Earthquake and Volcano Safety

Hope you are not visiting the Ruapehu area today, Mother Bear! :107:


Lahar passes Tangiwai, makes way to sea

Updated 3:00PM Sunday March 18, 2007

A moderate lahar, or mudflow, from Mt Ruapehu's crater lake has gone past the village of Tangiwai and is now on its way to the sea.

Ruapehu District Council spokesman Paul Wheatcroft told NZPA today the lahar had not caused any infrastructural damage which they knew of and was losing strength the further it went.

The lahar was following the route of the Whangaehu River and had passed the Marae Bridge and was now following the river's path through farmland, he said. "It will go all the way to the sea, near Wanganui, but it will be negligible how much of it will be left by then."

The lahar had followed the river's path which ran parallel to the Desert Road but had not crossed the road, he said. The river's water levels were much higher because of the lahar but were contained, he said.

The lahar broke through a rubble wall atop the mountain's crater lake about 10.47 am today, triggering an alarm, Horizon Regional Council said.

Conservation Department senior officer Dave Wakelin said it was a "moderate lahar" with no settlements in the immediate path of the flow.

Police and Civil Defence workers immediately closed roads round the southern base of the mountain including the North Island's main north-south State Highway 1 .

A lahar that tore down the same volcano in 1953 killed 151 people when it washed away a rail bridge, plunging a passenger train into the raging torrent of liquid mud.

(more on http://www.nzherald.co.nz/section/1/...ectid=10429432)

I think they are just itching for a bit more excitement! :)


After the big lahar, a swarm of earthquakes
5:00AM Tuesday March 20, 2007
By Errol Kiong ?

Sensors at the summit of Mt Ruapehu have recorded a series of small earthquakes since Sunday's spectacular lahar.

"The rapid removal of water from above a hydrothermal system can destabilise that system, resulting in small-scale eruptions," said Brad Scott, volcano surveillance co-ordinator at GNS Science, which maintains the sensor system.

The quakes measured up to magnitude 1.

Lowered lake levels could lead to increased heating and steam-driven eruptions, Mr Scott said. ?"If a small eruption occurred under the lake, it could generate waves large enough to overtop the hard rock rim of the lake, resulting in a small lahar."

He said an increase in quakes was common after volcanic lakes emptied and was a sign of changes to the hydrothermal system under the lake.

Mr Scott said hydrothermal eruptions were different from magmatic eruptions such as the 1995 event. ?"We're talking about eruptions that may dome up the middle of the lake by 15m to 20m. It's like a geyser."

The chance of another lahar was small but still probable, he said.

An inspection of the Crater Lake by Department of Conservation and GNS scientists yesterday morning confirmed that one part of the tephra dam had collapsed down to the original hard rock rim. ?The 7m-high soft rock and ash dam - created by the 1995 eruption and stretching 85m along the crater rim - disintegrated, releasing the pent-up acidic lake water.

As much as 1.3 million cubic metres of water and debris spilled from the Crater Lake and washed down the Whangaehu River to the sea near Wanganui 140km away.

The dam had been weakening under the pressure of the lake and erosion had been detected as early as December. ?Some 40mm of rain on Sunday morning is thought to have contributed to the dam's failure.

DoC senior conservation officer Dave Wakelin said the department still considered the Crater Lake a hazardous area but it had no power to bar the public. "All we can do is strongly advise people.

(more on http://www.nzherald.co.nz/section/1/...ectid=10429739)

One of my friend's work mate was at Taupo over the weekend when the Lahar occurred. He called back on the telephone to his boss on Monday..."Hey boss, I cannot come to work due to the Lahar".

I think it is another cool way to take off from work and yet not anger the boss! Only in New Zealand!!

In Wellington...maybe it goes like this.."Hey boss, I cannot come to work because of the wind...train cancelled" :D

[MotherBear]

NZ's tsunami warning system 'inconsistent'
5:00AM Thursday April 19, 2007
By Angela Gregory


Many coastal communities would not recognise a tsunami warning. Photo / Alan Gibson

Warning systems about possible tsunami heading to New Zealand are not consistent among the country's coastal communities, a natural disasters conference heard yesterday.

Mike O'Leary, operations manager for the Ministry of Civil Defence and Emergency Management, told the conference that getting warning information down to community level was patchy.

Mr O'Leary was specifically referring to the civil defence emergency management groups which were responsible for disseminating national warnings to local communities.

"That is our greatest vulnerability in New Zealand. There is a very patchy capability to do that across the country and in some cases it's not even identified."

Mr O'Leary said there were few proven and operating public alert systems such as sirens.

But he was personally not a great fan of the use of sirens in warning systems as their efficacy was debatable, there were problems with their maintenance and they could create a false impression of safety and security.

More here .

[MotherBear]

Central North Island sitting on magma film
By PAUL EASTON - The Dominion Post | Saturday, 15 September 2007

Scientists have discovered a film of molten magma under the central North Island, dispelling old ideas about the workings of the fiery region.

As a result of the find, monitoring of the potentially explosive Taupo Volcanic Zone, the scene of enormous eruptions in the past, will be improved.

It was thought magma lurked in unconnected pockets under volcanoes and geothermal zones, said Hugh Bibby of GNS Science.

But new measurements have revealed the molten rock lies across a zone 50 kilometres wide and 160km long, northeast of Taupo.

"The key is that it is like a continuous film wetting the surface. The wet surface is right across the Taupo Volcanic Zone, not just little blobs under each geothermal system or volcano," Dr Bibby said.

Scientists used magnetotellurics, which measure differences in the earth's magnetic field, to make the discovery. The research will lead to a better understanding of how the volcanic zone works, Dr Bibby said.

