Aug 17 2011 - July 2011 GeoNet roundup

The continuously-recording strong-motion instrument at Victoria University Law School. It uses the CUSP-3D instrument produced by Canterbury Seismic Instruments of Christchurch.

Additions and upgrades to the geophysical monitoring networks

• Four more strong-motion sites were installed in Lower Hutt and Wellington. They are at Fairfield (FAIS), Seaview (SEVS), Victoria University Law School (VUWS) and Randwick School (LRRS).

Earthquakes summary

• The most widely-felt earthquake of the month occurred on Tuesday, July 5, magnitude 6.5, 30 km west of Taupo at a depth of 150 km. We have received 4,114 felt earthquake reports to date. As is typical with deep North Island earthquakes, the strongest shaking occurred along the east coast, not at the epicentre.
• The preliminary locations of June's earthquakes located by our analyst team are shown below.

Volcano surveillance update and field trips

Summary

• No eruptive volcanic activity occurred at any of New Zealand's active volcanoes during July.
• The temperature of the Crater Lake at Ruapehu decreased rapidly early in the month, due partly to a large influx of rain and snow. By month's end, the temperature was around 20 °C.
• Routine gas flights were completed over White Island, Ruapehu and Ngauruhoe.
• Spring sampling was completed at Soda Springs, Waimangu, Reporoa and Waikite
• A sampling trip was completed at Kawerau geothermal area.

Friday July 1 - Gas flight over White Island

Conditions were good, with a 6.5 knot wind from the south-west. SO₂ and H₂S fluxes have risen since last month but the CO₂ remains at a similar level to the previous reading. These are all within normally expected ranges for the volcano.

Monday July 4 - Gas flight over Ruapehu and Ngauruhoe

Conditions were relatively windy at 18 knots. Both CO₂ and SO₂ have risen but no H₂S was detected; the readings are within the normal ranges for the volcano. The Crater Lake was overflowing and upwellings were not easily observed.

No gas was detected at Ngauruhoe.

Reported landslides from media sources

Friday July 1

• Rocks falling about 50 m from the cliff 300 m south of Rothesay Bay beach on the Hauraki Gulf coast north of Auckland killed a woman walking her two dogs on the narrow shoreline below the cliff.
• On-going landslides from the cliff at Muriwai Drive, Whakatane, buried an excavating machine and the driver had to flee.

Friday July 15

• SH 3, the Manawatu Gorge, was blocked by a slip at midday, but re-opened in the evening.

Sunday July 17

• SH 5, the Napier-Taupo Road, was closed by a large slip that blocked both lanes about 10 minutes north of Te Haroto. One lane was opened by midnight.

Monday July 18

• Roads in the area between Richmond and Motueka were partially blocked by slips at Mapua (Te Awa Awa Road and Westdale Road), Kina Peninsula Road and the Moutere Highway between SH 60 and Main Road, Lower Moutere. Clearance of the roads was expected by July 22.

Sunday July 24

• SH 1 was partially blocked by a slip between Puhoi and Warkworth, but it was soon cleared.

Felt earthquakes of
June 2011
(305 located).

Shallow earthquakes of
June 2011
(1,689 located).

Deep earthquakes of
June 2011
(330 located).