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31 March 14.30 pm
HMNZS Canterbury returned to Auckland this morning after a successful voyage to the Kermadec Islands. On board are staff from GNS Science, DOC and NZ Met Service. The GeoNet electronics team and three commercial divers have been upgrading and hardening one of the two tsunami gauge sites on the island, while volcano chemistry team have been sampling the volcano and geothermal features at Green Lake.
The tsunami sensors at Fishing Rock provide real-time sea level data as part of the LINZ tsunami network. GeoNet technician Kris O’Brien has reported over the weekend the two sensors at Fishing Rock were replaced with new sensors. The new installation is further along the shore platform and provides better protection from the sea. New cable armour which protects the fragile cable from the harsh conditions was installed, with part being re-routed to the new sensor location. The team also swapped out the satellite communications dish and replaced around 440 kg of batteries.
Dr Bruce Christenson has updated us on the gas and water sampling of springs and fumaroles in the Raoul Caldera. He has noted “overall the system is little-changed since September 2016, although water levels in Green Lake were lower”. The three main fumaroles were sampled as were the two crater lakes. They also sampled the springs in Marker Bay Pool and East Pool. The combination of fumarolic and pool gases, will provide some strong insights into the current hydrothermal system behavior, and provide constraints for modelling and monitoring future activity from the volcano.
GNS Science also had a team visiting Curtis Island to undertake research on the hydrothermal features there.
The HMNZS Canterbury has departed for the Kermadec Islands (1000 km NE of Auckland) transporting 60 personnel and about 15 tonnes of equipment and building materials to Raoul and Curtis Islands. Included in this large group are two GeoNet teams and a GNS Science team. GeoNet in collaboration with DOC and LINZ operate a variety of equipment on Raoul Island. We have a regional seismic station (RIZ), the regional GPS station RAUL, VSAT communications and tide gauges at two sites, along with equipment shared with DOC for the volcano monitoring.
The GeoNet electronics team and three commercial divers will be upgrading and hardening one of the two tsunami gauge sites on Raoul Island. We run two sites (with 2 gauges at each) due to the very exposed conditions on the island to provide redundency and reliability. Tsunami gauges have been installed around the New Zealand coast and on offshore islands and they transmit the relative sea level data in real time to the GeoNet Data Management Centre. They can provide confirmation that a tsunami has been generated. The Ministry of Civil Defence and Emergency Management (MCDEM) is responsible for the dissemination of national official tsunami notifications in New Zealand.
Raoul Island as an active volcano and Green Lake has been the focus of volcanic activity in 2006, 1964, 1870 and 1840. There was also activity in Denham Bay during the 1870 and 1840 eruptions when an island grew out of the sea. The GeoNet volcano chemistry team will be busy sampling the volcano and geothermal features at Green Lake.
A further team of GNS Science staff will also conduct research work on Curtis Island, a small volcanic island about 150 km SW of Raoul Island. The island has an active geothermal system. A Seasprite helicopter will be used to transport the team ashore.
The GeoNet teams last visited Raoul Island in September 2016 with support from the offshore patrol vessel HMNZS Otago and a Seasprite helicopter. GNS Science last visited Curtis Island in 2003.
With help of the HMNZS Otago crew and the NZDF’s Seasprite flight crew the GeoNet teams on Raoul Island have had a very successful trip. Access to the helicopter significantly reduced the logistics involved for the team.
The upgrade and hardening of the two tsunami gauge sites was one of the primary tasks for the GeoNet electronics team. They completed the 2nd phase of the upgrade of the Fishing Rock tsunami gauge. Work on this site was started during a visit last April. The second tsunami gauge site on Raoul, is at Boat Cove on the eastern side of the island in a sometimes very exposed bay. The tsunami gauge maintenance was completed with direct support from HMNZS Otago crew.
The NZDF’s Seasprite helicopter also provided logistic support at Green Lake. There the team was undertaking repairs and upgrade work on the seismic station and the Green Lake monitoring equipment. Green Lake has been the focus of volcanic activity in 2006, 1964, 1870 and 1840. The GeoNet volcano chemistry team was busy sampling the volcano and geothermal features at Green Lake.
