“essential part of volcanic risk preparedness”, used to “transfer the consensus of the scientific advisors to the responsible authorities, so they have the essential means for decision making” (De la Cruz-Reyna et al., 2000, p. 1205). Scales are often used to compress verbose
descriptions into shorthand, represented by a single number or short label (Grünthal, 1998). They are often descriptive rather than interpretive or analytical (Grünthal, 1998; Blong, 2003). An overview of New Zealand’s VAL system is provided here, in addition to some of the
methods used to determine VALs worldwide.
The following information describes the events preceding the development of New Zealand’s first VAL system. The Civil Defence Act was passed in December 1962 (Civil Defence public health seminar notes, Whakatane, 24–25 May 1974, GNS Science archives), stating that the DSIR had the obligation of advising the Ministry of Civil Defence (as it was then known) of observations relating to potential natural disasters (Ministry of Civil Defence., 1973, p. 21). Following the passing of the Civil Defence Act 1983 (and the occurrence of the 1983–84 unrest
episode at TVC), a meeting was held between the Ministry of Civil Defence and DSIR in January 1984 to discuss the need for improvements to New Zealand’s volcano monitoring network and warning systems. It was decided that in order to fulfil their obligations to warn the public of hazards, the “Ministry of Civil Defence will have to take the initiative in the establishment of an adequate volcanic warning system, for the rhyolitic volcanic fields in particular” (meeting notes from 16 January 1984, GNS Science archives).
It was proposed in 1989 that the Minister of Civil Defence should set up a National Civil Defence Scientific Advisory Committee, from which a sub-committee on Volcanic Hazards was formed. Members included a number of scientific institutions, and the group advised the Ministry of Civil Defence on volcanic matters. In January and February 1992, members of the Volcanic Hazards Advisory Group helped create the Nga Puia caldera eruption national exercise centred at OVC. This Group used a colour-coded VAL system based on the USGS system at the time to work through the exercise (pers. comm. V. Neall, 2012). In a post-exercise review of Nga Puia, Martin (1992) identified a couple of issues with the system. One issue identified was that there was no mention of public advice in the ‘Action’ column of the VAL system prior to a state of emergency being formally declared. The post-exercise review also stated that the duplicate use of colours in the VAL system as well as in the ‘control zones’ used in the exercise created confusion (Martin, 1992).
Following the Nga Puia exercise, it was recommended by the Volcanic Hazards Advisory Group that a National Volcanic Contingency Plan should be formed (as stated in correspondence between B. D. Sinclair (Ministry of Civil Defence) and Dr Ian Nairn (IGNS) on 8 September 1992, GNS Science archives). During a convenors meeting for the development of this plan on 30 September 1992, it was suggested that the VAL system should be a four or five stage alert system only, and it should be devised by the scientists (according to meeting notes taken, stored in GNS Science archives folder #5235). It was also suggested that time should be stated in numbers, evacuation areas should be depicted in colours, and the VAL system should “outline the actions to be taken by civil defence and also the other various organisations that would be required to respond”. Lessons from the Rabaul Caldera unrest and eruption response in the 1980s and 1990s were used to develop the new VAL system (Nairn & Scott, 1995).
In November 1994, Annexe C was added to the National CDEM Plan, and outlined warnings, responsibilities, and introduced the ‘Scientific Alert Level Table’ (SAL) for New Zealand’s active volcanoes (pers. comm. B. Scott, 2013; Table 2.3). In December 1994 activity at Ruapehu
Chapter 2 New Zealand’s Volcano Early Warning System
56
started to increase and the SAL had its first official use. Problems which arose from this system, according to B. Scott (GNS Science, pers. comm. 2013) included:
x no level zero recognising ‘no unrest’
x no clear differentiation between frequently active and reawakening volcanoes
x multiple different and conflicting definitions within one level
x there were difficulties applying this system to Ruapehu’s eruption activity.
Table 2.3. Scientific Alert Level Table introduced in 1994 (Annexe C from the CDEM Plan; sourced from B. Scott, 2013).
Scientific
Level Phenomena Observed Scientific Interpretation
1
Abnormal seismic, hydrothermal or other signatures
Initial sign of volcano reawakening. No eruption imminent.
Possible minor activity.
2
Increase in seismic, hydrothermal and other unrest indicators. Increase from usual background weak eruptions.
Indicators of intrusion process or significant change in on-going eruptive activity.
3
Relatively high and increasing unrest shown by all indicators.
Commencement of minor eruptive activity at reawakening vent(s) or increased vigour of on-going activity.
If increasing trends continue there is a real possibility of hazardous eruptive activity.
4
Rapid acceleration of unrest indicators. Established magmatic activity at
reawakening vents or significant change to on-going activity.
Hazardous volcanic eruption is now imminent.
5
Hazardous volcanic eruption in progress. Destruction within the Permanent Danger Zone (red zone) and significant risk over wider areas.
