有关地震烈度速报信息化发展的思考

汶川8.0级地震给我们很多警示,其中之一就是地震观测系统应当在大地震后快速产出地震烈度分布图。本文对快速产出地震烈度的策略和方法进行了探讨,着重介绍了用同震位移分布快速获得地震烈度产出的方法。实现地震烈度快速产出这一目标应当走测震学、强地面运动学与信息技术有效结合的道路,这是大震后地震烈度快速产出的有效途径。     

新疆中强地震序列特征参数与主震震级的统计关系

系统分析了1970~2007年间新疆境内70个5级以上地震序列的余震持续时间和余震区长轴与主震震级的统计关系,以及主震破裂方式对余震时空特征参数的影响。研究结果表明,新疆及分区地震带余震持续时间和余震区长轴分别与主震震级弱相关,主震震级较低时两者关系离散,震级较高时则呈线性增强。不同的地震带这种线性关系存在差异,对于相同的主震震级,天山地震带余震持续时间一般大于西昆仑地震带,而余震区长轴前者小于后者。新疆地区主震破裂方式对余震的持续时间影响不大,但对余震区长轴影响较大,走滑型主震余震区长轴一般大于逆断型地震。     

COSEISMIC SURFACE RUPTURES AND SEISMOGENIC MUJI FAULT OF THE 25 NOVEMBER 2016 ARKETAO MW6.6 EARTHQUAKE IN NORTHERN PAMIR

The M_W6.6 Arketao earthquake,which occurred at 14:24:30 UTC 25 November 2016 was the largest earthquake to strike the sparsely inhabited Muji Basin of the Kongur extension system in the eastern Pamir since the M 7 1895 Tashkurgan earthquake.The preliminary field work,sentinel-1A radar interferometry,and relocated hypocenters of earthquake sequences show that the earthquake consists of at least two sub-events and ruptured at least 77km long of the active Muji dextral-slip fault,and the rupture from this right-lateral earthquake propagated mostly unilaterally to the east and up-dip.Tectonic surface rupture with dextral slip of up to 20cm was observed on two tens-meter long segments near the CENC epicenter and 32.6km to the east along the Muji Fault,the later was along a previously existing strand of the Holocene Muji fault scarps.Focal mechanisms are consistent with right-lateral motion along a plane striking 107°,dipping 76° to the south,with a rake of 174°.This plane is compatible with the observed tectonic surface rupture.More than 388 aftershocks were detected and located using a double-difference technique.The mainshock is relocated at the Muji Fault with a depth of 9.3km.The relocated hypocenters of the 2016 Arketao earthquake sequence showed a more than 85km long,less than 8km wide,and 5~13km deep,NWW trending streak of seismicity to the south of the Muji Fault.The focal mechanism and mapping of the surface rupture helped to document the south-dipping fault plane of the mainshock.The listric Muji Fault is outlined by the well-resolved south-dipping streak of seismicity.The 2016 Arketao M_W6.6 and 2015 Murghob M_W7.2 earthquakes highlight the importance role of strike-slip faulting in accommodating both east-west extensional and north-south compressional forces in the Pamir interior,and demonstrate that the present-day stress and deformation patterns in the northern Pamir plateau are dominant by east-west extension in the shallow upper crust.     

RELOCATION OF MAIN SHOCK AND AFTERSHOCKS OF THE 2014 YINGJIANG MS5.6 AND MS6.1 EARTHQUAKES IN YUNNAN

Yingjiang area is located in the China-Burma border,the Sudian-Xima arc tectonic belt,which lies in the collision zone between the Indian and Eurasian plates.The Yingjiang earthquake occurring on May 30th,2014 is the only event above M_S6.0 in this region since seismicity can be recorded.In this study,we relocated the Yingjiang M_S5.6 and M_S6.1 earthquake sequences by using the double-difference method.The results show that two main shocks are located in the east of the Kachang-Dazhuzhai Fault,the northern segment of the Sudian-Xima Fault.Compared with the Yingjiang M_S5.6 earthquake,the Yingjiang M_S6.1 earthquake is nearer to the Kachang-Dazhuzhai Fault.The aftershocks of the two earthquakes are distributed along the strike direction of the Kachang-Dazhuzhai Fault (NNE).The rupture zone of the main shock of Yingjiang M_S6.1 earthquake extends northward approximately 5km.The aftershocks of two earthquakes are mainly located in the eastern side of the Kachang-Dazhuzhai Fault with a significant asymmetry along the fault,which differ from the characteristics of the aftershock distribution of the strike-slip earthquake.It may indicate that the Yingjiang earthquakes are conjugate rupture earthquakes.The non-double-couple components are relatively high in the moment tensor.We speculate that the Yingjiang earthquakes are related to the fractured zone caused by the long-term seismic activity and heat effect in the deep between Kachang-Dazhuzhai Fault and its neighboring secondary faults.Aftershock distribution of the Yingjiang M_S6.1 earthquake on the southern area crosses a secondary fault on the right of the Kachang-Dazhuzhai Fault,suggesting that the coseismic rupture of the secondary fault may be triggered by the dynamic stress of the main shock.     

