An Acoustic-Seismo Station for Detection and Early Warning of Debris Flows in Chile

Abstract

In 1985, more than 23,000 people died in the town of Armero, Colombia, as a result of a volcanic debris flow (lahar) generated by an eruption of the Nevado del Ruiz volcano. During the 1964 eruption of the Villarrica volcano in Chile, a lahar claimed the lives of 22 people upon reaching the town of Coñaripe. Globally, lahars have resulted in a loss of life and a substantial impact on infrastructure and economic livelihoods. Additionally, the occurrence of non-volcanic debris flows in Chile, such as the Santa Lucía debris flow in December 2017, has highlighted the need for monitoring tools and early warning systems that can reduce risk and ultimately minimise the impact on populations. However, in Chile, there is no appropriate and specific technology for monitoring, detecting, and alarming the occurrence of debris flows. The most significant challenges in developing and implementing such a system are as follows: 1) the components are expensive and must be imported; 2) experts are needed to build monitoring stations and process data; 3) there is a requirement to develop new detection algorithms; and 4) there are no protocols to integrate these types of stations into an early warning system that includes collaboration among different institutions.   Research on technologies for the detection of debris flows and other gravity currents based on infrasound and seismic measurements indicates that it is possible to implement an innovative, low-cost, and effective technology for the detection and early warning of debris flows. Some of the most important conclusions from previous research include: 1) the use of infrasound arrays is a suitable and convenient methodology for detecting the occurrence and progress of debris flows, offering significant advantages over other methods; 2) infrasound arrays can detect debris flows several kilometres away, increasing the time between detection and alarm, allowing people to move away from inundation areas; and 3) field studies of the deposits generated by the lahars associated with the 2015 eruption of the Villarrica volcano confirm observations made with infrasound arrays and seismicity.   This presentation describes the design of a monitoring, detection, and early warning system for debris flows, including infrasound and seismic sensors; data digitisation, processing, and communication; and the necessary processing algorithms to generate an effective detection and alert. (Note that this is NOT a predictive system requiring the evaluation of meteorological variables.) The equipment includes computational algorithms capable of performing efficient and effective detection, even in the presence of abundant atmospheric noise. Examples of its theoretical performance in both synthetic and real scenarios are presented. We acknowledge the support of FONDEF IT21I0086, ANID, Chile.