The SAL system was therefore reviewed, and a significantly revised and amended version was adopted in September 1995, just one week before the 1995–96 Ruapehu eruption episode started. The resulting system is the system currently in use (Table 2.4), and was renamed from SALs to VALs in 2008 as part of a review of the Guide to the National CDEM Plan. This system included a level zero for ‘no unrest’, and was split into two separate sections, one for
frequently active volcanoes, and the other for reawakening volcanoes. The volcanoes allocated to each are listed in VAL table (Table 2.4).
Table 2.4. New Zealand’s current Volcanic Alert Level system. Source: reproduced from the Guide to the National CDEM Plan (MCDEM, 2006).
Frequently active cone volcanoes
VOLCANIC ALERT LEVEL
Reawakening volcanoes
White Island, Tongariro/Ngauruhoe, Ruapheu, Kermadecs
Northland, Auckland, Mayor Island, Rotorua, Okataina, Taupo,
Egmont/Taranaki
Volcano status Indicative
phenomena
Indicative
phenomena Volcano status
Usual dormant, or quiescent state
Typical background surface activity, seismicity,
deformation and heat flow at low levels.
0
Typical background surface activity; deformation, seismicity, and heat flow at low levels.
Usual dormant, or quiescent state. Signs of volcano unrest Departure from typical background surface activity.
1
Apparent seismic, geodetic, thermal or other unrest indicators. Initial signs of possible volcano unrest. No eruption threat. Minor eruptive activity Onset of eruptive activity, accompanied by changes to monitored indicators.2
Increase in number or intensity of unrest indicators (seismicity, deformation, heat flow and so on).Confirmation of volcano unrest. Eruption threat. Significant local eruption in progress. Increased vigour of ongoing activity and monitored indicators. Significant effects on volcano, possible effects beyond.
3
Minor steam eruptions. High increasing trends of unrest indicators, significant effects on volcano, possible beyond. Minor eruptions commenced. Real possibility of hazardous eruptions Hazardous local eruption in progress. Significant change to ongoing activity and monitoring indicators. Effects beyond volcano.4
Eruption of new magma. Sustained high levels of unrest indicators, significant effects beyond volcano. Hazardous local eruption in progress. Large- scale eruption now possible. Large hazardous eruption in progress. Destruction with major damage beyond volcano. Significant risk over wider areas.5
Destruction with major damage beyond active volcano. Significant risk over wider areas.Large hazardous volcanic eruption in progress.
Chapter 2 New Zealand’s Volcano Early Warning System
58
The frequently active volcanoes system includes one level for unrest (VAL 1) and four levels of increasing magnitudes of eruption (VAL 2–5), whereas the reawakening volcanoes system includes two levels for unrest (VAL 1 and 2) and three eruption levels (VAL 3–5). The VAL is based on a volcano’s current status, and is not necessarily predictive (Scott & Travers, 2009).
Determining the VAL and ACC in New Zealand is currently the statutory responsibility of GNS Science, according to a Memorandum of Understanding with MCDEM (GNS Science & The Ministry of Civil Defence and Emergency Management, 2009). The decision is usually made by scientists once the monitoring data has been assessed and compared to background levels, subjectively ascertained from past activity. Further details on this process are described in Chapter 4. In the case of the need for an immediate response (e.g., an eruption has taken place), the GeoNet Volcano Duty Officer can make the VAL decision alone.
As identified by Newhall (2000), scientists must be willing to raise and lower the alert level as necessary to maintain their credibility. However, the decision to change the VAL can be challenging in the context of uncertainty (e.g., Metzger et al., 1999; Fearnley, 2011). Decision- making under uncertainty, including the determination of VALs and the ACC, is discussed further in section 2.4.4.
In New Zealand, the status of volcanic activity, including changes to the VAL and ACC, is communicated by the dissemination of VABs. These are issued by GNS Science and sent to anyone who registers to the list managed by GNS Science, including MCDEM, CDEM Groups, local government, lifelines utilities, emergency responders, tourist operators, major land managers, media, and members of the public. VABs usually include the time and date of dissemination; a summary sentence (or short paragraph) in bold font at the head of the one to two page document; photographs of points of interest (particularly during an episode of heightened unrest or eruption event); a description of the scientific data on which the information is based; a definition of the VAL, ACC, and the GeoNet monitoring project; and a short description of activities leading up to the issuance of the VAB. Occasionally, possible future scenarios are included in the VAB, and/or information relating to the threat. For
example, in a 2013 White Island VAB describing an overnight eruption which deposited tephra on the crater floor visited by tourists during daylight hours, it was stated “This eruption is larger than recent events and would have been life threatening to people on the island” (VAB WI-2013/23). VABs may be issued without a change in VAL to provide information on recent monitoring trips, to issue ashfall forecasts, or to simply state that no change of activity has
occurred. Up-to-date information on the current status and alert levels for New Zealand’s volcanoes, as well as the VAB just mentioned, and GeoNet ‘Volcano News’ articles (containing more general information, or items not deemed appropriate for a VAB) are available on the GeoNet website (http://www.geonet.org.nz/volcano/). The ‘Volcano News’ articles are a passive supply of information, requiring end-users to actively check the GeoNet website, or the GeoNet Facebook web page to be aware of the information.