共查询到20条相似文献，搜索用时 15 毫秒
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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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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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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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Paricutin volcano is a monogenetic volcano whose birth and growth were observed by modern volcanological techniques. At the time of its birth in 1943, the seismic activity in central Mexico was mainly recorded by the Wiechert seismographs at the Tacubaya seismic station in Mexico City about 320 km east of the volcano area. In this paper we aim to find any characteristics of precursory earthquakes of the monogenetic eruption. Though there are limits in the available information, such as imprecise location of hypocenters and lack of earthquake data with magnitudes under 3.0.The available data show that the first precursory earthquake occurred on January 7, 1943, with a magnitude of 4.4. Subsequently, 21 earthquakes ranging from 3.2 to 4.5 in magnitude occurred before the outbreak of the eruption on February 20. The (S - P) durations of the precursory earthquakes do not show any systematic changes within the observational errors. The hypocenters were rather shallow and did not migrate.The precursory earthquakes had a characteristic tectonic signature, which was retained through the whole period of activity. However, the spectra of the P-waves of the Paricutin earthquakes show minor differences from those of tectonic earthquakes. This fact helped in the identification of Paricutin earthquakes. Except for the first shock, the maximum earthquake magnitudes show an increasing tendency with time towards the outbreak. The total seismic energy released by the precursory earthquakes amounted to 2 × 1019 ergs. Considering that statistically there is a threshold of cumulative seismic energy release (1017–18ergs) by precursory earthquakes in polygenetic volcanoes erupting after long quiescence, the above cumulative energy is exceptionally large. This suggests that a monogenetic volcano may need much more energy to clear the way of magma passage to the earth surface than a polygenetic one.The magma ascent before the outbreak of Paricutin volcano is interpretable by a model of magma-filled crack formation proposed by Weertman, based on seismic data and other field observations. 相似文献
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将川滇菱形地块分为两个地块, 分别以形变确定应变速率、 深部速度构造确定弹性模量、 联合地块体积确定地块应变能积累与时间的关系, 结合历史强震研究应变能积累释放周期以及该周期内的强震活动, 进而研究应变能积累释放与强震活动的关系. 结果表明, 地块应变能积累释放存在周期性并可预测强震震级. 在应变能积累前期, 没有强震(M≥7.0)发生; 随着时间增加, 应变能继续增加, 地块上先后发生几次强震, 但每次强震震级均小于预测震级, 即一次强震只释放了一部分能量; 而后应变能积累继续增加, 直到一、 二次特大强震(M≥7.5)发生, 将绝大部分应变能释放. 至此, 老的周期结束, 新的周期开始. 应变能积累从小到大直到最后完全释放的周期性导致了地震的平静活跃周期, 地震活跃期比平静期长得多. 本文认为, 大区域地理范围因其含有多个地块, 不宜讨论其地震平静活跃周期, 而对于小范围单次强震也不宜讨论其复发周期. 虽然活跃期中的强震从时间上看并无任何规律, 但利用活动地块应变能的积累释放曲线所预测的震级与实际震级很接近. 本文结果对于地震安全性评价工作可能有重要意义. 相似文献
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7级以上的强震并不是在一片空白上突然发生的,而是在一种间歇性的地震活动背景下发生的,研究这种背景地震活动的规律,为判定一个活动期的强震的潜在震源区提供信息。本文通过对华北历史上记录到的18次7级以上强震的震前史和震后史的研究,提出了华北地区强震背景地震活动的四条规律:①强震前多有6级以上的背景地震发生;②并且多有信息地震发生;③短时间近距离的两个强震之间可能出现缓震现象;④强震具有一定的减震作用。文中根据这四条规律,对华北地区1501——1730年的强震潜在震源区做了判别分析。 相似文献
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历次中强地震发生前,孕震区附近的小震活动在时间上和空间上会出现从无序到有序的演化过程,反映了小震活动序列中隐含着许多与未来强震发生有关的重要信息。本文选取了河南及邻区小震活动资料,从系统的观点,利用地震活动信息熵值的变化探讨孕震体前后的某种整体行为。通过资料计算分析,河南及邻区中强地震前信息熵值的变化较为明显,中强地震一般发生在高熵值过后的下降段或恢复段,熵值的时序变化与地震序列具有较好的对应性;不同的地质构造地震活动差异,对熵值曲线的形态细节变化存在着一定影响,但对熵值总体变化趋势影响不大。 相似文献
