共查询到20条相似文献，搜索用时 140 毫秒
1.
后效严重型强震重复时间讨论 总被引：1，自引：0，他引：1
本文根据中国七个地区的古地震重复时间统计以及某些大震区的低电阻特性,建立了震源热模型并进行了定量计算。给出了后效严重型的大震(M≥7)的重复时间。 相似文献
2.
本文以宁夏区域地震台网为例，分析了波形互相关法在判定重复地震中可能存在的问题并讨论了相应的处理方法，通过构建三维非均匀体模型并利用谱元法数值模拟地震波的传播，统计了不同台站观测到的地震对波形互相关系数的分布，进一步研究了互相关系数与非均匀体性质及震源机制解之间的关系。结果表明:针对宁夏区域地震台网，利用波形互相关法判定重复地震比地震定位方法更有效；互相关系数在不同台站的取值与震源附近三维非均匀体强度和直达波与尾波的振幅比有关，对于相同的震源间距，较弱震源、较弱非均匀体或者较强振幅的直达波均会导致波形互相关系数变高，因此应选取更高的互相关系数阀值来判定重复地震。宁夏区域地震台网平均台间距为30—50 km，通过选取直达波较弱的台站或只截取尾波窗口计算互相关系数并设定较高的阀值，利用波形互相关法可有效地判定ML1.0—3.0重复地震，进而为重复地震的监测与研究提供依据。 相似文献
3.
4.
重复地震是发生在同一断层位置上的一组地震,具有相似的震级、高度相似的波形和震源机制。由于具有相同的震源和传播路径,重复地震的走时变化可以反应的介质波速的变化,从而可以作为测量地壳中介质波速变化的有力工具。而对区域地震的重复性研究,也可以反过来说明该地区地震发震机制的变化情况。利用波形互相关的方法对浙江温州境内珊溪水库附近发生的地震事件序列进行处理,计算波形互相关系数,选取相关系数大于0.8的地震对进行研究,分析珊溪水库地区地震事件的相似性和重复性,并分析此方法对地震研究的意义。 相似文献
5.
在自然和人类活动的作用下,地球内部的介质会产生变化。通过分析来自重复地震、背景噪音和重复性人工震源等的地震波,进而研究地球介质的变化,是近年来地震学研究的一个热点方向。这些研究为人类认识地震、火山等灾害的物理过程提供了重要的手段。本文介绍了过去10余年中我们在利用人工震源(尤其是大容量气枪震源)探究地下介质结构及其变化方面的研究进展,以期为今后类似的研究提供参考。本文首先介绍了在不同类型震源的性能、数据处理方法等方面的研究进展和主要认识,最后也给出了关于下一步人工震源研究方向的一些思考。 相似文献
6.
利用人工重复震源进行地下介质结构及其变化研究的探索和进展??? 总被引：11，自引：10，他引：1
在自然和人为活动的作用下,地球内部的介质会产生变化。通过分析来自重复地震、背景噪音和重复性人工震源等的地震波,研究地球介质的变化是近年来地震学研究的一个热点方向,这些研究为人类认识地震、火山等灾害的物理过程提供了重要的手段。本文介绍了过去10余年中我们在利用人工震源（尤其是大容量气枪震源）探究地下介质结构及其变化方面的研究进展,以期为今后类似的研究提供参考。本文首先介绍了不同类型震源性能的探索、数据处理方法等方面的研究进展和主要认识,最后也给出了关于下一步人工震源研究方向的思考。 相似文献
7.
重复地震研究综述 总被引：3，自引：0，他引：3
一个地区在某一时期内多次发生强震称为重复地震,按空间位置的分布,重复地震可分为原地重复、带内重复和构造重复三种。两次地震的震源区相连,极震区重迭称为强震的原地重复,如1303年山西洪洞地震和1695年的临汾地震。四川鲜水河地震带曾发生一连串强震,如1923年(7)1/4级地震和1973年7.6级地震等可称为带内重复。至于公元前70年山东诸城7级地震和1668年郯城-莒县(8)1/2级地震均发生在郯庐活动构造带内则称为构造重复。强震往往重复发生在某些特殊地质构造部位。如郯庐断裂、怀来-新活动断陷盆地带和在中国的中西部由三个地质孤状带构成的南北地震带等。强震重复在时间上多发生于不同的地震活动期中,如华北第三活跃期内的1679年三河-平谷地震和第四活跃期中的1976年唐山地震即为明显震例。大地震在某些条件下具有原地重演的现象已成为众所瞩目的事实。通过强震重复性研究,可以了解产生重复地震的原因和条件。深入对重复地震发展过程的认识并掌握它的活动规律,不仅可提高中长期地震预报水平,为工程建设提供可靠的科学依据,合理减少抗震设计投资;提出合适的措施避免地震造成的损失。还可以及时较准确地划出中短期的地震危险区,减轻地震灾害,为短临预报提供有发生强震的危险地点或较小的地区。本文综合评述了国内外有关重复地震研究的最新成果及发展动态,全文分三个部分。 相似文献
8.
