共查询到20条相似文献，搜索用时 15 毫秒
1.
O. I. Aptikaeva 《Seismic Instruments》2014,50(4):269-277
The spatial-temporal variations in localization of the sources of earthquakes with H ≥ 14 km are reviewed for the Garm region. The uneven distribution of such earthquakes is related to the block structure: their amount is higher in the weakened zones rather than in blocks. Three weakened zones are characterized by higher activity of deepened seismicity, which varies in time and increases before the earthquakes with K ≥ 12.5. The temporal variations in distribution of earthquake sources with depth allow a suggestion of the relation of the velocity of the Earth’s rotation and activity of deepened seismicity. 相似文献
2.
A. Ya. Sidorin 《Seismic Instruments》2007,43(1):11-20
As a result of the analysis of both the monitoring data of the electric resistivity of the Earth’s crust at the Garm test site using a modified method of dipole sounding and the earthquake catalogue of this test site it is shown that annual periodicity exists not only in the variations of the electric resistivity of the Earth’s crust but also in seismicity. It is not clear yet whether the appearance of the annual periodicity in the variations of electric resistivity is related to the influence of the periodic processes of earthquake nucleation on this process or both processes are synchronized by a third, unknown process. The results of the investigation show that the annual component of time variations in the electric resistivity contains important information about the processes in the Earth’s crust and should not be filtered out but, in contrast, studied in detail. The joint analysis of periodic components in the compared time series of the electric resistivity of the Earth’s crust and earthquakes opens new possibilities for deeper understanding of the processes of seismicity genesis and for improving the methods of strong earthquakes prediction. 相似文献
3.
A. Ya. Sidorin 《Seismic Instruments》2009,45(1):90-94
The diurnial periodicity of Garm Polygon earthquakes of various energy classes K [(magnitudes M): weak, K < 6.0 (M < 1.1); moderate, 6.0 < K < 8.0 (1.1 < M < 2.2); strong, K > 8.0 (M > 2.2)] has been studied. The time series of weak earthquakes is characterized by maximum activity at night and a clear diurnal periodicity that practically disappears for moderate earthquakes. Such periodicity can be traced again in the time series of the strong earthquakes practically antiphased to weak earthquakes; i.e., the maximum strong earthquakes occurred during the day time. 相似文献
4.
The depth changes in the b-value and density of the number of earthquakes in different magnitude bins (M ≥ 1.8, M ≥ 3.0, M ≥ 3.5) are analyzed using highly accurate seismological observations carried out in 1955–1991 at the Garm prognostic area in Tadjikistan. It is found that the observed b-values are controlled by the variations in the proportion between weak and strong earthquakes. Two horizons with different patterns of the b-value are identified in the Earth’s crust above and below a depth of 15–16 km. The b-value in the upper and lower horizons is close to 0.8 and 1.2, respectively. The lower horizon is marked by almost complete absence of relatively strong earthquakes with M ≥ 3.0. The observed changes in the b-value with increasing depth could probably be due to the increase in the strength of crustal material caused by the growth in temperature and confining pressure in the depth interval from 0 to 15 km. The transitional interval between the upper and lower crustal horizons (～13–18 km), which is characterized by a sharp drop in seismic activity, can probably be associated with the zone of the phase transition of crustal material from an elastic brittle state to a plastic state, as suggested by some authors. Typically, the top of this zone hosts the hypocenters of the strongest earthquakes in a given territory. The correlation is established between the crustal areas with low b-values and the locations of the strongest earthquakes in the region. It is suggested that the three-dimensional mapping of the b-value can be helpful for estimating the location, depth, and maximal magnitude of the probable strong earthquakes in seismically active regions and can be used to assess seismic risks. 相似文献
5.
Complex geophysical investigations of the earth dam of the Irkutsk hydroelectric power plant (HEP) revealed strong negative
anomalies of the natural electric field (NEF). These anomalies are associated with focal mechanisms of earthquakes, in which
subhorizontal compressive stresses prevail. The sources of such earthquakes are located in the south of the Baikal rift zone.
Their epicentral distances are comparable with the range of the action of precursors of earthquakes with M > 5. NEF anomalies correlate with an increase in the filtration at the earth’s dam base in the Angara fault zone along the
Angara River bed. In the shape of their plots, manifestations of these NEF anomalies are similar to variations in the ratios
of velocities of longitudinal and transverse waves before earthquakes in the Garm region. 相似文献
6.
