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对山西及邻区22次ML≥5.0地震前不同时间尺度的累积benioff应变释放特征进行分析,认为约55%的地震震前存在地震矩加速释放现象;同时对地震矩释放异常空间区与主震间的关系进行分析,结果表明,在震前1年内大部分地震震中附近出现大范围椭圆形的地震矩低值区域,且主震震中位于异常区内部或边缘。由此认为,地震矩加速释放现象在山西及邻区具有一定的普遍性,且为中期地震前兆异常。 相似文献
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中国大陆7级强震前中小地震应变释放特征 总被引：3，自引：0，他引：3
给出加速模型拟合的穷举方法,以中国大陆21次6.8级以上地震为例,在单个震例详细研究的基础上,总结中国大陆7级左右地震前地震应变释放的群体特征。 总的来看,7级左右地震前中小地震应变释放模式可分为5类,第Ⅰ类是震前震中周围较大范围应变释放加速、震中附近较小范围应变释放减速(DA),约占38%; 第Ⅱ类是震中附近较大范围应变释放减速、较小范围应变释放加速(AD),约占19%; 第Ⅲ类仅能检测出应变释放的加速特征(ASR),约占14%; 第Ⅳ类仅能检测出应变释放的减速特征(DSR),约占24%; 第Ⅴ类仅1例,各种尺度的时、空范围内,基本上呈现应变匀速释放特征(LSR)。 前兆性地震序列应变加、减速释放的持续时间一般相差3~6年,这表明增强基础上的平静往往是强震前中小地震活动典型的应变释放特征。 DA模式中震前具有稳定的应变加、减速释放特征的临界区域范围平均来看大约分别是震中附近260~400 km及100~200 km,大约分别是7级左右地震平均破裂尺度的3~5倍及1~2倍; AD模式与此相反。 模型参数m值具有较好的稳定性,就应变释放加速现象而言,无论何种应变释放模式、无论应变释放的绝对量如何,其加速释放速率大体相当。 而从应变释放减速情形来看,“外围增强、内部减弱”的DA模式,其应变减速释放特征最为明显。 相似文献
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中强震前地震活动矩释放加速现象(AMR)的普遍性问题 总被引：13，自引：0，他引：13
地震前的矩释放加速现象(AMR)作为一种预测中强震发生的方法，近年来得到普遍关注，所以有必要对这一现象的普遍性进行讨论。我们考虑1978年以来中国大陆Ms5．7以上地震的情况，用贝尼奥夫应变作为地震矩释放的量度。采用规则的空间区域和统一的时间尺度，通过直接判断和对曲线进行非线性拟合，最终确定矩释放的加速或减速特征。所考虑的1978年以来Ms5．7以上主震事件共109例，其中具有加速特征的55例，具有减速特征的23例，因数据不足而无法判断加减速特征的9例，加减速特征不稳定的22例。 相似文献
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1989年以来华北地区中强震前地震矩加速释放空间扫描特征的研究 总被引：1，自引：0，他引：1
利用地震矩释放程度m值对1989年以来华北地区12次MS≥5.0中强地震前的矩加速释放现象进行了研究。基于删除余震后的地震目录,提取了与矩加速释放相关的特征时—空尺度作为AMR现象在华北地区的扫描模型参数。采用震前1年逐3个月的扫描方式,得到了12次震例在震中附近与时间相依的m值的空间演变图像,并考察了震前震源区附近的Benioff应变释放情况。结果表明,华北地区MS5.0~5.5地震前AMR现象与实际震中和发震时刻的关联性不明显;而MS5.6~6.4地震前67%的震例在震中附近出现稳定和集中分布的矩释放加速区域,说明华北地区MS≥5.5中强震前AMR现象具有一定程度的普遍性,利用AMR现象对未来中强震发震地点的预测有一定的潜能和可挖掘性,但仍需其他方法相互佐证。 相似文献
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为考察中国东北地区中强震前是否存在与地震孕育过程物理相关的地震矩加速释放现象,利用"地震矩释放程度"m值对该地区第五活跃期内的5例中强震进行了时-空扫描研究.通过考察删除余震的影响,提取了MS5.0以上地震与地震矩加速释放相关的特征时、空尺度,并作为时-空扫描的模型参数.采用震前5个月逐月扫描的方式,得到了震前m值随时间变化的图像.结果显示,其中4例在未来的震中附近出现稳定和集中分布的地震矩释放加速区.这表明东北地区中强震前的地震矩加速释放现象具有一定的普遍性,矩释放加速扫描方法对判断未来可能的中强震破裂成核点有一定的指导意义.采用相同的计算参数设置,还考察了震前破裂成核点的Benioff应变释放情况.结果显示,有3例在破裂成核点的地震矩加速释放现象明显.这表明,对于东北地区的中强地震,利用矩释放程度时-空扫描寻找未来中强震的破裂成核点,尚需其它方法作为辅助. 相似文献
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利用云南区域台网地震目录资料,以地震应变能作为地震释放量度,基于应变释放加速模型对前兆地震序列进行非线性模拟. 结果表明: 云南地区1966—2013年发生的115例MS≥5.0地震中,具有加速特征的有79例,占69%;具有减速特征的有28例,占24%;数据太少无法判断加减速特征的有8例,占7%. 主震为孤立型的前兆地震序列,其减速或数据少类型所占比例远大于加速型;主震为走滑型的前兆序列,其加速型序列要比主震为正断型或逆冲型序列多15%左右. 搜索半径与前兆序列持续时间呈反比关系. 对前兆地震序列模拟结果表明,主震的预测震级和时间误差为±0.3和0.5年. 相似文献
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为考察2014年10月7日景谷M_S 6.6地震前的可能的中长期地震前兆现象以及相关的孕震物理过程,采用加速矩释放(AMR)现象对此次地震进行了分析,首先用T=15 a, R=100 km的时空窗对CBS释放曲线的均方根残差RMS在m-tf二维空间中的分布以及最小RMS对应的m值随时间的变化分析,然后用震前15个月地震资料以逐3个月的扫描方式,对T-M_C二维空间中矩释放指数m值的分布进行分析。结果表明:景谷M_S 6.6地震前在震中附近100 km范围内, m值随着时间逐渐逼近实际发震时刻而逐渐减小,时间上有逐渐趋近于临界状态的趋势,空间上震前似存在AMR逐渐向震中附近"迁移"的现象。 相似文献
