共查询到20条相似文献，搜索用时 15 毫秒
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The technology which is being developed based on the seismic entropy method for monitoring and forecasting the earthquakes in the territory of Russia is described. This technology relies on seismostatistics and makes it possible to automate the monitoring system and to efficiently tap the networks of ground-based and ground-and-satellite-based observations of operative precursors. The main seismic systems responsible for the preparation of the strong earthquakes with magnitudes М ≥ 5.5 are described. The track and energy diagrams constructed for each seismic system provide the means for monitoring the preparation and forecasting the strong earthquakes in the real-time mode. Forty-four seismic systems controlling almost all seismically hazardous regions in Russia were identified and tested in real time during the period from 2010 to 2015. The guidelines for the practical application of the results of monitoring and forecasting are developed. 相似文献
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S. Ts. Akopian 《Seismic Instruments》2018,54(1):113-120
The Armenian seismic system, which has a threshold magnitude of 6.2, has been identified based on the method of seismic entropy, makes it possible to monitor nucleation of strong earthquakes in the magnitude range of 6.2 ≤ M < 6.6, as well as to assess the seismic situation in Armenia and neighboring countries. A study of energy and track diagrams has revealed a fan-shaped tectonic pattern of stress concentrations with an apex in the Kurdistan knot. The analysis of entropy accumulation in seismic cycles carried out for the hierarchy of seismic systems of the Armenian Highlands helped in the identification of prognostic criteria. The results have been compared to the dynamics of Akhurian reservoir filling in 1983–2016. 相似文献
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M. V. Lemzikov 《Journal of Volcanology and Seismology》2008,2(2):108-117
This paper reports a study of intrinsic attenuation and scattering in the Klyuchevskoi volcanic edifice. The data set consisted of small volcano-tectonic earthquakes occurring as deep as 30 km beneath Klyuchevskoi Volcano and recorded by radio telemetry seismograph stations installed on the edifice and near it. The digital seismograms of small volcano-tectonic earthquakes were processed by the multiple lapse time window analysis (MLTWA) method currently in use in seismology. The method uses experimental normalized integrals of 3D seismic energy density determined from several time windows applied to earthquake records that have been put through bandpass filters. The parameters that characterize the intrinsic attenuation and scattering of seismic energy of small volcano-tectonic earthquakes in Klyuchevskoi Volcano were estimated by adjusting the coefficients to ensure the best fit between experimental and theoretical integrals. An analytical solution to the seismic energy transfer equation was used to calculate the theoretical integrals of 3D seismic energy. Reliable estimates of the parameters that characterize the intrinsic attenuation and scattering in the material of the Klyuchevskoi volcanic edifice have been obtained. Our estimates of the Q for the edifice are below those derived by other workers for the Kamchatka lithosphere. 相似文献
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A. V. Klyuchevskii 《Izvestiya Physics of the Solid Earth》2007,43(12):992-1004
The paper presents results of studying stresses and seismicity of the lithosphere in the Baikal rift zone at the present (instrumental) stage of its evolution. These results are well consistent with the theory of self-organization of complex dynamic systems and can be used for the classification of certain features and properties of the Baikal rift seismogenic system studied. Application of the theory of nonlinear dynamic systems to the analysis of stresses and seismicity allowed us to develop a concept of a complex spatiotemporal structure of the stress state of the lithosphere and seismicity in the region. In terms of this concept, the distribution of strong earthquakes in time is explained in terms of bifurcations (catastrophes) of stresses in the rift zone. Extrapolation of the results indicates that a stress catastrophe in lithosphere of the rift zone can take place in the next few years years, which increases the probability of occurrence of strong (M ≈ 7) earthquakes in the Baikal region. A model with bifurcation of triple equilibrium most consistent with the phase image of regional stresses is proposed as a scenario of the stress state evolution in the lithosphere of the Baikal rift zone. 相似文献