中国大陆强震有成组活动、远距离跳迁和不同时段形成主体活动地区的特征.本文利用强震发生位置处单元降刚法,对中国大陆地区强震的远距离跳迁和主体活动地区转移机理进行了数值模拟研究.得出的新认识是:(1)在地壳中存在初始应力场的环境中,已发生强震区部分丧失承载能力(模拟中作为显著降低单元组的弹性模量来处理),可以引起大范围兆帕量级的应力场调整,它是后续强震可远距离跳迁的主要因素;(2)一个活动期中,中国大陆强震主体活动地区及其迁移,受主要活动断层分布、初始应力场和边界载荷的配置方式的综合影响,但在十年左右的活动幕中,边界载荷的配置方式可能是控制主体活动地区及主体活动地区转移的重要因素. 相似文献
7.
Izvestiya, Physics of the Solid Earth - The conducted paleoseismological and archaeoseismological studies reveal three zones of concentration of the ancient and historical earthquakes in Gorny... 相似文献
8.
华南沿海温泉分布与地震活动关系初探 总被引：2，自引：0，他引：2
华南沿海温泉分布与新构造运动关系密切。温泉和地震是活动断裂体系中既相辅相成又互为消长的两个侧面。一方面,两者之间存在正相关关系,即中高温温泉密集区(带)地震(包括强震)活跃,温泉稀少区(带)地震微弱;另一方面,温泉的过度集中反而降低了该地段的强震发生可能性。笼统认为强震发生于非地热异常场的说法不确切,易引起误解。 相似文献
9.
Mokrushina N. G. Tatevossian R. E. Vakarchuk R. N. 《Izvestiya Physics of the Solid Earth》2021,57(6):886-893
Izvestiya, Physics of the Solid Earth - Abstract—Deep earthquakes occur in subduction zones—they play a key role in the global tectonic model. There are only a few places on the Earth... 相似文献
10.
V. P. Rudakov V. V. Tsyplakov A. V. Tsyplakov I. P. Shestopalov 《Izvestiya Physics of the Solid Earth》2017,53(6):860-863
By monitoring the variations in the subsoil radon concentration in one of the geodynamically active zones of the Moscow syneclise, the effects are detected of changes in the stress-strain state of the Earth’s crust which predetermined the development of the processes that caused the deep-focus earthquake in the Sea of Okhotsk on May 24, 2013. The joint analysis of subsoil radon variations and neutrino flow variations measured in the same structural–geodynamical conditions support the previous data on the global character of the processes contributing to the preparation of strong and catastrophic earthquakes. 相似文献
11.
统计分析了1962—2017年全球强震活动与地球自转角加速度变化过程的关系, 结果显示, 全球8级以上地震发生在地球自转角加速度下降期的概率相对自然概率高出12%, 达到64%, 统计结果具有显著性, 但7.5级和7.8级以上地震的统计结果没有显著性。 分区统计结果表明, 全球强震活动具有明显的区域性特征: 在地球自转角加速度上升期, 高于自然概率的强震主要分布在阿尔卑斯带中西段、 环太平洋地震带的琉球—菲律宾地区以及中国东部; 在地球自转角加速度下降期, 高于自然概率的强震主要分布在环太平洋地震带、 阿尔卑斯带中段(喜马拉雅弧)、 阿尔卑斯带东段(印尼岛弧海沟)以及中亚大陆地区。 分析认为地球自转角加速度变化过程与全球区域地震活动之间存在较强的相关性, 可能与地球自转角加速度变化引起板块间相互作用的强弱有关。 相似文献
12.
Based on historical earthquake data, we use statistical methods to study integrated recurrence behaviors of strong earthquakes along 7 selected active fault zones in the Sichuan-Yunnan region. The results show that recurrences of strong earthquakes in the 7 fault zones display near-random, random and clustering behaviors. The recurrence processes are never quasiperiodic, and are neither strength-time nor time-strength dependent. The more independent segments for strong earthquake rupturing a fault zone has, the more complicated the corresponding recurrence process is. And relatively active periods and quiescent periods for earthquake activity occur alternatively. Within the active periods, the distribution of recurrence time intervals between earthquakes has relatively large discretion, and can be modelled well by a Weibull distribution. The time distribution of the quiescent periods has relatively small discretion, and can be approximately described by some distributions as the normal. Both the durations of the active periods and the numbers of strong earthquakes within the active periods vary obviously cycle by cycle, leading to the relatively active periods having never repeated quasi-periodically. Therefore, the probabilistic assessment for middle- and longterm seismic hazard for entireties of active fault zones based on data of historical strong earthquakes on the fault zones still faces difficulty. 相似文献
13.
