Ground-shaking News
By Martin Scherwath
Exactly one week after the Alaska earthquake it's happening right outside our front door: An earthquake, initially estimated magnitude 6.7, later downgraded to 6.4, occurred just offshore of Vancouver Island, 20 km from Nootka Island. This location is very close to the Nootka Fault Zone where we have the greatest offshore seismicity, right between the Juan de Fuca and the Explorer tectonic plates. So, September 9, 2011 will certainly go into the local seismology history book as a big one, and we expect many immediate aftershocks around this location in the near future.
NEPTUNE Canada's main seismometers at sites ODP889 and ODP1027 show this earthquake again very clearly, but also bottom pressure recorders (BPR) show strong signals. Below are the two seismograms and one BPR record, showing ten minutes of data:
NEPTUNE Canada seismometer data at our ODP 1027 (above) and ODP 889 (centre) locations and bottom pressure recorder data from ODP 889 (below), showing 10 minutes of data at the time of the Nootka fault earthquake on 9 September 2011.
NEPTUNE Canada data specialist Dilumie scanned more stations with a pressure response to the earthquake and found that our Piezometer (at our ODP 1027 location), newly installed in July exhibits a great response, changing with depth. In this plot, we can see three sensors measuring differential pressure at the seafloor and depths of 1.6 and 3.2 metres.
IFREMER Piezometer pressure traces from 1.6-3.2m below the seafloor at ODP 1027.
And all this happens while NEPTUNE Canada is mobilizing for our September 2011 maintenance & installation cruise.
Busy times!
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