Archive for February, 2006

Another Strong Earthquake Near Fiji

Sunday, February 26th, 2006

New Zealand’s seismometers were triggered by a strong earthquake which struck 620 km south-east of Suva, Fiji at 3:08 p.m. New Zealand Daylight Time. The magnitude 6.5 earthquake was very deep at 545 km. The earthquake left traces on all of Geonet’s seismometers but was too distant to have been felt here.

The earthquake occurred in an area north of Raoul Island that is very active and hosts many deep earthquakes. Since February 20th, the USGS National Earthquake Information Centre has recorded three magnitude 4.6 earthquakes at various depths in the area near today’s earthquake.

Today’s earthquake occurred 200 km further south of the magnitude 7.1 quake that occurred at a similar depth on January 23rd (NZDT).

These earthquakes are occurring beneath the Tonga Microplate which sits at the edge of the much larger Australian tectonic plate. The activity is caused by the edge of the Pacific Plate sliding underneath the Australian Plate along the seafloor from near Samoa to just north of Cook Strait.

It is reasonable to expect that today’s earthquake has altered strain on the plate interface between Tonga and the Kermadec Islands in an indirect manner, owing to the greater depth of the earthquake. How the plate interface nearer New Zealand will react to this event, either by accepting more strain or through further slippage is less clear. This is part of a process that involves movements measured in mm per year with strain alternately building and then releasing during earthquakes.

It could equally be argued that today’s event is the result of the deep activity near the Kermadecs in recent months transferring strain to the north.

Seismologists study the inter-relationships between earthquakes over periods of years and decades in the hope of finding general trends.

s.s. Manapouri Tragedy 1886

Sunday, February 26th, 2006

Great excitement ran through Gisborne on the afternoon of Friday February 26th 1886 when the steamer Manapouri entered Poverty Bay flying signals for a doctor.


Earthquakes at Oamaru in 1876

Saturday, February 25th, 2006

Early on Saturday the 26th of February 1876, Oamaru residents were startled from their beds by the first of several large earthquakes. Earthquakes in this area of the South Island are unusual, and the shocks were unexpectedly large.


The 1863 Earthquake near Hawke’s Bay

Thursday, February 23rd, 2006

Nearly 90 years after the first earthquake was reported by a European in New Zealand, the residents of Hawke’s Bay experienced their first officially recorded major earthquake on this day in 1863.


The Pitter-patter of Tiny Li’l Feet

Tuesday, February 21st, 2006

This summer has seen the usual invasions of spiders and stick insects as well as wetas; but the weta invaders have been fewer in number than previous years.

The spiders are generally the jumping kind, and easily detected as they twitch to watch you as you walk into the room – the slight movement gives them away instantly. Removal needs to be quick because, if they decide to scarper, they can engage those eight legs in a very effective manner.

In years past I used to scoop them up and take them outside by hand. But on the last occasion, I paused to look more closely, and noticed how large their fangs are. “Oooh, errr,” I thought. “I might get a nasty nip if he decides that this trip isn’t to his liking.” Nowadays, they are swept up by a rolling motion of one of those fluffy dusters and carried outside to the garden. Painless for them, and lower stress for me.

The stick insects have been most co-operative this year. Usually they take their time in climbing onto a proffered piece of cardboard or greenery for their trip back outside. There have been fewer adults and more babies invading the house this year; a good sign, I hope, that they are breeding well. The youngsters seem quite happy to climb onto the sprig of greenery, possibly because they have quickly discovered that it is actually drier inside the house than out. However, they seem to enjoy the ride so much that they don’t want to get off at their destination. Perhaps, like the young humans of today, their expectations have risen; and they actually expect a trip to Fiji or somewhere exotic to be their due instead of a quick return to the same boring old garden.

The house was invaded by a hundred footer this morning. The appearance of a centipede near the kitchen door was a first. It was just a baby, so I’m wondering where mum is lurking – hopefully not in the nearby pantry gobbling up goodies with the rest of her brood.

Young Centy, as I named him (or her?) was most co-operative but rather fast moving when it came to the removal routine. At first he was reluctant to climb onto a sheet of cardboard, but soon realised that there was little alternative. Once aboard, the command “By the left, quick march!” was issued and like a platoon of soldiers he was off with his fifty left feet. Within a few seconds he’d managed to sinuously cover half of the cardboard and it looked like the trip might end in disaster. They don’t have sticky feet so I had anticipated that, like pre-Columbus humans, he would soon find the edge of his world and sail off the edge.

