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地震活动性总体参量Rt及其在地震预测中应用的研究 总被引：5，自引：0，他引：5
考虑到地震活动性综合分析在地震预测中的重要作用,提出一种地震活动性总体状态参量Rt。该参量由多项地震活动性预测因子构成,其中包括:地震频次、缺震、地震熵、b值和调制比,该参数描述了某时段内,多种地震活动性参量对正常状态的偏离。当Rt=1时,地震活动状态是稳定的,反之,当Rt<1时,则表明地震活动处于不同程度的不稳定态。文中对华北、东北和西北地区地震以及矿山地震的Rt值在强事件前后随时间的变化进行了研究,初步结果表明:在强震或较大矿震前Rt值明显偏离1。同时,对Rt值的地震预测效能进行了检验评估。 相似文献
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D. Legrand S. Barrientos K. Bataille J. Cembrano A. Pavez 《Continental Shelf Research》2011,31(3-4):154-161
A seismic swarm of more than 7200 earthquakes occurred in Aysen Fjord, southern Chile, from January to June 2007. It started suddenly on 23 January 2007 with an earthquake of magnitude Mw=5.3, followed by five earthquakes with magnitudes increasing from Mw=5.2 to 6.2 within three months. Two large earthquakes of magnitudes Mw=6.1 and 6.2 occurred on 02 and 21 April 2007, respectively. The latest earthquake generated landslides that induced a tsunami within the fjord, killing 10 people. This swarm has been examined using international seismic catalogues and seismicity located with a local seismic network; in particular its double tectonic and volcanic origin has been explored. All the focal mechanisms are compatible with the long- and short-term tectonics of the Liquiñe-Ofqui Fault Zone, a major intra-arc fault system of the Patagonian fjord land. The space, time, and size distributions of these earthquakes, that occurred within an active volcanic area revealed by the presence of several Holocene monogenetic volcanoes, may be explained both by fluid-induced (magma and/or hydrothermal fluids) activity combined with tectonic activity. The co-existence of these two tectonic and volcanic phenomena is a good example of retroactive links between fluids and tectonic fractures. 相似文献
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认为地震活动度5、P(b)值、A(b)值、b值、小震调制比Rm、地震时间熵Q^l、算法复杂性AC、地震非均匀度GL、多分维均值Dq、地震集中度C值、地震演化指数YH、地震强度熵Q^E、G-R关系偏离度η、缺震和等效震级M^*等15种地震活动时间扫描分析方法对东南沿海地震带西段4．8级以上地震的发震时间具有一定的预测能力,并将这些方法在震前所显示的异常同步性引伸为地震时间预测信度同步性,初步确定了各种地震活动参数首次出现异常后4．8级以上地震发生在不同时段上的信度,证实了震前预测地震时间信度的同步性要远好于异常同步性,进而计算出这15种分析方法的综合预测信度。研究发现,运用综合预测信度可以较为明确地预测出M≥4．8级地震的发生时段,如果在所预测时段内同步发生了地震活动度．S、P(b)、A(b)和b值异常(并非都要全部发生),则有可能做出6个月内发震的短期预报。 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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IntroductionMaximumentropyspectralmethod(MEM)(Burg,1972)hadbeenamethodusuallyusedinstudyingtheseismicityanditsmainpurposeistofindthedominantspectrainthelong-termseismicityprocessesinthepastyears(Zhu,1985).Inthispaper,themethodisappliedtostudywhethertherearesomespecialspectraofseismicityinsomespecificstagesinearthquake-generatingprocesses.Sowestudyseparatelythenormalandabnormalstageofearthquakeactivity,whoseactiveprocessisregardedasstablestochasticprocess,inordertofindtheirspectracharactersan… 相似文献
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江苏数字地震台网台站震级偏差的分析 总被引：1，自引：1，他引：0
利用江苏数字地震台网1999年1月1日-2008年12月31日3个以上子台记录到的约1 500条地震,以台网的平均震级为标准震级,详细分析了江苏数字台网子台的震级偏差原因,结果显示:①在震中距较小时(100 km),子台测定的震级偏小,在100 km△250 km范围内,震级偏差基本为零;②子台测定的震级偏差存在地域分布特征,随方位角显示趋势性变化,地区邻近的子台之间变化特征相近或相似;③江苏数字台网子台台基类型中松散沉积对震级影响最大,偏差均为正值,最大偏差约0.3级,灰岩类型的台基对震级测定影响最小,几乎为零。 相似文献
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S wave amplitude spectra from shallow earthquakes with magnitudes ranging between 4.2 and 6.2 in the Zagros region of Iran that occurred between 1998 and 2008 are used to examine source parameters and site response of S waves. A generalized inversion scheme has been used to separate the source, propagation path, and local site effects from S wave spectra. For removing the trade-off between source and site terms and propagation effects (including geometric and anelastic attenuation), the spectral amplitudes of the records used were corrected for attenuation and geometrical spreading function using a path model proposed by Zafarani and Soghrat (Bull Seism Soc Am 102:2031–2045, 2012) for the region. We assume a Brune’s point source model to retrieve source parameters like corner frequency, moment magnitude, and high-frequency fall off coefficient, for each event. When the source spectra are