震源机制以正断型为主,具有拉张应力状态。 相似文献
13.
2015年5月19日9时58分,云南双柏、峨山一带出现密集的小震活动,并于6月14日发生ML4.1地震,形成显著的震群事件。本文利用双差定位法对该震群进行精定位,结果显示,重新定位后震中分布优势方向更明显,主要沿绿汁江南段断裂呈NNE向分布,震源深度为6～12km,其中,又以8～10km最具优势。与原始数据相比,重定位后残差明显减小,走时残差平方和由原来的0.303s降为0.034s,震源位置估算误差在EW方向平均为0.21km,在NS方向平均为0.173km,在垂直方向平均为0.175km;利用广义极性振幅技术（GPAT）方法,计算得到了24个ML≥2.5地震的震源机制解,结果显示,此次震群的震源机制类型绝大部分表现为正断性质,与该区历史地震多为走滑的结果有所差异。结合震区附近的龙门水库蓄水水位和该震群的频度-震级关系分析认为,双柏震群活动与水库蓄水过程密切相关,该震群的发生是龙门水库水体载荷加载而引起正断层产生错动的结果。 相似文献
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Two felt moderate-sized earthquakes with local magnitudes of 4.9 on October 11, 1999 and 4.3 on November 08, 2006 occurred
southeast of Beni Suef and Cairo cities. Being well recorded by the digital Egyptian National Seismic Network (ENSN) and some
regional broadband stations, they provided us with a unique opportunity to study the tectonic process and present-day stress
field acting on the northern part of the Eastern Desert of Egypt. In this study, we analyze the main shocks of these earthquakes
and present 15 well recorded aftershocks (0.9 ≤ ML ≤ 3.3) which have small errors on both horizontal and vertical axes. The
relocation analysis using the double difference algorithm clearly reveals a NW trending fault for the 1999 earthquake. The
spatial distribution of its aftershocks indicates a propagation of rupture from the SW towards the NW along a fault length
~5 km dipping nearly ~40°SW. We also determined the focal mechanisms of the two main shocks by two methods (polarities and
amplitudes ratios of P, SV and SH and regional waveform inversion). Our results indicate a normal faulting mechanism with a slight shear component for the
first event, while pure normal faulting for the second one. The spatial distribution of the 1999 aftershocks sequence along
with the retrieved focal mechanism confirmed the NW plane as the true fault plane. While for the 2006 event, the few aftershocks
do not reveal any fault geometry; its focal mechanism indicated a pure normal fault nearly trending WNW-ESE that corresponds
more likely to the extension of the 1999 earthquake fault. The seismicity distribution between the two earthquake sequences
reveals a noticeable gap that may be a site of a future event. The NNE-SSW extensional stress indicated by the mechanisms
of these events is in agreement with the regional stress field and the rifting of the northern Red Sea in its northern branches
(Gulf of Suez and Gulf of Aqaba). The source parameters (seismic moment, moment magnitude, fault radius, stress drop and displacement
across the fault) were also estimated and compared based on both the regional waveform inversion and the displacement spectra
and interpreted in the context of the tectonic setting. The obtained results imply a reactivation of the pre-exiting NW-SE
faults as a result of extensional deformation from the northern Red Sea-Gulf of Suez rifts. 相似文献
15.
