212 The East Anglian Earthquake.
20. The chief damage occurred on the London Clay, a lesser
amount of destruction having taken place on the drift
and alluvium. There is no evidence to connect this
different amount of damage with the nature of the
ground, but it is probably due to the accidental
circumstance that the initial blow was delivered below
the London Clay.
21. At places near the origin the damage may in some
instances have been caused or increased by the
situation of the buildings at or near the junction of
heterogeneous geological formations, such as clay and
drift, clay and alluvium, &c.
22. The shock tended to make itself felt along free margins,
such as river-valleys, lines of outcrop (especially the
Cretaceous formations), and coast-lines.
23. The distribution of the shock does not appear to have
been influenced by any known lines of geological
faulting.
24. The general direction of the main axis of destruction
corresponds with the general direction of the coast-line
at this part of Essex.
25. The shock was probably spread widely round the origin
and its extent exaggerated by the propagation of the
vibrations along the better-conducting older rocks.
26. The main axis of destruction may possibly correspond
in its direction with that of known lines of disturbance
in the Chalk underlying Essex, Cambridgeshire,
Suffolk, and, across the Thames, in Kent, but the
evidence of such parallelism is not at present con-
clusive.
27. The seismic area is a region of slow subsidence. The
earthquake cannot be referred to the immediate action
of plutonic agencies.
28. The effects produced could have resulted from the rup-
ture of deep-seated rocks under strain or pressure,
such as the sudden production or extension of a line
of faulting.
29. The observations made during and after the earthquake