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Investigation and understanding of the present-day geodynamic situation are of key importance for the elucidation of the laws and evolution of the seismic process in a seismically active region. In this work, seismic moments of nearly 26000 earthquakes with K p ≥ 7 (M LH ≥ 2) that occurred in the southern Baikal region and northern Mongolia (SBNM) (48°–54°N, 96°–108°E) from 1968 through 1994 are determined from amplitudes and periods of maximum displacements in transverse body waves. The resulting set of seismic moments is used for spatial-temporal analysis of the stress-strain state of the SBNM lithosphere. The stress fields of the Baikal rift and the India-Asia collision zone are supposed to interact in the region studied. Since the seismic moment of a tectonic earthquake depends on the type of motion in the source, seismic moments and focal mechanisms of earthquakes belonging to four long-term aftershock and swarm clusters of shocks in the Baikal region were used to “calibrate” average seismic moments in accordance with the source faulting type. The study showed that the stress-strain state of the SBNM lithosphere is spatially inhomogeneous and nonstationary. A space-time discrepancy is observed in the formation of faulting types in sources of weak (K p = 7 and 8) and stronger (K p ≥ 9) earthquakes. This discrepancy is interpreted in terms of rock fracture at various hierarchical levels of ruptures on differently oriented general, regional, and local faults. A gradual increase and an abrupt, nearly pulsed, decrease in the vertical component of the stress field S v is a characteristic feature of time variations. The zones where the stress S v prevails are localized at “singular points” of the lithosphere. Shocks of various energy classes in these zones are dominated by the normal-fault slip mechanism. For earthquakes with K p = 9, the source faulting changes with depth from the strike-slip type to the normal-strike-slip and normal types, suggesting an increase in S v . On the whole, the results of this study are well consistent with the synergism of open unstable dissipative systems and are usable for interpreting the main observable variations in the stress-strain state of the lithosphere in terms of spatiotemporal variations in the vertical component of the stress field S v . This suggests the influence of rifting on the present-day geodynamic processes in the SBNM lithosphere. 相似文献
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T waves (seismic water waves), which were generated by deep-focused earthquakes, have been found by an array of sensitive ocean-bottom seismographic observations depolyed on the western Pacific basin. The points of generation of T waves have been exactly located by use of the accurate velocity of water waves which were known from explosions. The positions obtained are at the bottom of deep-sea trenches; however, the positions are slightly (10–35 km) ocean-side of the trench. T waves have been known to be generated by seismic waves which were transmitted from the focus to the trench bottom along the descending lithosphere. The intensity of the observed T waves implies that the Q value along the descending lithosphere is more than 4000. The positions of T-wave generation are consistent with the 8.2- to 8.6-km/s stratified structure of the oceanic lithosphere. T waves from shallow earthquakes beneath the lower continental slope are also clearly observed by bottom seismography. 相似文献
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Zhou Shiyong Zhu LingrenSeismological Bureau of Xinjiang Uygur Autonomous Region Urumqi China 《中国地震研究》1996,(2)
During the preparation process of a great earthquake, there are certain patterns of less randomness but more order in the space-time distribution of micro-earthquakes, which had been proved by seismic events and experiments. The information entropy concerning the dimension of the order in seismic distribution is systematically defined from the point of modern statistical physics in this paper. Relations of dynamic variations of information entropy with a strong shock occurrence time and the distribution of information with a strong shock occurrence place were approached through seismic data from the Wuqia, Xikar, Wushi, and Manasi regions in Xinjiang. It is indicated that before strong earthquakes, the value of information entropy often noticeably drops in seismic region, and generally much lower in the epicentral area than the surrounding regions. These two characters are of important significance in strong shock risk region determination and large shock tendency prediction. 相似文献
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V. B. Smirnov R. K. Chadha A. V. Ponomarev D. Srinagesh 《Izvestiya Physics of the Solid Earth》2013,49(2):243-257
In 2000, the region of the Koyna-Warna water reservoirs in West India was hit by two strong earthquakes, which occurred six months apart and had magnitudes M > 5. The Koyna-Warna seismic zone is a typical region of induced seismicity with a pronounced correlation between seismicity and water level variations in the reservoirs. This indicates that the stress level in the region is close to critical; thus, insignificant variations in stress caused by the variations in the water level may trigger a strong earthquake. In order to study the preparatory processes in the sources of the induced earthquakes, in this paper we analyze the seismic catalogue for the Koyna-Warna region before a pair of strong earthquakes of 2000. The induced seismicity is found to exhibit prognostic variations, which are typical of preparation of tectonic earthquakes and indicative of the formation of metastable source zones of future earthquakes. Based on the obtained results, we suggest that initiation of failure in these metastable zones within the region of induced seismicity could have been caused by the external impacts associated with water level variations in the reservoirs and by the internal processes of avalanche unstable crack propagation. 相似文献
