Changes in the near surface atmospheric electrostatic fields during the preparation period of crustal earthquakes in Japan and continental China

Korsunova L. P., Khegay V. V.
  1. Pushkov Institute of Terrestrial Magnetism, Ionosphere, and Radiowave Propagation, Russian Academy of Sciences (IZMIRAN), Troitsk, Moscow Region, 142190 Russia

According to the measurements at the Kakioka (Japan) observatory of near surface vertical gradient of the
electrostatic potential the specific maximums in the current daily Ez deviations from background variations,
typical for fair weather conditions, were identified. Earthquake delay times with respect to these maxima
moments demonstrate the behavior similar to lead times for medium-term ionospheric precursors of the same
earthquakes (IPE) which were previously identified according to the data of the vertical sounding Kokubunji
station (this station is located at the distance of 85 km from the observatory Kakioka). We also obtained the
empirical dependence for the lead times of earthquake precursors based on measurements carried out earlier
in continental China. The dependence relates the delay times between the appearance of significant negative
anomalies in the vertical component of quasi-electrostatic field (precursor) and the moments of the subsequent
strong earthquakes with the magnitudes of these earthquakes and the epicentral distances to the observation
point.