Happy Holidays ~ the last blog for 2011!

Hard to believe its nearly the end of the year already, and what a year its been!  From the hard times following the devastating quakes in Canterbury, to the highs of GeoNet turning 10. We are all hoping that 2012 will come with less geological hazard activity, well a little bit is OK - we are on a plate boundary after all!
I hope to blog more adventures with our technicians, and other exciting things that happen at GeoNet including the replacement of our earthquake location system (more info here )

The GeoNet tree - with quake proofing!

As many people begin the wind-down at work, i thought i would remind everyone that GeoNet is 24/7, when you feel any earthquakes over the break, don't worry our team will be onto it!  Each day (including Christmas) we have one seismologist - based at Avalon, and one volcanologist - based at Wairakei on duty, armed with pagers and close to their computers. So fingers crossed for a uneventful (hazard speaking) few weeks, with some nice weather for BBQs and fun at the beach!

Speaking of weather, my friend Philip Duncan runs the WeatherWatch website, and they have the official Christmas Day forecast here, and its looking good - don't forget your sunblock!

So happy holidays and thanks to all the GeoNet fans out there from myself and the team at GeoNet, we look forward to bringing you new and exciting things in 2012!

-  And i hope everyone remembered to quake proof their Christmas trees!

SARA

Nelson Rapid Response

With a state of emergency still in place in Nelson following last weeks heavy rain/flooding and landslides GeoNet are currently working with Civil Defence, with our landslide rapid response capability.

Sam working hard

Technicians are in Nelson today installing a continuous-GPS site at Grenville Terrace, on a major landslide where 30 houses have already been evacuated as further land movement is possible. cGPS sites, using satellites, allow scientists to accurately record ground movement

Info on GeoNets landslide rapid response capability here

Our thoughts are with all of the displaced families and those affected by the flooding/landslides especially so close to Christmas!

cGPS - freshly installed

Drill rig

Foo Fighters rocked Auckland!

You can almost pickout individual songs on the signal!

 
Two seismic stations in the Auckland GeoNet seismic network recorded the ground literally rocking to the Foo Fighters gig at Western Springs on Tuesday night.  The Herne Bay -HBAZ and Eden Park -EPAZ (with IESE-Auckland Uni) stations are 1.5 and 2km from Western Springs respectively and recorded a strong low frequency signal associated with the Foo Fighters gig.

The first vibrations were recorded around 7:30pm, part way through the Tenacious D set, but the biggest shakes started at 8:20pm when the Foo Fighters took the stage, and then it all went quiet at 11pm when the gig ended.
The concert vibrations were recorded as a semi continuous harmonic signal with a peak osculation of 3Hz,  ie the ground was shaking 3 times per second in a nice rhythmic motion.  There are lulls in the signal between the songs and peaks in signal intensity during the songs.

The cause of the shaking is most likely the weight of the 50,000 fans dancing, as 50,000 fans is equal to around 5,000 tonnes of mass moving(or moshing)on the ground for the duration of the concert.  This set up a nice harmonic vibration in the ground which was recorded in our nearby borehole seismometers.

The sound system, probably contributed as well, especially the bass frequencies coupling in to the earth.  The signal is similar to volcanic tremor that is recorded at places like Mt Ruapehu and White Island, however the strong correlation in time with the Foo Fighters concert and the fact it was only recorded on the 2 stations close to Western Springs assured us it was of man-made origin.

Detail of the signal showing the 3Hz vibration

This is not the first time the Auckland instruments have picked up neat sounds, the Rugby World Cup finals were also seen!

Thanks to Craig Miller and the Wairakei GeoNet crew for the info!