On Generation of Infrasound by Large Objects Falling Into Water

L.A.Ostrovsky (Zel technologies/NOAA ETL and Institute of Applied Physics, Boulder, Colorado, USA); A.J.Bedard (NOAA ETL, Boulder, Colorado, USA)

e-mail: lev.a.ostrovsky@noaa.gov

A large number of geophysical processes (e.g., avalanches, meteors, and earthquakes)  can be detected at long range using the low-frequency sounds generated. Here we consider  an important case: an object like a rock or ice shelf falls into water to generate an infrasound.  Neglecting the small-scale flash effects which would generate a higher-frequency (audible)  sound, we consider the water motions with scales of the order of that object (say, 100 m).  The theoretical problem is interaction between hydrodynamic ("incompressible") motions and acoustic radiation. It is shown that water surface displacements are able to radiate  infrasound with measurable intensity both in air and water. Some characteristics of this radiation  are considered. Also, parameters for laboratory modeling of such processes are estimated.


Section : 6