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讨论了华北地区中强地震前地震力标度的时空变化特征, 首先介绍了地震力标度的物理意义, 给出了由传统经验公式推导出的地震力标度σ值的计算方法, σ值是一个表征地震时震源处断层平均驱动力的物理量, 基于地震波能量推导得到, 介于地震频度和能量之间, 根据经典通用的经验公式, 地震力标度σ值与震级ML存在lgσ=1.14ML+6.22标度关系; 结合华北地区(34°~42°N ; 110°~124°E; )地震活动的特点, 利用1980年以来2500多次3级以上地震, 研究了MS≥5.0中强震前σ值的变化规律, 结果发现该指标能客观反映地震活动的增强与平静。 中强地震前存在σ值高值异常, σ值有由低转高, 在高值点发震的特征。 空间上σ值的分布与地质构造、 地震带和强震孕育过程有关, 中强震前地震力标度σ值有成片增加的过程, 对中强地震预测有一定的指导意义。 相似文献
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Geodetic deformation vs. seismic strain deduced by historical earthquakes across the Alborz Mountains 总被引：1，自引：0，他引：1
Mohammad Reza Zolfaghari 《Journal of Seismology》2009,13(4):647-663
Historical seismicity is used in order to map spatial distribution of seismic moment released by past earthquakes and to compare
strain rate deduced from seismicity to those measured by geodetic GPS survey. Spatial analyses are performed on the seismicity
of northern boundary of Central Iranian Block which coincides with the Alborz Mountains. This belt has been responsible for
several catastrophic earthquakes in the past. In this study, the records of historical and instrumental earthquakes in the
Alborz Mountains are used to calculate and plot geographical distribution of seismic moment released in time. A two-dimensional
distribution function is proposed and used here to spread seismic moment along causative tectonic features. Using accumulated
seismic moment, average slip rates across active faults are estimated for 32 sub-zones along the Alborz Mountains and western
Kopet Dag. Seismic moment released by historical and recent earthquakes on this belt accounts for slip rate of 3–5 mm/year
which is in good agreement with the geodetic vectors recently deduced from GPS survey in this region. The study also reveals
geographical variations of slip rates along some 900 km length of this zone based on seismic history. The results are compared
against finding from similar study in this region. Portions of Central and Eastern Alborz show lower seismic strain rate which
could imply aseismic motion or overdue earthquakes. Completeness of historical earthquake catalogue and its reliability with
regard to earthquake magnitudes, locations, and rupturing systems are among many plausible factors controlling the credibility
of such results. Therefore, any conclusions derived from these results remain as reliable as the data and assumptions used
for the analyses. 相似文献
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The fuzzy clustering and zoning method (FCAZm) of systems analysis is suggested for recognizing the areas of the probable generation of the epicenters of significant, strong, and the strongest earthquakes. FCAZm is a modified version of the previous FCAZ algorithmic system, which is advanced by the creation of the blocks of artificial intelligence that develop the system-forming algorithms. FCAZm has been applied for recognizing areas where the epicenters of the strongest (M ≥ 73/4) earthquakes within the Andes mountain belt in the South America and significant earthquakes (M ≥ 5) in the Caucasus can emerge. The reliability of the obtained results was assessed by the seismic-history type control experiments. The recognized highly seismic zones were compared with the ones previously recognized by the EPA method and by the initial version of the FCAZ system. The modified FCAZm system enabled us to pass from simple pattern recognition in the problem of recognizing the locations of the probable emergence of strong earthquakes to systems analysis. In particular, using FCAZm we managed to uniquely recognize a subsystem of highly seismically active zones from the nonempty complement using the exact boundary. 相似文献
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本文用灰色灾变预测方法，以两次中强地震的间隔时间或历次中强地震发生时间作为原始建模数列，分别建立扬铜地震构造带Ｍ＿Ｓ≥４．Ｏ和Ｍ＿ｓ≥５．０地震灰色预测模型。通过近年对该带中强地震发生时间预测实践，证明该模型的预测精度和效果均令人满意，说明灰色预测方法可以作为地震预报综合研究的内容之一。 相似文献
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Antonio Rovelli 《Physics of the Earth and Planetary Interiors》1984,34(3):159-172
The availability of accelerometric data for the Montenegro earthquake of 15th April 1979 makes it possible to investigate seismic Q of the lithosphere in that region, in particular, its dependence on frequency, on the depth reached by seismic waves, and on the length of time windows in which signals are processed. Two different spectral methods, S phase energy ratio and coda envelope decay, are applied, respectively, to direct and scattered shear waves. Similar results are obtained using different portions of the recordings, i.e., coda waves for the envelope decay fit and the S wave train, with a significant duration of ～ 10 s, for the energy ratios. The same apparent Q (Q ～ 40 f, where f is the frequency expressed in Hz) that is found for other neighbouring central Mediterranean regions (e.g., Ancona, on the central Italian Adriatic coast; Valnerina, in the central Apennines; Irpinia, in the southern Apennines) is also found for the southern Yugoslavian coast, in the band 1–25 Hz up to a maximum range of ～ 120 km from the focus. This strong frequency dependence is probably connected with the type of small-scale heterogeneity and the same geological age and level of tectonic activity peculiar to all these seismotectonic areas.In order to compare the apparent Q of the whole S wave train, ～ 10 s long, with the (intrinsic) apparent Q of