Temporary seismic quiescence: SE Turkey   总被引：2，自引：0，他引：2  

N. N. Ambraseys 《Geophysical Journal International》1989,96(2):311-331

Summary. The Border Zone that is the contact of the Arabian plate with the three plates of Turkey, Eurasia and Iran to the north has been remarkably aseismic during this century. By extending the period of observation backwards in time by a few centuries it is shown that this seismicity is atypical of the long-term behaviour of the zone and due to a quiescent period in the activity of the area during the 20th Century. In turn, this implies that short-term data alone do not provide a reliable assessment of earthquake hazard.  相似文献   

三性法及静中动方法对甘肃岷县漳县M_S6.6地震的趋势性前兆显现的回顾研究          下载免费PDF全文

郭安宁  郭增建  张炜超  赵乘程  李鑫 《地震工程学报》2013,35(3):522-528

针对2013年7月22日甘肃岷县漳县Ms6.6地震,本文用三性法、静中动两种方法,对其前兆显现、震前预测过程进行了回顾和分析.回顾表明,在2012年时,对甘肃东南部历史上8级、7级以及6级三个震级档的地震进行三性法分析后,预测在2013-2014年时间段内,天水地区可能有6级地震发生.圈定的地点是在天水为中心150 km的范围内.另外,注意到1987年1月8日迭部5.8级地震与“静中动地震”指标所要求与定义的震级和年份相近,因而以此地震作为“准静中动”地震判断地区,与该区域三性法所做的时间预测相配合,预测在1987年1月8日迭部5.8级地震周围大约150 km的范围之内,将也会在2012年以及2013、2014年发生一个6至7级的地震.而实际发生的岷县漳县地震震中距离天水123.8 km,距离迭部112.1 km,即该地震发生在预测的范围内.由于地震预测的复杂性,当用三性法以及静中动指标对全国和甘肃省的地震情况分析后表明,在别的地区还有更为显著的发震指标显现,出于危险区不能划得太多的限制,因而把针对甘肃东南部的预测列为第二个发震可能性的方案之中,遂在2012年只得出研究性的预测结果,没有提出预测意见.甘肃岷县漳县的Ms6.6地震实际发生验证,甘肃省首发的强震不是在一个最有可能的静中动指标所指明的地点之中,却在一个“准静中动地震”的地点发生.但该地震对三性法的震后验证表明,其方法还是有前兆性指标显示的.该次地震的发生,表明“准静中动指标”也是值得重视的预测指标.研究表明,三性法相比较常用的中期尺度的预测方法,它能在存在强震背景的情况下,在趋势上指出一个特定的时间段,这是其独特的地方,与多种方法结合后,将会进一步提高强震预测的效能.  相似文献   

地震平静特征与新疆的中强地震   总被引：6，自引：1，他引：5       下载免费PDF全文

王筱荣 《地震工程学报》2003,25(3):246-252

系统分析了新疆地震活动的平静现象,认为新疆中强震前地震活动以平静为主要特征．并通过统计提取了新疆中强震前地震平静的预报指标．  相似文献   

Evidence For Precursory Changes In the Frequency-Magnitude B-Value   总被引：2，自引：0，他引：2  

Warwick D. Smith 《Geophysical Journal International》1986,86(3):815-838

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Methods for Measuring Seismicity Rate Changes: A Review and a Study of How the M w 7.3 Landers Earthquake Affected the Aftershock Sequence of the M w 6.1 Joshua Tree Earthquake     

David Marsan  Suleyman S. Nalbant 《Pure and Applied Geophysics》2005,162(6-7):1151-1185

The development of fault interaction models has triggered the need for an accurate estimation of seismicity rate changes following the occurrence of an earthquake. Several statistical methods have been developed in the past to serve this purpose, each relying on different assumptions (e.g., stationarity, gaussianity) pertaining to the seismicity process.In this paper we review these various approaches, discuss their limitations, and propose further improvements. The feasibility of mapping robust seismicity rate changes, and more particularly rate decreases (i.e., seismicity shadows), in the first few days of an aftershock sequence, is examined. To this aim, the hypothesis of large numbers of earthquakes, hence the use of Gaussian statistics, as is usually assumed, must be dropped.Finally, we analyse the modulation in seismicity rates following the 1992, June 28 M_w 7.3 Landers earthquake in the region of the 1992, April 22 M_w 6.1 Joshua Tree earthquake. Clear instances of early triggering (i.e., in the first few days) followed by a seismicity quiescence, are observed. This could indicate the existence of two distinct interaction regimes, a first one caused by the destabilisation of active faults by the travelling seismic waves, and a second one due to the remaining static stress perturbation.  相似文献   

