藏东玉龙超大型斑岩铜矿床成岩成矿系统时间跨度分析   总被引：12，自引：5，他引：7  

梁华英  莫济海  孙卫东  喻亨祥  张玉泉  Charllote M. ALLEN 《岩石学报》2008,24(10):2352-2358

藏东玉龙超大型斑岩铜矿床是目前西藏发现的最大斑岩铜矿床,含铜岩体主要由早期石英二长斑岩及晚期正长花岗斑岩组成。本文用LA-ICP-MS法测定早期石英二长斑岩及晚期正长花岗斑岩锆石U-Pb年龄及Ar-Ar法测定钾质蚀变带黑云母的Ar-Ar年龄,发现玉龙含矿斑岩体早期石英二长斑岩锆石LA-ICP-MS U-Pb年龄(41.3±0.3Ma, MSWD=0.92)与晚期正长花岗斑岩锆石LA-ICP-MS U-Pb年龄(41.3±0.2Ma, MSWD=1.24)基本相同,也和黑云母Ar-Ar坪年龄(41.7±0.8Ma)及等时线年龄(41.3±0.8Ma)在误差范围内一致。玉龙斑岩铜矿早期及晚期岩体锆石U-Pb年龄一致表明含矿岩体在地质上的早期及晚期主要是岩浆在较短时间内脉动侵入所致。玉龙含矿岩体锆石U-Pb年龄(封闭温度约800℃)、³⁹Ar-⁴⁰Ar 年龄(封闭温度约300℃)及前人获得的Re-Os年龄40.1±1.8Ma(封闭温度约500℃)在误差范围内基本一致,表明含矿岩体岩体快速冷却,玉龙超大型斑岩铜矿床成岩成矿系统时间跨度小于1Ma。  相似文献   

大地震的强余震活动持续时间和重复时间   总被引：4，自引：1，他引：3       下载免费PDF全文

傅征祥 《地震地质》1990,12(1):15-20

1966—1981年中国大陆华北和西南地区发生了10次大地震(M_s≥6.9),其强余震活动持续时间有明显差异,从1天到1000天不等。它们似乎与主震震级大小无关,却依赖于不同主震的重复时间,即较长的持续时间对应较长的重复时间。基于地震力学的观点,较长的重复时间意味着地震断面静止接触时间较长,断面摩擦强度将增大,产生数量较多和面积较大的强固点,所以,有可能在断面主破裂之后,观测到较长持续时间的强余震活动(强固点破裂  相似文献   

南沙海区风浪分析与计算   总被引：3，自引：0，他引：3  

丁干龙 《海洋科学》1992,16(5):37-40

根据南沙海区风浪实测资料,阐述了南沙海区波高的分布规律。应用相关分析法,通过多元回归计算,得出波要素与风速、风时之间的关系。对波高、波周期的相互关系作了统计分析并利用永署礁海洋观测站1990年1～7月的实测资料对计算结果作了验证。结果表明,南沙海区波高、波周期的计算值与实测值基本吻合。  相似文献   

Characteristics of Strain Release before Large Earthquakes of M≥7. 0 in the Chinese Mainland     

Jiang Haikun  Miao Qingzhuang  Dong Xiang  Wu Qiong  Li Mingxiao  Song Jin 《中国地震研究》2010,24(1):1-12

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   

汶川地震近场加速度基本参数的方向性特征   总被引：6，自引：0，他引：6       下载免费PDF全文

胡进军  谢礼立 《地球物理学报》2011,54(10):2581-2589

以2008年5月12日的Ms8.0级汶川地震强震记录为基础,根据场地条件和断层距,选取198组三分量近场加速度记录,按照台站相对于破裂传播方向的位置将其划分为破裂前方和破裂后方两类场点.为了考虑破裂传播的方向性和地震辐射图对地震动不同分量的影响,将每组地震动的两个正交水平分量旋转成为垂直断层走向和平行断层走向的分量,然...  相似文献   

岫岩5.4级地震前后尾波振动持续时间比的演化特征   总被引：1，自引：0，他引：1  

曹凤娟  孙文福  李芳  于龙伟  于笑非 《东北地震研究》2003,19(3):18-23

本文在前人工作的基础上，从地震波的动力学特性出发，利用尾波振动持续时间比τH/τv方法，对1999年11月29日岫岩Ms5．4地震前后地震活动的演化特征进行了详细研究。结果发现在岫岩Ms5．4地震前，距震中相对较近台站记录到的尾波振动持续时间比一rH／TV存在一定程度的异常显示，而距震中较远外围地区的台站记录到的一τH／τv震前无明显的异常反应。认为尾波振动持续时间比τH／τv从统计意义上提供了研究介质物理性质的较好方法，对短临地震预报具有一定的参考意义。  相似文献   

