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依据区域小孔径数字地震台网对河北省唐山、张北、怀来，山西省大同和云南省剑川、禄劝、姚安等７次地震的定位或重定位结果，并结合相应区域个别大震用远场资料反演的震源深度结果，以及山西省临汾遥测地震台网重新测定的震源深度结果，与以往地震目录中给出的震源深度测定结果进行对比分析，发现小孔径台网的震源深度测定结果基本分布在地表至地下十几千米的范围内．而以往给出的测定结果中，震源深度大致分布在地表至地下30ｋｍ 的深度上，与其平均值相差一半至一倍，两者之间的差别非常显著．分析认为，小孔径数字地震台网的测定结果可能更接近震源深度分布的真实情况，即上述地区的地震应是发生在地壳浅层内．对造成上述情况的原因，进行了初步的讨论，并提出改善震源深度测定精度的建议和措施． 相似文献
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提出了联合使用反射波横波Ｓ１１,Ｓｉｌ,Ｓｉ２在地震台网较疏的地区求解地震震源深度的原理和方法,并以新丰江水库区１２次地震为例,对该方法的结果进行检验。结果表明,利用反射皮法测定的震源深度与新丰江遥测台网的测定结果吻合较好。 相似文献
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利用华北遥测台网和首都圈数字地震台网112个台站记录到的1993—2004年发生在首都圈地区3983次地震的P波绝对到时资料和相对到时资料,采用双差地震层析成像方法联合反演首都圈地区的地震震源参数,给出了2809次地震的重新定位结果.经地震重新定位后,P波绝对走时均方根残差由初始的1.2s降为0.3s,定位精度有了非常显著的提高.重新定位后的地震震中更集中分布在断层带地区,条带状更为清晰.在唐山地区的唐山—大城断裂带,地震主要集中在断裂带内,两侧的地震比较稀少.从重新定位后的震中分布可以看出,研究区域内的地震活动带呈现更明显的北北东向和北西西向的条带状分布,说明这两组方向的断裂最为活跃.用双差地震层析成像方法得到的唐山地区的地震震源位置,沿北东方向剖面在深度上呈现明显的3个小震群的特点,震源最大深度为25km.唐山地区地震重新定位结果的对比性研究表明,双差层析成像方法得到的震源参数的精度高于常规地震层析成像方法和双差法. 相似文献
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单台sPL震相测定珊溪水库地震震源深度 总被引：2，自引：0，他引：2
稀疏台网下的传统走时定位难以确定中小地震的震源深度，而地震波深度震相蕴含着震源深度信息，为确定地震震源深度提供了新的途径。近震深度震相sPL和直达Pg波到时差与震源深度呈线性关系，可用以约束地震震源深度。本文以珊溪水库2014年震群事件为例，利用单台sPL震相测定了地震震源深度。结果表明:震源深度的测定结果与基于水库台网高密度台站下Pg和Sg走时定位Hyposat方法和全波形拟合CAP方法测定的震源深度高度一致，为4—6 km，与区域活动断层探测结果相符。sPL震相的优势震中距为30—50 km，区域台网范围内sPL与Pg的到时差与震源深度的线性关系相对固定，因此利用单台sPL震相即可快速获取可靠的地震震源深度，适用于稀疏台网下的中小地震震源深度的确定，且误差可控制在1—2 km范围内。 相似文献
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双差地震定位法在北天山地区地震精确定位中的初步应用 总被引：16，自引：1，他引：16
对双差地震定位法的原理进行了阐述,并将双差地震定位法应用于北天山地区(42.5°—45°N,82°—89°E)地震的精确定位。利用新疆32个地震台站记录到的1336次MS≥2.0地震的22704条P波和S波震相读数资料,经重新定位后得到其中1133次地震的基本参数。重新定位结果显示了比较精细的震中分布图像和有所收敛的震源深度剖面图像,震源深度优势分布在6—35km,平均深度为20km,部分震中位置与震源深度变化较大的地震向断裂带靠近。 相似文献
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基于合成地震图，并与观测数据对比，对沉积层地区近震波形的频率成分、偏振和走时等特征进行了分析，确认了沉积-基底界面的Sp转换波.研究表明：在给定震中距时，Sp转换波与直达P波的到时差随震源深度的增加近似呈线性增加，可以用来较好地约束震源深度.以2015年4月19日河北文安M3.0地震和2006年7月4日河北文安M5.1地震为例，验证了使用近震Sp转换波测定沉积层地区震源深度的可行性.利用Sp转换波对2015年4月19日河北文安M3.0地震重新测定震源深度的结果为18 km左右，而不是地震目录中给出的29 km，说明该地震发生在中上地壳，而不是下地壳.本文给出的方法可应用于测定沉积层地区的震源深度. 相似文献
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介绍基于BLOC86程序的新疆地区震源深度定位软件的原理、主要功能模块和使用效果.利用该软件定位新疆测震台网地震,计算结果稳定性较好,与震中烈度结果有较好的对应关系,有效弥补了大震应急工作对震源深度参数的需求. 相似文献
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研究表明,远震直达体波波形(P波、SH波)是有效反演中强地震(M5.5~7)震源参数的重要资料.但是当震中距较大时,核幔边界全反射波ScS会进入SH波反演窗口,其未被传统的基于体波震源参数反演算法所考虑,从而导致反演结果偏差.本文通过TEL3与fk方法合成理论地震图,使用Jackknifing统计方法定量测试了不同情况下ScS震相对远震体波反演的影响.结果表明,当反演数据震中距位于70°~90°时,ScS震相会造成震源质心深度1km左右、机制解最大8°的系统偏差;使用震中距40°~90°的SH波进行抽样反演,机制解最大系统偏差可达5°;SH波与P波联合反演可减少ScS震相引起的震源参数结果系统偏差.因此,ScS震相对基于射线理论的远震体波震源机制解反演所造成的误差是需要给予考虑的. 相似文献
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在南北地震带地区,USGS全球地震目录中存在一些震源深度大于30km的地震.这些地震的震源深度是否可靠,对于研究这一地区的孕震机制、岩石圈强度和构造演化等科学问题具有重要意义.本文以南北地震带2012年发生的5个4~5级地震为例,利用区域地震台网的波形数据,基于sPL深度震相、短周期瑞利面波以及CAP等独立方法测定了其震源深度.结果表明:sPL深度震相和CAP方法给出的震源深度比较一致,差别小于2~3km,能够得到比较可靠的震源深度;短周期瑞利面波及其与P波振幅比也确定了地震震源深度较浅的特征.本文研究结果显示:宁夏会宁4.7级、云南富民4.8级和四川会东4.7级地震的震源深度约为8~12km左右,仍为发生于上地壳的地震,USGS地震目录给出的30km甚至更深的震源深度存在明显偏差;对于四川隆昌4.6和4.9级地震,本文给出的震源深度为1~2km,属于极浅源地震,USGS地震目录给出的10km和35km的震源深度结果尚需进一步改进. 相似文献