本文采用“剪切-粘贴”(CAP, Cut And Paste)方法, 分别利用区域地震台网的宽频带记录和全球地震台网宽频带记录, 独立反演和联合反演了云南盈江2014年5月24日5.6级和5月30日6.1级地震震源参数。 结果表明, 采用近震和远震数据联合反演结果更为稳定, 5月24日5.6级地震震源机制解两个节面分别为: 走向153°/倾向90°/滑动角171°和243°/81°/0°, 5月30日6.1级地震两个节面分别为172°/72°/180°和82°/90°/-18°。 两次地震断层参数较为接近, 均为走滑型地震, 结合区域构造背景和地震序列重定位结果认为其发震断层可能为近南北向苏典断裂。 震源机制解反演结果与震源区历史地震震源机制解和利用其它方法得到的机制解相近, 也符合震源区的区域应力场特征。 两次地震反演最佳震源深度分别为8 km和6 km, 均为发生在上地壳的浅源地震, 表明苏典断裂在此部位可能并没有切割到地壳深部。 相似文献
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2008年5月12日四川龙门山断裂带发生了汶川8.0级地震,之后四川境内发生了两次7.0级地震(其中一个是芦山地震),为了研究汶川地震之后龙门山断裂带及周边区域的地震活动性,本研究收集了国家地震台网和四川区域地震台网2010年1月1日—2017年12月31日四川地区发生的17次M≥5.0地震以及120多次5.0>M≥4.0地震的波形资料,利用波形拟合法反演了震源机制解及区域应力场.反演结果显示,位于龙门山断裂带上的地震,震源机制以逆冲型为主,鲜水河断裂带地震震源机制以走滑型为主,而川滇块体西南部的理塘断裂、金沙江断裂附近,震源机制解以正断层为主.根据震源机制解反演得到的龙门山地区、鲜水河地区的主压应力场方向为WNW、近EW向.川滇块体的巴塘、理塘等地区,其主压应力轴方向为12°左右,接近SN向,且仰角接近40°左右.本研究利用面波振幅谱特征对震源深度进行了精确定位,定位结果与中国地震台网中心(CENC),美国地震调查局(USGS),国际地震中心(ISC)等机构地震目录进行了对比.结果显示,四川地区强震震源深度主要分布在20km以上的中上地壳.龙门山地区震源优势分布在10～20km,鲜水河断裂地震震源深度在10km左右,川滇块体西南部的理塘断裂,巴塘断裂,金沙江断裂等地区,震源深度一般在5～10km范围. 相似文献
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We investigate the seismic properties of modern crustal seismicity in the northwestern Sierras Pampeanas of the Andean retroarc region of Argentina. We modelled the complete regional seismic broadband waveforms of two crustal earthquakes that occurred in the Sierra de Velasco on 28 May 2002 and in the Sierra de Ambato on 7 September 2004. For each earthquake we obtained the seismic moment tensor inversion (SMTI) and tested for its focal depth. Our results indicate mainly thrust focal mechanism solutions of magnitudes Mw 5.8 and 6.2 and focal depths of 10 and 8 km, respectively. These results represent the larger seismicity and shallower focal depths in the last 100 years in this region. The SMTI 2002 and 2004 solutions are consistent with previous determinations for crustal seismicity in this region that also used seismic waveform modelling. Taken together, the results for crustal seismicity of magnitudes ≥5.0 in the last 30 years are consistent with an average P-axis horizontally oriented by an azimuth of 125° and T-axis orientation of azimuth 241° and plunge 58°. This modern crustal seismicity and the historical earthquakes are associated with two active reverse faulting systems of opposite vergences bounding the eastern margin of the Sierra de Velasco in the south and the southwestern margin of the Sierra de Ambato in the north. Strain recorded by focal mechanisms of the larger seismicity is very consistent over this region and is in good agreement with neotectonic activity during the last 11,000 years by Costa (2008) and Casa et al. (in press); this shows that the dominant deformation in this part of the Sierras Pampeanas is mainly controlled by contraction. Seismic deformation related to propagation of thrusts and long-lived shear zones of this area permit to disregard previous proposals, which suggested an extensional or sinistral regime for the geomorphic evolution since Pleistocene. 相似文献
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We consider 16 earthquakes with Mw?=?4.2–5.2 that occurred in the south-eastern part of the Laptev Sea shelf, Lena River Delta, and North Verkhoyanye (Russia) in 1990–2014. Focal mechanisms, scalar seismic moments, moment magnitudes, and hypocentral depths of the seismic events have been calculated from the data on amplitude spectra of surface waves and P wave first-motion polarities. The obtained results sufficiently implement the existing dataset on reliable earthquake source parameters for the study region and prove the change of the stress-strain state of the crust from extension on the Laptev Sea shelf to compression on the continent providing finer spatial details of the deformation field in the transition zones such as Buor-Khaya Bay and the Lena River Delta. 相似文献
