Co-seismic geomagnetic fluctuations and atmospheric disturbances during the 2018 M 6.2 Hualien Earthquake

  • Author(s): Chun-Rong Chen, Jann-Yenq Liu, Chieh-Hung Chen, Tsung-Yu Wu, Horng-Yuan Yen, Strong Wen, Bor-Shouh Huang, Cheng-Horng Lin, Che-Min Lin, and Hung-Hao Hsieh
  • DOI: 10.3319/TAO.2019.03.11.01
  • Keywords: Geomagnetic QuakeFinder Infrasound Micro Barometer Tiltmeter
  • Citation: Chen, C.-R., J.-Y. Liu, C.-H. Chen, T.-Y. Wu, H.-Y. Yen, S. Wen, B.-S. Huang, C.-H. Lin, C.-M. Lin, and H.- H. Hsieh, 2019: Co-seismic geomagnetic fluctuations and atmospheric disturbances during the 2018 M 6.2 Hualien Earthquake. Terr. Atmos. Ocean. Sci., 30, 449-465, doi: 10.3319/TAO.2019.03.11.01
  • Co-seismic geomagnetic fluctuations can be amplified by not only seismicity intensity level but underground susceptibility
  • Micro-barometers and tiltmeters for the first time detect co-seismic fluctuations
  • Long lasting tiltings might result from underground water oscillations activated by seismic waves

The strong ground motion of 6 February 2018 M 6.2 Hualien Earthquake triggered a series of co-seismic geomagnetic fluctuations and seismo-traveling atmospheric disturbances (STADs) signatures in infrasonic waves and micro-pressures upon the seismic wave arrival. Networks of 9 QuakeFinder systems, 3 infrasound systems, 2 tiltmeters, 2 micro-barometers, and 11 co-located seismometers are used in this study. Each QuakeFinder system consists of a 3-axes induction magnetometer, an air conductivity sensor, a geophone, and temperature/relative humidity sensors. Co-seismic signatures clearly appear in the induction magnetometers, infrasound systems, and micro-barometers data. The magnetometers register both high- and lowfrequency pulsations. Geomagnetic fluctuations occur upon the seismic wave arrival but last a longer duration, while the STADs lag their co-located seismic waves by about 15 - 45 s. The long-lasting fluctuations recorded by both induction and fluxgate magnetometers suggest that the ground/underground water motion play an important role, which is further conformed by low-frequency fluctuations in the tiltmeter data. In general, the amplitude of geomagnetic fluctuations decays as away from the epicenter. However, unusual large co-seismic geomagnetic fluctuations are detected over areas of the abnormal seismic intensity level and/or the magnetic underground structure with anomalously high susceptibilities.

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