Feb 18 2011 - January 2011 GeoNet roundup

Earthquake details as viewed in Google Maps.

New website facilities

• A link allowing each earthquake location and its details to be viewed in Google Maps was added. The user can go on to save the KML file or instead view the details in the Google Earth application.

Additions and upgrades to the geophysical monitoring networks

• Two new continuous GPS sites were completed, one at Frasertown (FRTN), near Wairoa, and another at Norsewood (NRSW), in southern Hawke's Bay.

Earthquakes summary

• The most widely-felt earthquake of the month occurred on Thursday, January 20, magnitude 5.1, 10 km south-west of Christchurch at a depth of 10 km. We have received 2,421 felt earthquake reports to date, including three reports of structural damage.
• The preliminary locations of December's earthquakes located by our analyst team are shown below.

Volcano surveillance field trips

Tuesday January 11 - Gas flight over Ruapehu

The weather was good although the wind was fairly strong. The plume was surveyed between 7,000 and 9,600 feet. No gas was detected on any of the instruments; this is unusual for Ruapehu. The crater lake was green in colour with a strong grey upwelling visible over the central vent area.

Wednesday January 12 - Gas flight over White Island

Flying conditions were excellent. SO₂ and H₂S were up slightly from December's measurement, CO₂ was lower than the previous flight.

Wednesday January 12 and Thursday January 13 - White Island surveying

A 2 day field trip to White Island was led by the University of Canterbury which included some detailed soil gas measurements from GNS Science staff and University of Canterbury students. Crater Lake sampling, ground-penetrating radar (GPR) experiments, computer component experiments and sampling of past eruptive deposits were all undertaken by University of Canterbury staff, students and collaborators.

A detailed CO₂ soil gas flux survey was performed, with a total of 330 measurements being made on the Main Crater floor.

Gas sampling was done for carbon isotope analysis.

A GPR survey was performed to highlight structures below the surface.

The Crater Lake was sampled and a 15 litre bulk sample collected for the University ash laboratory. The lake temperature was 67.3 °C and the water level has fallen about 0.5 m from the November 2010 level.

Computer parts and running laptops were left out overnight to see the impact the White Island environment has on these components. This is a continuation of experiments done last year by the University’s ash laboratory.

Sampling was conducted of phreatic and phreatomagmatic deposits in the 1976 - 2000 eruption deposits sequence for new studies by the University on these processes.

Wednesday January 26 - Ruapehu Crater Lake visit

The first Crater Lake sampling trip of the year was made under very warm, still, summery conditions. Gas and water samples were taken and the temperatures measured.

The lake was calm and a marbled blue-green and grey colour, with more blue-green occurring at the edges of the lake. The central vent upwelling was visible as a change in lake surface expression only, with the north vent not visible at all. The Lake was vigorously overflowing. The temperature at the central vent was 28.3 °C and at the north vent was 28.5 °C

Reported landslides from media sources

Tuesday January 18

• SH 6 between Inangahua and Westport (the lower Buller Gorge) was blocked by a slip near Hawks Crag, closing the road for about 3 hours.

Thursday January 20

• A minor rock fall was reported in Ngauranga Gorge, SH 1 north of Wellington.

Sunday January 23

• SH 30 between Whakamaru Dam and Atiamuri was blocked by a large rock fall in the evening.
• SH 1 was closed at Wairakei by a washout in the evening.
• SH 2 Waioeka Gorge was closed by slips and a rock-fall in the evening.
• A slip blocked the road near the SH31/Honikiwi Rd intersection near Otorohanga in the late afternoon.
• A slip affected the railway line between Plimmerton and Paraparaumu.
• Slumping affected Mimi Rd and Pukearuhe Road in northern Taranaki.
• SH 43 between Stratford and Taumarunui was affected by a slip in the Tangarakau Gorge.
• Surface flooding and minor slips were reported in Rotorua.
• Minor slips were reported on SH 2 Napier-Wairoa, SH 3 Wanganui-Taranaki, SH 4 Wanganui-Raetihi, SH 5 Napier-Taupo.
• Slips on SH 1 at Brynderwyn.
• A car was damaged driving into a slip on SH 3 Manawatu Gorge.
• A slip occurred in Wharf Road, Waiheke Island, and a larger one on Tawa Street; another minor slip was reported in Great Barrier Road.

Monday January 24

• SH 3 Manawatu Gorge was closed by a slip affecting both lanes about the middle of the gorge early in the morning. It reopened about 3 pm, but further minor rock-falls continued to be a problem.
• SH 2 Waioeka Gorge was also still closed because of slips.

Saturday January 29

Cyclone Wilma affected Northland, Auckland, Coromandel, Bay of Plenty and northern Hawke’s Bay, causing widespread flooding and landslides:

• SH 25 north of Thames blocked by a large landslide near Ruamahanga. The road was expected to re-open on February 1. The slip had a volume of about 3,000 cubic metres. Several other slips were quickly removed, but the road remained blocked.
• SH 25 Hikuwai to Whangamata was closed by slips and downed trees.
• Two houses at Riverside, Whangarei, were evacuated because they were threatened by slips.
• At Stanmore Bay, Whangaparaoa Peninsula, 40 km north-east of Auckland, a landslide crashed into a house.
• Tauranga – all tracks on Mount Maunganui were closed due to landslides and mudslides overnight.
• A slip closed SH 38 at Frasertown, near Wairoa.
• A house collapsed at Onetangi, Waiheke Island, as a landslide occurred under it; for a time two people were reported missing but were later found safe and well.
• SH 29 between Te Poi and SH 24 were partly blocked by slips 4 km east of the summit.
• The Rotoma Hills road was the only road open between Rotorua and Tauranga, but numerous slips were reported to be on it.
• SH 5 north from Rotorua to Hamilton was closed by a slip about 100 m north of Tarukenga Road, near Lakeview golf course.
• SH 30 was down to one lane because of a slip near Hell’s Gate.
• SH 2 was affected by slips at Waiotahi Beach and the Matata Straights.
• Waimana Gorge near Taneatua was blocked by slips.
• More than 20 slips reported on Matakana Valley Road in Rodney.
• In the Whangarei district there were slips at Lemons Hill, Mason Road and Mititai Rd were closed by underslips, the Waipu Caves Road and Whananaki Road were reduced to one lane and a major slip closed SH 11 between Puketona and Kawakawa near the Rigden Rd junction.

Felt earthquakes of
December 2010
(135 located).

Shallow earthquakes of
December 2010
(1,359 located).

Deep earthquakes of
December 2010
(420 located).