When the system is stable, a layer of hot rock with its small amount of magma provides the heat necessary to fuel more than 20 geothermal systems in the region. But if there is too much magma it can build up at shallow depths, eventually leading to a giant eruption. About 26,000 years ago such an explosion formed what is now Lake Taupo.

Until now there had been little evidence about the extent of the magma system under the central North Island. The Taupo Volcanic Zone was a perfect place for the study, Dr Bibby said.

"Eruptions from the Taupo area are enormous, the scale is difficult to imagine. Ruapehu erupted about 0.1 cubic kilometres of material in the 1995-96 eruption. Imagine an eruption of 400 cubic kilometres of material."

From here .

[selchie]

Interesting stuff. Let's just hope the region stays rather quiet during our lifetimes.

[MotherBear]

Ruapehu eruption: Debris thrown 1.5km
Page 1 of 3 Updated 2:05PM Wednesday September 26, 2007
By Elizabeth Binning and Alanah May Eriksen and Edward Gay


Ash and a lahar are visible at the summit of Mt Ruapehu today. Photo / Alan Gibson

Mt Ruapehu has slumbered today after last night's eruption but experts are wary of saying the volcanic activity is over.

The eruption at Mt Ruapehu last night threw debris as far as 1.5km from the crater's edge, GNS said.

"Impact craters" 1-2 metres wide had been caused by the debris landing after being hurled into the air, Brad Scott - a volcanologist at GNS - said.

A considerable amount of water had also pooled at the top of the volcano and then run off down the Whangaehu and Whakapapa glaciers.

The lahars - mud flows - created by the eruption had been minimal, reaching only a short distance down the mountain and not causing any damage on the skifields.

From here .

Photos .

[MotherBear]

Powerful earthquake south of NZ
By MICHAEL FIELD - Fairfax Media | Sunday, 30 September 2007



A powerful earthquake has hit the Auckland Islands, south of New Zealand, but there is no indication of a serious tsunami risk, Civil Defence says.

A statement released by Civil Defence described the earthquake, which occured at about 6.30pm, as moderate and of between magnitude 7.3 and 7.4 on the Richter scale.

The Director of the Ministry of Civil Defence & Emergency Management, John Hamilton, said that there is nothing yet to suggest that a tsunami of any size has been generated.

As a precaution, the Otago and Southland Civil Defence Emergency Management groups have been advised.

The GNS Science convened tsunami expert panel and NIWA scientists are monitoring and assessing information about the earthquake and sea level movements.

The Pacific Tsunami Warning Centre (PTWC) in Hawaii has stated that there is no risk of a Pacific-wide tsunami but a small local tsunami could in theory be generated.

"We will provide updated information as it becomes available," Mr Hamilton said.

A spokeswoman from Invercargill police said she felt the quake, but it was not a strong shake.

"Just seemed to roll for a bit and rock for a bit," she said.

Earlier reports from the European Union-based Global disaster Alert and Coordination System reported the quake, at 6.23 pm New Zealand summer time, as 7.6 magnitude on the Richter Scale while the US Geological Survey (USGS) was posting it as 7.3.

The USGS said the quake was a shallow 18.9 kilometres deep and was 475 kilometres south west of Invercargill. It was 205 kilometres from the unpopulated Auckland Islands.

Meanwhile, AFP reported from Sydney that parts of southern Australia were on tsunami alert following the earthquake.

It quoted Geoscience Australia officials as saying the quake hit near the Auckland Islands at 6.24pm NZT and was centred 350km southwest of New Zealand and 1400km southeast of the state of Tasmania.

The Bureau of Meteorology issued a tsunami bulletin warning people in coastal areas in Tasmania and southeastern mainland Australia to listen to news updates.

"The Joint Australian Tsunami Warning Centre has detected a large undersea earthquake south of New Zealand in the Auckland Islands region and is seeking confirmation that tsunami have been generated," it said.

If tsunami have been generated, then they could start affecting southern Australia from 5.45pm (8.45pm NZT) and Sydney by 6.15pm (9.15pm NZT) it added. .

In historic terms the quake appears unusual.

Historic data shows it is much larger than usual in the area, and out of line with a fault line running southwest.

The EU sent a global email and mobile phone text warning about the quake.

- with NZPA

From here .

[MotherBear]

And there's more...... They're popping up all over the place.

Matata resident - You could hear it coming
5:00AM Monday October 01, 2007
By Simon O'Rourke

A "thunderous" noise woke many Matata residents from their sleep early yesterday morning before the onset of what some are saying was the biggest earthquake felt in the region this year.

"You could hear it coming," said Matata Superfoods owner Charlie Semmens.

"We've had a few this week, but it was definitely the biggest one I've felt. I was sleeping and the noise woke me up before it hit.

"Things rattled, hell yes, but only one thing of ours fell off, and that was a set of glass white elephants that were on the TV. In the shop all we could find that had fallen off the shelf was one tin of apple sauce."

He said a series of other jolts felt last week were tiny. Earthquakes were a regular feature of living in the eastern Bay of Plenty, and locals normally took the trembles in their stride.

More here .

[MotherBear]

String of quakes overnight
9:14AM Tuesday October 02, 2007

A string of earthquake jolted parts of New Zealand overnight.

These follow the magnitude 7.3 quake that struck near New Zealand's sub-Antarctic Auckland Islands on Sunday night.

GNS science recorded five earthquakes yesterday from Mount Cook to Turangi.

A magnitude 4.1 quake struck Mount Cook at 5.25pm. It was centred 30km north of the mountain and was 2km deep.

Earlier in the afternoon, a quake measuring 4.5 on the richter scale shook the central North Island.

The quake at 3.12pm was centred 10km northeast of Turangi and was 5km deep.

More here .