Jun 4 2010 - May 2010 GeoNet roundup

May 19: the gassy conditions encountered at White Island crater lake.

New facilities for researchers and data users

• All digital waveforms collected by the New Zealand National Seismograph Network have been loaded into our waveform repository, making them easily available to researchers along with the current GeoNet data. The first digital records began in September 1986 with instruments recording in the Wellington and Clyde (Central Otago) regions.
• The Quake Search application can now also output its data in KML format, making it work easily with Google Earth and Google maps (amongst others).

May 20: changing the batteries on the datalogger near Ruapehu's Crater Lake in preparation for the winter.

Additions and upgrades to the geophysical monitoring networks

• A new National Seismograph Network site was completed on Great Barrier Island (GRZ).
• A tsunami gauge was installed at Kaikoura (KAIT).
• A regional seismic site was completed at Matea Road (MRHZ), about 30 km south-east of Taupo.

May 31: a view into Ngauruhoe's crater after recent snow.

Earthquakes summary

• The most widely-felt earthquake of the month occurred on Wednesday, May 5, magnitude 5.1, 50 km south of Taupo at a depth of 60 km. We have received 342 felt earthquake reports to date.
• The preliminary locations of April's earthquakes located by our analyst team are shown below.

Volcano surveillance field trips

May 31: sampling on the shores of Lower Emerald Lake.

Wednesday May 5 - Gas flight over White Island

Conditions were very good, with clear sky and a steady 16 knot wind. Unfortunately, the Flyspec instrument didn’t work due to software problems. Results are shown below:

The Cospec SO₂ result was similar to a value recorded from two Flyspec passes carried out by helicopter on the May 2*. SO₂ was slightly higher than the previous survey (March 30) while CO₂ was lower.

Wednesday May 19 - Gas flight over White Island

A measurement of SO₂ emissions from White Island was made using the Flyspec mounted on the helicopter skid while on route to the crater for the chemistry sampling trip (see next item). Two passes were made. The wind was approximately 5 knots and conditions were good.

Wednesday May 19 - Spring and fumarole sampling at White Island

A soil gas survey was conducted, fumaroles and springs were sampled and some flows were measured. Fumarole temperatures were similar to the March readings. Discharges also appeared similar. Spring temperatures and flows also had not changed much since March. The lake was not sampled, as it had been done two weeks earlier, and it was too gassy to go down and measure the temperature. Lake level appeared slightly down compared to that observed two weeks ago.

Gas flux overall remains fairly low although the results were generally slightly higher than the previous measurement in February:

Thursday May 20 - Ruapehu Crater Lake visit

The trip was made to Ruapehu after a light dusting of snow. Gases and waters were sampled from the north vent (21.4 °C) and the central vent (20.5 °C); the outlet temperature was 19.7 °C. Upwellings were not visible, but when we went in to get the north vent sample we could see a slight disturbance in the lake surface in the general north vent region. The lake was a slightly darker colour than its recent blue green colour, with large patches of grey distributed throughout it. Outlet flow was higher than the April sampling trip, but not as high as the March sampling trip. We changed the batteries at the data logger, in preparation for a long winter covered by snow and ice.

Monday May 31 - Gas flight over Ruapehu

The mean wind speed was 4.1 m/s. Good peaks were obtained for CO₂ and Interscan SO₂. SO₂ was detected on the Cospec but not on the Flyspec. The gas flux appears to be stable, although there is a net increase in CO₂ flux compared to the previous flight. No gas was detected over Ngauruhoe.

Monday May 31 - Tongariro lake and fumarole sampling

The annual Tongariro trip was made in perfect conditions. All the lakes and fumaroles were visited and sampled, including the fumarole on Ngauruhoe. Temperatures and pressures in Red Crater and Te Māri areas and Ngauruhoe were similar to last year. The area below the Lower Emerald Lake appeared to be more active, with more fumaroles present, some very audible and producing a lot of steam, although the fumarole sampled was similar in temperature and pressure to last year. Central Crater fumarole is very weak and was not sampled.

Reported landslides from media sources

Sunday May 16

• Heavy rain in the Tapawera area south of Motueka caused flooding and slips that blocked roads and necessitated the evacuation of about 20 households. The situation was exacerbated by logging debris being swept into streams and rivers from on many recently-logged hill slopes in the area.

Friday May 21

• A rockfall blocked the road between Queenstown and Glenorchy at “the narrows” near Bob’s Cove. The slide was estimated at 1500 - 2000 tonnes (volume about 750 m3). The road was re-opened on Saturday May 22, but further stabilisation work was being considered.

Monday May 24 - Tuesday May 25

• Heavy overnight rain in the Bay of Plenty caused flooding around Whakatane with slips reported in Matata and another blocking a lane of Gorge Road, Whakatane with 500 m3 of debris.

Wednesday May 26

• Slip on SH 3 at Awakino Gorge, obstructing southbound lane 1 km north of Awakino Tavern.

Thursday May 27

• A rockslide near Duntroon in North Otago came down in heavy rain, blocking the entrance to a cave with ancient Maori rock art.

Friday May 28

• A slip at Aln Street, Oamaru resulted in evacuation of three residents.

Saturday May 29

• A slip impacted a building at a camping ground at Berwick, near Outram, damaging the building and four vehicles. Forty-two people had to be evacuated from the building after it was shunted about 6 m onto the road.
• Slips were also reported on the road along the Otago Peninsula at Portobello, Dunedin. A glasshouse and shed were swept down Portobello Road by a slip, closing the main route to Dunedin.
• At Moeraki an unoccupied “crib” was damaged by a slip.
• Two landslides on Hospital Hill, Napier, forced the evacuation of seven residents in five houses in Faraday Street. The first slip engulfed a car and was attributed to a broken water pipe (probably caused by incipient landslide movement), and the second damaged the wall of the Salvation Army building.

Felt earthquakes of April 2010 (29 located).

Shallow earthquakes of April 2010 (1352 located).

Deep earthquakes of April 2010 (484 located).