The electronic team also undertook an upgrade of the data-communications hub which is housed in the ‘met station’ building. Our data is transmitted off the island using a VSAT data link. This enables us to get near real time earthquake, GPS, tsunami and volcano monitoring data from this remote volcanic island.
Tsunami gauges have been installed around the New Zealand coast and on offshore islands and they transmit the relative sea level data in real time to the GeoNet Data Management Centre. They can provide confirmation that a tsunami has been generated. The Ministry of Civil Defence and Emergency Management (MCDEM) is responsible for the dissemination of national official tsunami notifications in New Zealand.
That's right, GeoNet's southern most site is in Antarctica! Last week, September 16th, the International GNSS Service network (see description below) announced the addition of the GeoNet site SCTB (aka Scott Base) to their network. Scott Base is a little slice of Kiwi in Antarctica and is located on Ross Island. It's home to 100's of scientists who fly from Christchurch to the base during the summer months to study everything that the frozen continent has to offer, including: climate, ice sheet behaviour, wildlife and even volcanoes.
Over the last year or so, GeoNet, Land Information New Zealand (LINZ) and our friends at Antarctica New Zealand have been busy upgrading our GPS/GNSS site. Getting the data back from Antarctica to New Zealand has been the biggest challenge and in the past we have only been able to download data once an hour. Now we have improved things so that data is streaming continuously.
Another unique feature of this equipment is that it is the first site in Antarctica to stream all available satellite constellations.
This site now provides precise location information for both the IGS network and the LINZ PositioNZ network. The data collected can be used for surveys and studying the deformation of the earth's crust.
And before you ask, yes, we are all jealous of our field technicians who get to go to Antarctica!
International GNSS Service (IGS)
The IGS retrieves data from high quality GPS instruments around the globe. The data collected contributes to the International Terrestrial Reference Frame (ITRF), which provides a reference frame for positions on earth at different times and locations, some of it's uses include navigation, surveying and maps. The IGS network also supports the work done by researchers who study how the earth deforms, variations in the ice-sheets and sea level and monitoring the earth's rotation.
Our field technicians have been busy over the last 6 months touring around New Zealand’s beautiful countryside upgrading our VSAT communication equipment. In all seriousness, this was not a tiki-tour but an important upgrade to modernise the network and assist with future expansion. The VSAT equipment is used to send data from our scientific instruments to Sydney via satellite links and then to our data centres either via the Internet or again via satellite.
GeoNet field teams went to 46 of our "backbone" sites that use VSAT and installed a new platform and upgraded some components of the equipment. The upgrade provides us with a more robust network that will respond better to fluctuations in data flow and network outages. This is especially important when earthquakes occur since extra "triggered" data is sent from the instruments. This extra data can sometimes overload communications and slow things down. Now, we can recover data more quickly after communications outages due to the increase in bandwidth.
Overall, this upgrade has also improved the latency (time it takes for the data to arrive at our centre) and is more cost effective. Added bonuses that we have noticed so far are that there appears to be more stability with the communications and it's slightly more power-efficient. We now don't have any individual caps to the amount of bandwidth we use at each station. Instead, we use a pool of bandwidth that we are currently only using 1/3rd of our allocated capacity. This means if a single site goes offline (e.g. solar panels covered in snow) it can catch up significantly faster when it reconnects, due to the extra available capacity. This will hopefully result in fewer gaps on the drums on our website.
These upgrades are also exciting for the future of GeoNet. When installing new instrumentation in the field we always have to think about how we get the data back to the data centre. In New Zealand, this can be one of the biggest hurdles because rough terrain can block cell phone and radio coverage. The new VSAT platform is more economical than before, making these hard to reach regions an option for future installations. This upgrade also provides us with the capacity to redirect our data to other monitoring networks such as Geoscience Australia or the USGS should a major communication outage occur across the country.
See our previous story about Improving our satellite comms for additional information.
