Mechanical deformations from within the earthquake preparation zones are believed to cause seismo-electromagnetic (SEM) emission in ultra-low frequency (ULF) band, i.e. between 0.001 and 10 Hz, and these are studied as a precursor for short range earthquake forecast. Data from highly noise-resilient, 3-component ULF induction coil magnetometers, installed at the Multi-parametric Geophysical Observatory (MPGO), Tezpur, which is situated at a very close proximity with the northern end of the Kopili Fault and the Bomdila Fault, the Main Boundary Thrust of the Eastern Himalaya, the Naga and Disang Thrust, the Assam Syntaxis Zone as well as the two tectonically active Precambrian shields – Shillong and Mikir, was used for the first time to study SEM emissions employing both polarization ratio analysis and fractal analysis in the background of an intense phase of seismicity during the campaign period of April 20 – September 3, 2019. Fifty-one events were filtered via strain radius and index of seismicity calculations to nominate credible events which were studied vis-à-vis polarization ratio and fractal dimension parameters of 3-h night time data, centered around local midnight contemporaneous with the 18–21 UT window of the K_P index (global geomagnetic activity index) in the 0.03–0.1 Hz frequency band. The findings show candidate SEM emissions, in the form of enhancements in S_Z/S_H, associated with all the seven credible events, even as nine enhancements could not be attributed to immediately adjacent credible events. The fractal dimensions, calculated with the spectral density method, ambiguously depicted a gradual increase prior to the intense phase of seismicity.

地震准备区内的机械变形被认为会导致超低频 (ULF) 频带内的地震电磁 (SEM) 发射，即在 0.001 和 10 Hz 之间，这些被研究作为短程地震预报的前兆。来自多参数地球物理天文台 (MPGO) 的高抗噪、3 分量 ULF 感应线圈磁力计的数据，该天文台与 Kopili 断层和 Bomdila 断层的北端非常接近，东喜马拉雅的主边界冲断层、纳迦和迪桑冲断层、阿萨姆合成带以及两个构造活跃的前寒武纪地盾——西隆和米基尔，0.03–0.1 Hz 频段内的_P指数（全球地磁活动指数）。研究结果显示候选 SEM 发射，以 S _Z /S _H增强的形式，与所有七个可信事件相关，即使九个增强不能归因于紧邻的可信事件。使用谱密度方法计算的分形维数模棱两可地描绘了地震活动强烈阶段之前的逐渐增加。