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Seismicityof the Novaya Zemlya archipelago: relocated event catalog from 1974 to 2014 总被引：1，自引：1，他引：0
Alexey N. Morozov Vladimir E. Asming Natalya V. Vaganova Yana V. Konechnaya Yana A. Mikhaylova Zinaida A. Evtyugina 《Journal of Seismology》2017,21(6):1439-1466
We have relocated seismic events registered in the area of the Novaya Zemlya Archipelago, which are not identified as nuclear explosions but are probably of tectonic nature. For the relocation, we collected all available seismic bulletins and waveform data. The location was performed by applying a modified method of generalized beamforming. Verification of the modified method and selection of the travel time model were performed using data on two Novaya Zemlya nuclear explosions that occurred on 02.11.1974 and 24.10.1990. The modified method and the BARENTS travel time model provide sufficient accuracy for event location in the region. The relocation procedure was applied for 9 seismic events registered in the area of the Novaya Zemlya Archipelago. As a result, the new coordinates of the five events turned out to be significantly different from those that were defined previously. 相似文献
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Application of an improved algorithm to high precision relocation of ISC test events 总被引：1，自引：0，他引：1
Eric Robert Engdahl 《Physics of the Earth and Planetary Interiors》2006,158(1):14-18
New location features for possible implementation by the International Seismological Centre in its standard location procedures are tested using a set of 156 well-located and geographically well-distributed earthquakes and explosions. The tests are performed using the Engdahl et al. ([Engdahl, E.R., Van der Hilst, R.D., Buland, R.P., 1998. Global teleseismic earthquake relocation with improved travel times and procedures for depth determination. Bull. Seism. Soc. Am. 88, 3295-3314]; EHB) location algorithm with the 1-D reference Earth model ak135 [Kennett, B.L.N., Engdahl, E.R., Buland, R., 1995. Constraints on seismic velocities in the Earth from travel times, Geophys. J. Int. 122, 108-124]. Weighting by phase variance as a function of distance improves location accuracy by 7%. Use of later phase arrival times does not result in a significant improvement in location or depth for events with observing stations well distributed in azimuth. However, with application of an improved phase identification technique, depth phases provide significantly better estimates of focal depth. 相似文献
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Dmitry A. Storchak 《Physics of the Earth and Planetary Interiors》2006,158(1):4-13
The International Seismological Centre (ISC) is charged with production of the definitive global bulletin of seismic events, based on the most comprehensive set of parametric data collected from all over the world. Almost every event in the bulletin retains the original hypocentral solutions reported to the ISC by contributing agencies. In addition, where possible, the ISC computes its own solution, which is intended to be the most accurate where the data from several networks are used. It is because of the requirement for consistency of the bulletin over the years that the procedures used at the centre to compute hypocentres have remained rather conservative despite considerable advances made in the field of earthquake location.The ISC has developed and put into operation a new data management system. As a result, it is now possible to review and subsequently introduce more up-to-date methods of locating seismic events into the operations. The ISC Governing Council called for a workshop dedicated to location procedures, which was held during the 2005 IASPEI General Assembly in Santiago, Chile.To compare the accuracy of different location algorithms, a list of 156 reference events (IWREF) was selected prior to the workshop. The list includes geographically well distributed earthquakes and explosions with positions known with an accuracy of up to 5 km. It covers the period of 1954-2001 and includes all station readings and hypocentral solutions of different agencies available for these events in the ISC bulletin. Although the original ISC solutions are included, these may be different from the solution obtainable now due to changes in the ISC procedures over the years. This paper presents the results of relocation of these events using standard ISC location procedures as of 2005. These new ISC locations and analysis of their shifts with respect to reference locations present a benchmark for further improvement. 相似文献
