德国大陆超深钻井注水诱发地震的精确定位

2000年8月21日～10月20日,德国大陆超深钻井(KTB)进行了为期60天的新一轮注水诱发地震实验．在对KTB台网所记录到的2 700多次地震的原始波形进行分析和处理的基础上,对其中的237次地震进行了精确定位．定位时,先采用和达法剔除了误识的非KTB诱发地震事件;然后,使用大折刀法求得了台站偏差的最佳值,以及中误差和平均误差;最后应用Geiger法进行修定,从而保证了237个事件定位的中误差达到0.1 km的高精度．定位结果显示,在大于9.3 km(几乎是主井底的深度)没有发生诱发地震．这一现象表明,在这个深度,应力可能低于摩擦强度,以至于由注水引起的孔隙压力的变化不足以诱发地震;在这样的深度不存在可渗透的、取向恰当的断层．这个深度也可能是这一区域内的地震活动性的最大深度,即在这一相对稳定地区的板块内部,主井底已接近脆-延性转换带．并用实验室的结果和超深钻井中所观测到的热流值资料解释了这一现象．     

河津地震序列的精定位研究

采用双差定位法,对2010年1月24日发生在山西河津与万荣交界的4.8级地震序列进行重新定位,结果显示,重新定位后,对于本次地震的发震构造,地震现场考察结果依据等震线图、余震分布特征,对震中区附近的主要活动断裂进行逐个排查分析,最终确定为NW向的西辛封断裂.     

1999年海城-岫岩地震序列的精准定位

1999年11月29日,北京时间12点10分39秒(04:10:39 UTC)在我国辽宁海城-岫岩地区发生了一次Ms5.4地震.这次地震是继1975年2月4日海城Ms7.3地震之后该地区发生的震级最大的一次地震.区域性的辽宁数字地震台网记录了这一序列的前震、主震与 余震.本文运用该台网的记录资料,用双差法对海城-岫岩地...     

基于双差定位方法的内蒙古中西部地区地震精确定位

针对测震台网定位存在偏差的问题,采用双差定位方法,对2008—2019年9月内蒙古测震台网及周边台站记录的内蒙古中西部地区4410个地震事件进行重新定位.研究表明,利用双差定位方法重新定位后地震分布更集中,更符合内蒙古中西部地区的地质构造特征,定位精度显著提高.     

上海地震台阵对2004年12月26日印度洋地震的精确定位

通过对上海地震台网和上海地震台阵对2004年12月26日印度洋地震的定位结果与NEIC定位结果的比较，得出上海台阵定位结果比上海台网的定位结果更加精确。     

云南地区地震精确定位及其构造意义分析

运用双差定位法，对云南区域数字地震遥测台网记录的1999—2003年云南地区ML≥1.0地震进行重新定位，得到3000多个地震的精确定位结果。重定位结果显示，在东经100。和103。线附近存在两个震源深度较深的区域，最深达50km，刚好对应金沙江一红河断裂带的北段和小江断裂带。这一结果一方面揭示出这两条深大断裂与地震活动之间存在密切关系，另一方面也表明重定位结果在震源深度和空间分布上都较以前有明显改善。同时，姚安、大姚地震序列的重定位结果也说明双差定位法是一种比较好的地震定位方法。     

Hypocenter location accuracy and seismicity distribution in the Central Apennines (Italy)

In this paper, we analyse the seismicity distribution in the CentralApennines (Italy) using the recordings of the Rete SismometricaMarchigiana (RSM). In particular, the selected events are relocated usinga 1-D model calculated by means of an inversion procedure. The robustnessof the 1-D model and the location accuracy are tested. The capability ofthe RSM to well constrain crustal and subcrustal events in the studied areais discussed. We find that in the inner side of the chain the seismicity liesin the upper crustal layers, following the structural trend of the Apenninicbelt. A W-deepening of the events is observed in the Apenninic foredeep,where the seismicity is mainly confined in the lower crust. This evidenceimplies the deepening of the brittle to ductile transition. Some well-locatedsubcrustal events are found. Their locations seem to confirm the W-dippingsubduction of the Adriatic lithosphere beneath the Apennines.     

江苏及周缘地区地震精定位与构造意义分析

采用双差定位方法,对江苏地震台网记录到的江苏及邻区地震事件(1990-2009年)重新定位,共获取1020个定位结果,震中平均误差为:南北向0.42 km,东西向0.43 km,垂直向0.53 km.精定位后约94%的地震事件震源深度分布在5-20 km范围内,平均震源深度为12.3 km.震源深度自东向西,从海域向陆...     