Our technicians were lucky enough to escape the office to the sunny Wairarapa to build a new GPS station. The new station ‘WRPA’ replaces one of GeoNet's original GPS stations, 'MAST' (named for Masterton) built 13 years ago. MAST was one of seven stations built in 2002. That year, GeoNet kicked off the campaign to expand the GPS monitoring network and our network increased from four to eleven stations. We now have nearly 200!
Why did we need to build a new station?
Unfortunately for us, what makes a good place for a GPS station also is a good place to build a house (flat land with good views, especially to the north). Our station’s new home is in a field of chicory, 130m from its original position.
Why do we need GPS stations?
GPS stations record (very slow) land movement. The stations are secured deeply into the ground - a station's 5 legs are drilled down 10m. This ensures that we're recording the tectonic plates moving, not local surface movements. In the 13 years that MAST has been running, it has tracked the Australian tectonic plate move more than 50cm to the northwest.
The old station will run in tandem with the new station for at least a month, so that we're able to tie the data from the two stations together, as one continuous data stream into the future. We'll then be able to use the old and new stations to track long-term trends over decades. The new GPS station is also a part of our PositioNZ. This Global Positioning System Active Control Network is in partnership with Land Information New Zealand (LINZ).
GNS Science first trialled satellite communications for seismographs back in 1998, a pilot project that featured four stations in Waikato (TOZ), Banks Peninsula (MQZ), West Coast (DSZ) and Hawke’s Bay (KNZ). These were our first real-time streaming sites, and since then we haven’t looked back. The funding from EQC that created GeoNet in 2001 meant we could expand the service to all of our remote national network seismographs, and this work was completed in 2005.
The capabilities of the service have improved markedly since those early days, with better capacity for our data streams and equipment that can be configured remotely. We prepare the equipment for each station upgrade at our Avalon base, using a satellite dish set up in our car park to perform testing. It takes a couple of hours to get this done, then it’s all ready to go to some far-flung part of New Zealand for installation by our field technicians.
This summer we are working through upgrading all of our 46 Optus Australia stations to their new platform together with a new data plan. This will significantly reduce operating costs, as well as provide extra bandwidth and options for future stations on satellite comms. Bringing the data down to earth in Australia gives us offshore redundancy for this data set should New Zealand be affected by any major loss of the internet. That means other agencies such as Geoscience Australia and USGS would continue to receive New Zealand's valuable seismic data.
The site replaces a previous gauge run by NIWA at this site. It has been added to our network to improve coverage along the west coast of New Zealand, a recommendation made by the 2012 GeoNet Strategic Review. In particular, tsunami waves travel very efficiently down the Lord Howe Rise from earthquakes occurring in the Solomon Islands, as was seen in April 2007 after a M8.1 quake in that region.
You can see the new recording on our tsunami gauge charts
We've changed the order of the tsunami gauge traces. It was very tempting to keep them in north-to-south order, but the tides vary greatly between west coast and east coast sites. So we've arranged them so as the tides don't cause the traces to cross one another.
This photograph has inspired us to tell you a bit more about our cGPS system and why it is so important to have this equipment dotting the landscape, collecting data.
New Zealand is a country always on the move; even if you are just visiting us briefly, chances are you have probably felt a bump or a shake. Our country moves quickly AND slowly. You may have heard about slow slip earthquakes; but we’ll sum up: these earthquakes move over days or months, slowly causing the earth to creep millimetres at a time. We’ve only known about these types of earthquakes for a little over a decade so there are a lot of questions we still don’t have answered like: does a slow slip earthquake cause larger, more sudden earthquakes? Or does it relieve tension on the fault and diminish the risk of sudden quakes? We think the answers to these questions are pretty important so that is why we put these cGPS sites in place.
So what is a cGPS site? Most of you may have a GPS in the pocket (if you have a smartphone), but the cGPS sites we build are very precise. They can track how much the land moves over time, millimetre by millimetre. We use the data to determine when this movement is faster (an earthquake that you can feel), medium speed (a slow slip earthquake is occurring) or when it is slower (a continuous and nearly undetectable shift caused by tectonic motion). Think of it like a hand mixer, the earth also moves at different speeds. It’s not a perfect analogy but it gives you an idea that different speeds exist.
