Ionospheric Quasi-static Electric Field Anomalies During Seismic Activity - Earth Science: New Methods and Studies - page 136

Figure 4a. Satellite orbits 193 and positions of the earthquake epicenters for period of seismic activity
in August 18-24, 1981.

The Eastern Canada is a part of the relatively stable interior of the North American
Plate, but not on a plate boundary. May be the North American Plate is in processes
of transformation, fragmentation and division. The EQ 23 (see Table 1) occurred in the
Labrador seismic zone on August 24, 1981 (latitude 61.22

W,
11:20:33 UTC and depth 10 km) with M 4.8. The pass of INTERCOSMOSBULGAR-
IA-1300 for orbits 193 is shown in Figure 4a. (Observations in) Figure 4b indicates
two anomalous disturbance zones: the fi rst one is to the south of EQ 6 with an increase
in the Ez component of about 5 mV/m, 62 hr after this event and the second one to the
south of EQ 23 and it is of about 10 mV/m, 79 hr before this event. It should be noted
that the observations are taken in a quiet day (K p = 2) and the events EQ 6 and EQ 23
occurred in isolated time-space domains.

° N, longitude 59.01 °

Figure 4b. Disturbances in Ez component of the quasi-static field, orbit 193.