断层滑动速率,地震重复时间和平均应力降 总被引：5，自引：0，他引：5
本文综述了国内外大地震复发间隔研究的现状，系统整理了中国大陆活断层滑运速率，已发现的古地震遗迹及古地震复发间隔，结果表明，在滑动速率较在的活断层发现的古地震复发间隔较短，Ｋａｎａｍｏｒｉ和Ａｌｌｅ（１９８５）研究了具有大范围重复时间（２０年到几千年）的板内大地震的震源参数，发现复发间隔较长的大地震具有较高的平均应力降，我们在实验室内研究了应变速率不同时固体围压三轴压缩下完整花岗岩破裂后的粘滑现象。 相似文献
9.
相似地震是具有相似波形记录的一组地震,往往以地震丛集的方式发生.而重复地震是一种特殊的相似地震,一般具有相近的震源机制解和几乎重合的破裂面积.对相似地震特别是重复地震的研究是我们认识断层的结构和变化的重要手段.本文提出了一种基于相似度距离概念和聚类分析技术的相似地震识别方法,可以利用单个台站对其记录到的地震事件进行快速的相似地震和重复地震识别.我们将此方法应用于汶川地震东北端的余震序列,获得了该地区相似地震的分布图像,并对其中存在的重复地震的发震机制进行了讨论分析. 相似文献
10.
利用2000—2013年四川数字地震台网和水库台网的波形资料以及川西流动台阵的事件波形,通过辨识发生在同一断层位置上的重复地震来定量研究鲜水河断裂带南段的深部变形.针对研究区台站分布稀疏的客观情况,应用了子采样条件下基于S-P相对到时差来约束震源位置一致性的方法,在鲜水河断裂带识别出11组重复地震,并利用连续波形资料进行了重复地震完整性的初步测试,同时运用结合波形互相关资料的双差法来完成研究区背景地震和重复地震位置的精确定位.重新定位后的地震图像展示研究区中上地壳存在明显缺震层,其与壳内的低速低阻层相吻合.利用重复地震的地震矩和重复间隔,估算出鲜水河断裂带南段孕震深部的滑动速率为3.0~10.2mm·a-1,显示研究区不同地震构造区的深部滑动速率存在明显差异. 相似文献
11.
Statistical analysis on temporal-spatial correlativity within temporal doublets of strong earthquakes in North China and its vicinity 总被引：1，自引：0，他引：1
Introduction Being the important evidence of seismic trend prediction, the characters of spatial-temporal distribution of strong earthquakes can, to some extent, reflect the gestation mechanism and the migration law of strong quakes. From temporal point of view, a number of scholars consider the occurrence of strong earthquakes as the independent events, i.e., Poisson process. Based on this assumption, various predicted models are brought forward, such as stationary Poisson model, subsection … 相似文献
12.
13.
Sławomir Jerzy Gibowicz 《Acta Geophysica》2006,54(2):142-157
The following criteria for selection of doublets at Polish coal mines were accepted: the difference in magnitude (based on
seismic moment) of two events not larger than 0.15, the distance between their hypocenters not greater than 150 m, and the
time interval between their occurrence not longer than 10 days. Similarly, the criteria for seismic events at copper mines
are: the difference in magnitude not exceeding 0.15, the distance not greater than 200 m, and the time interval not longer
than 20 days. Seismic events from the Wujek and Ziemowit coal mines that occurred between 1993 and 1995, and seismic events
from the Polkowice copper mine that occurred between 1994 and 1996 and from the Rudna copper mine that occurred between 1994
and 2004 were considered. Their source parameters and focal mechanisms were known in most cases from previous studies. Altogether
108 seismic pairs from coal mines and 118 pairs from copper mines were found, forming doublets, triplets and quadruplets,
within the magnitude range from 0.7 to 3.5. The distance and time intervals between two events forming pairs are not dependent
on magnitude of these events.