2013年4月20日四川芦山地震强地面运动三要素特征分析   总被引：14，自引：0，他引：14       下载免费PDF全文

任叶飞  温瑞智  周宝峰  黄旭涛 《地球物理学报》2014,57(6):1836-1846

2013年4月20日四川省芦山县境内发生M_S7.0级地震,地震造成196人死亡,21人失踪,11470人受伤,震中最大烈度IX.地震发生后,中国数字强震动观测网络和成都市地震烈度速报网络分别获得了114组和63组3分量强震动记录.记录得出在近场加速度幅值较高,与汶川地震峰值相当,然而震害却不严重.本文介绍了这些记录的基本情况,分析了其地震动三要素（幅值、持时、频谱）特征以及对建筑物结构的潜在影响.分析结果表明：芦山地震PGA（地震动峰值加速度）与我国常用的霍俊荣地震动预测方程较一致,高于即将颁布的第五代区划图中使用的预测方程;PGV（地震动峰值速度）与第五代区划图中使用的预测方程基本一致;Significant持时和Bracketed持时高于全球经验预测方程,且Bracketed持时衰减显著慢于全球平均水平;典型11个幅值较大记录的5%阻尼比加速度反应谱峰值周期都在0.1~0.2 s范围内,且谱值远高于规范设计谱,但在周期0.3 s之后迅速下降至设计谱以下;芦山地震地震动PGV值较小以及对应我国中小城市和城镇主要建筑物的结构自振周期范围（0.3~1 s）内加速度反应谱远低于规范设计谱,可用于解释其震害相对较轻的原因.  相似文献   

Scaling relations of moment magnitude,local magnitude,and duration magnitude for earthquakes originated in northeast India          下载免费PDF全文

Dipok K. Bora 《地震科学（英文版）》2016,29(3):153-164

In this study, we aim to improve the scaling between the moment magnitude (M _W), local magnitude (M _L), and the duration magnitude (M _D) for 162 earthquakes in Shillong-Mikir plateau and its adjoining region of northeast India by extending the M _W estimates to lower magnitude earthquakes using spectral analysis of P-waves from vertical component seismograms. The M _W-M _L and M _W-M _D relationships are determined by linear regression analysis. It is found that, M _W values can be considered consistent with M _L and M _D, within 0.1 and 0.2 magnitude units respectively, in 90 % of the cases. The scaling relationships investigated comply well with similar relationships in other regions in the world and in other seismogenic areas in the northeast India region.  相似文献   

Strong ground motion modelling of causative fault for the 2002 Avaj earthquake, Iran   总被引：1，自引：0，他引：1  

H. Hamzehloo 《Tectonophysics》2005,409(1-4):159-174

The suitability of a very fast method for obtaining synthesizing accelerograms has been demonstrated for a hybrid simulation technique of source wavelet and acceleration envelope waveform for the 2002 Avaj earthquake. This method is based on the amplitude modeled white noise and envelope waveform. The estimation of peak acceleration from a preliminary simulated record is based on using modeling parameters of rupture plane instead of empirical relations for peak acceleration. Based on comparison between observed and simulated strong ground motion data, a fair agreement is observed between simulated and observed records up to distances 40 km for peak acceleration and duration. The most important feature of the recorded strong motion is decay up to a distance of 40 km which is due to direct upgoing shear waves. At distance of 50 to 60 km peak acceleration increase, which is due to postcritical reflection from velocity gradient in the lower crust. A flat trend is observed for peak acceleration at distance of 60 to 100 km. The simulation indicates that the rupture is started at depth of 8 km and propagated from northwest to southeast. The causative fault for the 2002 Avaj earthquake shows similar mechanism to the 1962 Buin-Zahra earthquake.  相似文献   

九寨沟M_S7.0地震强地震动模拟及漳扎镇地震动强度预测          下载免费PDF全文

李宗超  高孟潭  陈学良  吴健  周红  李铁飞  李昌珑  吴清  卜春尧 《地球物理学报》2019,62(7):2567-2581

破坏性地震强度预测可用于工程领域抗震设防以及地震危险性分析评估,是防震减灾中一项很重要的基础工作.为了再现九寨沟地震的地震动强度,评估缺失强震记录的九寨章扎台站的地震动强度,本文用经验格林函数法对九寨沟地震进行了数值模拟.选取了震源周边地震动峰值加速度超过10 Gal的10个强震台站进行模拟.因未得到九寨沟地震的余震,初次尝试将汶川地震和定西地震的余震作为格林函数模拟九寨沟地震.模拟结果整体上可以反映各台站地震动的强度特征,尤其是地震动高频成份拟合较好.模拟值的地震动峰值加速度、时程数据、反应谱等与观测值拟合较好.预测结果显示漳扎镇的地震动峰值加速度值约为180~200 Gal.预测结果也表明在缺少大震的余震记录时,经验格林函数法使用其他大震的余震同样可以再现目标地震的强度特征.本研究也为经验格林函数方法在缺乏小震记录地区的使用积累了经验.最后总结了格林函数的选取标准,为经验格林函数方法来预测未来强震动特征积累了经验.  相似文献