From my location in Green Is., Dunedin, NZ. I record earthquakes from all over NZ and the
larger ones from around the Southwest Pacific. At the moment I am using the standard rotating
drum, paper and ink pen seismograph with a short period horizontal seismometer orientated E-W.
The seismometer is a 'Mark Products' L15BH geophone resonant at ~4.5 Hz and is potted in a 0.5m
length of pvc tubing. The tube is mounted vertically in the ground and in the lower end of it is
a 7 cm dia. cylinder of ~2 kg of lead for extra mass ( improves sensitivity no-end).
As of Dec 1996, my digital recording system is now up and running and working well. It is
Larry Cochrane's 8 channel 12 bit A to D board and his SDR logging software. I have two short period
seismometers connected to it at present: 1 vertical and 1 E/W. They are Geo-Space, model GS-11D geophones
very similar to the one mentioned above and are housed in a similar manner. A long period horizontal
seismometer will also be added to the system as time permits and this will greatly enhance the
recording of the large distant events. Keep an eye on Larry's
New Earthquake Data Files for quakes uploaded from my system.
Remember that UT is 12 hours behind NZST and that I am only one recording station so I can
determine distance and magnitude but not location. Three stations minimum are needed for a good
triangulation location. But a reasonable knowledge of South Island seismicity allows me to be
confident in saying that most events with a S-P of ~22-26 seconds (~210 - 245 km) from Dunedin are
likely to be in the Fiordland Seismic Zone.
