Overcoming barriers to progress in seismic monitoring and characterization of debris flows and lahars

Abstract

Debris flows generate seismic signals that contain valuable information about events as they unfold. Though seismic waves have been used for along-channel debris-flow and lahar monitoring systems for decades, it has proven difficult to move beyond detection to more quantitative characterizations of flow parameters and event size. This is for two primary reasons: (1) our limited understanding of how the radiated wavefield relates to debris flow characteristics and dynamics, and (2) difficulties quantifying the effects of heterogeneous shallow earth structure on the observed wavefield. The latter issue, essentially our inability to sufficiently separate seismic path effects from source information, is a barrier to improving our understanding of the first issue. We review the progress that has been made toward establishing the theory, models and methods required to use seismic observations to make quantitative measurements of flows and summarize the practical, social, and scientific barriers to progress. We discuss some specific ongoing efforts to overcome some of these barriers, with a focus on how we are using large-scale seismic experiments at the U.S. Geological Survey debris-flow flume to develop methods for directly measuring path effects and to develop and validate theoretical debris flow seismicity models.