Near-field temporal electric current after the 2024 Mw 7.4 Hualien earthquake

At 23:58:08 UT on April 2, 2024, an M7.4 earthquake occurred near Hualien, Taiwan region, triggering geomagnetic variations. Seismic waves typically induce geomagnetic disturbances that exhibit time delays that are dependent on epicentral distance in previous studies. In this study, simultaneous perturbations in three-component geomagnetic field were observed within 114 km of the epicenter. The out-of-phase perturbations in the Z-component between the geomagnetic stations near the epicenter suggest a local electric current triggered by the earthquake. The height and orientation of the currents were estimated to be approximately 99 km and 247 ° (southwest), respectively. The magnetic field and high-frequency Doppler sounder observations indicate that acoustic waves are triggered by the earthquake. This was consistent with the sound propagation of the NRLMSISE−00 atmospheric model. The acoustic waves propagate from the ground to ionosphere, causing plasma to move across the Earth’s magnetic field, which leads to the generation of electric current. This study suggests that earthquake-triggered acoustic waves can change the dynamics of the ionosphere. These findings provide new insights into earthquake-ionosphere coupling, indicating that earthquakes can trigger temporal ionospheric currents near the epicenter.