用成都遥测台网记录判定深远震的几个问题

因成都遥测台网使用的记录器不同,通过对１９９６～１９９８年两年多的资料分析,发现采用常规的分析处理方法,有可能将深远震误作浅源震,其结果是震中位置偏差最大可达１５度。鉴于此情况,提出一种新的简易办法,可以改善深远震定位精度。     

The crustal structures of the central Longmenshan along and its margins as related to the seismotectonics of the 2008 Wenchuan Earthquake

In 2010, a 500-km-long wide-angle reflection/refraction seismic profile was completed, running northwest from the central Sichuan Basin. This profile orthogonally crosses the meizoseismal area of great Wenchuan earthquake of 12 May 2008, which occurred in the central part of the Longmenshan. The profile also passes through the northwestern Sichuan Plateau, along which a new deep seismic sounding observation system was set up that was much improved over previous datasets and enabled abundant observations to be recorded. Seismic wave phase records that reflect the structural characteristics of different tectonic blocks, especially the complicated phase features associated with the Wenchuan earthquake, were calculated and analyzed in detail. A 2D crustal P-wave velocity model for the orogenic belt in the central Longmenshan and its margins was determined, and crustal structure differences between the stable Sichuan Basin and the thickened northwestern Sichuan Plateau were characterized. Lithological variations within the upper and lower crust in the interior of the plateau, especially a great velocity decrease and plastic rheological properties associated with strong lithologic weakening in lower crust, were detected. From west to east in the lower crust beneath the orogenic belt lying between the Sichuan Basin and the northwestern Sichuan Plateau, a giant shovel-like upwelling is observed that dips gently in the lower part and at higher angles in the upper part; this is inferred to be related to the fault systems in the central Longmenshan. An upwelling in the upper-middle crust along the eastern margin of the orogenic belt is associated with steeply dipping thrusts that strongly uplift the upper crust and crystalline basement beneath a central fault system in the Longmenshan. The data, combined with an understanding of the regional tectonic stress field and previous geological results, enable a discussion of basin-and-range coupling, orogenic tectonics, the crustal fault system, and the seismogenic tectonic environment of the central Longmenshan along the eastern margin of the Qinghai-Tibet Plateau.     

大岗山水库地震台网水库诱发地震常规定位方法对比

采用MSDP软件中的单纯型、HypoSat和LocSat定位方法,从震源深度及残差等方面,对比分析2014年大岗山水库区域内123次M_L≥2.0地震的定位结果,选择适用于水库诱发地震的最佳定位方法,并以库区17次定点爆破事件为例,验证最佳定位方法的可靠性。结果认为,LocSat定位方法更适用于水库诱发地震。     

中国大陆东部地区地震活动图像及其含义

定量处理了中国大陆东部地区2000～2002年的中小地震活动图像,分析了地震活动密集值的相对变化及其含义,探讨了其在中期地震预测中的应用。     

江苏宝应4.9级地震序列双差定位处理

运用双差定位方法,对2012年7月江苏省宝应县4.9级地震序列重新精定位.精确定位结果与原始定位结果比较发现,精定位后震中位置更加集中,呈条带状分布,与现场烈度保持一定的相似性,震源深度集中于10 km与14 km附近两个区间,相比原始定位结果更加收敛.     

二滩水库蓄水1年的地震活动

二滩水电站于1998年5月1日下闸蓄水,至今已有1年多。1年来,库首区周边出现了少量与库水位涨落有关的弱震活动。本文使用了二滩水库遥测地震台网的8个高增益子台、1个低增益子台共23道记录的地震分析资料。通过对蓄水前后发生地震比较,重点对1998年5月发生在龙胜乡的小震群,6月鱼干鱼乡西北的小震群及8月发生于大坝附近的小震序列进行了分析研究。探讨了1998年5月至1999年5月的水库水位变化与地震次数及震级大小的关系。由此,得出了二滩水库蓄水初期的地震活动性研究的初步结论:蓄水后数10亿吨库水的加载导致岩石形变附加剪切应力可能是导致初期水库周边弱震活动增加的诱发因素。笔者认为加强对大坝及周围地区的地震监测和对水库诱发地震的预测研究,减轻未来可能发生的构造型诱发地震灾害是下一阶段的首要任务。     

Accurate relocation of earthquakes in central-western China using the double-difference earthquake location algorithm

The double-difference earthquake relocation algorithm (DD algorithm) has been applied to the accurate relocation of 10057 earthquakes in the central-western China (21°-36°N, 98°-112E°) during the period of 1992-1999. In total, 79706 readings for P waves and 72169 readings for S waves were used in the relocation, and the source parameters of 6496 events were obtained. The relocation results revealed a more complete picture of the hypocentral distribution in the central-western China. In several seismic belts the relocated epicenters present a more defined lineation feature, reflecting the close correlation between the seismicity and the active tectonic structures. The relocated focal depths confirmed that most earthquakes (91 percent of the 6496 relocated events) in the central-western China were located at shallower depths not deeper than 20 km. The distribution of focal depths indicates that the seismogenic layer in the central-western China is located in the upper-mid crust with its thickness no deeper than 20 km.     

