GeoNet Site Expands Volcano Coverage

GeoNet has changed its volcano webcam and drum page, allowing it to extend coverage to another eight locations regularly monitored by New Zealand’s vulcanologists.

The new layout allows GeoNet to more easily manage information about centres of activity when they occur. Twelve volcanic areas are identified on the new Current Activity tab of the website, covering the frequently active volcanoes of the Kermadecs, White Island, Ruapehu, Ngauruhoe and Tongariro. The caldera volcanoes of Rotorua, Okataina and Taupo have their own sections, as do Northland, the Auckland volcanic field, Mayor Island and Taranaki (Mt. Egmont).

Page layouts for each area follow a standard pattern, showing maps of the area overlaid with the locations of seismic instruments and global positioning emplacements. A map showing earthquakes that have occurred during the last two months is included, but it should be noted that the events shown are both tectonic and volcanic earthquakes, derived from GeoNet’s databases. These events require analysis by seismologists before being added to the database, so the earthquake maps are not updated in “real time.” Larger earthquakes are usually analysed within 15 to 30 minutes, but the more numerous smaller events are processed on the next working day at which time they appear in the database and then on the maps. Minor events may take days to appear, unless of special interest.

Pages for the four locations with webcams provide a link to the latest image (just click on the thumbnail image), and two series of images taken half-hourly during the immediate last 12 hours, and the 38 hours prior to that. Animations made from the still images are also available.

The former webcams page that provided a handy set of thumbnail images from the webcams and seismic drums at White Island, Ngauruhoe, Ruapehu and Taranaki has been discontinued, and regular visitors will soon find that the old link no longer works. I have found that this single page provided a handy snapshot of activity for New Zealand’s most active volcanoes, and have suggested that a similar overview page should be restored to the website in the future.

There are currently no plans to recommence the regular reporting of volcanic observations that were discontinued when the Hazard Watch site was scaled back in June 2007. Nevertheless, Wild Land continues to lobby for this as readers have indicated that they are interested in hearing about activity as it develops, rather than waiting for an alert bulletin to inform us of significant changes.

The most significant development in the expansion of the volcano pages has been making more seismic drums available to the public. Eleven of the twelve monitored sites have seismic drum pages and Ruapehu now sports two drums – old faithful at the Far West T-bar has been joined by the drum at Wahianoa. Access to the Kauri Point drum is now available via the Auckland page, Omahuta via the Northland page and Mayor Island has been added. Mt. Tarawera’s drum is available via the Okataina page, Utuhina via the Rotorua page, Rangitukua via the Taupo page, and West Tongariro drum is available via the Tongariro page.

The seismic drum pages are a little shy, but can be found at the top right of the page hiding behind the “Drums” and the enigmatic “RSAM & SSAM” buttons. The RSAM and SSAM plots show more information about the amplitude i.e. size of seismic events that have occurred at the site during the past 5 weeks. The RSAM (Real-time Seismic Amplitude Measurement) plot is quite straightforward, showing the level of tremor over time. When condensed over five weeks the traces show that volcanic areas experience cycles of tremor punctuated by individual events such as earthquakes (both local and distant), wind, trampers walking past the monitor, the occasional herd of cows tootling off to be milked, wind gusts and, of course, movements of molten rock and gas.

The SSAM (Seismic Spectral-Amplitude Measurement) plot is a little more complex as it combines both the frequency of the tremor and a logarithmic measurement of the strength of the tremor in one plot. The frequency component of the tremor and its strength can tell a vulcanologist a great deal about the volcanic activity that is occurring. It will be interesting to observe the plots during an actual volcanic event, but the untrained observer can probably learn little from the day to day activity that is recorded. Nervous watchers should remember that vehicle traffic, strong winds, maintenance work and other incidental activity will show up on the plots if it occurs nearby.

The only location that does not show a seismic drum is Raoul Island on the Kermadecs page. The seismometer at Raoul is run by a different network, and linking it to the GeoNet network is problematic. However, it is planned to have one of GeoNet’s own seismic instruments installed at Raoul later in the year. At the same time, Raoul will also appear on the Tsunami monitoring page when the appropriate equipment is installed. Landing a team with the equipment at Raoul volcano is difficult, and expeditions have been thwarted by the weather in the past. Nevertheless, it is hoped that Raoul will be fully equipped with a webcam, seismometer and tsunami measuring station by the end of 2008.

The expanded volcanic coverage can be found on the GeoNet website’s Current Activity page.

2 Responses to “GeoNet Site Expands Volcano Coverage”

  1. Darren says:

    Hey – are these Taupo quakes been reported simply because of the upgrade to GEONET or are these new a swarm? Any idea?

    There’s been 7 or 8 reported since May 23rd – with the drum starting to look busier this morning displaying another 7-8. I wish as could see hydrothermal activity status reports also…

    I know I know… give an inch and we want a mile…

  2. Darren says:

    Another 15 or so since midday.
    It’s starting to look like Matahi on a bad day!

    I would love to learn more about these and this area.
    They are under the lake so I gather the trigger couldn’t have been hydro related.

    It would be cool if we had access to the GPS data as well…. I would love to know ‘what moved where’! 🙂

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