interpreted in terms of Brune’s model, the average stress drops obtained are about 7.1 and 5.9 MPa (71 and 59 bars), respectively for the eastern and western Zagros regions. Stress drops range from 1.4 to 35.0 MPa (14 to 350 bars), with no clear dependence on magnitude. The results in terms of stress drop and S wave seismic energy indicate that the Zagros events are more similar to interplate earthquakes of western North America than to intraplate events of eastern North America. The method also provides us with site responses for all 40 stations individually and is an interesting alternative to other methods, such as the H/V method. A new empirical relationship between body-wave magnitudes and moment magnitude has been proposed for the Iranian plateau using derived seismic moment from the inversion. 相似文献
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Thierry Camelbeeck Pierre Alexandre Kris Vanneste Mustapha Meghraoui 《Soil Dynamics and Earthquake Engineering》2000,20(5-8):405-414
In western Europe, the knowledge of long-term seismicity is based on reliable historical seismicity and covers a time period of less than 700 years. Despite the fact that the seismic activity is considered as low in the region extending from the Lower Rhine Embayment to England, historical information collected recently suggests the occurrence of three earthquakes with magnitude around 6.0 or greater. These events are a source of information for the engineer or the scientist involved in mitigation against large earthquakes. We provide information relevant to this aspect for the Belgian earthquake of September 18, 1692. The severity of the damage described in original sources indicates that its epicentral intensity could be IX (EMS-98 scale) and that the area with intensity VII and greater than VII has at least a mean radius of 45 km. Following relationships between average macroseismic radii and magnitude for earthquakes in stable continental regions, its magnitude Ms is estimated as between 6.0 and 6.5. To extend in time our knowledge of the seismic activity, we conducted paleoseismic investigations in the Roer Graben to address the question of the possible occurrence of large earthquakes with coseismic surface ruptures. Our study along the Feldbiss fault (the western border of the graben) demonstrates its recent activity and provides numerous lines of evidence of Holocene and Late Pleistocene large earthquakes. It suggests that along the 10 km long Bree fault scarp, the return period for earthquakes with magnitude from 6.2 to 6.7 ranges from 10,000 to 20,000 years during the last 50,000 years. Considering as possible the occurrence of similar earthquakes along all the Quaternary faults in the Lower Rhine Embayment, a large earthquake could occur there each 500–1000 years. These results are important in two ways. (i) The evidence that large earthquakes occur in western Europe in the very recent past which is not only attested by historical sources, but also suggested by paleoseismic investigations in the Roer Graben. (ii) The existence of a scientific basis to better evaluate the long-term seismicity in this part of Europe (maximal magnitude and return period) in the framework of seismic hazard assessment. 相似文献
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在新的地震活跃期中，台湾海峡７．３级地震和北部湾两次６级地震的发生，标志着华南弧岛系统相应了进入了强烈活动阶段，它们虽然都受控于太平洋板块（包括菲律宾海弧块）的西向挤压，但由于块体运动的主支与被动，作用力量级的不同和地质构造的差异而存在强度和诸多参数的差别。尽管如此，两处地震无疑都属于板内地震，利用它们和板缘地震的关系，可宏观地观测华南大陆的地震活动趋势。 相似文献
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The paper presents the method of local magnitude determination used at Polish seismic stations to report events originating
in one of the four regions of induced seismicity in Poland or its immediate vicinity. The method is based on recalculation
of the seismic moment into magnitude, whereas the seismic moment is obtained from spectral analysis. The method has been introduced
at Polish seismic stations in the late 1990s but as of yet had not been described in full because magnitude discrepancies
have been found between the results of the individual stations. The authors have performed statistics of these differences,
