NHRP / Hazard themes / Risk / Research Highlights 2015-16 / Riskscape & Volcanic Hazards

Developing RiskScape for Volcanic Hazards

George Williams (UC) examining ballistic impacts to Toyako Kindergarten, 600 metres from the vent of the Mt Usu eruption. Photo: University of Canterbury.

By Daniel Blake (UC), Rebecca Fitzgerald (UC), George Williams (UC), Natalia Delign (GNS SCIENCE), Tom Wilson (UC), Graham Leonard (GNS Science) and Ben Kennedy (UC).

RiskScape vulnerability modules define the way that “assets” − buildings, roads, electrical cables − respond to a given hazard. Compared to many other natural hazards (e.g., earthquakes, floods) there has been limited data on volcanic hazards to inform RiskScape development. Over the past few years, we have been enhancing RiskScape’s capabilities for volcanic risk analysis. Here we report on two particular volcanic hazards – ballistic impacts and volcanic ash. These studies have only been possible through our ongoing local and international collaborations.

Understanding Ballistic Impacts: Lessons from Japan

A volcanic eruption can result in the ejection of ballistic projectiles – fragments of lava or rock  of varying sizes that explode from the volcano at high velocity. Volcanic ballistics are a major hazard to both life and infrastructure, and are among the most frequent causes of fatalities on volcanoes. Many New Zealand volcanoes, including Ruapehu, Tongariro and the Auckland Volcanic Field, produce ballistics.  A high number of people may be in proximity on any given day.

NHRP UC ballistics

Vulnerability testing of building material (weatherboard) to ballistic impacts using the UC pneumatic cannon. Photo: University of Canterbury.

The University of Canterbury (UC) is leading the study of ballistic impacts using data gathered in New Zealand and Japan.  In mid-2015, researchers from UC and GNS Science travelled to Mt Usu, Japan.  which erupted in 2000 ejecting ballistics that caused severe damage to many buildings.  Due to successful warnings and evacuation of the immediate area, there were no fatalities. Ten impacted buildings − constructed of varied materials similar to those used in Auckland’s building stock − were assessed by our team to understand the range of damage that can occur from ballistic impacts.

Back at home, UC developed a pneumatic cannon to systematically test the vulnerability of weatherboards, corrugated iron and reinforced concrete to ballistic impact – all building materials used throughout New Zealand. The aim was to define the probability of different damage intensities (for example, superficial damage, roof puncture) occurring for a given intensity of ballistic impact.  The findings will be included in RiskScape so that impact and loss can be estimated, providing hazard and risk managers with data to make informed decisions.

Ash Impacts on Roads: Lessons from Kagoshima, Japan

In 2015, PhD student Daniel Blake visited Kagoshima to learn how local authorities deal with frequent volcanic ashfall from nearby Sakurajima Volcano. Kagoshima’s regular ashfalls and similar infrastructure to New Zealand make it an ideal study site. This visit allowed Daniel to compare results from UC’s Volcanic Ash Testing Laboratory (VAT Lab) with real-life situations, including understanding skid resistance on ash-covered roads and airfield surfaces, visibility of road markings covered by ash and visibility through airborne volcanic ash.

NHRP volcanic ash Japan

Vehicles driving in low visibility (left) and covered road markings (right) caused by volcanic ash in Kagoshima. Photos courtesy of Kagoshima City Office.

The Kagoshima authorities reported that a common impact on drivers is reduced visibility – sometimes to just 20 metres – from ash particles suspended in the air. They also reported that just 1 millimetre of volcanic ash accumulation is enough to make road surfaces slippery. In lab findings we found that just 0.1 millimetre of fine-grained ash accumulation is enough to obscure markings on the road, reducing safety. In addition, ash of more recent eruptions (from the Showa crater of Sakurajima) appears to be less slippery than that of older eruptions (from the Minami-daki crater), probably due to the smaller particle size associated with the recent eruptions. These findings from the field align well with recent lab results and emphasize the importance of different ash characteristics (not just ash depth) when considering the exposure of assets to volcanic ash.

Contact: Tom Wilson, University of Canterbury

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Last updated 13 Sept 2016