前兆异常与强震时空点的研究   总被引：2，自引：0，他引：2  

杨桂芬  王华林 《地震研究》1999,22(3):221-227

本文研究了云南三次７ 级以上强震前的小震活动, 前兆异常总台项频数变化, 地下水时空特征。得出在大震前３ ～６ 个月前兆异常台项总频数的升高现象与３０ ～３９ 级小震向震中区收缩的时间大致同步, 可能是大震前的异常从短期向短期临震过渡的时间标志。震前１ ～３ 个月出现的前兆台项总频数异常峰值和水位、水氡的场兆现象则是异常进入短期临震的时间; 峰值回落是震源区进入临震状态的时间。  相似文献   

前兆场动态演化与强震成组活动     

李丽  张国民 《中国地震》1999,15(4):310-323

本文选取了我国两个前兆台网较密集的地区进行了前兆异常场时空扫描。这两个地区分别是南北带中南段(20°～35°N,95°～110°E)和华北地区(36°～42°N,110°～120°E)。在空间上以05°×05°为一个窗口,025°为一个滑动步长;在时间上以4个月为一个窗口,1个月为滑动步长,对这两个地区分别从1994年1月和1995年1月开始进行前兆异常密度时空扫描。所用前兆异常来自中国地震局分析预报中心全国震情研究室和首都圈震情研究室的《月会商纪要》。针对所得扫描结果,试图用一种具有鲜明物理机制的构造块体孕震模型来解释前兆场演化的物理机制。在孕震块体模型中,设定各潜在震源区的强度是随机分布的,由于模型中各孕震体的强度不均匀,因而在给定边界条件后,模型系统出现应力分布不均匀的状态。在系统边界定常应变速率的作用下,模拟的孕震体在应力超过自身静摩擦强度后发生破裂。但由于模型系统是含有耦合作用的网络结构,各孕震体的应力可以相互传导和相互影响,因而在孕震系统应力场发展演化和震源孕育破裂之间呈现为相当复杂的图像。多数震源的破裂是应力增高造成的,但也有一些震源在高应力作用下没有发生破裂,另外有部分应力并不十分高的孕震体由于受周围地震应力调整的影响而发生破裂。以上结果为前兆异常与地  相似文献   

Study on the Criterion of the Correlation between Deformation Precursors and Earthquakes   总被引：1，自引：0，他引：1  

NIU Anfu  ZHAO Jing  YAN Wei  ZHANG Jing  ZHANG Lingkong  YUAN Zhengyi  YUE Chong 《中国地震研究》2020,34(3):394-405

The relationship between pre-seismic anomalous changes and earthquakes is one of the most basic information to comprehend the process of earthquake preparation and conduct earthquake prediction research. However, few researchers have carried out relevant investigations for a long time. In this paper, the distribution characteristics of deformation anomalies before the Wenchuan earthquake are analyzed, and the widespread distribution area is discussed. Based on previous studies, we improve the relationship between anomaly duration t and magnitude M by introducing distance D. The new model is characterized by lower magnitude fitting error, making it possible to establish the correlation between deformation precursors and earthquakes. The correlation standard between precursors and earthquakes here is defined as Niu''s criterion, which is applied to analyze and interpret the relationship between the short-term anomalies of Hongliuxia fault leveling and the Wenchuan and Jiuzhaigou earthquakes.  相似文献   

The physical implication of coda amplitude ratio and its possible application     

Tian-Zhong Zhang  Yun-Sheng Ma  Rong-Liang Huang 《地震学报(英文版)》1998,11(4):441-448

The physical implication of coda amplitude ratio is discussed in term of energy ratio. The digitized data recorded at the station of Beijing Telemetered Seismograph Network between 1989 and 1990 are used to calculate amplitude ratios of coda to direct S wave, and energy ratios. The spectral energy ratios are used to estimate the coda Q and mean free path l in the Beijing area, as well as the two quality factors Q _i and Q _S separately due to intrinsic absorption and scattering attenuation. The decay of seismic waves in their propagation seems mainly resulted from the intrinsic absorption in Beijing region. The temporal variations of amplitude ratio and energy ratio at Changli station during the above two years are inspected; some of them largely depart from their mean value. It may reflect the seismogenic process, but using the data lasting longer time with more case histories needs further study. This study is sponsored by the Key Project of State Science and Technology of China, No. 96-918.  相似文献   

Temporal changes in shear-wave splitting at an isolated swarm of small earthquakes in 1992 near Dongfang, Hainan Island, southern China   总被引：14，自引：0，他引：14  

Yuan Gao  Peide Wang  Sihua Zheng  Ming Wang  Yuntai Chen  & Huilan Zhou 《Geophysical Journal International》1998,135(1):102-112