The focal mechanism of seismic events forming pairs is similar in over 60 percent of pairs at coal mines and in about one
third of pairs at copper mines. Spatial distributions of doublets in particular sections of coal and copper mines display
dominant linear trends, characteristic for a given area, which are often in conformity with the direction of nodal planes
determined by fault plane solution of one or both the events forming a doublet. In such cases, the rupture plane can be discriminated
among the nodal planes. 相似文献
14.
For the Fiji-Tonga-Kermadec area and for the period from January 1977 to July 2003, the Harvard CMT catalogue lists 1022 shallow,
410 intermediate and 633 deep earthquakes of moment magnitude from 4.9 to 8.0. The magnitude threshold, above which the catalogue
is complete, is 5.3–5.4, and the number of earthquakes of magnitude above this value is 691 for shallow, 329 for intermediate
and 476 for deep events, respectively. The proportion of earthquakes associated with doublets and multiplets against the total
number of earthquakes is approximately the same in both data sets and therefore all earthquake pairs were considered regardless
of their magnitude. We investigated all the pairs of earthquakes that occurred at a centroid distance of less than 40, 60
or 90 km from each other and within a time interval of 200, 300 or 450 days, depending on their magnitude. We found 208 pairs
of shallow, 31 of intermediate and 92 of deep events. To ascertain whether these earthquakes in pairs are not connected by
chance, the possibility of their occurrence in an uncorrelated Poissonian catalogue was considered. It was assumed that in
such a catalogue the inter-event time is exponentially distributed, the earthquake magnitude follows the Gutenberg-Richter
relation, and the distribution of centroid distances between the events in pairs is controlled by its non-parametric kernel
estimate. The probability of the appearance of the observed proportion of doublets of shallow earthquakes in the Poissonian
catalogue was found to be very low. The low probability of occurrence in a semi-random catalogue, created by randomising centroid
locations in the actual data set, also indicates major importance of the distance criterion used for a doublet specification.
In general, shallow earthquakes tend to form pairs at shorter distances and within shorter time intervals than deep earthquakes.
Both the distance and the time intervals do not depend on the magnitude of involved events. The largest number of pairs of
deep earthquakes is observed at a depth of about 600 km, and the proportion of deep events associated with doublets against
the number of all events increases with depth. From comparison of the focal mechanism of earthquakes in pairs, measured by
the 3-D rotation angle, it follows that deep earthquakes forming pairs have a more diverse focal mechanism than shallow events;
the rotation angle for three quarters of shallow pairs and only for about one third of deep pairs is reasonably small. The
azimuth between two events forming a doublet is in about 60–65% of cases close to the strike of one of nodal planes of the
first or the second event. 相似文献
15.
基于2009—2017年新疆区域数字地震台网记录的地震波形数据,利用波形互相关技术及主事件定位方法识别并重新定位了新疆天山中段及其周缘的重复地震。以波形互相关系数0.9作为阈值来确定研究区的重复地震事件,统计结果显示3万零181个事件中的1万1 618个为重复地震事件,这些重复地震事件组成了2395组重复地震对和重复地震丛,占总事件数的38.5%。根据重复地震重定位前后地震对之间距离的统计结果推测,该区域的系统定位误差约为5—10 km。进一步结合该区域最新的震源分类结果对不同震源类型重复地震的时空分布特征予以分析,结果显示:重复矿山爆破事件在空间上呈丛集性分布,且其中的93.6%发生于白天,同时呈现季节性发生模式,即爆破多发生于夏季,而冬季较少;而重复构造地震在空间上大多沿断层分布,24小时内呈随机分布的特征,且研究时段内每个月的活动水平相对平稳;重复诱发地震成丛分布于靠近油气田和水库的区域,但其中部分诱发地震的位置与构造地震重叠,发震时间特征与构造地震相似,为随机分布。 相似文献
16.
I. V. Radhakrishna Murthy 《Pure and Applied Geophysics》1970,80(1):193-198
Summary A simple method for the interpretation of the vertical magnetic anomalies of dipping doublets is presented. In the first step, the line integrals of the anomalies along theX direction, which represent the anomalies of a vertical line double are utilised to obtain the depths to the two poles. In the second step, the profile alongY, through the point of intersection of the doublet with theX axis is used to determine the dip of the dipole. 相似文献
17.