How do we choose a cGPS site? Sites are chosen not just because of their beauty, no matter how spectacular this Takaka Hill site looks. First, the site has to be worth studying e.g. there is a phenomenon that we want to monitor. Then we chose a site that moves consistently with the phenomenon we want to study: we don’t place sites in flood plains or landslides (unless the landslide is what we want to look at!). We often place sites on mountain or hilltops and on bedrock so we can make sure it is strong enough to not get blown over in high winds. We also have to consider access to these sites; as much as we like a good helicopter ride, it isn’t the most cost effective way make repairs if needed. We also need to guarantee that the sites can communicate; it needs to have coverage so we can get data. It also needs to be away from trees and other impediments that interfere with the quality of the data collection.
GeoNet's cGPS network.
This beautiful site on Takaka Hill was chosen way back in 2010 and was scheduled to be made live in 2013. As we all know, the Canterbury earthquakes shook up the country and we diverted much of our resources into Canterbury. Had we been able to put this site up, we would have been able to record more information regarding the onset of the Kapiti slow slip earthquake but don’t worry, the slow slip earthquakes repeat in time and TKHL will catch the next one! In fact some slow slip earthquakes, like the one in Gisborne, happens every one to two years and are a regular occurrence like the migration of the Godwits from Alaska to Canterbury. The slow slip event in Kapiti is looking like it happens every five years but we only have three recorded events. Again, we are learning more all the time, so watch this space.
Our beautiful wee Takaka Hill site will contribute information we need to better understand slow slip events for years to come.
For more information about our cGPS network, go to:
Here at GeoNet we’ve just finished installing a new National Network earthquake station at Greta Valley, North Canterbury. The site is located on farmland to the east of the township and took our technicians around a week to construct. The Greta Valley station is GeoNet’s 52nd of its kind to join the network in New Zealand, and is the last National Network station planned for the next few years, with the focus changing to regional stations for the upper South Island.
National Network stations have our highest calibre of equipment with a broadband seismograph and an accelerograph, allowing the station to record a range of earthquakes regardless of depth, distance, or magnitude. Most of our stations around the country use cell phone or radio communications, however because National Network stations are our most important type and we want them to keep working in the event of a major earthquake, these stations relay their data back to GeoNet using satellite communications.
After an earthquake occurs, the recorded data are sent back to GeoNet offices, assessed by computer programs, and then posted on our GeoNet webpage. Thanks to our new GeoNet Rapid system this all happens within five minutes of the earthquake. I have yet to beat the system; every time I have felt an earthquake, GeoNet Rapid has already posted preliminary details of the earthquake by the time I have located my phone or turned on the computer.
As part of GeoNet’s expansion of the Wellington earthquake monitoring network, our technicians installed a new strong motion seismic site on Matiu-Somes Island in the Wellington Harbour late last week. The site is part of our expansion of strong motion accelerographs in the Wellington region which are used to study different rock types as well as the region’s faults.
The site was installed in a shed on the island with the data being transmitted back to GeoNet in real-time via radio transmitters. As power on the island is expensive and limited, our site is powered using solar panels.
Earthquakes are best located if instruments surround the fault, therefore the island’s unique position in the middle of the Wellington Harbour provides a valuable data-collection location, increasing our azimuthal coverage for Wellington earthquakes.
Matiu-Somes Island has a rich history, having been occupied by Māori for generations. It is now a predator-free scientific reserve, but in European history it has been used as a both an animal and human quarantine station, and a defence post during World War II. The Island is well worth visiting for a day trip.
