强震前电磁辐射异常演化特征及其机理探索研究

发布时间：2018-04-15 07:36

本文选题：电磁辐射 + 低频段　；参考：《中国科学技术大学》2017年博士论文

【摘要】：地震在孕育和发生过程中往往会产生低频电磁辐射现象,已被越来越多的强震所观测到,这为地震监测预测提供了一种可能。由于电磁辐射是来自震源的直接信息,电磁波的趋肤深度大于地震震源深度,震前观测到低频电磁辐射源于孕震区的概率很大,且一般又在地震孕育的后期出现。因此,具有短临预测地震的应用前景。本研究基于我国地基电磁台站数据联合空间电磁卫星数据,收集、整理了100多个数字化电磁台站及电磁卫星观测数据,并对台站数据内在质量进行分级评估。对所选用的观测数据,首先进行预处理分析,识别与排除地面及空间各种非震干扰因素影响;然后利用小波变换、极化分析、希尔伯特黄变换、偏振主轴计算、归一化月速率及频谱分析等方法,研究发生在中国大陆地区的典型强震震例,提取地震前较为可靠的电磁辐射异常信息,归纳与总结电磁辐射所显示的各种波形、场强变化及频谱特征等;建立地震电磁场模型,探索地震电磁辐射异常信号形成、孕育及传播机理。利用希尔伯特黄变换方法研究发现,地震前三个月内地磁D分量具有明显异常变化。地磁场极化分析认为,大部分地震前呈上升、振幅增大的异常变化形态。通过地震电磁场模型研究得到了地震前电磁辐射异常在时间上、频段上均表现出阶段性的进程,异常特征遵循了地震孕育、发展及发生规律。对强震前地磁场进行内、外源场分离及等效电流体系反演发现,地震前出现了内、外源场电流体系的同步变化,磁场产生的电流涡焦点向纬向进行偏移,与"地磁低点位移"异常在时间上基本同步。利用归一化月速率方法,对汶川、玉树地震前视电阻率的各向异性进行计算发现,在地震断层带上及附近区域的视电阻率各向异性变化反应更敏感,而断裂带两侧区域反应较弱,在方向上具有显著差异性。对汶川8.0级地震前上空Demeter电磁卫星6条轨道数据分析发现,5月6号电场Ex、Ey分量,磁场Hx、Hy分量在370-400Hz处存在窄频带电磁辐射增强,持续时间约两分钟、5月9号两条经过震源区上空的轨道发现了电场Ex分量幅度增大现象,而5月11号和5月12号异常仍然存在,且地震前一天的电场Z分量增大幅度比地震前2小时更显著。对于空间电离层的分析发现,50-300Hz为地震电离层效应的优势频段;距离地震空间位置越近,地震异常越显著;不同半球的地震,异常方向和方位不同。
[Abstract]:In the earthquake preparation and occurrence process tends to produce low frequency electromagnetic radiation phenomenon, has been more and more strong earthquakes observed, which provides a possibility for earthquake monitoring and prediction. The electromagnetic radiation is directly from the information source, the electromagnetic skin depth is greater than the depth of earthquake source, large earthquakes observed low frequency electromagnetic radiation source in the seismogenic zone, and also in the late earthquake occurred. Therefore, applications with short impending earthquake prediction. This study collected the joint space of our ground station data electromagnetic electromagnetic satellite data, based on finishing the more than 100 digital electromagnetic electromagnetic stations and satellite data, and classification assessment the internal quality of station data. The observation data of the selected first, preprocess the analysis, identification and removal of the ground and the space of various non seismic interference factors; then using wavelet transform Change, polarization analysis, Hilbert Huang transform, polarization axis calculation, normalized monthly rate and frequency spectrum analysis method, the study took place in Chinese mainland typical strong earthquake cases before the earthquake, extracting reliable electromagnetic radiation anomaly information, summary of electromagnetic radiation shows various waveforms, field changes and spectral characteristics of the establishment of earthquake; electromagnetic model, earthquake electromagnetic radiation anomaly signal formation, breeding and propagation mechanism. Based on Hilbert Huang transform, three months before the earthquake of geomagnetic D component has changed significantly. The magnetic polarization analysis, most before the earthquake is rising, the abnormal morphological changes of amplitude increase. By studying the seismic electromagnetic field model are obtained before the earthquake electromagnetic radiation anomalies in time and frequency showed a staged process, following the earthquake anomaly characteristics, development and The occurrence regularity of geomagnetic field before strong earthquakes. In the field, it was found that exogenous separation and inversion of the equivalent current system, before the earthquake occurred within the current system of the synchronous change of external field, the current focus of vortex generated magnetic field to the zonal migration and the geomagnetic low point displacement "anomalies in the time of Wenchuan using the basic synchronization. The normalized monthly rate method, and the anisotropy of the Yushu earthquake to calculate the apparent resistivity before found more sensitive in anisotropic changes in apparent resistivity response of seismic fault zone and near the region, with the region on both sides of fracture was weaker, with significant difference in direction. The analysis of over 6 Demeter electromagnetic satellite orbit data of Wenchuan 8 before the May 6th earthquake, electric field Ex, Ey component of magnetic field, Hx, Hy components in the 370-400Hz are narrow band electromagnetic radiation, lasted about two minutes, after May 9th two over the source region The track was found Ex component of electric field increased phenomenon, and in May 11th and May 12th anomaly still exists, the day before the electric field Z component and earthquake magnitude of increase than before the earthquake 2 hours more significant. For the analysis of the ionosphere, 50-300Hz band for the advantage of seismo ionospheric effect; earthquake location distance closer, more seismic anomaly significant; different hemispheres of the earthquake, different direction and range.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：P315.728

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