云南地震台网与中国地震台网、美国地震台网测定震级的对比     

杨晶琼  杨周胜  许亚吉  秦敏  张会苑  张国权 《地震研究》2020,(1):57-63

利用云南地震台网全面数字化之后(2008-2017年)的记录资料,按照《地震震级的规定》(GB17740-2017)规定的测定方法,对云南地震台网记录的ML≥4. 0地震,重新人工测量其宽频带面波震级MS(BB)和矩震级Mw,与中国地震台网测定的MS7以及美国地震台网(NEIC)测定的MW(NEIC)进行对比分析。结果表明:①MS(BB)和MS7测量方法相同,量规函数相等,两者一致性最好。②对于面波震级与矩震级,当MW在3. 5左右时,MS7,MS(BB)与MW一致性最好;MW<3. 5时,MS7和MS(BB)均小于MW;MW> 3. 5时,MS7和MS(BB)大于MW。③MS(BB)与美国地震台网相比较,MS(BB)在5. 5和6. 0左右时,与MW(NEIC)一致性最好,几乎相等;MS(BB)<5. 5时,MS(BB) 6. 0时,MS(BB)> MW(NEIC)。④MW和MW(NEIC)之间存在偏差,MW整体小于MW(NEIC)。  相似文献   

张掖M_S 5.0地震前山丹地震台地电阻率异常分析     

王志栋  雷正超  寇俊阳  张成军  吴敏  安张辉 《地震地磁观测与研究》2020,41(4):83-89

通过分析山丹地震台地电阻率资料发现,在2019年9月16日张掖M_S 5.0地震前地电阻率出现了明显的异常变化,即2016年11月开始EW测道观测数据出现年变畸变异常,年变幅度几近消失,该异常持续至2018年年底。采用傅里叶滑动去年变分析发现,同段年变消失,去年变后数值出现超阈值异常;采用矩平处理方法分析发现,2016年11月至2018年10月观测值小于矩平拟合值,出现低值异常。研究表明,该异常可能与2019年9月16日张掖M_S 5.0地震有关。  相似文献   

基于重力梯度张量曲率的边界识别          下载免费PDF全文

汤井田  史庆斌  胡双贵  任政勇  肖晓  曲毅  杨磊  侯振隆  庞成 《地球物理学报》2019,62(5):1872-1884

重力梯度张量曲率目前广泛用于重力数据的处理和解释中.为了拓宽重力梯度张量曲率的应用,本文回顾了重力梯度张量曲率的定义,从等位面的曲率定义出发,讨论了正确计算曲率的测量参考系及局部旋转的相关理论,并以单个球体和棱柱体为例来说明曲率的正确计算方式.然后,在正确计算重力梯度张量曲率的基础上,将重力梯度张量曲率应用到重力数据的边界识别中,通过理论模型和实际数据详细分析和比较了各种曲率在重力边界识别中的应用效果.结果表明:基于等位面的局部旋转坐标系是各种曲率正确计算的先决条件,纠正了曲率计算的误区;在边界识别中,局部坐标系下所计算的高斯曲率进行边界识别能够较好的圈定地下地质体的边界.  相似文献   

Angle-domain common-image gathers in reverse-time migration by combining the Poynting vector with local-wavefield decomposition     

Wu Chengliang  Wang Huazhong  Zhou Yang  Hu Jiangtao 《Geophysical Prospecting》2019,67(8):2035-2060

Angle-domain common-image gathers are an important tool in the post-processing of seismic images and for reservoir characterization. The generation of angle gathers is a very important issue when dealing with angle-domain images. Efficiency and robustness are the main concerns in the generation of angle gathers. In this paper, we propose two methods for producing angle gathers based on the implementation of a reverse-time migration. In the hybrid method, we adopt the local-plane-wave decomposition method to extract the local plane waves and obtain two possible opposite propagation directions in the time-wavenumber domain. Then, Poynting vectors are used to determine the correct propagation direction. The hybrid method achieves a satisfactory balance between robustness and computational efficiency. Furthermore, in the improved hybrid method, additional computational acceleration is obtained by separating the overlapping and non-overlapping wavefield areas. The hybrid method is only applied in these areas with overlapping wave fronts, and the Poynting-vector-based method is adopted in the other areas. The location of the overlapping events is determined using the eigenvalues of the structural tensor. Finally, the two-dimensional synthetic and field examples demonstrate the effectiveness of both methods.  相似文献   

用应变地震观测求解震源矩张量的基本原理          下载免费PDF全文

邱泽华  唐磊  赵树贤  郭燕平 《地球物理学报》2020,63(2):551-561

震源机制解,即对地震矩张量的推断,对于地震研究具有至关重要的意义.应变地震观测是张量观测,与摆式地震仪的位移矢量观测不同,可以为地震研究提供新的数据源.本文讨论用应变地震观测求解震源矩张量的基本原理.在距离震源足够远的地方,地震波可以看成平面波,其性质决定于震源矩张量.假设平面地震波的应变张量可以由震源矩张量通过坐标变换计算得到,就可以通过观测应变地震波求解震源机制.这个假设至少对于双力偶震源机制是成立的.由此可以证明,在理想的无限介质中,只要有两个以上不同地点的应变地震波观测,就可以解出震源矩张量.这为解决震源机制问题提供了新的方法.目前的地震矩张量求解方法需要两方面的条件:或者需要很多观测点(例如体波反演),或者需要长周期地震波资料(例如面波反演).这些方法只适用于分析比较大的地震.对于小震,因为通常其震中周围不会有足够多的摆式地震仪观测点观测到其地震波,而地震波周期又短,难以利用传统方法给出可靠的震源机制解,所以只需少数观测点就能求解震源矩张量的新方法特别有意义.用应变地震观测求解震源机制,可以给出更为精确的结果.  相似文献   

