Relocation of Early and Late Aftershocks of the 2001 Bhuj Earthquake Using Joint Hypocentral Determination (JHD) Technique: Implication toward the Continued Aftershock Activity for more than Four Years     

Prantik Mandal  R. Narsaiah  B. Sairam  C. Satyamurty  I. P. Raju 《Pure and Applied Geophysics》2006,163(8):1561-1581

We employed layered model joint hypocentral determination (JHD) with station corrections to improve location identification for the 26 January, 2001 M_w 7.7 Bhuj early and late aftershock sequence. We relocated 999 early aftershocks using the data from a close combined network (National Geophysical Research Institute, India and Center for Earthquake Research Institute, USA) of 8–18 digital seismographs during 12–28 February, 2001. Additionally, 350 late aftershocks were also relocated using the data from 4–10 digital seismographs/accelerographs during August 2002 to December 2004. These precisely relocated aftershocks (error in the epicentral location<30 meter, error in the focal depth estimation < 50 meter) delineate an east-west trending blind thrust (North Wagad Fault, NWF) dipping (~ 45°) southward, about 25 km north of Kachchh main land fault (KMF), as the causative fault for the 2001 Bhuj earthquake. The aftershock zone is confined to a 60-km long and 40-km wide region lying between the KMF to the south and NWF to the north, extending from 2 to 45 km depth. Estimated focal depths suggest that the aftershock zone became deeper with the passage of time. The P- and S-wave station corrections determined from the JHD technique indicate that the larger values (both +ve and -ve) characterize the central aftershock zone, which is surrounded by the zones of smaller values. The station corrections vary from −0.9 to +1.1 sec for the P waves and from −0.7 to +1.4 sec for the S waves. The b-value and p-value of the whole aftershock (2001–2004) sequences of M_w ≥ 3 are estimated to be 0.77 ± 0.02 and 0.99 ± 0.02, respectively. The p-value indicates a smaller value than the global median of 1.1, suggesting a relatively slow decay of aftershocks, whereas, the relatively lower b-value (less than the average b-value of 1.0 for stable continental region earthquakes of India) suggests a relatively higher probability for larger earthquakes in Kachchh in comparison to other stable continental regions of the Indian Peninsula. Further, based on the b-value, mainshock magnitude and maximum aftershock magnitude, the Bhuj aftershock sequence is categorized as the Mogi's type II sequence, indicating the region to be of intermediate level of stresses and heterogeneous rocks. It is inferred that the decrease in p-value and increase in aftershock zone, both spatially as well as depth over the passage of time, suggests that the decay of aftershocks perhaps could be controlled by visco-elastic creep in the lower crust.  相似文献   

SHORT COMMUNICATION A PROGRAM FOR THE SIMULTANEOUS POTENTIOMETRIC DETERMINATION OF PROTONATION CONSTANTS AND ELECTRODE CALIBRATION PARAMETERS     

J.J.BAEZA  G.RAMIS  C.MONGAY 《地理学报(英文版)》1988,(Z1)

A program for the potentiometric determination of the protonation constants of mononuclear polyproticsubstances is described.A maximum of twelve parameters can be determined simultaneously,includingup to six protonation constants,four electrode calibration parameters,the protolysis constant of thesolvent and the titrant concentration.Optimization is carried out by using the non-simplifiedNewton-Raphson method,which is potentiated by the Marquardt algorithm and a distance speeding-upcoefficient.A direct search method is also used to improve the initial set of values.Variances arecalculated very accurately,since the real Hessian function is used.Statistical weights and ionic strengthcorrections are also considered,The program has been tested by using simulated titration curves ofpolyprotic acids with close constants.  相似文献   

陕西省丹凤地区商丹断裂南侧糜棱岩的岩石学研究     

胡能高  安三元 《地球科学与环境学报》1989,(3)

以往都将研究区内商丹断裂南侧的岩石定为角岩化碎屑岩或火山岩,划归泥盆系青石垭组或加里东蛇绿岩套。笔者认为这些岩石是一套糜棱岩,不是一个独立的地层单位。对该区的长英质、富铝质、斜长角闪质和碳酸盐质四类糜棱岩,分别做了岩相学特征描述。通过化学成分、矿物成分、碎斑矿物特征和变余构造恢复了各种糜棱岩的原岩。并讨论了这些原岩的时代归属,认为这些原岩分别来自秦岭群、丹凤群和中泥盆统,说明有不同时代、不同成因的地质体卷入了这条韧性剪切带。  相似文献   