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根据地震构造类型、规模及大地震的强度和累积地震矩,将12个大震系划分为4个层次。在一个大震系中,累计的地震数为7—10次,最大地震的地震矩约为总地震矩的0.5左右。用分数维的概念对大震系中大震的频度和能量特征作了初步分析。对大震系内的地震的时间分布,可以用随机统计的方法给出其统计的规律。多数大震系的地震累计数N可近似地用时间t的指数函数表示:N=AeBt 相似文献
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地下水动态的超远强震异常问题 总被引：5，自引：0，他引：5
自２０世纪８０年代以来，在我国地震地下水动态观测网中陆续发现井水位在超远距离强震前的异常现象。这种异常表现为井水位的振荡与阶变，多出现在震前几小时至几天内，有一定的重现性。对这种异常的形成机制有多种不同观点，其中具有代表性的有强震的前驱波作用观点与强震孕育的林构造牵动观点等。 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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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
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熵的原理与地震活动研究 总被引：3，自引：2，他引：3
熵是多种学科的一个重要交叉点。熵的原理广泛适用于物理、化学、生物、医学、气象乃至社会经济等科学领域,并已取得了令人注目的成果。本文以熵的基本含意出发,简要地阐述了熵概念的扩展,包括热温熵、信息熵以及条件熵等。将地震孕育过程作为一个复杂的开放系统,基于耗散结构理论的基本思想,为定量描述地震活动时、空、强分布的有序度,引入地震活动熵作为序参量,并将其应用于大地震前后地震活动演变特征的研究。初步结果表明,随着临近大地震的发生,在一定范围内地震活动熵值减小,即地震活动分布状态从无序趋向有序。可以预期,把熵的原理引入地震研究领域必将加深人们对地震发生物理过程本质的认识。同时也将为探索地震预测提供新的思路和新的途径。 相似文献
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P. I. Tokarev 《Bulletin of Volcanology》1971,35(1):243-250
An increase in cumulative seismic strain release from volcanic earthquakes prior to eruptions of Bezymyanniy Volcano in 1955–1961 and Sheveluch Volcano in 1964 in Kamchatka, and of Tokachi-dake Volcano on Hokkaido Island in 1962 occurred in accordance with a hyperbolic law. The relationship obtained may be universal for andesite volcanoes. Knowing the law of the increase of cumulative seismic strain and carrying out continueus observations of the seismic regime of andesite voleanoes makes it possible to prediet time and energy of eruptions. By observation of volcanic earthquakes it is also possible to predict the place and time of the occurrence of lateral craters. 相似文献
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在大地震发生之前, 伴随着应力的集中加强及其在震源附近区域引起的非弹性变形, 区域地震活动性可能呈现某些异常特征.本文选择一些有明显物理意义并得到岩石破裂实验支持的地震活动性参数, 例如有震面积数 A、平均释放能量E、地震累加频度 N 和大小地震比例系数 b 值等, 采用扫描方法在大范围内搜索, 识别孕育强震的危险地区, 并对假想孕震区进一步做时间扫描计算, 寻找并判断大震前由中期异常过渡到中短期异常的阶段, 在对华北、西南及东北若干强震资料扫描计算的基础上, 着重剖析唐山地震前华北地区区域地震活动异常变化的一些特征.讨论了上述地震活动性参数在强震中期预报中的不同效能, 认为这种时空扫描方法, 特别是 b 值扫描应用于强震的中期预报是有一定意义的. 相似文献
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华北地区强震前的信号震及其预测意义 总被引：3，自引：0，他引：3
根据对华北地区1970年以来MS≥6地震以前中小地震活动空间图像变化特征的分析, 研究了“信号震”发生的时空特征及其地震活动背景, 由“场-源”关系特征对一般地震进行严格的筛选识别, 从而得出信号震的有关预测指标。 信号震一般发生在强震前的2年之内, 多数发生在15个月内; 信号震与强震的距离不超过200 km, 多数在100 km之内; 震级强度一般为ML4.0～5.3。 信号震一般发生在局部的ML≥4.0地震平静区内, 一般发生在中小地震条带上或条带附近, 在其周围或附近存在中小地震空区。 检验结果表明, 信号震发生后的9个月之内, 其预测概率Pt即超过0.5, Rt值达到0.27; 预测区域半径在距信号震震中100 km之内时, 其发生概率Pd可以达到0.73; 预测强震震级一般为MS≥6.0。 研究表明, 信号震的环境应力值τ0明显高于其他地震, 显示了高应力背景的异常显著性, 它所辐射的地震波中很可能含有未来强震孕震区的大量的本质性信息。 相似文献
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Subduction zone seismicity and the thermo-mechanical evolution of downgoing lithosphere 总被引：1，自引：0，他引：1
In this paper we discuss characteristic features of subduction zone seismicity at depths between about 100 km and 700 km, with emphasis on the role of temperature and rheology in controlling the deformation of, and the seismic energy release in downgoing lithosphere. This is done in two steps. After a brief review of earlier developments, we first show that the depth distribution of hypocentres at depths between 100 km and 700 km in subducted lithosphere can be explained by a model in which seismic activity is confined to those parts of the slab which have temperatures below a depth-dependent critical valueT