the single direct S wave (usually 1 s or less), the maximum entropy method is applied in the energy spectrum computation for shorter wave trains. The use of shorter time windows does not reveal any significant variation in the tendency of Q to increase linearly with frequency as the length of the time window containing the sample of the S waves decreases. This seems to indicate that scattering-dependent Q is generally inseparable from intrinsic Q in the lithosphere when estimates based on variations with distance of the seismic signal spectrum are used. While the type of linear growth with frequency does not seem to undergo any variations (it remains of the Q = qf type), the data show there are a considerable decrease in the coefficient of proportionality Q with decreasing duration of the window of S waves analysed, probably as a result of variations in seismic attenuation with depth. 相似文献
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S. Ruiz E. Kausel J. Campos G. R. Saragoni R. Madariaga 《Pure and Applied Geophysics》2011,168(1-2):125-139
The Chilean subduction zone is one of the most active of the world with M?=?8 or larger interplate thrust earthquakes occurring every 10?years or so on the average. The identification and characterization of pulses propagated from dominant asperities that control the rupture of these earthquakes is an important problem for seismology and especially for seismic hazard assessment since it can reduce the earthquake destructiveness potential. A number of studies of large Chilean earthquakes have revealed that the source time functions of these events are composed of a number of distinct energy arrivals. In this paper, we identify and characterize the high frequency pulses of dominant asperities using near source strong motion records. Two very well recorded interplate earthquakes, the 1985 Central Chile (Ms?=?7.8) and the 2007 Tocopilla (Mw?=?7.7), are considered. In particular, the 2007 Tocopilla earthquake was recorded by a network with absolute time and continuos recording. From the study of these strong motion data it is possible to identify the arrival of large pulses coming from different dominant asperities. The recognition of the key role of dominant asperities in seismic hazard assessment can reduce overestimations due to scattering of attenuation formulas that consider epicentral distance or shortest distance to the fault rather than the asperity distance. The location and number of dominant asperities, their shape, the amplitude and arrival time of pulses can be one of the principal factors influencing Chilean seismic hazard assessment and seismic design. The high frequency pulses identified in this paper have permitted us to extend the range of frequency in which the 1985 Central Chile and 2007 Tocopilla earthquakes were studied. This should allow in the future the introduction of this seismological result in the seismic design of earthquake engineering. 相似文献
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IntroductionMaximumentropyspectralmethod(MEM)(Burg,1972)hadbeenamethodusuallyusedinstudyingtheseismicityanditsmainpurposeistofindthedominantspectrainthelong-termseismicityprocessesinthepastyears(Zhu,1985).Inthispaper,themethodisappliedtostudywhethertherearesomespecialspectraofseismicityinsomespecificstagesinearthquake-generatingprocesses.Sowestudyseparatelythenormalandabnormalstageofearthquakeactivity,whoseactiveprocessisregardedasstablestochasticprocess,inordertofindtheirspectracharactersan… 相似文献
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L. P. Vinnik I. M. Aleshin M. K. Kaban S. G. Kiselev G. L. Kosarev S. I. Oreshin Ch. Reigber 《Izvestiya Physics of the Solid Earth》2006,42(8):639-651
A 3-D velocity model of the Tien Shan crust and upper mantle is constructed through the inversion of the receiver functions of P and S waves together with teleseismic traveltime anomalies at nearly 40 local seismic stations. It is found that in the vast central region, where no strong earthquakes have been known over the past century, the S wave velocity at depths of 10–35 km is lower than in adjacent regions by up to 10%. These data are evidence for mechanical weakness of the crust preventing the accumulation of elastic energy. Apparently, the lower velocity and the weakness of the crust are due to the presence of water. The weakness of the crust is one of the possible reasons for the strain localization responsible for the formation of the present Tien Shan but can also be due in part to the young orogenesis. The crustal thickness is largest (about 60 km) in the Tarim-Tien Shan junction zone. The crust-mantle boundary in this region descends by a jump as a result of an increase in the lower crust thickness. This is probably due to the underthrusting of the Tien Shan by the Tarim lithosphere. This causes the mechanically weak lower crust of the Tarim to delaminate and accumulate in nearly the same way as an accretionary prism during the subduction of oceanic lithosphere. In the upper mantle, the analysis has revealed a low velocity anomaly, apparently related to basaltic outflows of the Upper Cretaceous-Early Paleogene. The Cenozoic Bachu uplift in the northern Tarim depression is also associated with the low velocity anomaly. The Naryn depression is characterized by a high velocity in the upper mantle and can be interpreted as a fragment of an ancient platform. 相似文献