On 17 July 2009, the GNS Science response team deployed six portable seismometers in southern Fiordland to help record the aftershock sequence of the magnitude 7.8 Dusky Sound earthquake. The seismometers were installed to improve instrument coverage across a broad area where the mainshock originated and where aftershocks were expected to occur, supplementing the existing GeoNet seismograph stations at Deep Cove and Puysegur Point. The temporary sites at Dagg Sound, Supper Cove, Duck Cove and Last Cove were successfully retrieved in mid-September 2009. The final two sites at Breaksea Sound and Lake Frazer were collected last week, on 9 and 10 December.
The earthquake data recorded by the temporary seismometers are being analysed over the next three months. The preliminary locations of about 2,000 aftershocks that occurred in the five months following the 15 July earthquake will be refined by analysts from GNS Science and Victoria University of Wellington. They will incorporate the data from the temporary seismographs to calculate more precise epicentres, depths and magnitudes. In turn, these revised solutions will give seismologists a greater understanding of the Dusky Sound earthquake, including what part of the crust ruptured in the event, and how it affected local fault systems.
The new camera has a 90 degree field of view and has been aimed to include a small portion of the bay where the tour operators land so that they can see landing conditions on the island. The operators often send us photos and updates from the island and it's useful for them to know the landing conditions in advance. The camera also has infra-red night time functionality so look out for nice night time shots when a full moon is around. The camera is also recording 1 frame per second video onto an onboard memory card so that in the event of an eruption we will hopefully have some good footage of it. The memory card will hold about 10 days' worth of images. A couple of photos from the installation trip can be seen below.
It goes without saying that Dino has resumed his role as the GeoNet mascot on White Island, now looking clearer thanks to the new camera.
The camera housing support on White Island has become badly degraded by the ravages of time and the environment. The picture on the left shows the camera housing levitating on the wall of the old factory on the island. Two rusty expansion bolts were all that was holding the camera up!
The housing has now been placed in a shallow hole until a new, permanent installation is built. So the images you are seeing since noon yesterday have a new field of view. This new webcam position is about 100 metres further back from the crater, and the view overlooks the factory up towards the crater. Most importantly Dino was given a new home on a conveniently located rock just in front of the camera.
The camera is showing its age, and we plan to replace it in the not-too-distant future.
One of the team, Andrew Cowie, was injured in an accident at Boat Cove on Raoul Island on the afternoon of Friday, 15 May. He was about to step off the boat when unfortunately a swell caught the boat and threw him up against the boat railing. He was transported back to base camp on Raoul Island where a doctor checked Andrew for any obvious injuries. He was in a lot of pain and it appeared he may have broken ribs, together with the possibility of internal injuries and bleeding. The doctor advised that Andrew should be taken back to New Zealand as soon as possible. A helicopter brought Andrew and the doctor back to Tauranga, arriving at 3pm Saturday, where Andrew was met by his partner and young son. It was confirmed that he had cracked and broken ribs, but no other complications, and he is now recuperating at his home in Featherston.
Raoul Island is part of the Kermadec Islands, 750 to 1,000 km north-north-east of New Zealand, and are of volcanic origin. They are uninhabited, except for Raoul Island where a team of Department of Conservation staff carry out weed control work and make meteorological observations. There are also many submarine volcanoes in this chain.
The last eruption on Raoul was on 17 March, 2006 at about 8:20 in the morning, when without warning rocks and mud were ejected from the Green Lake area. Equipment on the island at the time showed the eruption continued for around 30 minutes. Satellite images taken after the eruption confirmed that the volcano belched 200 tonnes of sulphur dioxide during the eruption and in the following 5 hours. Tragically, a Department of Conservation employee was killed by this eruption.
The volcano monitoring equipment will improve the safety of personnel on the island as well as building up a long-term history of the characteristics of this volcano. Of most interest will be the webcam on Mount Moumoukai, showing a view towards the north-west encompassing Green and Blue Lakes. Unlike the more well-known New Zealand volcanoes, this will be a new sight for most people.
Raoul Island also adds a vital location into the global network of seismographs and GPS receivers, as well as its tsunami gauges confirming whether or not a tsunami may be en route to the New Zealand mainland. This long-planned mission is now complete and we look forward to the data collected by these instruments contributing a greater understanding of New Zealand's natural hazards.