东北地震活动性短期预报方法研究

研究了1970年以来东北地区发生的MS≥5·0浅源地震孕育过程中地震活动性参数和地震活动图像的变化特征,并对地震活动性参数进行了比较系统地综合预报效能评价,结果显示:东北9次(组)浅震地震前,所研究的5项地震活动性参数中,88·9%出现了持续3个月以上的短期异常变化,且5项参数R值评分结果都满足97·5%的置信水平;88·9%地震前震源区附近出现了孕震空区,有87·5%孕震空区在空区边缘或空区内部出现了ML≥4·0逼近地震,逼近地震以单个或成对的形式出现。66·7%的地震在震源区附近出现了地震条带异常。最后给出东北地区中强震的短期预报方法,这对未来东北地区的地震预报工作将起着一定的参考意义。     

三峡库区地震精定位中确定速度模型的方法

研究三峡库区地震精定位中确定速度模型的方法,分析不同速度模型对地震定位精度的影响,并选取多种方法来定量评价不同速度模型的地震定位精度。当地震分布或台站能够较好的覆盖研究区域,采用Kissling方法拟合观测数据得到的速度模型地震定位精度最高。当地震分布不能较好的覆盖研究区域,由人工地震测深结果得到的速度模型地震定位精度次之。当没有足够的观测数据,也没有人工地震测深结果,综合研究区域内的相关研究成果确定的速度模型也是可用的,但是地震定位的精度不高,特别是震源深度的精度很差。     

Accounting for source location errors in the bayesian analysis of seismicity and seismic hazard

A method is presented for incorporating the uncertainties associated with hypocentral locations in the formulation of probabilistic models of the time and space distributions of the activity of potential seismic sources, as well as of the resulting seismic hazard functions at sites in their vicinity. For this purpose, a bayesian framework of analysis is adopted, where the probabilistic models considered are assumed to have known forms and uncertain parameters, the distribution of the latter being the result of an a priori assessment and its updating through the incorporation of the direct statistical information, including the uncertainty associated with the relations between the actual hypocentral locations and the reported data. This uncertainty is incorporated in the evaluation of the likelihood function of the parameters to be estimated for a given sample of recorded locations. For the purpose of illustration, the method proposed is applied to the modelling of the seismic sources near a site close to the southern coast of Mexico. The results of two alternate algorithms for the incorporation of location uncertainties are compared with those arising from neglecting those uncertainties. One of them makes use of Monte Carlo simulation, while the other is based on a closed-form analytical integration following the introduction of some simplifying assumptions. For the particular case studied, accounting for location uncertainties gives place to significant changes in the probabilistic models of the seismic sources. Deviations of the same order of magnitude can be ascribed to differences in the mathematical and/or numerical tools used in the uncertainty analysis. The resulting variability of the seismic hazard at the site of interest is less pronounced than that affecting the estimates of activity of individual seismic sources.     

福建台网接入台湾台站对定位台湾中深源地震精度影响分析

福建台网负责监测中国台湾地区地震。对于中深源地震使用何种定位方法能获得较好的地震参数,这直接影响到地震定位精度。利用JOPENS系统中交互分析软件MSDP提供的定位方法,对同一地震进行两次定位,即不使用和使用接入的台湾台站,将福建台网得出的两次结果与中国台湾公布的地震参数进行对比,分析定位精度,进而找出适用于台湾地区中深源地震的定位方法,以便进一步判断在地震速报中使用这些台站进行辅助定位的可行性,并给出相关的操作方法及建议。     

关于2002年3月31日台湾M 7.5强震的临震预报

2002年3月31日，在台湾以东海中发生7.5级强烈地震。这次地震前，笔者在2002年3月21日分析预报中心预报部会商会上，明确提出临震预报意见：3月底前后台湾地区将发生6级左右地震，并上报到有关部门。这次地震虽然发生在我国台湾地区，但它是一次成功的临震预报的尝试。