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利用双差定位法对2009—2015年大柴旦M 0.5以上地震重新进行精确定位，并绘制区域地震震源深度频数直方图。根据地震精定位结果，选取地震波形记录较好的事件进行特征分析。结果发现，重新定位后，大柴旦地区约65%的地震震源深度分布在6—10 km，震源深度较浅，地震波列衰减快，经过滤波，在直达波后观测到新的震相，初步推测为康拉德界面反射波。 相似文献
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Some evidences for earthquake occurrence in the shallow crust in some areas of North China and Southwest China 总被引：1，自引：0，他引：1
IntroductionThe hypocentral location parameters (the longitude and latitude of epicenter and the focal depth) are important fundamental data for the study of seismology and the earth interior physics. To locate the seismic source precisely is the basis for the study of seismicity patterns, relation between earthquake and active structures, engineering seismology, etc (WANG, et al, 1995). Among these parameters, the precise measurement of focal depth is closely related to the correct understa… 相似文献
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In this paper,a test or alternative scheme for studying large earthquake sequences through the study of small earthquake sequences is suggested,and a small earthquake sequence,the Lima earthquake sequence for which analogue records have been turned into digital data,is used here.In order to provide the deep construction background and the spatial distribution of structure for generating earthquakes,the P-wave and S-wave layered velocity models in this area are obtained by using mine explosion and earthquake observed records; then,the hypocenter locations and focal depths of the Lima earthquake sequence are determined adopting the velocity models given above and using a location method with numerical properties for a microseismic monitoring network(Zhao et al.,1994)and a new method for determining focal depth from data of a local seismographic network(Zhao,1992); finally,based on this,the variation of quality factor Q of the crustal medium during the period of the sequence is estimated.The obtained resul 相似文献
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Günter Bock 《Physics of the Earth and Planetary Interiors》1981,25(4):360-371
P-wave travel-time residuals at the Warramunga Seismic Array (WRA) in the Northern Territory, Australia, have been studied from 49 earthquakes with epicenters south of 19°S in the Fiji-Tonga region. Focal depths are between 42 and 679 km as determined from pP-P. Using the Jeffreys-Bullen and the Herrin travel-time tables the epicentral parameters have been redetermined by considering only “normal” seismic stations in the location procedure. These are those stations where P-wave travel times are probably not affected by lateral heterogeneities caused by the lithosphere descending beneath the Tonga trench. Epicenters of deep earthquakes below 300 km have been relocated by using stations at Δ > 25° only. Epicenters from shallower-depth earthquakes have been recalculated without using stations between 35 < Δ < 75° epicentral distance. In both cases focal depths were determined from pP-P times. The resulting pattern of P-residuals at WRA does not show any significant change with depth below 350 km. The residuals become more negative for shallower earthquakes above about 250 km. P-waves to WRA are advanced by approximately 2 s compared with those from deep earthquakes. The results do not essentially differ for the two different travel-time tables used. The observations can be interpreted by P-wave velocities that are higher in the sinking slab down to 350–400 km by 5±2% than in both the Jeffreys-Bullen and Herrin models. Without considering possible elevations of phase boundaries this estimate yields a temperature contrast of 1000±450°C between slab and normal mantle material in this depth range. 相似文献