Fortunately, Centy seems to have had proper military training and executed a very deft U-turn about three-quarters of the way across the sheet and started heading back from whence he came. This gave just enough time to get him to the safety of the lawn where he stomped off the edge of the sheet without flinching.

Ah. The delights of the leafy section. If only the fauna would stay amongst the flora and refrain from coming indoora.

Tragic Flash Flood, 1938

Sunday, February 19th, 2006

An unexpected deluge on the East Coast caused widespread damage and claimed 22 lives on the 19th of February 1938. Communities between Wairoa and Te Araroa were swamped by what was described as a “cloudburst” which carried away bridges and houses, and washed away roads and hillsides.


Sponge Bay Uplift, 1931

Friday, February 17th, 2006

On the afternoon of the 17th February 1931 an extraordinary event occurred at Sponge Bay, 3.5 kilometres from Gisborne. Men engaged in obtaining stone supplies on the beach of Tuamotu Island stated that a reef “just rose out of the sea without warning.” The 2 acre boulder bank rose an average of 2 metres without perceptible shaking of the ground in the immediate area or surrounding district.


Earthquake in Cook Strait

Friday, February 17th, 2006

A magnitude 4.0 earthquake struck near Wellington at 6:25 this morning. The magnitude 4.0 quake was centred 30 km south-west of Wellington, and 50 km deep.

The area has experienced several earthquakes so far this month. They were:
Feb 16th: Mag 5.9, 180 km deep, 80 km north-east of Collingwood
Feb 9th: Mag. 3.4, 40 km deep, south-west of Kapiti Island
Feb 8th: Mag 3.3, 40 km deep, off coast at Porirua
Feb 3rd: Mag 3.8, 50 km deep, north of Kapiti Island
Feb 1st: Mag 3.7, 40 km deep, off coast at Porirua

These earthquakes have occurred within the Pacific Plate which is subductiing (sliding) under the Australian Plate in this area. They represent the changing stresses in the area as the two tectonic plates collide.

Earthquake off the North Island’s West Coast

Thursday, February 16th, 2006

An earthquake off the North Island’s West Coast was widely felt in central New Zealand at about 1:17 this morning.

The magnitude 5.9 earthquake which was centred in the Tasman Sea 80 km north-east of Collingwood and 180 km deep occurred at 1:15 a.m. according to Geonet.

Two earthquakes occurred in this area during January. On January 16th a magnitude 4.6 earthquake, 160 km deep struck 60 km east of Collingwood. The following day, a shallow magnitude 3.8 earthquake 5 km deep occurred 60 km north of Collingwood.

This morning’s event, whilst noisy, was probably too deep to have caused notable damage. The pronounced rumble was heard for more than 10 seconds in Tawa and attracted the attention of people as far north as Wanganui.

January 2006 Much Windier Than Previous Three Years

Wednesday, February 15th, 2006

Manual weather data has been collected at Tawa since 2003 and in 2005 it was augmented by the installation of an automatic weather station. This report blends the historical data from both sources to provide a 4-year climate overview.

The manual readings are obviously subjective, and represent the microclimate where the observations were made. The weather station is sheltered from the south owing to local topography. Manual data for January 2003 is incomplete.

Tawa’s climate during January 2006 was much windier but drier than the previous three years.

Readings taken at Tawa:
The lowest January temperatures were 7 (2003), 10 (2004), 8.2 (2005) and 8.2 (2006).
The average daily low temperatures were 13 (2003), 12 (2004), 11 (2005) and 13 (2006).
The highest January temperatures were 29 (2003), 28 (2004), 28.3 (2005) and 29.7 (2006).
The average daily high temperatures were 23 (2003), 19 (2004) 18 (2005) and 23 (2006).
Average temperature: 17.7°C (2005), 18.0°C(2006).
Average humidity: 80% (2005), 75% (2006)

Days with frost: no data (2003), none (2004), none (2005), none (2006).
Days with rain: no data (2003), 11 (2004), 10 (2005), 8 (2006).
Days with thunderstorms: no data (2003), none (2004), 1 (2005), none (2006).
Days with hail: no data (2003), none (2004), none (2005), none (2006).
Days with strong winds: no data (2003), 7 (2004), 5 (2005), 15 (2006).
Flood events: no data (2003) none (2004), 1 (2005), none (2006).
Rainfall: 99 mm (2005), 58 mm (2006).

A sudden storm event on the 8th and 9th of January 2004 brought strong winds from the northerly quarter, with gusts up to 120 km/h being recorded in the Wellington area. Later in the month, a southerly storm on the 20th and 21st brought a sudden downpour and temperatures plunged as low as 10°C.

