Sunday, February 22, 2015

The Future of GeoNet Revisited - Part 4: Early Warning

Early Warning....
Let me state up front that I have mixed feelings about early warning for geological hazards events. It is very hard to do well, and the consequences of false alarms can be severe. Also, technology is a very small part of the end-to-end process. Detecting the hazard is in many cases the easy part - getting the message to affected communities in forms that can easily be acted upon is the really hard part of the complete package. Finally, any system has to be super robust. It may be in place for decades before a devastating event occurs. And when disaster strikes, will the early warning system (end-to-end) still be fully functional?

 Another issue I will get off my chest at this stage is that there is a danger that early warning is used as a funding opportunity by researchers (often with the best of intentions), particularly those not involved in operational systems. It is easy to say that someday this wonderful research I am doing will lead to early warning. This is the "I can cure cancer" syndrome we all know about. How many times have the media announced a cure for cancer? What is obvious is we are slowly moving to be able to treat (or at least delay) many cancers - but there is no one silver bullet. I believe it is the same with early warning for geological hazards.

GeoNet and Early Warning....
GeoNet has much of the infrastructure and technology necessary to contribute to a forecasting and early warning capability for New Zealand for some perils. GeoNet is currently set up to collect research data and report on geological hazards and would require considerable reconfiguration for short term early warning. The lack of a fully staffed 24/7/365 warning centre is a major component not currently available. GeoNet operates a duty system rather than being staffed 24 hours a day every day of the year. Sensor network expansion and increased robustness is required, and research and development is needed to take the outcomes of scientific research and transform these into operational tools if GeoNet’s role was expanded to include warning centre capabilities.

For the record, forecasting is a form of time-dependent hazard assessment, whereas early warning requires the identification of an imminent peril and the likely time of impact.  Some geological hazards are easier to forecast than others, and the benefits of the forecasts can vary considerably. Let's briefly look at the perils we face.

Volcano Early Warning....
The GeoNet volcano monitoring programme already provides a level of volcano forecasting which would be enhanced by a 24/7/365 warning centre, improved remote data collection systems and additional research and development. Let's look at the example of the eruption of Te Maari craters on 6 August 2012, following nearly 120 years of inactivity of Tongariro volcano. It followed three weeks of unrest including an increase in earthquake activity and changes in fluid chemistry, leading  GeoNet to raise the alert level for the volcano. Although the alert level is not designed to be predictive, the increased activity triggered increased community and land owner (Department of Conservation) consultation and resulted in a better prepared community when the eruption took place. This is an example of effective volcano forecasting in practice.

Tsunami Early Warning ...
The compelling case for early warning capability in New Zealand is the potential for local or near-regional source tsunami. The 2013 update of the 2005 tsunami hazard assessment for New Zealand demonstrated that a regionally generated tsunami from a Kermadec earthquake could impact highly populated parts of the North Island from Bay of Plenty through the Auckland and Northland regions with travel times of between one and two hours. Further, it is likely the causal earthquake would not be strongly felt because the volcanic region reduces the earthquake shaking, negating the effectiveness of using natural warning signs. Local-source tsunami caused by an earthquake on the Hikurangi subduction zone offshore of the east coast of the North Island also poses a threat, making tsunami the most crucial of the perils requiring early warning capability. 

Figure 1. A scene from within the Pacific Tsunami Warning Centre (PTWC) in Hawaii. PTWC currently provides tsunami advice on ocean-wide tsunami to all countries in the region (including New Zealand) using internationally available seismic and sea level data. The alerts provided by PTWC come around 10 minutes after a tsunami-generating earthquake so can only be used for distant and regional source tsunami warning.
Landslide Potential ...
Landslide potential is site specific, but forecasting can be based on rainfall rates, earthquake shaking and volcanic activity (lahars and other forms of debris flows) and the severity of likely landslides reported. This is an area of active research which is likely to bear fruit in the next decade.


Earthquake Early Warning....
Earthquake early warning, on the other hand, although already operational in places like Japan, is probably the lower priority for New Zealand because of the very short warning times, marginal outcome improvements and the much higher requirements for robustness and sensor densities for its effectiveness. Earthquake early warning is fundamentally different to the other early warning capabilities discussed above. We cannot predict the location or size of future earthquakes. We can only detect the start of an earthquake near where it ruptures and warn at a distance because seismic waves travel slower than electronic signals. Earthquake early warning times are measured in seconds, unlike the tens of minutes to hours and days possible with the other perils discussed above. New Zealander's live on top of our earthquakes! And we often have earthquakes in unexpected places making earthquake early warning very difficult. The Alpine Fault is the only structure in New Zealand where someday we may be able to deploy a cost effective earthquake early warning system.

Resources and Priorities....
For GeoNet to take on a leading role in event forecasting and early warning would require considerably more resources. Such an undertaking would be a step up in capability (people, expertise and resources) at least as large as when GeoNet was established in 2001. There is a compelling case for the establishment of a New Zealand tsunami early warning system for near-regional and local source events. But GeoNet can only provide part of the solution. Education, evacuation zone and route planning and a very effective public alerting system are also requirements for an effective end-to-end tsunami warning system.

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