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1.
C.W.A. Browitt 《Physics of the Earth and Planetary Interiors》1979,18(2):127-134
The IGS operates an eight-station, 100-km aperture network linked by radio to a central recorder in Edinburgh. It has been an observatory station for eight years supplying a rapid data input service to world agencies. The importance of infrequent local and regional seismic vibrations has been recognized by engineers as well as scientists involved in the study of intra-plate tectonics. In cooperation with other groups the IGS has embarked on a programme of more detailed monitoring within the United Kingdom and is anticipating closer links with other European stations in order to improve knowledge of the seismicity of the North Sea. The latter is particularly important because of the level of economic activity in the area, the sparse historical record, and the recently demonstrated potential for significant local earthquakes.Overseas, the IGS has instrumented the 20-channel array (SAAS) in Brazil, which is operated in collaboration with the University of Brasilia, and is providing technical support for the Turkish-U.K. network (MARNET) to monitor seismicity in the Marmara Sea. 相似文献
2.
--In this comprehensive study of seismicity and seismotectonics of the peninsular Indian shield region, seismic data of regional earthquakes spanning two decades (1978-1997), obtained at Gauribidanur seismic array (India) and integrated where necessary with data from other seismological stations in the region, have been analyzed in detail. With a slow rate of stress accumulation, the shield is found to have low to moderate seismicity that takes into account a couple of earthquakes of magnitude slightly larger than 6. The frequency-magnitude analysis of the data set gives a b value of 1.18. The spatio-temporal pattern of occurrences of the earthquakes combined with their magnitude and seismic energy distribution is consistent with the view that the peninsular seismicity is low to moderate and episodic in nature. Regions of moderate seismicity and its low-grade counterpart constituted by microearthquakes (magnitude less than 3), appear correlated to the areas traversed by known geologic faults and subfaults, shear zones, and other such tectonic features. Microearthquakes represent about two-thirds of the total regional seismic events during the past two decades. 相似文献
3.
Daniela Veronica Ghica 《Journal of Seismology》2011,15(3):487-506
Data recorded with the Bucovina Romanian Seismic Array (BURAR) seismic array between January 2005 and December 2008 were analyzed
to verify the monitoring capabilities of regional and distant seismicity. For this time interval, nearly 35,000 events detected
by BURAR and identified in seismic bulletins (Preliminary Determination of Epicenters and Romanian Earthquake Catalogue) were
investigated using parameters as backazimuth, epicentral distance and magnitude. A remarkably detection capability is emphasized
for teleseismic observations (Δ > 20°). BURAR onsets could be associated to almost 60% of all events in the teleseismic distance,
with a magnitude detection threshold of 4.5 (mb). When no threshold magnitude is applied, the full detection capability of
BURAR is in the same order as the performance of GERES array, which is one of the most sensitive stations in Central Europe.
For regional events, detection capability decreases to about 16% of all events within regional distance range. The site conditions
(crustal structure and high frequency cultural noise) as well as array dimension, affect the signal coherency and reduce the
array detection capability for regional events. For both teleseismic and regional distances, a monthly variation of BURAR
detection capabilities has been found; the number of events detected during the summer time is diminished by the specific
seasonal human activity and atmospheric conditions (thunderstorms). To prove the good detection capability of the BURAR for
teleseismic distances, a comparison with the observations of the Romanian Real Time Network in terms of magnitude and epicentral
distance was carried out. The higher signal detection capability of BURAR is due to the array techniques applied in data processing,
which enhance the signal-to-noise ratio. The monitoring performed by the BURAR seismic array provides a good azimuthal coverage
of the regional and distant seismicity, in a large range of epicentral distances. 相似文献
4.
V. A. Saltykov Yu. A. Kugaenko N. M. Kravchenko A. A. Konovalova 《Journal of Volcanology and Seismology》2013,7(1):58-75
This paper presents a set of seismicity parameters that are estimated at the Kamchatka Branch of the Geophysical Service, Russian Academy of Sciences based on the regional catalog data with the purpose of routine monitoring of the current seismic situation in the region. The focus is on the identification of changes in the seismic regime (seismic quiescences and seismicity increases) in earth volumes adjacent to the maturing rupture zone of a large earthquake. The techniques we use include estimation of the seismicity level for the region using the SOUS’09 scale; calculation of the variations in the slope of the recurrence relation, identification of statistically significant anomalies in the slope using the Z test, and calculation of the seismic activity A 10; monitoring the RTL parameter and variations in the area of seismogenic ruptures; using the Z test to detect areas of statistically significant decreases in the rate of seismicity; and identification of earthquake clusters. We furnish examples of such anomalies in these seismicity parameters prior to large earthquakes in Kamchatka. 相似文献
5.