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The enumerating algorithm has been introduced into the fitting procedure of the ASR model. Based on the detailed study of 21 large earthquakes with M≥6. 8 in the Chinese Mainland,the statistical features of seismic strain release before large earthquakes have been summarized. In the mass,the strain release models can be divided into five types. The first is the DA model,in which the strain release accelerates in broader areas and decelerates in small areas around the epicenter. Approximately 38% of earthquake samples are of this type. The second is the AD model,in which the strain release decelerates in broader areas and accelerates in smaller areas around the epicenter with an occupying ratioof approximately 19%. The third is ASR,in which only accelerating strain release can be observed. Cases of this model amount to about 14%. The fourth is DSR,in which only decelerating strain release can be checked,amounting to about 24%. There is only one earthquake sample of the fifth type (LSR),which shows a linear strain release. There is a 3～6 years difference in the duration of pre-shock sequences between the accelerating and decelerating models. This means that seismic quiescence against a background of increased seismicity of small earthquakes before large earthquakes are a typical feature in general. For the DA model,the average size of critical regions for steady accelerating and decelerating strain release is about 260km to 400km and 100km to 200km,respectively,3 to 5 times and 1 to 2 times the rupture size of an earthquake of magnitude 7. 0. The AD model is the opposite of the DA model. The model parameter,m value,has good stability. The ratio of ASR is about the same for accelerating seismic strain release phenomena,no matter what the strain release models are,or how large the strain release quantity is. With regard to decelerating seismic strain release phenomena, the DA model has the most distinctive decelerating strain release characteristic and is the typical feature of seismic strain release,i. e. "decelerating in-accelerating out seismic strain model". 相似文献
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B. C. Papazachos E. M. Scordilis C. B. Papazachos G. F. Karakaisis 《Journal of Seismology》2006,10(2):213-224
Accelerating strain energy released by the generation of intermediate magnitude preshocks in a broad (critical) region, and decelerating energy released in a narrower (seismogenic) region, is considered as a distinct premonitory pattern useful in research for intermediate-term earthquake prediction. Accelerating seismicity in the broad region is satisfactorily interpreted by the critical earthquake model and decelerating seismicity in the narrower region is attributed to stress relaxation due to pre-seismic sliding. To facilitate the identification of such patterns an algorithm has been developed on the basis of data concerning accelerating and decelerating preshock sequences of globally distributed already occurred strong mainshocks. This algorithm is applied