In 2005 a storm on the 5th and 6th of January brought torrential rain, with 41 mm being recorded by the newly installed weather station on the 5th, with a maximum rain rate of 32 mm/hr at 8:55 p.m. By late morning, State Highway 1 had been washed out at McKay’s Crossing, and there was flooding at Otaihanga and in the Hutt Valley. Conditions eased until a powerful thunderstorm dumped another 40 mm at Tawa on the 8th, with the rain rate reaching 86 mm/hr at its peak. There was surface flooding at Tawa, Paekakariki and in the Hutt Valley. Both State Highways to the north were closed, and Wellington was isolated.

January 2006 was certainly windier than the three previous years, and gusts of 165 km/h were recorded at Mt. Kaukau, and 120 km/h in Wellington on the 3rd. A gust of 50 km/h was recorded at Tawa on the 5th. In all there were strong winds blowing on 15 days during the month.

Minor flooding resulted from a downpour on January 25th, 2006, when 32 mm of rain fell in Tawa, with the rain rate hitting 120 mm/hr at 2:29 p.m. Whilst traffic was disrupted, the event was short-lived and things returned to normal by late evening. In Wellington city storm drains backed up and there were reports of flash floodwaters up to 1 metre deep in a few places.

Don’t Supersize Me

Tuesday, February 14th, 2006

Fear not. This is not another tirade against a certain multinational plagued by customers who don’t know that coffee is hot and a varied diet is required to be healthy. It is, however, a gripe about sandwich and coffee bar operators who inflict change upon their customers for illogical reasons or pure humbug.

I like variety in my food, and a nice savoury sandwich in bouncy fresh bread is one of my regular choices when out and about.

Perhaps a simple ham and lightly curried egg sammie, hoping that the sandwich maker has gone to the effort of adding some chopped chives or parsley to the mashed egg to give it piquancy. Crispy bacon and avocado is another favourite. So are roast beef and onion, beef and horseradish, ham and asparagus, sliced lamb and mint sauce, sliced chicken with tomato and lettuce and mayonnaise … the list goes on. Then, of course there are the old-time favourites asparagus rolls and chicken and mayonnaise rolls – small affairs with the filling wrapped in a single slice of fresh bread with the crusts cut off.

Soon to be extinct, it would seem, are club sandwiches – small finger or triangular sandwiches made up of three slices of white and brown bread with double fillings such as beef and wholeseed mustard with sliced tomato, ham and peppered tomato with a savoury cheese, ham with asparagus, roast pork with lettuce and cucumber and, of course, ham and tomato with curried egg.

Not only are these dainties slowly disappearing, but so is the choice of having one of those, a club and one of those with a dish of hot coffee while jaw-boning with friends.

Over the last few years, sandwich and coffee bars have started packaging their sandwiches in pairs in those hideous triangular packs of rigid plastic. I’ll give some of them the benefit of the doubt, by suspecting that some may have done so for hygiene reasons in situations where some customers were uplifting sandwiches with their hands from self-serve cabinets.

But in doing so, the food outlet has limited my choice – no longer can I have three different sandwiches for lunch, I have to have two or four, and limit myself to one or two flavours.

Nonsensically, I have seen these hideous packs used in coffee bars where the sandwiches are kept in chilled glass cabinets from which they are dispensed by staff. As soon as I see this, I immediately suspect that the motive is supersizing – selling more and increasing income.

I’ve also noticed the twin packs appearing in self-serve sandwich cabinets alongside individual sandwiches which can be selected using tongs. What often annoys me when I see this, is that only certain sandwiches are available singly, and the more popular concoctions are twin-packed. In such a situation, hygiene concerns are obviously not the motivation for the change.

Many of my regular haunts have started this practice in recent times, and have been rewarded with my departing feet. The malarkey has spread to Tawa too – although the pairs of sandwiches are packed in cling film rather than rigid plastic packs. And malarkey it is too, as the sandwiches are housed under glass and dispensed by the staff. Once a popular calling point for a sandwich or two whilst out on a walk, this business has now lost my custom.

Businesses should be aware that their customers are not stupid. Don’t supersize me.

Hawke’s Bay Earthquakes 1931

Monday, February 13th, 2006

A pair of magnitude 7 earthquakes shook Hawke’s Bay during February 1931. The first was a magnitude 7.8 quake that struck on Tuesday 3rd February near the shoreline 8 to 24 kilometres north of Napier.

