Oct 7 2011 - September 2011 GeoNet roundup
Last month's new sites, volcano surveillance results, earthquake summaries, data products and other news from GeoNet, New Zealand's geological hazard monitoring system.
Additions and upgrades to the geophysical monitoring networks
The completed Whangaehu Valley Road continuous GPS site near Taihape.
- Strong-motion sites were installed at Gisborne Hospital Hill (GHHS), Cuba Street (CUBS) and Parkway Basin (PRKS), the latter two being in Wellington and Wainuiomata respectively.
- The North Cape tsunami site was extensively damaged by a lightning strike to the nearby Maritime New Zealand beacon; all electronic equipment was damaged. The site has now been restored except the sensors which are planned for replacement in October.
- A continuous GPS site at White Island Summit (RGWI) was installed on White Island.
- A continuous GPS site at Whangaehu Valley Road (WHVR), about 30 km west of Taihape, was completed.
Earthquakes summary
- The most widely-felt earthquake of the month occurred on Friday, September 16, magnitude 4.3, 10 km west of Porirua at a depth of 50 km. We have received 1,617 felt earthquake reports to date.
- The preliminary locations of August'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 September, except for ongoing submarine activity at Monowai Volcano.
- This month we completed gas flights at Ruapehu, Ngauruhoe and White Island and a Crater Lake sampling trip to Ruapehu.
Wednesday September 21 - Gas flight over White Island
White Island crater lake on September 21.
Both CO2 and SO2 have decreased since the August flight.
| Method |
21/09/2011 |
02/08/2011 |
|---|---|---|
| SO2 emission (Cospec) | 138 | 554 |
| SO2 emission (Flyspec) | 169 | 619 |
| CO2 emission (Contouring) | 928 | 1,220 |
| H2S emission (Contouring) | NA* | 1.6 |
| SO2 emission (Contouring) | 88 | 205 |
| * NA - not available due to instrument fault | ||
Thursday September 22 - Gas flight over Ruapehu and Ngauruhoe
Conditions were excellent with a light 6 knot breeze. No gas was detected at Ngauruhoe.
| Method |
22/09/2011 |
03/08/2011 |
|---|---|---|
| SO2 emission (Cospec) | ND* | ND |
| SO2 emission (Flyspec) | ND | ND |
| CO2 emission (Contouring) | 347 | 234 |
| H2S emission (Contouring) | 1.6 | 0.2 |
| SO2 emission (Contouring) | 42.4 | 6.0 |
| * ND - not detected | ||
Thursday September 29 - Ruapehu Crater Lake visit
The lake was a greeny-grey colour and the level was just above the overflow. The temperature at Central vent was 17.6 °C; it was sampled for gas and water.There was a strong smell of gas on the downwind side of the volcano while the team were flying there.
Reported landslides from media sources
Thursday September 1
- A landslide in the Callery River near Franz Josef formed a small landslide dam about 4 km upstream from the confluence of the Callery and Waiho Rivers. Tracks in the area were closed as a precaution. However, it is considered unlikely that the dam will cause major problems downstream due to its relatively small size (20 to 40 m high and 30 to 40 m wide) and the fact that it is formed by large boulders of schist.
Tuesday September 6
- SH 3, the Manawatu Gorge, remains closed due to further slippage of landslides at the Ashhurst end. The road is now not expected to re-open until October.
Sunday September 11
- The Tasman Valley Road was closed due to rock falls at The Bluffs, cutting off vehicle access to the Tasman Glacier walking tracks.
Felt earthquakes of
August 2011
(134 located).
Shallow earthquakes of
August 2011
(1,288 located).
Deep earthquakes of
August 2011
(406 located).