测定水中硫酸根方法的概述   总被引：16，自引：1，他引：16  

宋金如  刘淑娟  朱霞萍 《华东地质学院学报》2002,25(2):154-158

介绍了测定水中硫酸根的方法和几种常用方法在水质分析中的应用。  相似文献   

汕头地区地壳平均波速比的联合测定     

刘特培 《华南地震》1992,12(2):38-41

本文根据汕头传输台网测定的96次地震走时数据,用联合测定法计算了该区地壳波速比,得到地壳平均波速比为1.707±0.005。此值较华南区域平均波速比1.692略高。因研究时段区内无M≥5级地震,故1.707±0.005应视为该区地壳波速比正常背景值。  相似文献   

火花源质谱法测定高纯银粉中六个微量元素     

周之荣  李炳林 《华东地质学院学报》1995,18(4):381-384

本文利用同位素稀释法和内标法相结合，建立了火花源质谱法同时测定高纯银粉中六个微量元素的分析方法，对通常使用的内标公式进行了扩展、使其更为普遍适用，方法测定灵敏度可达０．１μｇ／ｇ，相对标准偏差为９．３％￣１６．５％。  相似文献   

用ASTER数据提取云南个旧西区矿化蚀变信息   总被引：2，自引：0，他引：2  

陈小云  胡光道 《云南地质》2008,27(4):502-508

以ASTER影像为数据源、野外实测波谱数据为参考,用光谱角分类法（SAM）在个旧矿区提取矿化蚀变信息。为剔除假“异常”信息,用ASTER热红外波段的比值计算定义硅酸盐、碳酸盐和超基性岩指数作RGB合成得反应岩性信息的影像,据此确定西区重点研究区。在此区域再次用SAM提取矿化蚀变信息,结合用ASTER短波红外数据的比值计算增强的构造信息,分析提取的重点研究区矿化蚀变信息结果,为该矿区找矿工作提供了参考。  相似文献   

EH-4连续电导率剖面法在金牛厂铅锌矿的应用   总被引：1，自引：1，他引：0  

曾玉娇  李文尧  赵会会  刘慧鹏  朱杰勇 《云南地质》2008,27(4):491-495

金牛厂铅锌矿产状陡、下延不清,采用其他物探方法效果不够好,本文介绍在该区开展EH4方法有效性研究及其成效。  相似文献   

原子荧光光度法测定地质化探样品中的砷、锑、铋     

刘瑛 《江苏地质》2003,27(2):92-93

原子荧光光度法分析As、Sb、Bi已被广泛应用，但由于仪器没有色散系统，所以干扰因素较多。阐述了原子荧光光度分析法中常见的干扰及其消除方法。方法简单、快速、灵敏、低耗。  相似文献   

The determination of total dissolved free primary amines in seawater: Critical factors, optimized procedure and artefact correction     

Alain Aminot  Roger Krouel 《Marine Chemistry》2006,98(2-4):223-240

The paper reviews the methods described in the literature for the determination of total dissolved free primary amines (TDFPA) by fluorescence. A wide set of reaction conditions can be found, but they rely on few experiments for their validation. Among fluorogenic compounds, o-phthaldialdehyde (OPA) is more sensitive than fluorescamine and was thus examined here. However, the use of mercaptoethanol (ME) in the reaction (as an additional derivatization compound) is able to generate unreliable results, in particular when standardization relies on glycine. We suggest replacing ME with 3-mercaptopropionic acid (MPA) which induces more stable and comparable fluorescence among amine compounds. A systematic study was therefore undertaken to define reagent concentrations and pH effects on the reaction rates for a variety of primary amines with particular focus on amino acids. The reaction rate is increased by increasing OPA concentration and pH, but slowed by excess MPA. Ammonium interference is influenced by several factors, but spectral investigation showed that the choice of conditions can drastically reduce it. The magnitudes of natural and OPA-induced background fluorescence signals have been assessed in various mediums and it is shown that their contribution to the signal amounts to a large fraction, when not most, of the measured fluorescence. A segmented flow method is proposed with a protocol for adequate correction of biases.  相似文献