We analyse spectral ratio of the coda of doublets of microearthquakes. Our purpose is to find evidence for temporal changes of the attenuation in the crust before a large magnitude earthquake. A Moving Window Cross Spectral analysis of the coda of doublets gives a plot of the spectral ratio as a function of lapse time along the seismogram, for several frequency bands (SR(T, f) plot). From a certain pattern in theSR(T, f) plot, we should infer a temporal change in coda attenuation. Several doublets recorded in Central California by the USGS network are analysed.Using events very close in time from one another, we show that the radiation pattern can be different enough to induce important variations in the spectral ratio of the first arrivals and of the coda.Another doublet exhibits a strong variation of the low frequencies for stations in the region of Hollister (California), wherePhillips andAki (1986) have noted a strong amplification of low frequencies, that they attribute to site effects on unconsolidated sediments in the fault zone. These variations could be related to slight changes in local conditions (creep, or water table).On the other hand, some doublets, in the vicinity and close in time to the August 1979 Coyote Lake Earthquake (M=5.9), show no variation inSR(T, f) related to this earthquake: this proves that there was no major change in attenuation in the crust preceding this large shock. If a change occurred, it should have been confined to a very limited region, which was not sampled by the many paths we studied.The employed method probably provides today the most accurate estimation of spectral ratio in the coda of microearthquakes. It shows that there are numerous kinds of variations and that it is not straightforward to relate them to coda attenuation changes only. Also, we must be circumspect when dealing with the coda of microearthquakes in relation to forecasting earthquakes. 相似文献
18.
Introduction Whether static stress change generated by earthquakes can trigger subsequent earthquakes heretofore is still in debate. Some researchers believe that seismic Coulomb failure stress change generated by earthquake can affect the seismicity nearby (King, et al, 1994; Toda, et al, 1998; Stein, 1999; Seeber, Armbruster, 2000). However, some researchers believe that this model is wrong. For example, Beroza and Zoback (1993) found that stress change generated by the 1989 Loma Prieta … 相似文献
19.
《中国科学:地球科学(英文版)》2017,(10)
The active sources generate seismic waves transmitting appropriate through the deep is underground key and can be used to image Abstract high-resolution subsurface structures.Therefore,an seismic source the factor to active source exploration.In order to study the structure of continental crust and its temporal variations,we selected an artificial seismic source generated from releasing air bubbles in water(airgun source hereinafter)out of a variety and of artificial sources like the is explosion,new electronic sparkers,source hammering,eccentric proven vibration,be heavy-duty train vibration,vibroseis etc.Airgun Three source Fixed a type of artificial that have been to environmentally friendly,safe,and highly efficient.Airgun western Signal China Transmission and Stations(FASTS)have been for built a few years ago in Yunnan,Xinjiang,and Gansu provinces in have been continuously them running several years.Seismic waves generated away by the the airgun sources are highly seismic reproducible waves and stacking in of can produce can good seismograms on 1300 stations km far from source,for instance,an produced Xinjiang FASTS be well about recorded 60 nearly away after 5000 stacking,China covering area of 6 million km2 and penetrating down to of a depth of km.Establishing about 10 FASTSs in would enable long-term illuminate continuous subsurface underground structures,monitoring can all 9.6 million km2 of land area.Treating from airgun sky active sources as lanterns to we achieve the situation with"Beidou surveys the and lantern illuminates underground". 相似文献
20.
曹妃甸地震台网天然地震与人工爆破时频分析 总被引：1，自引：1，他引：0
搜集2014—2015年曹妃甸测震台网记录的各类爆破与天然地震事件,基于Matlab软件,编制程序实现短时傅里叶变换,对比分析核爆炸、化学爆炸、矿爆炸与天然地震的特征,分析频率随时间的变化规律。研究结果表明,天然地震与爆破在频率范围、频率分布和时频聚集性等方面具有各自特点,主要表现在:天然地震的时频图"多峰"且复杂,频率分布范围更广,频率成分集中在S波段;人工爆破的时频图"少峰"且简单,频率范围较窄,频率成分集中在P波段。本文的研究成果能够为今后区分天然地震和爆破提供依据。 相似文献