EARTHQUAKE RECORDS

Evening Star, Issue 18161, 29 December 1922, Page 3

EARTHQUAKE RECORDS

USES OF THE SEISMOGRAPH. [Special to the ‘ Star.’] CHRISTCHURCH, December 28. Upon reading that “ the very violence of the earthquake last Monday militated against a complete seisraographic record ” some people have jumped to the conclusion that the seismograph at the Christchurch Observatory is next door to useless. It is admitted that the instrument is some twenty years old, hut it is submitted that any similar apparatus would have been thrown out of adjustment as the result of such a violent quake. A reporter had an interesting chat yesterday with Mr H. .F. Skey, the officer in charge of the observatory, on the subject. “ The seismograph,” Mr Skey said, “ is most delicately adjusted. It is, in fact, as delicately adjusted as a chemist’s balance, and one would not expect a chemist to go on weighing while an earthquake was being experienced. Tho seismograph is not rigidly attached to the earth, nor even to the top of tho pillar on which it rests. It is supported by three levelling screws, which simply rest upon metal pieces let into the cement on the top of the pillar. Consequently the boom of the seismograph is easily displaced, and tho whole apparatus is thrown absolutely out of level whenever any violent earthquake occurs. “ The seismograph,” Mr Skey went on to remark, “ is, of course, primarily designed for recording earthquakes that originate five or six thousand miles away. These, from the point of view of geophysics, are more important - than those originating nearer the recording station, because from these we are able to deduce the velocity of travel of the earthquake waves through the ears. Tho importance of this is that we are able to demonstrate that there are various waves generated in the earth by earthquake shocks.”