I. P. Dobrovolsky 《Izvestiya Physics of the Solid Earth》2006,42(5):429-433
In the 20th century, observations conducted with the local leveling network of the Garm research area revealed vertical displacements of the Earth’s surface that were considered as precursors of the earthquakes of September 13, 1973 (M = 4.2), and June 9, 1975 (M = 5.2). In this paper, these observations are used to solve inverse problems of the theory of earthquake preparation in relation to the prediction problem. On the basis of such observations immediately before an earthquake, only the location and energy of the forthcoming earthquake could be determined. Results obtained for the stronger earthquake show satisfactory agreement with parameters of the real event. Results for the weaker earthquake are less satisfactory, but the disagreement cannot be regarded as absolutely unacceptable. 相似文献
14.
A. V. Guglielmi L. E. Sobisevich A. L. Sobisevich I. P. Lavrov 《Izvestiya Physics of the Solid Earth》2014,50(4):501-507
The specific enhancement of ultra-low-frequency (ULF) electromagnetic oscillations a few hours prior to the strong earthquakes, which was previously mentioned in the literature, motivated us to search for the distinctive features of the mechanical (foreshock) activity of the Earth’s crust in the epicentral zones of the future earthquakes. Activation of the foreshocks three hours before the main shock is revealed, which is roughly similar to the enhancement of the specific electromagnetic ULF emission. It is hypothesized that the round-the-world seismic echo signals from the earthquakes, which form the peak of energy release 2 h 50 min before the main events, act as the triggers of the main shocks due to the cumulative action of the surface waves converging to the epicenter. It is established that the frequency of the fluctuations in the foreshock activity decreases at the final stages of the preparation of the main shocks, which probably testifies to the so-called mode softening at the approach of the failure point according to the catastrophe theory. 相似文献
15.
The coordinates of more than 90000 earthquakes at the Garm geophysical test site during the period of 1955–1991 calculated using three different algorithms are compared. On the basis of the results obtained, the location uncertainties of the earthquake sources are estimated and analyzed. The estimates are compared with the results of the previous investigations. A considerable spatial nonuniformity of systematic discrepancies of depths in the catalog versions calculated using different algorithms is revealed. 相似文献
16.
Historical earthquakes and a tsunami in Bohai Sea 总被引：1，自引：0，他引：1
王健 《地震学报(英文版)》2007,20(5):584-592
Quantitative analysis on seismicity showed that there are several seismic dense zones in Bohai Sea. These seismic dense zones of modern small earthquakes behave prominent NE orientation, although a seismic dense zone with NW direction exists actually. Taking 39°N as a boundary, seismicity in the south is different from that in north of Bohai Sea. Almost all strong earthquakes and seismic dense zones are concentrated in the southern part. Based on archives and seismic dense characteristics, we amended the epicenter of strong earthquakes in 1548 and discussed about magnitude of the earthquake in 1888. Possibility of the event in 173 as a tsunami was discussed. The event in 1597 was doubted as a strong earthquake in Bohai Sea. 相似文献
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O. I. Aptikaeva 《Seismic Instruments》2018,54(2):184-198
The results of studies of the shear wave attenuation field in source zones of the 2003 Chuya, 1970 Ureg-Nur, 1991 Busingol, 2011 Sayan, and 2011–2012 Tuva earthquakes are presented. Attenuation fields in these source zones include blocks with a high Q-factor and linear weakened zones. The surface ruptures from the mainshocks of the 2003 Chuya and 2011–2012 Tuva earthquakes are located in the zones of strong attenuation. Epicenters of the mainshocks are located where the maximum contrast in attenuation is observed. In the source zones of large earthquakes in the Altai–Sayan region or near them, the zones similar to so-called seimogenic bodies described in the literature are found. These objects tend to linear zones with high attenuation and are characterized by an increased density of deepened earthquakes and also by deformations of near-vertical elongation. The obtained data suggest that the fluid factor could play certain role in the occurrence of large earthquakes in the Altai–Sayan region. 相似文献
20.
Huang Deyu Chen Yong Zhu Yuanqing Ji YingCenter for Analysis Prediction SSB Beijing China 'State Seismological Bureau of China Beijing China !Setsmological Bureau of Shanghai Shanghai China 《中国地震研究》1995,(1)
This paper researches TIP before 23 strong earthquakes occurring in the eastern part and the southern and northern zones of the western part of China and their nearby areas in recent decades.The results show that 18 strong earthquakes occurred within the diagnosed TIP.The TIP precaution occupies about 30% of the total space-time domain which we researched,indicating quite good results of intermediate-term prediction of earthquakes.The algorithm CN can thus be used as an intermediate-term prediction method for strong earthquakes. 相似文献