Earthquake Electromagnetic Precursor Anomalies Detected by a New Ground-based Observation Network

It is a debated topic if there are any observable precursor anomalies prior to the earthquake(EQ hereafter)and if the stronger EQ can be successfully predicted.During last few decades quite a lot of observable electromagnetic(EM)precursors were published by using techniques equipped in either satellites or on ground-based stations.But there are only a few cases that the shortterm precursor anomalies of EM field before earthquakes were observed by using alternate EM fields on ground.This paper will present a new EM observation network built in recent years and show a new finding of EM field with the variation of a one-year cycle observed using the network.As an example,the short-term precursor anomalies of apparent resistivity before the Yangbi EQ(Ms 5.1)occurred on March 27,2017 in Yunnan Province will be studied.The observed anomalous phenomena indicate that the anomaly before the EQ can be captured only if reasonable effective methods including sophisticated analytical techniques are used,and it is believed that continuously observed data on the fixed observation network for a long time is an effective means for studying anomalies that appeared before earthquakes.This network can also play an important role in studying the EM environment from space.

Automatic Anomaly Detection for Swarm Observations

The Swarm satellite mission was launched on 22 November 2013,it is the first European Space Agency’s constellation of three satellites,dedicated to monitoring geomagnetic field changes.The measurements delivered by the three satellites are very valuable for a range of applications,including the earthquake prediction study.However,for more than 5 years,relatively little advancement has been achieved in establishing a systematic approach for detecting anomalies from the satellite measurements for predicting earthquakes.This paper presents the challenges of developing a pragmatic framework for automatic anomaly detection and highlights innovative features of functional components developed.Through a case study we demonstrate a functionality pipeline of the system in detecting anomalies,and present our solutions to coping with data sparsity and parameter tuning as well as insights into the differences between discovering seismic anomalies from periodic and non-periodic data observed by the Swarm satellites.

The Extremely Low Frequency Engineering Project for Underground Exploration

1.Introduction Super-low-frequency(SLF)(30-300 Hz)electromagnetic technology was first used in military to submarine deep water communications.In the 1950s,to strengthen the concealment and survivability of strategic missile nuclear submarines,both the United States and the Soviet Union began to study SLF communications,with the aim of achieving communications between land command centers and submarines at depths of below 100 m and distances of thousands of kilometers.

Identifying and localizing of seismogenic electromagnetic anomalies from data observed by permanent MT stations

In this research, an arbitrarily oriented electric dipole at subsurface is used to simulate Seismogenic Electromagnetic(SEM) radiation emanating from a seismic zone during its gestation phase. Analytical synthesis of responses at the Lijiang magnetotelluric(MT) station has revealed that SEM radiation could induce identifiable anomalies in the electromagnetic(EM)spectrum, apparent resistivity and phase within specific frequency bands. Background variations were extracted from long-term observation data of Dali and Lijiang MT stations, enabling the identification of SEM anomalies related to the Yunlong and Yangbi earthquakes. Multiple parameters of dipole sources at subsurface were obtained by applying the Differential Ant Colony Optimization(DACO) algorithm to anomalous data of two stations with multi-frequencies and various response functions. The spatial distribution of these predicted dipoles is predominantly clustered in or around the seismogenic area, with their azimuthal orientation aligning towards the seismogenic fault in general. This study has demonstrated the potential of using subsurface electric dipole simulations for SEM radiation analysis, offering a feasible approach for the prediction and understanding of seismogenic zones.

A review of seismo-electromagnetic research in China

The seismo-electromagnetic(EM)method is an important geophysical method that plays a major role in the observation of seismic anomalies related to earthquake precursors.It is the most promising method for a breakthrough in short-term earthquake prediction.The digital transformation and network upgrading implemented in the“Ninth five-year plan”and“Tenth five-year plan”have optimized the original observation system,improved the quality of observed data,enriched the seismicelectromagnetic information,and enhanced the analysis capability and timeliness of seismic-electromagnetic anomalies.These improvements are of major importance for the research on seismo-electromagnetics as well as for the development of new technologies.Since the beginning of the 21 st century,China has launched a satellite named CSES that was designed for the generation and study of seismo-electromagnetic data and built a high-power transmitting source and a new CSELF observation network that is used specifically for earthquake monitoring.This platform has promoted the full-time three-dimensional EM monitoring and the identification of earthquake anomalies.Based on the study of anomalies related to earthquake precursors,the physical and numerical simulations,and the study on generation mechanism of anomalies in China,we summarize the characteristics of earthquake EM anomalies and discuss the advantages and disadvantages of different EM observation methods.Finally,considering the related questions of the seismo-electromagnetic prediction and implementing the recent developments both in China and abroad,we review the current status of seismo-electromagnetic research and propose strategies for future research.