The Cascades Volcano Observatory uses Acoustic Flow Monitors (AFMs) to detect lahars originating on Cascades volcanoes. While typical seismometers will sometimes capture ground shaking, AFMs are designed to detect ground vibration at frequencies specifically associated with lahars, and are located in river valleys subject to frequent lahars. Data from an AFM station is radio telemetered to CVO, where computer processing allows for automated data screening and threshold exceedance notification. Currently, CVO operates a network of AFMs at Mount St. Helens, and cooperates with state and local agencies to maintain an AFM network at Mount Rainier. Additional AFM instruments can be deployed at other Cascades volcanoes when conditions warrant.
Learn more about monitoring lahars: