The ultra-low-frequency magnetic disturbances associated with earthquakes

The ultra-low-frequency (ULF) electromagnetic emission is recently recognized as one of the most promising candidates for short-term earthquake (EQ) prediction. This paper reviews previous convincing evidence on the presence of ULF emissions before three major EQs. Then, we present further statistical study on the ULF occurrence, our networks of ULF monitoring in different spatial scales in Japan and finally we present several signal processings to identify the seismogenic emissions by showing latest results for recent large EQs.     

震前深井电磁短临前兆信息的观测和研究

本文应用大量震例研究了地震前深井电磁波短临前兆信息。研究结果表明，在１．９和２７ｋＨｚ信道上，地震前２－４个月和１０－６Ｏ天，可观测到短临型、短期型和临震型三种电磁波信号。电磁信号增强时段与孕震区小震频度增强同步，表明这些信号可能与孕震区微破裂有关。本文还利用信息包源偶全体模型定量计算了组成变化的电磁场的准静场、感应场、辐射场随观测距离及方位的变化，据此对观测结果进行了初步解释。     

震前深井电磁短临前兆信息的观测和研究

本文应用大量震例研究了地震前深井电磁波短临前兆信息。研究结果表明，在１．９和２７ｋＨｚ信道上，地震前２－４个月和１０－６０天，可观测到短临型，短期型和临震型三种电磁波信号。电磁信号增强时段与孕震区小震频度增强同步，表明这些信号可能与孕震区微破裂有关。本文还利用信息源偶电体模型定量计算了组成变化的电磁场的准静场，感应场，辐射场随观测距离及方位的变化，据此对观测结构进行了初步解释。     

Determination of directions of horizontal principal stress and identification of active faults in Kachchh (India) by electromagnetic radiation (EMR)

The Kachchh basin in the western India is known for its recent high seismicity. This study presents an application of the geogenic Electromagnetic Radiation (EMR) technique for deciphering the directions of principal horizontal stress in the eastern Kachchh. The principal direction of horizontal stress obtained from EMR differs from those obtained from earthquake focal plane solutions. The major horizontal principal stress based on the EMR study shows an azimuth of N60°E ± 10°. The principal directions of EMR emissions are parallel to the acute bisector of conjugate microcracks. The azimuthal distribution of EMR signal and dimension of microcracks suggest that the EM emissions are transversely polarized.The study also deals with the first application of electromagnetic radiation emissions to identify active fracture planes in sandstones that could become potential active faults later, which might be seismogenic or nonseimogenic. This study is based on linear profiling at six different places across two major faults, the Kachchh Mainland Fault (KMF) and the South Wagad Fault (SWF) in the eastern Kachchh. Anomalously, high EMR emissions are observed in the eastern part of the KMF, indicating active surface deformation.     

地震前的电磁效应

伴随着孕震后期加剧的岩石应变与破裂过程,孕震区及其附近岩层出现机-电能量转换,并相应地激发了某些电磁效应。文中主要分析了地震前的电离层电磁效应,提出了附加电离区的VLF电波检测等监测手段,对强震的短临预测具有较为重要的意义     

地震电磁辐射研究的新进展

本文简要评述了近年来震前电磁辐射研究的新进展和发展方向,以及今后的重点研究课题.已取得的初步结果表明,新发现的震前电磁辐射现象是一种客观存在,并可能是具有良好应用前景的短临前兆.鉴于地震电磁辐射机制及其空间耦合与时间变化过程的复杂性,必须深入探索电磁辐射前兆现象与孕震过程之间的内在联系,使观测工作与理论研究很好地结合起来,并结合多种前兆进行综合诊断.      

孕震区产生电磁辐射的电学模型

震前电磁辐射是一种与孕震活动有关的客观现象,通过讨论孕震区的力学性质和电学性质,提出了孕震区产生电磁辐射的电学模型,并对这个电学模型作了尝试性的探讨。     

电磁辐射与孕震过程的初探

通过1994年青海共和的几次强余震和1999年河南县Ms5.1，玛沁Ms5.0，以及2000年甘肃景泰Ms5.9，兴海Ms6.6级地震前后平安电磁波资料的分析，总结了电磁辐射在进入短临阶段后的一些特征，得出了在孕震过程中电磁辐射异常与地震的关系，并初步探讨了地震电磁辐射源的形成与影响电磁辐射的可能因素。     

Recent advances in the research on seismo-electromagnetic emissions

The paper briefly reviews the recent advances and the main trend, as well as the major subjects for future study in the research on seismo-electromagnetic emissions. The preliminary results obtained show that the recently discovered electromagnetic emission phenomena prior to earthquake events are objective facts and may be prospective precursor applicable for short term earthquake prediction. Considering the complexity of the generation mechanisms, as well as the space coupling and the time variation processes of the seismo-electromagnetic emissions, we must deeply study the essential connection between the precursory emission phenomena and the seismogenic processes. Closely connect the field observations and theoretical research and try to comprehensively diagnose by correlating with other precursors. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 254–258, 1991.     