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We select the Xiluodu-Wudongde reservoir area in the downstream of Jinsha River as the research area, and use the CAP and GPAT method to obtain focal mechanisms of ML ≥ 2.0 earthquakes from 2016 to 2017 in this region. Then, we analyze the spatial distribution characteristics of focal mechanism solutions in each local region and investigate the relationship between seismicity and regional structures. According to 414 focal mechanism solutions we get following conclusions:1)The Xiluodu dam began to impound water on May 4, 2013, and seismicity increased significantly after impoundment. We get 49 focal mechanisms in the Xiluodu dam and its adjacent area which are dominated by thrust faulting and next by strike-slip faulting, which are mainly distributed near the middle section of the Ebian-Jinyang fault zone. The distribution of nodal planes striking in NNW to NE direction is consistent with that of regional faults, and some large earthquakes are controlled by regional structures. 2)There are 39 and 24 focal mechanisms obtained in the unimpounded Baihetan and Wudongde dams and adjacent areas, and the spatial distribution of focal mechanism solutions are relatively consistent, dominated by strike-slip faulting with a small amount of thrust and normal faulting. The sinistral strike-slip earthquakes are consistent with the activity of Xiaojiang fault zone and Puduhe-Xishan Fault. The strikes of the nodal planes are distributed discretely, and many groups of faults intersect with each other in the area, suggesting that the seismogenic environment is relatively complex. 3)The seismicity in Ludian continues to be active after the Ludian M6.5 earthquake. By the end of 2017, we got 260 focal mechanism solutions in the aftershock area of the Ludian MS6.5 earthquake of Aug 3rd, 2014, which show an "L-shape" in distribution and are dominated by thrust and strike-slip faulting. The long axis is distributed in EW direction, and the short axis is distributed in near NNW direction. The strikes of nodal planes are mainly near EW and near NE, and the nodal planes in the NW direction are less. According to characteristics of a large number of focal mechanism solutions, we deduce that there may exist a buried structure in the EW direction, the seismicity is controlled by different types of faults and the seismogenic structure is very complex. 4)The centroid depth in each region is concentrated in the range of 5~15km, indicating that the seismogenic layer in the study area is 5~15km deep in the middle and upper crust. 相似文献
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Recent improvements in the seismological networks on the Ibero-Maghrebian region have permitted estimation of hypocentral location and focal mechanisms for earthquakes which occurred at South Spain, Alboran Sea and northern Morocco of deep and intermediate depth, with magnitudes between 3.5 and 4.5. Intermediate depth shocks, range from 60 to 100 km, with greater concentration located between Granada and Málaga. Fault-plane solutions of 5 intermediate shocks have been determined; they present a vertical plane in NE-SW or E-W direction. Seismic moments of about 1015 Nm and dimensions of about 1 km have been determined from digital records of Spanish stations.P-wave forms are complex. This may be explained by the crustal structure near the station, discontinuities in the upper mantle and inhomogeneities near the source. Deep activity at about 650 km has only 3 shocks since 1954 (1954, 1973, 1990). Shocks are located at a very small region. Fault-plane solutions show a consistent direction of the pressure axis dipping 45° in E direction. For the 1990 shock seismic moment is 1016 Nm and dimensions 2.6 km. TheP-waves are of simpler form with a single pulse. The intermediate and deep activities are not connected and no activity has been detected between 100 and 650 km. The intermediate shocks may be explained in terms of a recent subduction from Africa under Iberia in SE direction. The very deep activity must be related to a sunk detached block of lithospheric material still sufficiently cold and rigid to generate earthquakes. 相似文献