ted
ods
ber
)88)
cent
cent
slide
=
and with the isoseismes (Fig. 8). Landslides reach a
density of 100% in the central area. The reliability of the
isoline shape is supported by the following data: i)
variations of slope dip above an inclination of 20-30* did
not influence the landslide distribution, ii) the average
slope steepness of the landslided area is almost equal to
the conterminous zones exept eastwards where it
gradually passes to the Amazon Platform, iii) isolines
crossing the geological limits show a minimum influence
of changes in rheological characteristics of rocks.
Comparison of landslide distribution with topography, in
the sense of slope orientation and inclination, shows that
landsliding was denser along the slopes facing ESE. This
discovery is particularly interesting because the geometry
of slope failures could be linked to the dominant WNW
dip of active fault planes (for geometry of active faults see
also the focal mechanism solutions of Fig. 6 and
Pasquaré et al, 1990). If this relationship will be
confirmed in other areas, it could represent a stimulating
topic for further seismic studies.
5. CONCLUSIONS
The integrated use of aerial stereophotos and radar and
satellite images enabled to recognize recent fault motions
and several landslides triggered by earthquakes in the
Ecuadorian Andes. Coregistration and comparison of
these data with topographical and geological maps
allowed to reach the following results:
N ,
teen
D iun
0
0°
SAZ
os] - a0
TX
= 6.0
= Dal)
= 4.0
t UNKNOWN
79° 78° 779
Figure 6. Epicentre distribution map of period 1903-1987. Numbers 1, 2 e 3 refer to microseismicity analyses
discussed in the text. Letters refer to focal mechanisms:
Clyde (1981); Black arrows show the horizontal direction of the P axis; Schmidt projection, lower hemisphere. CO
Cordillera Occidental, IV Interandean Valley, CR Cordillera Real, SAZ Sub-Andean Zone. Box - figure 7.
b and c after Barberi et al. (1988), e after Woodward &
277
ILLO
=
UE Ei Le
cs cu
a t:
fi
x
i
i
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