The Geodynamic Mechanism of the M_S8.0 Wenchuan Earthquake

Located on the east boundary of Qinghai-Xizang (Tibet) Plateau, the M_S8.0 Wenchuan earthquake is the strongest event to hit the active block since the 2001 Kunlun Mountains Pass earthquake. In this study, a simplified source model of the Wenchuan earthquake is constructed based on the deep/shallow tectonic settings and crust/mantle structure features of the Longmenshan thrust fault zone. On the basis of dynamic model abstraction, we construct a system of dynamical equations for the seismogenic process and obtain the analytical expressions of stress and strain in the seismogenic process. A preliminary study of the seismogenic process of the M_S8.0 Wenchuan earthquake, based on the analytical solution of the model and observation of tectonic deformation in the Longmenshan region, indicates that the seismogenic process of the Wenchuan earthquake took place over a period of more than 3200 years. The slow process of seismogeny and the long recurrence period of strong earthquakes are attributed to the low deformation rate of the Longmenshan tectonic zone.     

孕震空区的环境应力特征及其机理探讨

利用地震波资料对几个典型震例孕震空区的环境应力特征进行了研究, 并对其机理进行了探讨。 研究结果显示, 逼近地震的环境应力值高于同时期构成空区的一般性(非主震震源区附近)小震, 发生在未来主震震源区及附近小震的环境应力值较高等。 上述结果的机理可用坚固体模型来解释。 研究结果有助于提高孕震空区的预报效能, 进一步提高对地震孕育过程中力学机理的认识。     

地震空间分维Dq及b值的临震变化特征及其非线性机制分析

对云南省几个不同地区的强震孕震阶段及临震时的地震空间分维Ｄｑ（ｑ＝０，１，２，）及ｂ值进行了计算和研究，发现虽然在孕震阶段各地区的Ｄｑ及ｂ值均有着共同的下降主趋势，但临震时不同区域的Ｄｑ及ｂ的变化形态却存在着差异，大地震可能发生在Ｄｑ及ｂ值均降至最低时，也可能发生在Ｄｑ及ｂ值下降后又回升之时，还可能发生在Ｄｑ回升而ｂ值仍保持最低时。本着重对Ｄｑ及ｂ值的临震变化特征及其个体差异从非线性的角度作了物     

2015年4月25日尼泊尔M_w7.8地震孕育过程分析与震后趋势研判

基于作者提出的孕震断层多锁固段脆性破裂理论及板间地震区划分原则,划分了伊斯兰堡—加德满都地震区.从孕育周期界定与主震事件判识角度,分析了该地震区大(巨)震事件的孕育过程,研判了其未来震情.结果表明:伊斯兰堡—加德满都地震区至少已经历三个完整的孕育周期,是一个Mw8.3~8.6地震危险区;2015年4月25日尼泊尔Mw7.8地震,是该区当前孕育周期第三锁固段损伤累积至峰值强度点时发生的一次标志性大震事件;2015年5月12日尼泊尔Mw7.3地震发生后,该地震区再次处于临界状态,将发生Mw8.0~8.2地震.     

Pre-Seismic Electromagnetic Effects

Along with intense rock strain and rock bursting processes at the late stage of earthquake preparation, mechanical-electrical energy conversion appears in the seismogenic region and its nearby rock formations, which correspondingly stimulate certain electromagnetic effects. The paper mainly analyzes the pre-seismic electromagnetic effect of the ionosphere and proposes a method of monitoring VLF radio waves over the additional ionized region and so on. It is deemed that the method is of significance for short and imminent term prediction of strong earthquakes.     

以菏泽地震为例探讨地震学综合预测方法

在前人提出的地震预测方法基础上提出一种地震学综合预测方法。 首先利用动态图像方法(地震条带与地震空区)大致确定潜在地震危险区; 然后利用中、 强地震产生的库仑应力确定孕震区; 最后利用地震矩快速释放模型和相关长度增长模型判断孕震区是否进入短临状态。 在地震三要素预测中, 发挥地震学典型预测方法的优势, 并且对相关性较小的预测方法的预测结论相互对比、 印证, 以便得出更可靠的预测结果。 文中还利用这种综合预测方法对1983年菏泽5.9级做了简略研究, 结果表明这种综合预测方法的预测结果和菏泽地震基本上是一致的。     

昆仑山口西8.1级地震前后地壳垂直运动的负位错模型

利用昆仑山口西8．1级地震震区外围格尔木一五道梁300km长水准测线在1979,1991和2002年3期垂直形变资料,借助研究改进的负位错模型获取发震构造及其相关断裂的运动、变形特征及应力应变积累部位和强度,对与此次大震有关的区域构造形变背景及可能的震后影响进行了研究。结果表明：1991～2002年相对1979～1991年垂直差异运动及应变积累加速增强的特征与昆仑山口西8．1级地震孕育有关;且这样的一个地壳垂直运动加速过程可能还未因地震发生而结束,发震构造相关的断裂构造部位仍有发生较强地震的可能。     