provide their explanation and calculate station corrections for each station and each event source region. The limitations
of the method are also discussed. The method is found to be a good and reliable method of local magnitude determination provided
the limitations are observed and station correction applied. 相似文献
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S. Gentili 《Pure and Applied Geophysics》2010,167(8-9):933-958
The Region–Time–Length (RTL) algorithm has been applied to different instrumental catalogues to detect seismic quiescence before medium-to-large earthquakes in Italy in the last two decades. RTL performances are sensitive to the choice of spatial and temporal parameters. The method for automatic parameters selection developed by Chen and Wu has been applied to twelve Italian earthquakes with magnitude greater than 5. The limits of the method in constructing maps of seismic quiescence before the earthquake are demonstrated, and a simple improvement is proposed. Then a new technique, namely RTLsurv, is proposed for routine surveys of the Italian seismicity. RTLsurv has been applied to all the earthquakes with magnitude greater than 4 in the Italian area in the time interval 1994–2004; four different sub-areas have been identified, with different characteristics in the level of recorded seismicity. One subarea—Tyrrhenian Sea—was characterized by a too low level of recorded seismicity for the application of the method. In the other three subareas a seismic quiescence was detected before at least the 66% of the earthquakes with magnitude greater or equal to 4 and all the earthquakes with magnitude greater than 5. 相似文献
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Tameshige Tsukuda 《Pure and Applied Geophysics》1988,128(1-2):261-279
To detect any temporal change in coda-Q associated with an earthquake of M 6.2, digitized data from analog magnetic records of microearthquakes for a small confined region just around its hypocenter have been processed, with special attention to measuring errors. The M 6.2 earthquake took place at the Misasa town, Tottori Prefecture, in southwest Japan with preceding anomalous seismicity changes. TheQ values were elevated 20% around three years before the M 6.2 event for frequencies of 5 to 20 Hz, and tended to decrease around two years before. Data with high quality show undulated temporal variation with a period of 5–6 years before the earthquake, which is correlated with the regional seismic activity. There is a possibility that the observedQ change stands for precursory effect of the medium-scale earthquake. The aftershock sequence also shows an undulated temporal variation ofQ with a period of 150 days for around 10Hz, correlating also with the seismic activity. The fracturing processes by numerous microearthquakes may be responsible for the attenuation property of randomly scattered seismic waves. 相似文献
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Since 1984, a seismic surveillance at the Baix Ebre Region (NE of the Iberian Peninsula) has been carried out from a seismic network consisting of two digital and one analog stations. Large discrepancies between the recorded amplitudes and the magnitude estimates given by different agencies have been observed. To explain these discrepancies, that consist of a large reduction of amplitude and a strong dependence of the azimuth, a local magnitude formula for the area has been computed, using the analog records obtained at EBR short-period station. Global results show an average station correction factor between the computed local magnitude and the reported magnitude of the order of 1, presenting large variations around the mean value with a clear dependence on the azimuth. A detailed analysis of this variation around the mean value reveals that earthquakes can be classified according to their location in different geological units, thus obtaining for each zone a distinct station correction factor that can fluctuate as much as 0.6 around the average. These large lateral variations of the magnitude are in good agreement with previous studies of coda-Q attenuation. 相似文献