EAPSI: Hazard Analysis of Deadly Mud Flows at Mt. Ruapehu Volcano, New Zealand

Schaefer Lauren N, Hancock MI

Investigators

Abstract

Volcanic mud flows, termed lahars, are among the deadliest of volcanic phenomena, having killed 40,000 people worldwide since the late 1700?s. On steep volcanoes, lahars can exceed speeds of 200 km/hr, traveling over 100 km and growing up to 10 times their initial size as they ensnare loose soil and rock. The active Mt. Ruapehu Volcano, located on the north island of New Zealand, is one of the world?s most regular producers of lahars due to the presence of a lake in its crater rim. Since 1861, 22 lahars have occurred at this volcano, most of which initiate when water overflows the crater rim during eruptions. However, the most destructive events occur when the crater rim breaks, causing a massive outpouring of water; such an event killed 151 people in 1953. This study aims to reveal the risk of future lahars by understanding the strength of the rock that composes the crater rim and analyzing possible scenarios that could lead to its collapse. This is critical for mitigating the risk to climbers and skiers on the volcano?s flanks, which on busy days can reach over 10,000 people. This research will be conducted in collaboration with Dr. Ben Kennedy, a leading researcher in experimental volcanology, at the University of Canterbury in Christchurch, New Zealand. The objectives for the study are: (1) understand how the stress and strain of the rock composing the crater rim evolve during strain events, and; (2) determine the probability of crater rim failure using computational models. Specifically, seismic waves will be pulsed through rock samples during cyclic stressing experiments to determine the material?s susceptibility to damage during repeated loading events (e.g. crater lake water level rise and earthquakes). These material properties will then be used in 2- and 3-D numerical models to simulate such events. This will reveal the most influential variables in crater rim stability, the scenarios in which the crater rim may collapse, and the size and direction of possible future lahars. For people living in the vicinity of active volcanoes prone to lahars, such as Mount Rainier (USA), understanding volcanic material behavior can improve hazard monitoring, ultimately reducing risks associated with dangerous volcanic phenomena. This award under the East Asia and Pacific Summer Institutes program supports summer research by a U.S. graduate student and is jointly funded by NSF and the Royal Society of New Zealand.