Determination of moment tensor and location of microseismic events under conditions of highly correlated noise based on the maximum likelihood method          下载免费PDF全文

E.V. Birialtsev  D.E. Demidov  E.V. Mokshin 《Geophysical Prospecting》2017,65(6):1510-1526

We examine the problem of localization of a single microseismic event and determination of its seismic moment tensor in the presence of strongly correlated noise. This is a typical problem occurring in monitoring of microseismic events from a daylight surface during producing or surface monitoring of hydraulic fracturing. We propose a solution to this problem based on the method of maximum likelihood. We discuss mathematical aspects of the problem, some features and weak points of the proposed approach, estimate the required computing resources, and present the results of numerical experiments. We show that the proposed approach is much more resistant to correlated noises than diffraction stacking methods and time reverse modeling.  相似文献   

Earthquake‐induced loss assessment of steel frame buildings with special moment frames designed in highly seismic regions          下载免费PDF全文

Seong‐Hoon Hwang  Dimitrios G. Lignos 《地震工程与结构动力学》2017,46(13):2141-2162

This paper discusses an analytical study that quantifies the expected earthquake‐induced losses in typical office steel frame buildings designed with perimeter special moment frames in highly seismic regions. It is shown that for seismic events associated with low probabilities of occurrence, losses due to demolition and collapse may be significantly overestimated when the expected loss computations are based on analytical models that ignore the composite beam effects and the interior gravity framing system of a steel frame building. For frequently occurring seismic events building losses are dominated by non‐structural content repairs. In this case, the choice of the analytical model representation of the steel frame building becomes less important. Losses due to demolition and collapse in steel frame buildings with special moment frames designed with strong‐column/weak‐beam ratio larger than 2.0 are reduced by a factor of two compared with those in the same frames designed with a strong‐column/weak‐beam ratio larger than 1.0 as recommended in ANSI/AISC‐341‐10. The expected annual losses (EALs) of steel frame buildings with SMFs vary from 0.38% to 0.74% over the building life expectancy. The EALs are dominated by repairs of acceleration‐sensitive non‐structural content followed by repairs of drift‐sensitive non‐structural components. It is found that the effect of strong‐column/weak‐beam ratio on EALs is negligible. This is not the case when the present value of life‐cycle costs is selected as a loss‐metric. It is advisable to employ a combination of loss‐metrics to assess the earthquake‐induced losses in steel frame buildings with special moment frames depending on the seismic performance level of interest. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

新的震级国家标准的技术要点与主要特点     

刘瑞丰  陈运泰  王丽艳 《地震地磁观测与研究》2017,39(1):1-11

新的震级国家标准《地震震级的规定》（GB17740—2017）是一个国家强制性标准,已于2017年5月12日由国家质量监督检验检疫总局、国家标准化管理委员会发布。本文介绍了震级国家标准修订的必要性,以及新的震级国家标准的主要内容、技术要点和主要特点,以便于在实际工作中能更好地应用。  相似文献   

大地电磁资料精细处理和二维反演解释技术研究(五)——利用阻抗张量成像识别大地线性构造   总被引：9，自引：6，他引：3       下载免费PDF全文

陈小斌  郭春玲 《地球物理学报》2017,60(2):766-777

大地线性构造往往与块体或物性的边界、断裂的几何延伸相关联,是地学研究的重要目标构造.在大地电磁法中,传统的方法是通过反演得到的电性结构的差异来解译线性构造,是一种间接分析方法.由于线性构造发育处走向和倾向明显,二维性较其他地方一般会更强,故而在阻抗张量成像分析中,相应的二维有效因子就会比较大,最佳主轴统计分布会更加明显.据此,本文利用大地电磁阻抗张量成像(包括最佳主轴统计成像、构造维性成像)来探测识别大地线性构造.本文首先通过三维理论模型的研究结果来验证这一技术在线性结构探测中的有效性,然后将其应用于郯庐断裂带南段实测剖面的具体分析中,展示了这一技术在线性构造探测中的实用性及其数据处理与分析过程.本文研究表明,大地电磁阻抗张量成像技术可独立于反演为地质解释尤其是线性构造的解释提供诸多参考信息.  相似文献   

MRELBP特征、Franklin矩和SVM相结合的遥感图像建筑物识别方法     

周建伟  吴一全 《测绘学报》2020,49(3):355-364

为了进一步提高遥感图像建筑物区域的识别精度,提出了一种基于中值稳健扩展局部二值模式(median robust extended local binary pattern,MRELBP)、Franklin矩和布谷鸟优化支持向量机(support vector machine,SVM)的分类方法。首先,通过MRELBP特征算子计算图像块的纹理特征向量,并根据Franklin矩得到形状特征向量,组合图像块的纹理特征向量和形状特征向量得到综合特征向量;然后,利用训练样本对SVM进行训练,同时由布谷鸟搜索算法对SVM的核函数参数和惩罚因子进行优化;最后,通过训练好的SVM得到建筑物区域识别结果。通过30组试验的结果表明,与基于三原色(red green blue,RGB)和SVM的分类方法、基于LBP和SVM的分类方法、基于Zernike矩和SVM的分类方法相比,本文提出的方法所识别的遥感图像建筑物区域准确度更高。  相似文献