May 7 2010 - April 2010 GeoNet roundup

Putting the finishing touches to the seismic vault at Hossack Road (HSRZ).

Additions and upgrades to the geophysical monitoring networks

• Two new continuous GPS sites have been commissioned, one at Minginui (MING), near Murupara and one at Te Kuta (KUTA), north of Napier.
• Two new regional seismic sites were completed in the area between Taupo and Rotorua, one at Hossack Road (HSRZ) and one at Kaahu Road (KUTZ).
• A borehole seismometer was installed at Wahianoa (WNVZ) on Mount Ruapehu, replacing the surface instrument. This complements the borehole seismometer installed near the Chateau in November 2009.
• A trip was made to Raoul Island to repair the radio repeater on Mount Moumoukai and to do maintenance work on the tsunami gauges and the satellite data telemetry. The radio repeater had been damaged by lightning. The camera also turned out to be damaged but unfortunately this could not be repaired on site. A replacement camera will not be able to be installed until October 2010 at the earliest. We are very disappointed to have lost our photos from Raoul for the time being.

Earthquakes summary

• The most widely-felt earthquake of the month occurred on Sunday, April 4, magnitude 3.8, 30 km north of Christchurch at a depth of 35 km. We have received 525 felt earthquake reports to date.
• The preliminary locations of March's earthquakes located by our analyst team are shown below.

Volcano surveillance field trips

Monday 29 March - Gas flight over Ruapehu

The wind speed was 4.3 m/s. Good peaks were obtained for CO₂ and Interscan H₂S and SO₂. SO₂ was not detected on the Cospec or Flyspec. Overall the gas flux appears to be decreasing, though there is a slight increase in H2S flux compared to the previous flight. Cloud prevented transects below 7,800 feet being flown, but gas levels at this altitude were very low or nil and we got a good 1,000 feet of plume above the cloud barrier. Ngauruhoe was unable to be flown due to cloud build up. The results were as follows:

The buoys on Crater Lake were spotted and photographed. The lake was a uniform aquamarine colour and no upwellings were observed.

Tuesday 30 March - Gas flight over White Island

Flying conditions were very good. The wind speed was about 10 m/s. CO₂ flux decreased while SO₂ flux was slightly up. The results were as follows:

Friday/Saturday 9/10 April - Ruapehu Crater Lake visit

The weather was once again excellent over the two days.

On Friday, the team collected lake bathymetry and gas flux data, along with water and gas samples. The inflatable boat was once again used successfully. A hydrophone sensor was also installed. This will collect audio signals and provide data on total power in various frequency bands. While there, we also replaced the anchor brick (which was brittle and partially dissolved after a year in the lake). The sensors are now mounted in a large concrete cinder-block. We repositioned the sensors further out and in deeper water, using rubber waders for access. It was noted that the sensors appeared to have shifted closer to the shore at some point since they were last repositioned (8 December 2009). Hopefully with the larger anchor and being positioned in deeper water, they should now stay put. The data from the meteorology buoy were collected and the radio removed.

On Saturday, the meteorology buoy was removed from the crater lake. Its weather station was found to still be in good serviceable condition and there was no evidence of leakage in the buoy. We had used some ballast which consisted of sections of large steel pipe with lead lining, having a steel wall thickness of approximately 8 mm. We noted that the steel had 90% dissolved, although the lead was mostly intact. Additional lake bathymetry data were also collected.

Reported landslides from media sources

No landslides were reported during April 2010.

New facilities for researchers

• A spreadsheet of moment tensor solutions for New Zealand earthquakes has been added to the Resources section. These will be updated monthly:
  • Moment Tensor Solutions (122.75Kb)
    
• The Common Waveform Buffer repository of seismic and tsunami data is accessed by a Java client. We have been working in collaboration with Victoria University students over the past few months to improve the functionality of this. Its main strength is the output of seismic data in SAC format; SAC (Seismic Analysis code) is a very popular time series data package used by researchers.
• A round of outreach visits to New Zealand universities kicked off at Victoria in Wellington. The aim is to hold seminars at each of the earch science universities in New Zealand early in the academic year. Staff and students will be given an update about GeoNet's data resources and their access methods. Visits to Canterbury and Auckland are planned for May, with other universities to be added next year.

Felt earthquakes of March 2010 (18 located).

Shallow earthquakes of March 2010 (1351 located).

Deep earthquakes of March 2010 (473 located).