丽江7.0级地震预报判据及地震学主要异常     

陈立德  龙晓帆 《地震》1997,17(4):340-348

介绍了丽江７．０级地震裂度、地震地质及中、短、临预报简况。中、短期预报准确，短临预报向云南省政府打了招呼。重点讨论中短期预报中使用的主要地震学判据。指出丽江７．０级地震前，中甸一下关地震带６级地震时间间隔已达１９ａ，超过历史极限。该带北段１９８３－１９９３年１０ａ内无Ｍ≥５地震；震中周围形成一长约１５０ｋｍ空段，１９９０－１９９５年６ａ内震源区Ｍ≥３．５地震出现平静异常。总之，震源周围地区小震及中  相似文献   

Two current seismic quiescences within 40 km of Tokyo     

Max Wyss  Stefan Wiemer 《Geophysical Journal International》1997,128(2):459-473

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Evaluation of precursory seismic quiescence in sixteen subduction zones using single-link cluster analysis     

Rebecca L. Wardlaw  Cliff Frohlich  Scott D. Davis 《Pure and Applied Geophysics》1990,134(1):57-78

This paper describes a new method, single-link cluster analysis (SLC), to evaluate percursory quiescence for shallow earthquakes in sixteen subduction zones, using data from the ISC catalog. To define quiescent regions, we divided the catalog into time intervals with a durationT, overlapping byT/2. We considered all earthquakes having magnitudes larger than some magnitudeM _min, lying within a specified distance of a great circle which is approximately coincident with the trench near a subduction zone. Within each time interval we connected or linked all earthquakes lying within some cutoff distanced of one another. We then projected all these links onto the great circle, and defined a region to be quiescent if it was not covered by the projection of any links. For this study,T was two years,M _min wasm _b =4.9, and we variedd from 100 to 400 km. We defined an earthquake as following quiescence if it occurred within two years following, and within 75 km of a quiescent zone as defined above. The primary conclusion of this study was that earthquakes with surface wave magnitudes 7.2 and greater were about 5–15% more likely to follow quiescence than were the smaller background earthquakes withm _b >-4.9. A chi-squared analysis shows that this result is significant at the 99% level. In contrast, earthquakes with surface wave magnitude of 6.7 to 7.1 were no more likely to follow quiescence than were background earthquakes. Of sixteen individual regions, Central America, Japan, and Peru-Chile were the only regions where large earthquakes were more likely to occur following quiescence than were background earthquakes. For a cutoff link length of 300 km, only in Central America was the difference between large earthquakes and background earthquakes significant at the 95% level of significance. For a cutoff link length of 250 km, the significance level exceeded 95% only in Japan. The SLC method is an objective, quantitative method for evaluating large data catalogs, or for monitoring quiescence in regions where quiescence is conjectured to precede large earthquakes.  相似文献   

Seismic quiescence: a test of the hypothesis and a precursor to the next Parkfield, California, earthquake     

Max Wyss  R. E. Habermann  P. Bodin 《Geophysical Journal International》1992,110(3):518-536

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An improved region–time–length algorithm applied to the 1999 Chi-Chi, Taiwan earthquake     

Chien-Chih Chen  Yi-Xuan Wu 《Geophysical Journal International》2006,166(3):1144-1148

By means of the region–time–length (RTL) algorithm, which is widely used for investigating the precursory seismicity changes in China, Italy, Japan, Russia and Turkey, we examine the precursory seismic activity occurred prior to the 1999, M _w = 7.6, Chi-Chi earthquake around its epicentre. Based on our calculation of the RTL values, the epicentral area has been found to strongly exhibit the signature of anomalous activity, associated with the seismic quiescence and activation, before the main shock. Also proposed in this study is a helpful method for determining two important parameters used in the RTL analysis, the characteristic time and distance. Such method will largely reduce the ambiguity in the original RTL algorithm.  相似文献