THE RESEARCH OF THE SEISMOGENIC STRUCTURE OF THE LUSHAN EARTHQUAKE BASED ON THE SYNTHESIS OF THE DEEP SEISMIC DATA AND THE SURFACE TECTONIC DEFORMATION

The seismogenic structure of the Lushan earthquake has remained in suspensed until now. Several faults or tectonics, including basal slipping zone, unknown blind thrust fault and piedmont buried fault, etc, are all considered as the possible seismogenic structure. This paper tries to make some new insights into this unsolved problem. Firstly, based on the data collected from the dynamic seismic stations located on the southern segment of the Longmenshan fault deployed by the Institute of Earthquake Science from 2008 to 2009 and the result of the aftershock relocation and the location of the known faults on the surface, we analyze and interpret the deep structures. Secondly, based on the terrace deformation across the main earthquake zone obtained from the dirrerential GPS meaturement of topography along the Qingyijiang River, combining with the geological interpretation of the high resolution remote sensing image and the regional geological data, we analyze the surface tectonic deformation. Furthermore, we combined the data of the deep structure and the surface deformation above to construct tectonic deformation model and research the seismogenic structure of the Lushan earthquake. Preliminarily, we think that the deformation model of the Lushan earthquake is different from that of the northern thrust segment ruptured in the Wenchuan earthquake due to the dip angle of the fault plane. On the southern segment, the main deformation is the compression of the footwall due to the nearly vertical fault plane of the frontal fault, and the new active thrust faults formed in the footwall. While on the northern segment, the main deformation is the thrusting of the hanging wall due to the less steep fault plane of the central fault. An active anticline formed on the hanging wall of the new active thrust fault, and the terrace surface on this anticline have deformed evidently since the Quaterary, and the latest activity of this anticline caused the Lushan earthquake, so the newly formed active thrust fault is probably the seismogenic structure of the Lushan earthquake. Huge displacement or tectonic deformation has been accumulated on the fault segment curved towards southeast from the Daxi country to the Taiping town during a long time, and the release of the strain and the tectonic movement all concentrate on this fault segment. The Lushan earthquake is just one event during the whole process of tectonic evolution, and the newly formed active thrust faults in the footwall may still cause similar earthquake in the future.     

龙门山南段飞来峰构造变形及形成演化

龙门山前山构造带中分布着大量的飞来峰。为了解其构造演化过程,主要通过分析研究龙门山南段白石-苟家飞来峰和金台山飞来峰内部及下覆地层的构造变形特征,确定出其至少经历了5个构造变形序列,并结合前人资料讨论龙门山南段飞来峰的形成和演化。     

Preliminary study on aftershock decay rate of the 2013 Ms7.0 Lushan earthquake

We obtained a catalog of early aftershocks of the 2013 Lushan earthquake by examining waveform from a nearby station MDS which is 30.2 km far away from the epicenter, and then we analyzed the relation between aftershock rate and time. We used time-window ratio method to identify aftershocks from continuous waveform data and compare the result with the catalog provided by China Earthquake Networks Center （CENC）. As expected, a significant amount of earthquakes is missing in CENC catalog in the 24 h after the main shock. Moreover, we observed a steady seismicity rate of aftershocks nearly in the first 10,000 s before an obvious power-law decay of aftershock activity. We consider this distinct early stage which does not fit the Omori law with a constant p （p - 1） value as early aftershock deficiency （EAD）, as proposed by previous studies. Our study suggests that the main shock rupture process is different from aftershocks＇ processes, and EAD can vary in different cases as compared to earthquakes of strike-slip mechanism in California.     

基于序列参数的水库地震类型综合判定研究

收集整理了我国大陆东部地区44 组水库地震序列,其中震群型32 组,主余型和孤立型12 组。分别计算了44 组序列的h 值、b 值、归一化熵值K、能量均匀度U、地震发生方式参数ρ 等5 个序列参数。在95% 的置信水平下,对每一参数分震群型、主余型加孤立型两大类进行差异性检验。结果表明,h、U、ρ 值对水库地震序列类型的分类能力不强;b 值平均值虽存在一定差异,但数值分布范围有部分重叠;K 值差异性显著,K = 0. 35 可作为区分震群型与主余型加孤立型两类水库地震序列的判别指标。在此基础上,建立以上述5 个参数为自变量的Fisher 判别函数,用于序列类型的综合判定。结果显示,所有数据全部参与建立判别函数并进行回溯性内符判别检验,识别正确率为97. 6% ;利用32 组序列参数参与判别函数建立,另外10 组进行外推检验,识别正确率为100% ,表明上述综合判别方法具有较高的水库地震序列分类能力。     

2013年甘肃岷县漳县M_S6.6地震及其余震序列重定位

使用甘东南地区三维速度模型,利用三维网格搜索法和双差地震定位法对2013年7月22日甘肃岷县漳县MS6.6地震及其震后三天的余震序列进行了精确定位,结合地质构造资料对本次地震的发震构造进行了初步研究。其结果显示:主震的震中位置为34.54°N,104.189°E,震源深度13.5km;余震震中呈NW或NWW方向分布,与临潭-宕昌断裂的走向基本吻合,主要分布于5～20km的深度,震中在深度剖面上呈SW向;发震断裂为倾向SW的隐伏断层,位于临潭-宕昌断裂NE方向,距临潭-宕昌断裂约20km。     

余震信息在岷县漳县6.6级地震震后应急救援重灾区快速判定时作用探讨

利用震后可以快速获取的余震信息,迅快速判定出地震重灾区的范围,为震后快速应急救援提供决策服务是十分重要的。本文利用甘肃岷县漳县6.6级地震后12小时余震分布,以1小时为单位,分时段绘制余震空间分布图,结合居民点的空间分布、发震断层走向和地形地貌条件,与实际考察得到的烈度图进行比较,初步得出以下认识:震后3小时左右余震分布集中的区域可能是破坏最严重的地区;沿余震展布方向需要考虑震区地形地貌和降雨等次生灾害因素所引起的破坏;由余震分布范围来确定重灾区时,长轴方向需要参考发震断层的走向进行调整;依据震区居民点分布密度调整重灾区位置;考虑各种致灾因素的影响,综合判定重灾区的范围。