An isolated swarm of small earthquakes occurred in 1992, near Dongfang on Hainan Island, southern China. The Institute of Geophysics, State Seismological Bureau of China, monitored the swarm with five DCS-302 digital accelerometers for three months from 1992 June 1. 18 earthquakes, with magnitudes M _L ranging from 1.8 to 3.6, were well located by five stations, and shear-wave splitting varying azimuthally was analysed on 27 seismic records from these events. The mean polarization azimuth of the faster shear wave was WNW. Time delays between the split shear waves at two stations varied with time and space. The time delays at one station fell abruptly after earthquakes of magnitudes 3.1 and 3.6, but did not change significantly at the second station. This behaviour is consistent with the delay-time changes being caused by changes in the aspect ratio of vertical liquid-filled (EDA) cracks. Thus, the variation in shear-wave-splitting time delay could be due to changes in crustal stress related to nearby small-magnitude earthquake activity. The connection between earthquake activity and crustal stress variation measured by shear-wave splitting leaves the door open for possible observations of crustal stress transients related to the onset of an earthquake; however, our data cannot be considered as definite evidence for such precursors.  相似文献   

Simulated Sensitivity of Ozone Generation to Precursors in Beijing during a High O3 Episode     

Meng CUI  Xingqin AN  Li XING  Guohui LI  Guiqian TANG  Jianjun HE  Xin LONG  Shuman ZHAO 《大气科学进展》2021,38(7):1223-1237

This study uses the WRF-Chem model combined with the empirical kinetic modeling method (EKMA curve) to study the compound pollution event in Beijing that happened in 13-23 May 2017. Sensitivity tests are conducted to analyze ozone sensitivity to its precursors, and to develop emission reduction measures. The results suggest that the model can accurately simulate the compound pollution process of photochemistry and haze. When VOCs and NOx were reduced by the same proportion, the effect of O3 reduction at peak time was more obvious, and the effect during daytime was more significant than at night. The degree of change in ozone was peak time > daytime average. When reducing or increasing the ratio of precursors by 25％ at the same time, the effect of reducing 25％ VOCs on the average ozone concentration reduction was most significant. The degree of change in ozone decreased with increasing altitude, the location of the ozone maximum change shifted westward, and its range narrowed. As the altitude increases, the VOCs-limited zone decreases, VOCs sensitivity decreases, NOx sensitivity increases. The controlled area changed from near-surface VOCs-limited to high-altitude NOx-limited. Upon examining the EKMA curve, we have found that suburban and urban are sensitive to VOCs. The sensitivity tests indicate that when VOCs in suburban are reduced about 60％, the O3-1h concentration could reach the standard, and when VOCs of the urban decreased by about 50％, the O3-1h concentration could reach the standard. Thus, these findings could provide references for the control of compound air pollution in Beijing.  相似文献   

A method developed for predicting potential precursors of earthquakes     

Guo Hang 《地球空间信息科学学报》2013,16(2):47-52

This paper describes the methodology used to eliminate environmental effects to a time series of short distance (24m) leveling across a geological fault in order to detect potential precursors of earthquakes from the residual time series. First, linear trends and periodic signals are removed from the observations with the help of a recursive least squares method. Then, a controlled autoregression model is used to predict the environmental contribution due to precipitation and evaporation. The difference between the leveling data and these predictions are considered to be due to endogenic crustal processes. Applying this methodology to leveling data of approximately 13 years at Niukouyu crustal deformation station near Beijing reveals an anomalous deformation before the Tangshan earthquake (M7.8), which has its epicenter about 180 km from the survey site. However, in the time period considered, another anomaly occurred which cannot be related directly to a seismic event.  相似文献   

强震预警指标工作方法的实践与研究     

牟雅元 《国际地震动态》2005,(9):1-5

通过近年来研制川南及邻区(25°40′~29°40′N,100°~104°E)可供今后参考的强震(三色)“预警指标”。最大收获是初步探索出了一套完整的研制和检测“预警指标”的工作方法,供大家参考。  相似文献   

Geospace perturbations induced by the Earth: The state of the art and future trends     

《Physics and Chemistry of the Earth》2015

A systematic multi-parameter and multi-platform approach to study the slow process of earthquake preparation is fundamental to gain some insights on this complex phenomenon. In particular, an important contribution is the integrated analysis between ground geophysical data and satellite data. In this paper we review some of the more recent results and suggest the next directions of this kind of research. Our intention is not to detect a particular precursor but to understand the physics underlying the various observations and to establish a reliable physical model of the preparation phase before an impending earthquake. In this way, future investigation will search for suitable fore-patterns, which the physical model of multi-layers coupling predicts and characterizes by quasi-synchronism in time and geo-consistency in space. We also present alternative explanations for some anomalies which are not actually related to earthquakes, rather to other natural or anthropic processes.  相似文献   

VLF/LF signal studies of the ionospheric response to strong seismic activity in the Far Eastern region combining the DEMETER and ground-based observations     

《Physics and Chemistry of the Earth》2015

The paper presents the results of a joint analysis of ground-based and satellite observations of very low-frequency and low-frequency (VLF/LF) signals during periods of strong seismic activity in the region of Kuril Islands and Japan in 2004–2010. Ground and satellite data was processed using a method based on the difference between the real signal in nighttime and that of a model. The results of the analysis show a good correlation between ground-based and satellite data for several cases of strong (M ⩾ 6.8) earthquakes.  相似文献