I. O. Kitov S. G. Volosov S. B. Kishkina N. L. Konstantinovskaya K. S. Nepeina M. A. Nesterkina I. A. Sanina 《Seismic Instruments》2016,52(1):19-31
A small-aperture seismic array consisting of seven three-component seismometers carried out continuous measurements of regional seismicity in a selected area of the Nizhni Novgorod nuclear power plant during four months of 2013. Automatic signal detection using beamforming was applied separately for each motion component. Two horizontal components were transformed into radial and transverse components for the given values of the velocity and azimuth of the plane wave front. We have investigated the dependence of the coherence of microseismic noise on frequency, azimuth, and slowness, as well as determining the level of cross-correlation between signals on separate channels in order to estimate expected improvement in the signal-to-noise ratio, which is crucial for signal detection. Most signals detected by the seismic array from regional sources are associated with quarry blasts. Using repetitive explosions at seven quarries, we have quantitatively estimated and compared the increase in detection efficiency of regional seismic phases using a three-component small aperture seismic array and a subarray of vertical sensors. Horizontal sensors showed a higher efficiency in the detection of transverse waves, while the subarray of vertical sensors missed S-waves from certain events. For one of the nearby quarries, the vertical subarray missed up to 25% of events (5 of 20). The results of the investigation point to the need for the use of three-component seismic arrays for the study of regional seismicity. 相似文献
6.
We investigated the seismicity in the aftershock area of a great earthquake occurring on April 20, 2006 (21:04 LT) in the
area of the Koryak Autonomous Okrug. This analysis of the aftershock process was based on a complete catalog of the earthquakes
that were recorded during April–May 2006 by the regional network of seismic stations operated by the Kamchatka Branch of the
Geophysical Service of the Russian Academy of Sciences. We also made use of a catalog of low magnitude events for May 2–17
as recorded by a mobile seismic network deployed in the rupture zone. We provide a review of seismicity for the Koryak Upland
for the period of instrumental observations in the 20th and early 21st centuries. 相似文献
7.
Pisarenko V. F. Ruzhich V. V. Skorkina A. A. Levina E. A. 《Izvestiya Physics of the Solid Earth》2022,58(3):329-345
Izvestiya, Physics of the Solid Earth - Abstract—A joint analysis of seismicity in the Baikal Rift Zone (BRZ) is carried out using modern instrumental data (Baikal Branch of the Federal... 相似文献
8.
—?Detailed studies of the low to intermediate seismicity in two coastal regions of Norway have been used in a comparison between earthquake locations from local high-precision networks on the one side and locations using a sparse regional array network on the other side. To this end, a reference set of 32 low-magnitude earthquakes have been located using two local temporary networks in northern and western Norway, with estimated epicenter accuracies better than 5 and 10?km, respectively. Comparisons are made between the local network solutions and the NORSAR Generalized Beamforming (GBF) system, which provides automatic phase association and location estimates using the Fennoscandian regional array network. The median automatic GBF location error is of the order of 20–30?km when four or more arrays detect the event, increasing to about 80–100?km when only two arrays are available, and the automatic GBF bulletin is essentially complete down to magnitude ML = 2.0. Most of the mislocation vectors of the NORSAR GBF solutions are oriented perpendicular to the Norwegian coast, and with a tendency to pull the location in a southeasternly direction. The GBF performance is clearly better, both in terms of accuracy and completeness, than the performance of the automatic bulletin of the Prototype International Data Center (PIDC) which uses data from essentially the same network. The analyst reviewed NORSAR and PIDC bulletins show, not unexpectedly, an improvement in location accuracy compared to the automatic solutions and appear to be of similar quality for the few common events, with an average mislocation of about 20?km. The NORSAR reviewed bulletin is more complete at low magnitudes compared to PIDC, and there appears to be a potential for significant improvements in the PIDC processing of small seismic events in this region. 相似文献
9.
本文对泉州市区域地壳结构、地质构造、构造应力场和地震活动性进行了综合分析。结果表明,泉州市在第四纪中更新世之前位于环太平洋中、新生代构造一岩浆活动带中,地壳运动频繁而又强烈,地质构造复杂;现代处于菲律宾海板块对欧亚板块挤压形成的“台湾动力触角”影响区,但区内的断裂不具全新世活动性,新构造运动不强烈,有史以来未见≥5．0级地震记载,属于地壳相对稳定区,未来遭遇6．0级地震的危险性不大,其地震破坏性影响主要来自周边孕震区,特别是东部海域,与“台湾动力触角”的作用和滨海断裂带的活动有关。 相似文献
10.
