Jan 10 2011 - December 2010 GeoNet roundup

Jeremy Cole-Baker re-deploying the Ruapehu Crater Lake sensors after maintenance on December 1.

An aerial view of White Island on December 6. Boats can be seen anchored in Crater Bay at the lower left.

Getting information to you efficiently

We have been working hard to make sure our website is there for you when you need it, so it was pleasing to see that our efforts have been rewarded by an overall second place for the most optimised home page of the Top 100 websites based in New Zealand! You can read the full results at ProjectX Technology.

Additions and upgrades to the geophysical monitoring networks

• A new continuous GPS site was commissioned at Terawhiti (TRWH), south-west of Wellington.
• The final seismic site of the Auckland volcano monitoring network, a 371 m borehole, was completed on the Awhitu Peninsula (AWAZ).

Earthquakes summary

• The most widely-felt earthquake of the month occurred on Sunday, December 26, magnitude 4.9, centred under central Christchurch at a depth of 12 km. We have received 1,609 felt earthquake reports to date, including eight reports of structural damage.
• The preliminary locations of November's earthquakes located by our analyst team are shown below.

Volcano surveillance field trips

Wednesday December 1 - Ruapehu Crater Lake visit

Gas and water samples were taken and the temperatures measured in the Crater Lake. The lake was calm and a uniform blue-green colour; no upwellings were visible. The lake was overflowing and the level was similar to the last visit on November 2. Temperatures were 29.0 °C at the Central vent and 29.5 °C at the North vent.

The lake level sensor was replaced as it had been producing a poor signal. The sensor package was attached to a new anchor made from heavy lead pipe (approximately 25 kg) and placed back in the lake.

Wednesday December 1 - Gas flight over Ruapehu

Conditions for flying were good with a low winds. Sparse clouds were present just above 8,500 feet precluding measurements above the clouds. SO₂ emission was low but detectable. Ngauruhoe was not surveyed because of the clouds surrounding it.

Monday December 6 - Gas flight over White Island

Flying conditions were windy but suitable, and a reasonable plume was detected and measured. The CO₂ emission was slightly higher than last month with little change in the other gases.

Reported landslides from media sources

Sunday December 12

• Two landslides on Mount Taranaki at 7:45 and 7:52 pm from just north of Bob’s Bluff sent debris flows down the Oaonui Gorge and into the Waiaua headwaters. It raised a huge dust cloud around the base of Fantham’s Peak.

Monday December 20

• SH 35 between Opotiki and East Cape was affected by a slip on the Maraenui Bluff detour, but the road remained open.

Tuesday December 21

• SH 94 to Milford Sound was closed from Knobs Flat by an overnight slip. The road was expected to reopen the next morning.

Tuesday December 28

• A slip closed SH 6 between Franz Josef and Fox Glacier, but the road re-opened about 10am.
• A landslide during torrential rain damaged a car just after it emerged from the Mount Messenger tunnel on SH 3 between New Plymouth and Mokau.
• A slip blocked SH 6 at Canvastown, 5 km west of Havelock.
• SH 73, Arthur’s Pass highway, was closed by rock falls between Bealey and Otira.
• The Heaphy Track was closed because of the risk from slips and fallen trees
• Continuing heavy rain from December 28 also caused extensive flooding in the Nelson-Tasman areas, and the Aorere River bridge was washed away. Many landslides were reported affecting SH 69 between Inangahua and Reefton, and SH 6 (the Lower Buller Gorge) between Inangahua and Westport.

Felt earthquakes of
November 2010
(207 located).

Shallow earthquakes of
November 2010
(1,632 located).

Deep earthquakes of
November 2010
(469 located).