Posted: Sat Nov 19, 2011 3:07 pm Post subject: New Zealand volcano, small earthquakes
Strong earthquakes strike off northeastern New Zealand
18 November 2011 TIKITIKI, NEW ZEALAND (BNO NEWS) - Two strong earthquakes struck off the east coast of the North Island in New Zealand on early Friday evening, seismologists said. There were no reports of damage or casualties.
The first earthquake at 4.34 p.m. local time (0434 GMT) measured 5.8 on the Richter scale and was centered about 140 kilometers (87 miles) east of Tikitiki, a small town about 100 kilometers (62 miles) northeast of Gisborne. It struck about 33 kilometers (20 miles) deep, making it a shallow earthquake.
Several hours later, at 7.51 p.m. local time (0751 GMT), a stronger earthquake measuring 6.1 on the Richter scale struck the same area at a depth of 40 kilometers (25 miles), according to the Institute of Geological and Nuclear Sciences (GeoNet), the country's seismological agency.
GeoNet said especially the second earthquake could be felt in some parts of the eastern region of the North Island. However, officials said there were no reports of damage or casualties from either earthquake and no tsunami alerts were issued.
New Zealand has been struck by several earthquakes during the past year. On June 13, a strong 6.3-magnitude earthquake struck near the city of Christchurch on the South Island, injuring 46 people. It followed a 6.3-magnitude earthquake on February 22 near the same city, killing 181 people and injuring more than 1,500 others.
The earthquake in February was the country's deadliest disaster since a powerful 7.8-magnitude earthquake struck the Hawke's Bay region on February 3, 1931, killing at least 256 people and injuring thousands more.
3 earthquakes rumble near New Zealand’s volcanic White Island
April 1, 2012 – NEW ZEALAND – Three earthquakes, the largest measuring magnitude-4.8, have been recorded near volcanic White Island within half-an-hour each other. GNS Science reported a 4.8 quake at 4.08 pm, 110 km north of White Island, which sits off New Zealand in Bay of Plenty. A second quake, measuring 4.7 struck at 4.24 pm, followed by a 4.1 quake at 4.30 pm. All three quakes were shallow, with the focal depth of each quake being measured at between 3 km to 6 km. The first two tremors were reportedly felt in Coromandel. White Island, New Zealand’s largest volcano last erupted in 2000. GNS Science could not immediately be reached for comment on whether the earthquakes might affect volcanic activity on the island. –Stuff.NZ
Two quakes shake New Zealand
May 06, 2012 TWO earthquakes have hit parts of New Zealand today.
A magnitude 4.2 earthquake shook people in the Wellington region and parts of the top of the South Island at 11.33am (9.33am AEST).
The tremor was centred 10 kilometres southwest of Wellington, at a depth of 30km, GeoNet says.
The second quake, also measuring 4.2 on the Richter scale, struck at 12.31pm and was felt on the west coast of the South Island.
It was centred 10km south of Ross at a depth of 15km.
Police told AAP they had received no reports of damage.
Strong quake rattles central North Island
7/8/12 North Islanders were again rattled by a strong earthquake yesterday, but experts say the tremor was not related to a much larger quake four days earlier.
GeoNet reported a magnitude 5.7 quake struck 10km south of Turangi at 12.50pm. The quake was 90km deep and, though police said there were no reports of damage, some residents said trinkets had been smashed.
Rumblings under Tongariro volcano NZ
July 20, 2012
Scientists have raised the Volcano Alert Level at Mt Tongariro after a series of quakes beneath the volcanic complex.
GeoNet said typically Tongariro experienced two such quakes - magnitude 2.5 or less - a year, but there had been more than 20 since July 13.
In a Volcanic Alert Bulletin issued this afternoon, it said the sequence started on July 13 and declined for a period, before restarting on July 18 and increasing in number yesterday.
‘‘These indicate unrest at Tongariro and give reason to change the Volcanic Alert Level to level 1 [from 0] and the aviation colour code to yellow [from green].’’
‘‘These earthquakes are small (magnitudes <2.5 ) and have only been well recorded by a few of the seismometers in our permanent network.
The earthquakes cluster in a zone between Emerald Crater and the Te Mari craters at 2-7km depth.