Discrimination of induced seismicity by full moment tensor inversion and decomposition 总被引：3，自引：1，他引：2
Human activities, including operations related to mining and reservoir exploitation, may induce seismicity and pose a risk for population and infrastructures. While different observations are commonly used to assess the origin of earthquakes, there is a lack of rules and methods for the discrimination between natural and induced seismicity. The inversion and decomposition of the full moment tensor and the observation of relevant deviation from a pure double couple (DC) model may be an indicator for induced seismicity. We establish here a common procedure to analyse a set of natural and induced events of similar magnitude, which occurred in Germany and neighbouring regions. The procedure is based on an inversion method and on a consistent velocity model and recording network. Induced seismicity is recorded during different mining and/or reservoir exploitations. Moment tensors are inverted using a multi-step inversion approach. This method, which was successfully applied in previous studies at regional and teleseismic distances, is further developed here to account for full moment tensor analysis. We first find a best DC solution and then perform a full moment tensor inversion, fitting full waveforms amplitude spectra at regional distances. The moment tensor solution is decomposed into DC, compensated linear vector dipole and isotropic terms. The discrimination problem is then investigated through the evaluation of distributions of non-DC source components for natural and induced data sets. Results illustrate the potential of the inversion and discrimination approach. Additional detailed analyses are carried out for the two most significant induced earthquakes, and rupture models are compared with the full moment tensor solutions. 相似文献
11.
精确的地震位置对于地震活动性、地震层析成像和地壳应力场反演具有相当重要的意义,对于地震速报也具有重要的应用价值。将观测到时的不确定性、台站高程、地震震源深度进行约束的同时,根据反演理论给出了地震震源位置精确估计和误差估计的方法。该算法联合考虑Pg波、Sg波、Pn波和Sn波的到时进行反演,数据量的增加可以增强地震位置的准确性,并可同时应用于地方震和区域地震。采用模拟数据对该地震定位算法进行检验发现,该算法在观测数据的不确定性不等时明显优于其他方法。将该算法应用于四川地区2001-2008年间的地震定位,得到的地震位置更加符合地震的丛集性并集中于断裂带附近。这些结果为四川地区的地震活动性、断层构造以及地震层析成像研究打下了基础,并且为汶川地震之前的地震活动前兆研究也提供了有益帮助。 相似文献
12.
Dezsö Nagy 《Pure and Applied Geophysics》1973,102(1):5-14
Summary The gravity effect of a right rectangular prism is calculated by a graphical procedure. The basis of the calculation is an algorithm for the linear combination of readings taken from a chart which has as ordinates and abscissas the body coordinates of the prism normalized with respect to the depth to the top and bottom surfaces.Gravity Division, Earth Physics Branch, Department of Energy, Mines and Resources, Ottawa, Canada. Contribution No. 425. 相似文献
13.
Jagdish C. Gupta 《Pure and Applied Geophysics》1983,121(1):109-123
IMS data from Ottawa, Canada are analyzed to study the propagation characteristics of Pc1 pulsations. The majority of pulsations
observed possessed periods of 1 second and lasted less than an hour. Shorter-period Pc1s are observed during the summer than
during the winter. Periods of pulsations are also shorter during the noon hours than in the morning, and shorter during intervals
of high magnetic activity. The diurnal variation of period at Ottawa is different from that at high-latitude stations. For
Pc1s the calculated ratio of the spacing period to the pulse period at Ottawa is 86, in good agreement with values found for
both higher- and lower-latitude stations.
An IPDP (intervals of pulsations of diminishing periods) event occurred on April 19, 1977. The analysis supports the view
that the energy dispersion of storm time protons, as well as the earthward movement of the instability region due to increasing
magnetic activity, are involved in the production of such events.
Earth Physics Branch Contribution No. 1087. 相似文献
14.
GUI-PING LIU 《地震学报(英文版)》1999,12(3):277-284
The time and spatial feature of the regional seismicity triggered by the Hyogo-Ken Nanbu, Japan, M=7.2 earthquake on January 17,1995, was studied. The concerned region is about several hundred kilometers in length and breadth surrounding the epicenter (33°～37°N, 133°～138°E). It is divided into 16 subregions. The seismicity of these subregions from January of 1976 to June of 1996 has been analyzed. It is showed that,① there were significant seismicity changes in 10 subregions triggered by the Hyogo-Ken Nanbu, Japan, M=7.2 earthquake on January 17, 1995. These changes passed a Z statistic test exceeding 0.95 confidence level and the greatest epicenter distance of these subregions was 280 km;②seismicity changes were triggered within 1～5 days in three subregions near the main shock while in other subregions the seismicity changes were triggered within several ten days after the main shock;③ the greatest triggered event is 5.4, which is about the same size as the greatest aftershock;④the regional stress change resulted from the main shock may be the triggered mechanism of the regional seismicity. 相似文献
15.