Writing in The New Zealand Journal of Science and Technology, July 1933, F.R. Callaghan of the DSIR described the earthquake as follows: “The consensus of opinion is that there were two shocks of very different characteristics, occurring within a brief interval of some thirty seconds of one another. The first shock developed rapidly in intensity, had a distinctly uplifting motion associated with violent and confused swaying. Then followed a pause of about half a minute, till the second shock occurred, with a motion resembling a sharp bump downwards.” Callaghan quoted the radio operator of the m.v. “Taranaki” as stating “… the tremors continued for two and a half minutes from the time of the first noticeable shock.”

The earthquake was felt throughout New Zealand with the exception of Northland and Otago. In Hawke’s Bay, the main earthquake was followed by a brief period of quiet, but before long tremors commenced and continued for some days. Official records recorded 151 aftershocks that day, with 55 on the 4th, 50 on the 5th, 29 on the 6th and 24 on the 7th. The number of aftershocks then eased to less than 20 per day.

However, the rapid decline of the aftershocks was not to last. At about 1.30 p.m. on Friday 13th February another huge earthquake shook the Hawke’s Bay area. This event was officially set at magnitude 7.3 and centred about 50 km east of the earthquake of the 3rd.

In his book “Quake Hawke’s Bay 1931” Matthew Wright reports that this second event was New Zealand’s fourth strongest recorded earthquake. He writes, “Power failed three seconds before it was felt in Napier. People from Napier to Dannevirke ran for their lives as damaged buildings cracked and fell.”

He adds, “Some inland parts of Hawke’s Bay felt this aftershock more strongly than the 3 February quake. In Taupo, goods were thrown from shop shelves, but ‘there was no damage of any moment’. People rushed into the streets in Dannevirke and Masterton. In Wellington all but one of the clocks stopped in the Dominion Observatory, and ceiling lights in the Evening Post offices swayed ‘more vigorously’ than they had the week before.”

The earthquake of February 13th 1931 is widely regarded as an aftershock of the larger event ten days earlier. But Messrs Adams, Barnett and Hayes commenting on the rapid decline in the frequency of aftershocks in the Journal of Science & Technology stated, “The fresh outbreak on the 13th February, due to the severe shock on that date, may almost be regarded as a separate disturbance, although it probably arose from conditions produced by the original shock on the 3rd.” Earthquake counts shot up to 81 on the 13th, before dropping to 23 on the 14th, 18 on the 15th, 19 on the 16th and then slowly dropping away.

In all, 597 earthquakes were recorded at Hastings during February 1931.

The next event of note was to occur further north on February 17th.

Thunderplump at Tawa

Friday, February 10th, 2006

A late afternoon thunderstorm plunged Tawa into gloom late today before pelting the area with rain. Between 4:45 p.m. and 5:20 p.m. rainfall rates briefly reached 72 mm/hr although only 9 mm fell. The thunderplump was just in time to dampen the spirits of end-of-week commuters as they headed home.

The thunderstorm was short-lived, but lively, and only minor disruptions to the electricity supply were observed.

Most importantly, the storm gives me the opportunity to use the wonderfully evocative word, thunderplump. I chanced across it in the erudite Frank Haden’s column in The Dominion Post on Wednesday January 11th. Haden writes that thunderplump means “a sudden heavy thunder-shower.” He says the word is of Scottish origin and is “… ideal for the sort of changeable holiday weather we’re getting.” I can only agree!

Tawa recorded 30 mm of rain yesterday, and an additional 3 mm early this morning. The thunderplump added 9 mm and intermittent rain has since added another 9 mm. By early evening today’s total has reached 21 mm, bringing the month’s rainfall to 59 mm – close to the monthly total for February last year (but records for Tawa are incomplete for February 2005, due to a system crash).

Geological Summary for New Zealand area, January 2006

Thursday, February 9th, 2006

Geonet, the USGS (NEIC) and IGNS reported 35 earthquakes in the New Zealand area between the Kermadec Islands in the north, and the Auckland Islands to the south during January 2006. The magnitude distributions were as follows:
M5 to 5.9 (5), M4 to 4.9 (21) M3 to 3.9 (9).
An additional 3 events in the magnitude 2 range were deemed worthy of mention.

Seismological activity was noticeably quieter in January, compared with December. There were no distinct earthquake swarms, but the interesting sequence of deep earthquakes near the Bay of Plenty continued, as did the cluster of deep earthquakes further north in the Kermadec Islands.