cr.Second, the variation of seismic energy release (frequency of events, magnitude) with depth is addressed by inferring a rheological evolution from the slab's thermal evolution and by combining this with models for the system of forces acting on the subducting lithosphere. It is found that considerable stress concentration occurs in a reheating slab in the depth range of 400 to 650–700 km: the slab weakens, but the stress level strongly increases. On the basis of this stress concentration a model is formulated for earthquake generation within subducting slabs. The model predicts a maximum depth of seismic activity in the depth range of 635 to 760 km and, for deep earthquake zones, a relative maximum in seismic energy release near the maximum depth of earthquakes. From our modelling it follows that, whereas such a maximum is indeed likely to develop in deep earthquake zones, zones with a maximum depth around 300 km (such as the Aleutians) are expected to exhibit a smooth decay in seismic energy release with depth. This is in excellent agreement with observational data. In conclusion, the incoroporation of both depth-dependent forces and depth-dependent rheology provides new insight into the generation of intermediate and deep earthquakes and into the variation of seismic activity with depth.Our results imply that no barrier to slab penetration at a depth of 650–700 km is required to explain the maximum depth of seismic activity and the pattern of seismic energy release in deep earthquake zones. 相似文献
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V. V. Adushkin N. G. Gamburtseva M. A. Nesterkina I. A. Sanina D. D. Sultanov O. A. Usol’tseva 《Izvestiya Physics of the Solid Earth》2010,46(3):244-256
The results of long-term sounding of the lithosphere by seismic waves from the deep-focus Hindu Kush earthquakes are presented.
The travel time series of the first longitudinal wave on a fixed base are constructed for six seismic observation stations
(SS) located on the Russian Platform (the Obninsk SS), on the Siberian Platform (the Eltsovka SS), on the Cis-Ural Trough
(the Arti SS), in the Central-Ural Megazone (the Sverdlovsk SS), in the Transbaikalia (the Bodaibo SS), and in the Northern
Tien Shan (the Przhevalsk SS). The time series duration in years for these stations ranged from 1964–1970 to 2007. The travel
time series of seismic waves for the stations indicated are characterized by multi-slope negative linear trends caused by
changes in the stress-strain state of rocks. From the comparison of the trend slopes at different stations it follows that
the changes in the stress conditions within the lithosphere are relatively weak in the aseismic regions of the Russian and
Siberian Platforms and in the Ural Megazone, whereas in the seismically active regions of Tien Shan, Transbaikalia and the
Cis-Ural Trough they are more pronounced. The correlation has been observed between the time series trends of the average
annual travel times of seismic waves and the time series of the Earth’s rotation speed. The strongest correlation between
the series can be seen for the stations, located on the platforms with weak manifestations of both seismicity and active geodynamic
processes. Within the long-term periods of deceleration and acceleration of the Earth’s rotation, travel times of seismic
waves are decreased and increased, respectively. 相似文献
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南北构造带是中国大陆东西部大地构造的主要分界,也是大陆内部强烈地震发生的主要地区之一.2008年汶川MS8.0地震发生后,在南北构造带及周边地区进行了大量的野外科学考察、深部地球物理探测和流动地震观测,在岩石圈结构与构造、强震发生的深部构造环境和动力学过程等方面获得了重要的进展.本文综述近年来发表的一批研究成果,包括岩石圈结构的深部地球物理探测和成像,地震层析成像,地震各向异性和壳幔变形,与近期发生的强烈地震相关研究,以及与大陆动力学有关的研究等.自2000年以来,我国建成了具有1000多个地震台站的国家和区域地震台网.它们在实时为地震监测服务的同时,其产出的海量数据还提供用于地球科学研究.一批作者在国内外发表了研究成果,大大提高了对南北构造带的认识.我们虽然取得许多共识性的重要成果,但是也存在一些问题,发现不同作者的结论是相互矛盾的.其原因之一可能是,现有台网的数据成像分辨率和精度仍不足以识别在地壳深处的细节,例如在孕震尺度概念下的地震危险区.加强流动地震观测,提高台站分布的密度,取得高可信度的目标模型是解决问题的重要方面.近年来"中国地震科学台阵观测"计划在南北构造带上实施的大型流动台阵观测,结合固定地震台网的资料,加上高分辨率深部地球物理探测,以获得高可信度的地壳上地幔三维精细结构及物性成像,是提高地震科学和大陆动力学研究水平的一个有效途径. 相似文献