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Seismic and acoustic recordings of an unusually large rockfall at Mount St. Helens, Washington
Author(s) -
Moran S. C.,
Matoza R. S.,
Garcés M. A.,
Hedlin M. A. H.,
Bowers D.,
Scott W. E.,
Sherrod D. R.,
Vallance J. W.
Publication year - 2008
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2008gl035176
Subject(s) - rockfall , geology , seismology , lava , strombolian eruption , volcano , infrasound , explosive eruption , plume , lava dome , explosive material , meteorology , landslide , magma , acoustics , physics , chemistry , organic chemistry
On 29 May 2006 a large rockfall off the Mount St. Helens lava dome produced an atmospheric plume that was reported by airplane pilots to have risen to 6,000 m above sea level and interpreted to be a result of an explosive event. However, subsequent field reconnaissance found no evidence of a ballistic field, indicating that there was no explosive component. The rockfall produced complex seismic and infrasonic signals, with the latter recorded at sites 0.6 and 13.4 km from the source. An unusual, very long‐period (50 s) infrasonic signal was recorded, a signal we model as the result of air displacement. Two high‐frequency infrasonic signals are inferred to result from the initial contact of a rock slab with the ground and from interaction of displaced air with a depression at the base of the active lava dome.