Sunday, 21 June 2015

Mobile School Seismology in the Chiller ... by Tim Pharaoh

Tim Pharaoh holding the compact
 seismic sensor and data logger
Tim Pharaoh visited Iceland in April at the invitation of Greenhead College, Huddersfield. He accompanied a 40-strong party of AS level Geography and Geology students and their teachers on a 5 day itinerary in the SW part of the island. Following the 'classic' route through the 'Golden Triangle', the party discovered the benefits of geothermal energy at the 'Blue Lagoon'; experienced ocean-free Mid-Atlantic Ridge at  Þingvellir; observed dramatic glacier recession; and a host of 'alien' volcanic, landscapes. These are now immortalised in TV shows like 'Game of Thrones' and 'Fortitude', and films such as 'Prometheus', 'Interstellar', 'Thor' (predictably!) and 'The Secret Life of Walter Mitty'. The excursion enabled deployment of a new compact 3-component seismic sensor and data logger manufactured by Gulf Coast Data Concepts (www.gcdataconcepts.com), packaged in a waterproof case and no bigger than a lunchbox.

The objective was to carry out a sensitivity test of the device with a view to possible wider use in the BGS School Seismology programme. The sensor records up to 30 days of seismological data onto a micro-SD card, which can be analysed subsequently using SeisGram2K software on a laptop PC, either in the field or in the lab. The sensor was deployed in the grounds of Hotel Laki, Kirkjubæjarklaustur, in the surreal setting of a 'whale cemetery' at the rear of the hotel. Interlopers to this scene may have thought they were caught up in the filming of 'Walter Mitty 2'! The students helped to bury the device, and recover it 36 hours later. The theoretical sensor self-noise (i.e. acceleration detection limit) is just above 0.02m/s/s. At this level, signal from an M2 event would only be detectable closer than 10 km from the sensor; from an M3 event, closer than 60 km from the sensor; from an M4 event, closer than 120 km from the sensor.  The record from the Icelandic Meteorological Office (IMO) shows that there were no significant seismic events in the vicinity during the deployment, the eruption of the Bárðarbunga volcano having ended a few weeks previously. As a result, no seismic events were detected by the sensor, only 'cultural noise' from Max as he recovered it with a shovel. However, the ease of deployment was demonstrated and the sensor should be capable of delivering useful and interesting data from an active seismogenic zone. Since nature was not forthcoming with a seismic signal, we had to improvise with our own Vibroseis source!


Greenhead College students and Tim Pharaoh burying the sensor 
Should your school or college have the opportunity to visit such a region for a reasonable period in future, you may want to try it out for yourselves!  If so, please contact Paul Denton, of the BGS Schools Seismology Programme, directly.

Thanks to a relay of individuals who allowed the transfer of the sensor from Fulneck School to Greenhead College before the trip! The assistance of Richard Brewster, Becky Gould, Frédérique Jaffeux and their students with this experiment is gratefully acknowledged. We also thank Hotel Laki, a great place to stay, for their hospitality.

Contacts:  

Paul Denton, Schools Seismology Programme, BGS Keyworth (pdenton@bgs.ac.uk)
Web www.bgs.ac.uk/ssp     Facebook www.facebook.com/UKSS Twitter @schoolseismo

Tim Pharaoh, Energy and Marine Geoscience Programme, BGS Keyworth  (tcp@bgs.ac.uk)
Richard Brewster, Geography Department, Greenhead College, Huddersfield (RBrewster@greenhead.ac.uk)
Becky Gould, Geology Department, Greenhead College, Huddersfield
Hotel Laki,  Kirkjubæjarklaustur (www.hotellaki.is)


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