Modeling of thundercloud VHF/UHF radiation on the lightning preliminary breakdown stage

It is well known that there are two basic parts of electromagnetic emissions from a thunderstorm cloud. The first one is due to a return stroke and the second is generated by microdischarges on the lightning preliminary stage and between successive return strokes. The purpose of this paper is to consider the second part of electromagnetic emissions from thunderstorm clouds in a frequency range from one to hundreds of MHz. A new approach is developed, which is based on a three-dimensional computer simulation of microdischarge activity in thunderstorm clouds. We suggest that microdischarges on the lightning preliminary stage are connected with the growth of internal electric cell structures in a thunderstorm cloud. The characteristic scale of cells ranges from ten to hundred meters. The source of these cells can be a beam-plasma-like instability in the thunderstorm cloud medium where microdischarges appear as a saturation mechanism for this instability. Interaction of neighboring cells leads to the formation of dynamic chains of microdischarges. Following step-by-step computer simulations, we calculate radio emissions from every microdischarge and sum up the wave amplitudes from all intracloud volume at the reception point. The standard model for a separate microdischarge current is adopted, and the electromagnetic radiation is estimated in the far zone. We obtain the waveforms of electromagnetic field, the temporal development of radiation and the number of electromagnetic pulses. We have found that signal statistics and calculated frequency spectra exhibit a universal power-law (fractal) behavior. The results of simulations are found to be in satisfactory agreement with the experimental data, because the model waveforms demonstrate a close similarity to the observed ones. Also the temporal development with the duration of pulse trains from ten to hundreds of microseconds and the microdischarge number rate up to hundreds of thousands per second are in agreement with the corresponding experimental data.     

Seismic hazard of the Northern Apennines based on 3D seismic sources

Seismic hazard has been computed for the Northern Apennines in northern Italy based on a new seismogenic zonation. This zonation considers inclined (dipping) planes as seismogenic sources, defined on the basis of all the seismotectonic information available so far. Although these geometries are extremely rough because they simplify with a few inclined elements the totality of faults constituting a source, this model mimics the tectonic style better than that based on horizontal planes. Nevertheless, for a comparison between the new ground motions obtained and those available in the literature, the plane version of the zonation has been developed, where horizontal areas (the standard seismogenic zones), representing the surficial projection of the inclined planes, are used as seismogenic sources.     

2008年汶川MS8.0地震前定点观测电磁异常回溯性分析

对2008年汶川M_S8.0地震周围定点台站观测的电磁异常的相关研究进行了简要的回顾分析,以期加深对汶川地震孕震过程中电磁异常的解读.震中周围8个地电阻率台站震前出现不同形态的异常变化,结合震后地电阻率变化形态分析,仅近邻地震破裂带的成都和江油台异常变化符合已有的地电阻率孕震异常机理.在4月24日和5月9日大致沿南北地震带出现两条南北走向的低点位移线,成都台地磁转换函数、谐波振幅比、帕金森矢量和垂直极化强度等主要反映了地下介质电性在震前出现的异常变化;断裂带附近的地电场和电磁扰动在震前出现波形畸变和能量增强,距离较远的西昌台阵和天祝—松山台阵内地电场也出现功率谱能量增加和裂隙渗透方位角扰动等短期异常现象,甚至沿龙门山断裂带NE方向1300km外的河北电磁扰动台网震前数月也出现自观测以来最大幅度的异常变化.     

Estimating the validity of the recognition results of earthquake-prone areas using the ArcMap

In 1972, V. Keilis-Borok and I. Gelfand introduced the phenomenological approach based on the morphostructural zoning and pattern recognition for identification of earthquake-prone areas. This methodology identifies seismogenic nodes capable of generating strong earthquakes on the basis of geological, morphological, and geophysical data, which do not contain information on past seismicity. In the period 1972–2018, totally, 26 worldwide seismic regions have been studied and maps showing the recognized earthquake-prone areas in each region have been published. After that, 11 of these regions were hit by earthquakes of the relevant sizes. The goal of this work is to analyze the correlation of the post-publication events with seismogenic nodes defined in these 11 regions. The test was performed using the NEIC earthquake catalog because it uniformly defines the location and magnitudes of earthquakes over the globe. The ArcMap facilities were exploited to plot the post-publication events on the maps showing the recognized seismogenic nodes. We found that about 86% of such events fall in the recognized seismogenic nodes. The performed test proved the sufficient validity of the methodology for identifying areas capable of strong earthquakes and confirms the idea on nucleating strong earthquakes at the nodes.