Dynamics of the 13 October 2012 Te Maari, New Zealand Dam Breakout Lahar Determined from Multi-Parameter Data and its Implications for Monitoring

Abstract:

On 6 August 2012 a 7.0x10⁵ m³ debris flow dammed up the Upper Te Maari flow channel forming a 50,000 m³ ephemeral lake. The ephemeral lake filled up from runoff and heavy rainfall over a two month period until 13 October 2012 where saturated sediments and trapped lake water overtopped the debris flow dam at 11:20 UTC, thus creating a lahar approximately 10 minutes later at 11:30 UTC through remobilizing the older debris flow deposits. The lahar lasted for about 30 minutes flowing down the channel as a succession of multiple surges that could possibly be attributed to a series of down cuts and subsequent breakouts of the debris flow dam. A correlation between the lahar seismic signals and active seismic source data collected in February 2013 from the same flow channel is used to understand the dynamics of the 13 October 2012 lahar. In comparing the two data sets a frequency band of 3-10 Hz is used to estimate the lahar energy at 4.87x10⁹ Nm. The best correlated location for the lahar from the active source data is estimated to be at the ephemeral lake or within 1.0 km down the channel. Through the use of the active source method to determine the dynamics of the lahar, monitoring and the understanding of mass flows in the Te Maari area can be improved.