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利用玉树震区21个应急流动地震台站和青海省地震台网固定地震台站的观测数据,采用双差层析成像方法,对2010年4月14日至6月15期间发生的地震进行了重定位,并反演得到了玉树地震震源区的三维速度结构.重定位结果揭示余震主要沿NW向成窄带状分布在断层的两侧,表明脆性破裂应力释放主要集中于一个狭窄的区域内.在西北端,余震偏离玉树—甘孜断裂分布,在SW向也有分布,推测可能与南西向次级断裂有关.双差层析成像得到的速度结构在浅部与地表地质构造相一致,中上地壳的速度结构显示巴颜喀拉地块为高速异常,羌塘地块为低速异常.玉树地震余震分布与特定的速度结构存在相关性：主震发生在高低速过渡带偏高速体的一侧,余震主要分布在高速体外围,高速体内部几乎没有余震分布.一般说来,中上地壳的高速体通常具有较高的强度,可以积累较强的孕震能量.主震发生后,高速体内积累的弹性能量向周边释放,可能是导致高速体周边余震发生的主要原因. 相似文献
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紫坪铺水库库区地震精定位研究及分析 总被引：10，自引：0，他引：10
利用双差定位法, 对紫坪铺水库台网8个地震台站记录到的2004年8月16日至2008年5月10日的1569个小震进行重新定位。 结果显示, 重新定位后的小震主要集中分布在龙门山推覆构造带的中央北川—映秀断裂、 前山灌县-江油断裂和后山汶川—茂汶断裂上, 其中大部分地震位于北川—映秀断裂并收敛于紫坪铺水库的两端, 走向NE向; 震源深度集中在5~15 km范围内, 平均深度为7.8 km, 15~30 km也有少量地震发生。 水库区域小震活动频度与水库水位存在一定的相关性。 精定位后, 到时残差的均方根平均值为0.048 s, 震源位置的估算误差在水平方向上平均为0.63 km, 在垂直方向上平均为0.51 km。 文中还讨论了紫坪铺水库区震源分布和地质构造的关系。 相似文献
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日本所在的西太平洋地区是世界上中深源地震发生最为频繁的地区. 早期研究已表明, 日本东北地区下方的中深源地震呈双层分布. 为进一步分析该双震带的空间分布特征, 本文通过方法测试证明了采用球坐标系下的三维射线追踪法改进后的双差定位法进行地震重定位的精确性和有效性, 对使用该方法进行重定位前、 后各方向上的误差进行了分析, 并确定了最佳的定位参数. 在此基础上, 对日本东北地区的中深源地震进行了高精度重定位, 并对重定位得到的震源位置进行了空间拟合, 其结果表明地震呈明显的双层分布, 且与西太平洋俯冲板块几近平行. 本文研究结果对揭示双震带中地震的发震机理以及俯冲板块内的精细结构均具有重要意义. 相似文献
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—?A crustal velocity model has been developed for Fennoscandia, the Baltic shield and adjacent areas. This model represents a simplified average of various models developed for parts of this region. We show that P-wave travel times calculated with this model provide an excellent fit to observations at the Fennoscandian, KRSC and IRIS station networks for a set of seismic events with known or very well-constrained locations. The station-event paths cover large parts of Western Russia and the Barents Sea, thus indicating that this model, which we denote the Barents model, is appropriate for this entire region. We show by examples that significant improvements in event location precision can be achieved compared to using the IASPEI model. We finally use the Barents model to calculate locations of recent small seismic events in the Novaya Zemlya region of interest in a CTBT monitoring context. 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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Location Calibration Data for CTBT Monitoring at the Prototype International Data Center 总被引：3，自引：0，他引：3
—?Ground-truth information is essential for location calibration of the International Monitoring System network being developed under the Comprehensive Nuclear-Test-Ban Treaty. The objective of the calibration effort is to improve the accuracy of seismic event locations and to reduce the size of the error ellipse, both in automatic and in human analyst-reviewed bulletins, in order to meet the On-Site Inspection requirement for the size of the inspection area. Several databases were compiled and are maintained at the Prototype International Data Center (PIDC) to support calibration efforts. The Nuclear Explosion Database contains most readily accessible information about all nuclear explosions worldwide. The events in the Calibration Event Bulletin (CEB) carefully selected well located events from the PIDC Reviewed Event Bulletin and relocated using additional arrivals from regional networks requested from various National Data Centers. The Ground-Truth Database contains carefully selected events with known or well estimated location accuracies from the Nuclear Explosion Database, CEB, as well as from bulletins of U.S. National Earthquake Information Center and International Seismic Centre. It also contains data on chemical explosions and quarry blasts when confirmed by local or national authorities. Ground-truth events are subdivided into various ground-truth categories according to their location accuracy. The databases have been used in various calibration studies to derive and test corrections to improve event locations. Several location calibration techniques are briefly described. The validation test for any proposed operational change requires that the results meet the location calibration metrics developed and implemented at the PIDC. 相似文献
