Multi-instrument observation on co-seismic ionospheric effects after Japan’s Tohoku earthquake

【作者】 郝永强； 肖佐； 张东和；

【机构】 北京大学地球与空间科学学院；

【摘要】 After Japan’s Tohoku earthquake on Mar. 11, 2011 evidences of quake-excited infrasonic waves are comprehensively provided first by multi-instrument observation. The observations of co-seismic infrasonic waves are as follows: 1, effects of surface oscillations are observed by local infrasonic detectors, and it seems these effects are due to surface oscillation-excited infrasonic waves instead of direct influence of seismic vibration on the detector; 2, these local excited infrasonic waves propagate upwards and correspond to ionospheric disturbances observed by Doppler shift measurements and GPS/TEC; 3, interactions between electron density variation and currents in the ionosphere caused by infrasonic waves manifest as disturbances in the geomagnetic field as observed via surface magnetogram; 4, within 4 hours after this strong earthquake, disturbances in the ionosphere related to arrivals of Rayleigh waves were observed by Doppler shift sounding three times over. Two of the arrivals were from epicenter along the minor arc of the great circle (with the second arrival due to a Rayleigh wave propagating completely around the planet) and the other one from the opposite direction. All of these seismoionospheric effects were observed after arrivals of surface Rayleigh waves, with a time delay of 8-10 min. This is the time required for infrasonic wave to propagate upwards to the ionosphere.更多还原

【Abstract】 After Japan’s Tohoku earthquake on Mar. 11, 2011 evidences of quake-excited infrasonic waves are comprehensively provided first by multi-instrument observation. The observations of co-seismic infrasonic waves are as follows: 1, effects of surface oscillations are observed by local infrasonic detectors, and it seems these effects are due to surface oscillation-excited infrasonic waves instead of direct influence of seismic vibration on the detector; 2, these local excited infrasonic waves propagate upwards and correspond to ionospheric disturbances observed by Doppler shift measurements and GPS/TEC; 3, interactions between electron density variation and currents in the ionosphere caused by infrasonic waves manifest as disturbances in the geomagnetic field as observed via surface magnetogram; 4, within 4 hours after this strong earthquake, disturbances in the ionosphere related to arrivals of Rayleigh waves were observed by Doppler shift sounding three times over. Two of the arrivals were from epicenter along the minor arc of the great circle (with the second arrival due to a Rayleigh wave propagating completely around the planet) and the other one from the opposite direction. All of these seismoionospheric effects were observed after arrivals of surface Rayleigh waves, with a time delay of 8-10 min. This is the time required for infrasonic wave to propagate upwards to the ionosphere.更多还原