The sequence of deep earthquakes offshore to the north of Rotorua and Gisborne continued with two distinct phases. The first phase involved a series of 7 earthquakes migrating southward along a line from 190 km north-east of Rotorua to 70 km south-west of the city between the 2nd and the 17th. As the epicentres progressed southward, the depths increased from 120 km to 280 km on the 15th, and then began rising to 157 km. One anomalous event defied this pattern at 12 km depth on the 5th.

The second phase of the sequence commenced activity on the 22nd at 190 km north of Rotorua but lacked the steady southward trend of the first phase. Epicentres in this series of 5 earthquakes ranged between 185 km north-east and 50 km south-west of Rotorua and depths ranged between 33 km and 252 km.

Earthquakes in both phases of the sequence ranged in magnitude between 5.5 and 4.0. The final event in the sequence was a magnitude 5.5 quake at 170 km depth located 30 km north-west of Taupo on the 28th. This earthquake was widely felt because of its magnitude and depth, and Geonet advise that it was felt from diverse locations in Hawkes Bay, Manawatu, Kapiti Coast and Wellington.

Activity in the cluster of earthquakes in the Kermadec Islands eased from its January peak, with 5 events between magnitude 4.5 and 5.2 occurring between the 17th and 30th. A subset of 3 events occurred between 150 km and 180 km north-east of L’Esperance Rock with magnitudes between 4.9 and 5.2 and depths between 10 km and 43 km.

A cluster of 3 earthquakes in southern Hawkes Bay occurred on the 7th, 23rd and 28th of January. Magnitudes ranged between 3.6 and 4.4 and depths between 20 km and 50 km. The magnitude 4.4 event on the 23rd which was located 10 km north of Waipukurau was one of the month’s 3 damage-causing earthquakes, with minor damage being noted by Geonet.

The other notable sequence of earthquakes was located within 5 km of Upper Hutt. When looked at in isolation, the pair of earthquakes seem to be a classic foreshock and mainshock pair. The first event was magnitude 3.3, 30 km deep on the 1st. The second was magnitude 4.3, 35 km deep on the 13th. However, these seem to be members of a long-term swarm that has been happening near Upper Hutt at various intervals since April 2004.

Only minor damage resulted from the three damaging earthquakes during January according to Geonet. They were:
January 7th, mag. 4.1, 30 km deep, 10 km west of Porirua. Items off shelves.
January 23rd, mag. 4.4, 20 km deep, 10 km north of Waipukurau. Unspecified minor damage.
January 29th, mag. 3.9, 5 km deep, 20 km east of Arthurs Pass. Unspecified minor damage.

Vulcanologists report that activity at the nation’s volcanoes is little changed from December. Their status can be summarised as follows:
Mt Ruapehu (Alert Level 1).
White Island (Alert Level 1).
Mt Tongariro (Alert Level 0).

Mt Ruapehu’s crater lake cooled to 28° C during the first half of the month, with the lake level rising slightly due to snow melt. Seismic activity remained at a low level.

White Island’s crater lake dropped slightly during the month, and seismic activity remained low. Surface features such as small collapse holes, mud pots and dry areas developed during January. Sulphur dioxide emissions increased slightly.

The numerous small earthquakes beneath Mt Tongariro continued at the increased level observed in recent months.

Earthquakes Near Porirua

Wednesday, February 8th, 2006

Some Tawa residents felt the small earthquake that occurred 10 km north-west of Porirua this morning. The magnitude 3.3 quake occurred at a depth of 40 km at 1:01 a.m. Today’s earthquake is the latest in a series of small events that have been occuring near Porirua since December.

The first event in the series was a magnitude 4.6 quake at 30 km depth, 10 km north-east of Porirua on December 13th at 9:09 p.m. This event was felt from Wanganui to Wellington, and in Wairarapa and Marlborough. Geonet reported that items were thrown from shelves around the Wellington region.

On January 6th, a magnitude 4.1 earthquake at 30 km depth centred 10 km west of Porirua was felt from Levin to Wellington and in Marlborough at 5:24 a.m. Geonet reported that, once again, items were reported to have tumbled from shelves in the Wellington region.

On February 1st, a magnitude 3.7 earthquake at 40 km depth centred 10 km west of Porirua was felt at Linden (near Tawa) and Titahi Bay at 10:01 a.m. Geonet did not report any damage from this event.

Earthquakes have also occurred nearby at Upper Hutt, Waikanae, further west near Farewell Spit, as well as near Seddon and the Marlborough Sounds during January and February.