in the present work to identify regions, which are currently in a state of accelerating seismic deformation and are associated with corresponding narrower regions, which are in a state of decelerating seismic deformation in California. It has been observed that a region which includes known faults in central California is in a state of decelerating seismic strain release, while the surrounding region (south and north California, etc.) is in a state of accelerating seismic strain release. This pattern corresponds to a big probably oncoming mainshock in central California. The epicenter, magnitude and origin time, as well as the corresponding model uncertainties of this probably ensuing big mainshock have been estimated, allowing a forward testing of the model's efficiency for intermediate-term earthquake prediction. 相似文献
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近年来,国际上对于强震前的加速矩释放（AMR）现象是否可作为一种可靠的、带有普遍性的地震前兆现象争议较大.本文以2008年3月21日新疆于田MS7.3地震为例,试图从前兆存在的客观性和与地震发生的物理相关性两方面考察本次地震前的AMR现象.用“破裂时间分析”方程中的幂指数m作为描述震前加速矩释放“程度”的参量,在时间-空间-地震序列截止震级组成的三维参数空间（T,R,Mc）内考察AMR现象存在的客观性.考虑了多种因素对m（T, R, Mc）分布图像可能的影响,其中,余震是否删除和Mc对计算影响不大,但ML6.0以上“干扰”事件的影响则较大.结果表明,于田地震前的确存在AMR现象,但得到的m（T, R, Mc）分布图像较为复杂,可观测到两个明显的AMR集中分布区.此外,在以实际震中为圆心的多个圆形区域内,使用固定时间窗向实际发震时刻滑动逼近,可观测到m值逐渐减小,即加速特征逐渐明显的过程.对震前矩释放程度m值的时-空扫描结果显示,出现AMR现象的空间区域与震中位置似有较好的对应,但其时-空演化图像与滑动时-空窗的选取有关.这表明,本次MS7.3地震前的确存在AMR现象,并与其孕震过程在物理上相关.但本文仅是一个震例的研究,无法给出具有统计显著性的结论,此外,用AMR来约束地震发生的时间看来是困难的. 相似文献
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We systematically analyzed the Benioff strain release before 65 earthquakes with MS over 6.0 in China from 1978 to 2003 to investigate the generality of the widely discussed accelerating moment release (AMR)
phenomenon before strong and intermediate-strength earthquakes. In this approach, a strong or intermediate-strength earthquake
is selected as a ``target earthquake,' and retrospective analysis of seismic activity before the ``target earthquake' is
performed. Simple searching area (three circular areas with different radius centered at the epicenter of the ``target earthquake')
and unified temporal range (8 years) are taken in the analysis. Justification of whether AMR exists is by both visual inspection
and by power-law curve fitting. It is found that more than 3/5 of the earthquakes under consideration exhibit clear pre-shock
AMR property, and 1/3 of the events seem to be sensitive to the searching area. AMR behavior shows apparent focal mechanism
dependence: 15 out of 17 dip-slip earthquakes with stable moment release characteristics against the changing of searching
areas exhibit AMR behavior, while 16 out of 25 strike-slip earthquakes with stable moment release characteristics exhibit
AMR behavior. 相似文献
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根据富蕴地震台地倾斜观测资料,对距该台360 km范围内地震震前异常进行了分析.结果表明:①一般情况下,异常的持续时间越长,资料的异常变化幅度越大,震级越大;②地倾斜观测资料的异常形态与震中位置有关,通常是单分量图和矢量图的拐弯处指向震中位置,震前震源区的应力集中往往造成矢量图畸变,单分量图形出现加速的异常特征;③阶跃... 相似文献