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Figure 5b.
Disturbances in
E
z
component of the quasi-static field, orbit 250.
A similar disturbance zone from EQ
29
we observe for orbit 251 (see Table 1).
It should be noted that these measurements are made in a quiet day (K
p
= 3), so the
anomalies are not caused by a solar-terrestrial disturbance. The West coast of South
America is outlined by the eastern border of the Nazca tectonic plate and it is charac-
terized by its extremely high seismicity. There is a narrow seismic belt (100-150 km
wide) between the Andes Mountain Range and the Peru-Chile Trench (Gagnon et al.,
2005). Five earthquakes EQ
12,14,66,69,72
in the area of the West coast of South America
between 22 and 40
S latitudes are as large as M 4.8. The seismic events occur in and
near the territory of Chile. Chile is located on a plate boundary and in a subduction
zone called the Peru-Chile Trench. The fi rst EQ
12
is an event with magnitude M 4.9
and occurs in the Province of Antofagasta. Later in the same day another earthquake
EQ
14
with M 4.9 occurs in the region near Valparaiso. Figure 5c (orbit 250) illustrates
a disturbance zone of about 7 and 8 mV/m in
E
z
component of the quasi-static electric
fi eld, 97-120 hr after EQ
12
and EQ
14
, respectively. The disturbance zone is in a wide
latitudinal interval. We consider that the width of disturbance zone is probably de-
termined by time-shift post effect of EQ
12
and EQ
14
. A similar disturbance zone from
EQ12 and EQ
14
we establish for orbit 251 (see Table 1). Anomalies of about 10 mV/m
are marked in the
E
z
components of the quasi-static electric fi eld 8-25 hr before EQ
72
and EQ
73
(see Figure 5d--orbit 602 and Table 1). Such pre-and post seismic infl uence
of EQ
55,72,73
(orbits 349, 546) is observed in the
E
z
components of the quasi-static elec-
tric fi eld and listed in Table 1.
°
Figure 5c.
Disturbances in
E
z
component of the quasi-static field, orbit 250.