GeoNet said to better understand the significance of the quakes it was planning to put portable seismic recorders around the epicentres and conduct sampling of selected hot springs, crater lakes and fumaroles in the area.
The Te Mari craters, about 2km east of Ketetahi hot springs on the north side of Mt Tongariro, were the last craters confirmed as active on Tongariro.
In 1869 a large eruption accompanied by an earthquake at Tongariro formed the upper Te Mari Crater during an explosive eruption.
Maori descriptions talked of "bright red flame through the smoke that would burst and fall like snow", GeoNet said.
5.8 quake off NE off NZ North island
July 21, 2012
A 5.8 earthquake was recorded 150km east of Ruatoria this afternoon.
But despite the strength of the quake – which was felt as far away as Whakatane, Opotiki and Wairoa – locals reported no damage.
The shake -which was centered off the coastline – occurred at 4.54pm.
It comes as a series of quakes in the central North Island saw the Volcano Alert Level at Mt Tongariro being raised on Friday.
GNS Science volcanologist Brad Scott told Stuff on Friday the increased activity ‘‘just means that something has upset Tongariro, and some subterranean process is occurring’’.
NEW ZEALAND * Geyser may be coming back to life on North Island after 43 years
July 28, 2012 – A long forgotten geothermal spectacle on New Zealand’s North Island could be coming back to life after more than 40 years, scientists said. In the first half of the 20th century the Waikite Geyser in the Whakarewarewa geothermal area near Rotorua was known for its spectacular hot water eruptions reaching up to 65 feet but had not produced a significant eruption since 1969, the Institute of Geological and Nuclear Sciences said. However, in the past year scientists have increasingly noticed geothermal waters coming into the throat of the geyser, a major tourist attraction, the official Chinese news agency Xinhua reported. Geothermal features like geysers can be naturally variable and stay dormant for years, GNS geothermal scientist Ed Mroczek said in a statement. “This makes it difficult to distinguish what is part of a natural cycle and what is disruption caused by human activity,” he said. Scientists say they believe a sharp increase in the number of bores drilled in Rotorua since the 1950s by homeowners and businesses seeking cheap energy caused underground pressures to drop. But new research at Whakarewarewa suggests pressure has increased and water from deeper in the earth was being pushed toward the surface, scientists said. “We have no way of knowing if Waikite will recover to its former magnificence, but the signs we are seeing are very encouraging,” Mroczek said. –Terra Daily
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August 2, 2012 several quakes east off the North island of NZ in the past few days.
5.2, 4.8 and 4.5 quake Aug 2
5.1 quake Aug 1
PLENTY of shaking in the Bay of Plenty NZ
Active volcano's alert level raised. An active volcano in the Bay of Plenty is showing signs of increased activity.
The aviation alert level for White Island off the coast Whakatane has been lifted by GNS from green to yellow.
Its crater lake had recently started to re-fill and gases were now "vigorously streaming through it.
White Island volcano is showing signs of increased activity.
The volcano, about 49 kilometres off the coast of Whakatane, is a popular tourist spot, but GNS volcanologist Michael Rosenberg says those visiting it should be cautious even though the alert level for the island had not changed.
"Eruptions can occur at any time with little or no warning. The recent changes in activity suggest that the hydrothermal system has become unstable, and as a result the risk has increased," Rosenberg said.
GNS Science has changed the volcano's code from a "normal, non eruptive state" to "experiencing signs of elevated unrest above known background levels".
The volcano's lake level quickly rose by about three to five metres sometime between Friday and Saturday last week, exposing a "vigorous" flow of gas and steam into the air, Rosenberg said.
It has risen in the past, but took much longer than the 24 hours it took to rise three to five metres on Friday and Saturday, he said.
During the past few weeks there had also been some minor volcanic tremor, including several hours on Saturday, Monday and Tuesday.
Last year and earlier this year the lake started to evaporate and exposed steam vents and two large muddy pools.
"These phenomena are typical for White Island’s activity, but are the first substantial changes to occur in the last few years," Rosenberg said.
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NEW ZEALAND Tongariro erupts, alert level raised
Loud explosions, lightning, plumes of smoke; first activity in 100 years
August 6, 2012 - The volcanic alert level for Mt Tongariro has risen from 1 to 2 after the central North Island volcano erupted for the first time in more than a century late last night.
