92 The East Anglian Earthquake.
districts to the north-east of this village is certainly sugges-
tive of the Colne Valley having acted as a barrier against
which the wave was broken and reflected, giving rise to the
complicated effects observed, and confusing the original
direction of the disturbance. The tract of country to the
north-east of Wivenhoe appears in fact to have been in
" seismic shadow."
Summary of Observations in the Area of Structural Damage.
The area now described, comprising some 50 to 60 square
miles of country in north-east Essex, may be considered to
include the whole region over which the disturbance was
of sufficient intensity to cause structural damage to buildings.
In the outlying districts a few isolated cases of damage have
been reported, but these are exceptional, and refer only to
old and shaky structures (generally chimneys) which might
have been toppled over by a very moderate amount of
oscillation.
Within the area of destruction there occur certain maxima,
which when plotted on a map in the order of intensity, give
the impression of being somewhat irregularly distributed, but
the main axis of disturbance extends on each side of a line
about five miles in length, having a direction N.E. and
S.W. from Wivenhoe to Peldon. Along this axis the
greatest intensity was manifested, as shown by the large
percentage of dislodged chimneys, dismantled roofs, &c, and
more especially by the fracturing of solid masonry.
In estimating the severity of the shock in the various
parts of the chief seismic area, the local conditions must be
taken into consideration. Thus the amount of damage at
Colchester, when laid down on the map, appears excessive,
but this is no doubt due to the larger amount of material
which the earthquake had to operate upon. On the other
hand, the absence of a large amount of damage cannot be
taken as conclusive evidence that the disturbance was not
severe at any particular place ; it may simply indicate the
absence of damageable buildings.