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On 16th September 2013, an M5.1 earthquake occurred in Badong County, Hubei Province, which is the biggest one since the first water impounding in 2003 in the head region of the Three Gorges Reservoir area. The crustal velocity information is needed to determine the earthquake location and focal mechanism. By comparison, the 1-D velocity structure model from Zhao was adopted in this study. Double difference location method was applied to determine the precise locations of the M5.1 earthquake sequence. Relocation results show that the dominant distribution of this sequence is along NEE direction. In order to understand its seismogenic structure, focal depth profiles were made. Profile AA' was along the sequence distribution, and the earthquake sequence extended about 12km. Focal depth of mainshock is deeper than that of aftershocks, and earthquake rupture propagated laterally southwestward. The seismic profile BB' and CC' were perpendicular to profile AA', which represent the dip direction. Both profiles show that the focal depth becomes deeper toward southeast, and dip angle is about 50°. It means that the possible seismogenic fault strikes NEE and dips southeast. Focal mechanism could provide more information for judging the seismogenic structures. Many methods could obtain the focal mechanism, such as P-wave first motion method, CAP method, and some other moment tensor methods. In this paper, moment tensor inversion program made by Yagi Y is adopted. 12 regional seismic stations ranging from 100~400km are picked up, and before the inversion, we removed the mean and trend. The seismic waveforms were band pass filtered between 0.05 and 0.2Hz, and then integrated into displacement. Green's functions were calculated using the discrete wavenumber method developed by Kohketsu. The focal mechanism of the M5.1 mainshock manifests that the NEE-striking fault plane probably is the possible seismogenic fault, which is consistent with the analysis of focal depth profiles. The focal mechanisms of the ML≥2.0 aftershocks are retrieved by P-wave first motion method, and the nodal plane I is in accordance with the earthquake sequence distribution and the fault plane of the mainshock. FMSI program was adopted to inverse the stress field in the earthquake area, and the results show that the earthquake sequence is under the control of the regional stress field. The earthquake sequence occurred on the stage of slow water unloading, and ETAS model was introduced to testify the influences of water level fluctuations on earthquakes. The results denote that the reservoir played a triggering role in the earthquake, however, the NEE-striking seismogenic fault is the controlling factor. 相似文献
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对山西地震的震源深度空间分布进行了分析和归纳。得出：山西地震的震源深度最深的为３５ｋｍ，浅的６－８ｋｍ，大多数为１０－２５ｋｍ。 相似文献