Mario Octavio Cotilla Rodriguez 《Journal of Seismology》1998,2(4):323-335
The seismicity of Cuba is briefly presented together with a few fundamental neotectonic elements of the adjacent Caribbean region. The Cuban seismicity catalogue has been extended back to 1528 and it shows that the largest earthquakes occurred in 1766 and 1852 (I = IX MSK). Two types of seismicity (intraplate and interplate) can be distinguished in Cuba. Western and Eastern Seismotectonic Units correspond to intraplate type and the Southeastern Seismotectonic Unit to interplate type. Western Cuba is characterized by a low frequency of earthquake occurrence. Distribution of epicenters is not regular and the most important events mainly concentrate along two regional active fault system (Nortecubana and Surcubana). Due to the lack of seismic stations in this region, the characterization of seismicity is frequently done on the grounds of historical data available from 1693. The main seismogenic source for Cuba is the Bartlett-Cayman fault system, but inland there are other active structures. Some issues about historical and present day Cuban seismological research are also showed. 相似文献
16.
通过分析昭苏6．1级地震序列特征、震源与介质破裂特性、震源环境与历史地震活动类比及区域地震和前兆资料的异常变化等，对该震前的区域地震活动背景、震后的震情趋势等有了较为细致的了解和判定。主要结果有：①在2003年新疆境内中强地震成组活动的背景下，于现代地震活动很弱的昭苏盆地内发生了6．1级地震；②6．1级地震为主一余型地震序列，震后序列衰减正常；③主震震源机制解结果与现代区域构造应力场特征吻合，表明构造活动具有明显的继承性，并对地震活动有着控制作用；④震源区域构造应力释放充分，区域应力场处于相对稳定的调整状态。综合各类分析结果后认为，震区发生更大地震的可能性很小。 相似文献
17.
Peter R. Vogt 《Earth and Planetary Science Letters》1978,37(3):465-475
Anomalously high mid-plate and Mid-Oceanic Ridge seismicity apparently characterizes the flanks of the regional free-air gravity and topographic high roughly centered on the postulated Iceland hot spot; anomalously high mid-plate seismicity also occurs around the deep free-air gravity low centered just south of India. Although the correlation between gravity and seismicity is still somewhat inconclusive, it seems to suggest active asthenosphere flow associated with the regional gravity anomalies. Added to other stresses in the plate, the stress transmitted to the plate by this flow would encourage its fracture. 相似文献
18.
19.
The seismicity that accompanied the Tolbachik Fissure Eruption was recorded by additional seismic stations that were installed in the southern Klyuchevskoi Volcanic Cluster area in January to October 2013. We used broadband (0.033–50 Hz) three-component digital Guralp CMG-6TD seismometers. This temporary network provided seismicity data at a lower energy level than can be done using the regional seismograph network of Kamchatka. The processing of the resulting digital records supplied data for compiling a catalog of over 700 M L = 0–3.5 (K S = 1.5–8.5) earthquakes, which is an order of magnitude greater than the number of events located by the regional network for the same period of time. The seismicity in the area of Ploskii Tolbachik Volcano was found to concentrate mostly in spatially isolated areas during the eruption. The main isolated clusters of earthquakes were identified both in the eruption area itself and along the periphery of Ploskii Tolbachik Volcano, in the area of the Zimina volcanic massif, and in the Tolud epicenter zone; the eruption zone was not dominant in the seismicity. The region of a shallow seismicity increase beneath Ploskii Tolbachik before the eruption was not found to exhibit any increased activity during the time the temporary seismograph network was operated, which means that a seismicity inversion took place at the beginning of the eruption. We discuss the question of what the earthquake-generating features are that we have identified. 相似文献
20.
Huai Zhang ZhongLiang Wu DongNing Zhang Jie Liu Hui Wang ZhenZhen Yan YaoLin Shi 《中国科学D辑(英文版)》2009,52(10):1585-1598
Reasonable use of mathematical modeling and numerical simulation of regional earthquake activities has attracted more and more attentions in realistic seismicity studies in recent years. The inherent nature of their attendant multi-scale properties, from either the temporal or the spatial direction, necessitates the use of the cutting-edge massive parallel data processing techniques. Our study here is focused on the model construction and numerical simulation of the regional stress evolution after large ear... 相似文献