GNS science is reporting that at approximately 11:50pm on Monday night ash fall began to be reported in the volcano's vicinity - it has since been reported as far east as SH5 near Te Haroto and in Napier.
Tongariro volcanic alert maintained
August 6, 2012 The weather TV channel reported this is a hazard to planes.
- Mt Tongariro erupted at 11.50pm last night, hurling rocks up to 1km.
- Ash cloud drifting to the east of Tongariro, landing as far as Napier city
- SH1 and SH46 have reopened. Flights to and from Napier cancelled, while other North Island services have been delayed.
- GNS: It was a hydrothermal-driven eruption, rather the magmatic
- It was the first eruption in more than a century
- Turoa and Whakapapa skifields remain open
The aviation colour code around Mt Tongariro has been downgraded from red to orange, but the volcanic alert level remains where it was after the mountain burst into action last night.
A plume shot almost 7000m into the air, "which is not insignificant'', Civil Aviation Authority manager of meteorology Peter Lechner said.
The plume was now sitting over the volcano and to the east towards Hawkes Bay.
Lightning seen around erupting White Island
August 09, 2012 Flashes of lightning have been reported coming from White Island as the volcano continues to erupt.
White Island, which lies 48 kilometres off the Bay of Plenty coast, was raised to a Volcanic Alert Level 2 after a surveillance camera captured a small eruption from its crater last week.
Whakatane Police said they received a number of calls reporting lightning of different colours since just after 7pm.
GNS visited the island, which is New Zealand's most active cone volcano, this morning and confirmed it was still erupting with a 300 metre plume of ash spewing from the crater.
GNS scientist Michael Rosenberg said volcanic lightning is quite common and is a result of ash generating static electricity.
Giant mass of floating pumice indicates third volcanic eruption near New Zealand
August 10, 2012 – NEW ZEALAND - A floating mass of the volcanic rock, pumice, reportedly covering 25,000 square km, has been found floating in the South Pacific, indicating a third volcano is active near New Zealand. The New Zealand Defense Force (NZDF) said Friday the floating pumice, measuring 250 nautical miles long and 30 nautical miles wide, was first spotted by a New Zealand air force Orion on a maritime patrol from Samoa to New Zealand. The Orion relayed the information to New Zealand navy vessel HMNZS Canterbury, which spotted the pumice late Thursday about 85 nautical miles west southwest of Raoul Island, one of the Kermadec Islands that lie 750 to 1,000 km northeast of New Zealand. Lieutenant Tim Oscar, a Royal Australian Navy officer on exchange with the Royal New Zealand Navy, described the pumice as “the weirdest thing I’ve seen in 18 years at sea. The lookout reported a shadow on the ocean ahead of us so I ordered the ship’s spotlight to be trained on the area,” Oscar said in the NZDF statement. As far ahead as I could observe was a raft of pumice moving up and down with the swell,” he said. The rock looked to be sitting 2 feet (60 cm) above the surface of the waves, and lit up a brilliant white color in the spotlight. It looked exactly like the edge of an ice shelf.” Oscar said he had been briefed by a volcanologist from New Zealand’s Institute of Geological and Nuclear Science (GNS Science) the previous day when the ship encountered another area of pumice from an undersea volcano. I knew the pumice was lightweight and posed no danger to the ship. Nonetheless it was quite daunting to be moving toward it at 14 knots. It took about three to four minutes to travel through the raft of pumice and as predicted there was no damage,” he said. “As we moved through the raft of pumice we used the spotlights to try and find the edge – but it extended as far as we could see.” HMNZS Canterbury was en route to Raoul Island with a party of GNS scientists aboard at the time. The Commanding Officer, Commander Sean Stewart, changed course to intercept the pumice and retrieve samples, which would be analyzed to determine which volcano they came from, said the statement. According to GNS Science, the underwater volcano, Monowai, had been active along the Kermadec Arc and the pumice could be a result of that activity, said the NZDF statement. The find comes after eruptions from Mount Tongariro, in New Zealand’s central North Island, late Monday and White Island, a marine volcano about 50 km off the east of the North Island, two days later. The GNS scientists aboard the Canterbury believed the volcanic activity of Tongariro, White Island and along the Kermadec arc was unrelated, said the NZDF statement. –News Track
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