TITLE:
Ultra-Low Frequency Electromagnetic Emissions Registered during the 21 May 2021 Yangbi MS 6.4 Earthquake in China
AUTHORS:
Chuanfang Xiang, Mei Li, Zhaoli Ma, Chuanqi Teng, Zhirong Li, Zhigang Shao
KEYWORDS:
ULF Electromagnetic Emissions, Yangbi M 6.4 Earthquake, Synchronous Variation
JOURNAL NAME:
Natural Science,
Vol.14 No.1,
January
7,
2022
ABSTRACT: Four ULF (0.01 Hz - 20 Hz) electromagnetic stations had been gradually
established and put into service from 2010 to 2011 in Zhaotong area, Yunnan
province. Two stations of Qiaojia and Yongshan have been running with
continuous and high quality recordings and free of influence of solar
activities, like magnetic storms. In this investigation, daily recordings from
1 January 2020 to 22 May 2021 have been examined of these both stations. The
results show that weak anomalous signals appeared at the beginning of March
2021 with relative low magnitudes of 0.6 nT at Qiaojia station and 0.3 nT at
Yongshan station. At the end of this month, the emissions gained an abrupt
increase and the amplitudes reached up to 3.8 nT at Qiaojia station and 1.2 nT
at Yongsha station. Then, the amplitude decreased to be 0.5 - 1.5 nT and 0.6 -
1.3 nT respectively at both stations but with a high variation frequency in all
components. This situation lasted till the Yangbi MS 6.4 earthquake happened on May 21, 2021, more than
300 km away from these two ULF observing stations. Totally, the ULF magnetic
emissions had been characterized by a synchronous variation in all components
at two observing stations.