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We compare the locations obtained from arrival times collected by the International Seismological Centre from a network of regional and teleseismic stations for a cluster of Italian earthquakes with the locations of the same events obtained by the dense national seismic network operated by the Istituto Nazionale di Geofisica e Vulcanologia. We find mislocations on the order of 15 km for epicentral coordinates and on the order of 25 km for depths calculated from the regional and teleseismic network and using the standard IASP91 travel times. These mislocations are generally larger than the sizes of the respective error ellipse semi-axes. We then show that systematic shifts of hypocentral coordinates can be substantially reduced by applying source-specific station corrections. Moreover, we find that the size of error ellipses characterizing the teleseismic locations is significantly reduced by the application of such corrections. Our travel time corrections are compared and found fairly consistent with information available in the literature on tomographic studies on the crust and upper mantle in the European-Mediterranean region. 相似文献
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IntroductionUnderstandingthemechanismofcontinentalearthquakesisveryimportantforseismichaz-ardpreventionandearthquakeprediction.Themodernseismotectonictheoryandtheideaofearthquakepredictionaredevelopedmainlyfromthestudiesoninterplateearthquakes,whicharedifficulttoexplainthephenomenaofintraplateearthquakes,suchasthecontinentalearthquakesoccurredinChinesemainland.Whiletheinterplateearthquakesoccurredalongtheplatebounda-ries,theintraplateearthquakesdistributediffuselyintheinterioroftheplates.Thus… 相似文献
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T. S. Sakulina Yu. V. Roslov G. A. Pavlenkova 《Izvestiya Physics of the Solid Earth》2009,45(3):231-238
Extensive seismic investigations of the crust and upper mantle have been carried out in the region of the Barents and Kara seas during the past decade. One of the profiles (2-AR) measured by FGU NPP “Sevmorgeo” with the CDP and deep seismic sounding methods was successfully used for comparatively analyzing different technologies of constructing seismic sections and for demonstrating a high information content of the method of mathematical modeling and the constructions of wave sections from supercritical reflected waves. It is shown that the crusts of the North Barents and South Kara basins are different. In the first case, the velocity section changes insignificantly, whereas, in the second case, velocities in the crust increase under the basin and the M boundary rises. The crust of the Novaya Zemlya orogen has a thickness of 48 km, and its average thickness on the profile is 35 km. 相似文献
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天山东北部地震的重新定位和一维地壳速度模型的改善 总被引：1，自引：1，他引：0
We apply three methods to relocate 599 earthquake events that occurred from August 2004 to August 2005 in the northeastern Tianshan Mountains area ( 85°30’ ～ 88°30’E,43°00’ ～ 44°40’ N ) by using travel times recorded by regional seismic network and 10 portable seismic stations deployed around the Urumqi city. By comparing the reliability of different results,we determined a suitable location method,and an improved 1-D crustal velocity model of the study area. The uncertainty of earthquake location is significantly reduced with combined data of seismic network and portable stations. The relocated events are clearly associated with regional tectonics of the northeastern Tianshan Mountains area, and are also in agreement with the existence of active faults imaged by deep seismic reflection profile. The relocated seismicity discovers some potential traces of buried active faults,which need to be validated further. 相似文献
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天山东北部地震的重新定位和一维地壳速度模型的改善 总被引：6，自引：4，他引：2
根据布设在乌鲁木齐市活断层探测区内的流动宽频带地震台阵,结合区域地震台网的走时数据,利用3种不同的定位方法对新疆天山东北部地区(E85°30′～ 88°30′,N43°00′～44°40′) 2004年8月至2005年8月发生的599个地震进行了重新定位.通过比较不同方法的结果合理性,确定了适合于当地震源精定位的程序,并改善了一维地壳速度模型.结果表明:联合使用流动地震台阵和区域台网的资料,显著提高了研究区的地震定位能力,精定位后震中分布图像更加集中,展示出了天山东北部地区更为明显的与活动构造相关的条带状地震活动分布图像,除了一些与已知断层相关的地震事件外,还发现一些有待证实的活断层. 相似文献
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本文利用结合了波形互相关技术的双差定位法对龙滩库区2006年至2007年发生的地震进行了精确定位,并对其活动特征进行了分析.通过定位结果的比较,证明利用波形互相关技术提取的地震对的P、S波走时差数据及双差精定位法显著地提高了定位的精度和质量.对龙滩库区地震活动特征的研究结果表明,龙滩库区的地震活动与水库蓄水过程密切相关,成丛分布的地震活动分别表现出对水库蓄水过程不同的响应过程和活动特征,反应了龙滩库区在岩性特征、渗透条件、地质构造及应力场等方面存在局部性差异. 相似文献
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利用2017年8月1日至2017年12月31日四川地震台网和甘肃地震台网记录到的发生在青藏高原东缘的731个地震事件的9 284条Pg震相到时数据,首先反演了该地区的“最小一维速度模型”,并将该模型和选取的速度模型建立对比模型,以九寨沟地震序列为研究目标,定量讨论了两种速度模型分别在绝对定位和相对定位方法中对定位结果的影响。所得定位结果表明:反演获得的“最小一维速度模型”在重定位中可以有效地减小地震走时均方根残差;绝对定位比相对定位更加依赖于一维速度模型,一维速度模型会直接影响绝对定位结果中的震源分布形态,但在相对定位结果中仅起到调整地震事件相对位置的作用;在地震绝对定位中,震级越大的地震对于速度模型越敏感,而这一特点在相对定位中表现得并不明显。通过本项研究可知,在地震定位研究中,联合采用绝对定位和相对定位方法是最佳策略。 相似文献