Seismic disturbances (6)
I believe the answer is:
shocks
'seismic disturbances' is the definition.
('shock' can be a synonym of 'seismic disturbance')
This is all the clue.
(Other definitions for shocks that I've seen before include "Sudden upsetting or surprising events" , "Appals" , "Jolts, jars" , "Surprises, sometimes electrical" , "Effects of charges of electricity" .)