Please use this identifier to cite or link to this item: http://hdl.handle.net/2122/1328
AuthorsMusumeci, C.* 
Malone, S. D.* 
Giampiccolo, E.* 
Gresta, S.* 
TitleStress tensor computations at Mount St. Helens (1995-1998)
Issue DateOct-2000
Series/Report no.43/5
URIhttp://hdl.handle.net/2122/1328
KeywordsMount St. Helens (USA)
fault-plane solutions
inversion
stress field
Subject Classification04. Solid Earth::04.06. Seismology::04.06.08. Volcano seismology 
04. Solid Earth::04.07. Tectonophysics::04.07.05. Stress 
04. Solid Earth::04.08. Volcanology::04.08.99. General or miscellaneous 
AbstractFault plane solutions of 459 events occurring between 1995 and 1998 at Mount St. Helens (State of Washington, Northwest U.S.A.) were considered in order to infer the state of stress beneath the volcano. These events occurred in two distinct depth zones. The shallower zone is between 2 and 5.5 km, with shocks clustering in a tight cylindrical distribution about 1 km in radius directly beneath the crater. The deeper events are spread over a larger volume from 5.5 to 10 km depth and surround an aseismic zone below and slightly west of the lava dome. Faulting is characterized by a mixture of strike-slip, reverse and normal faults with maximum compression axes which do not cluster around a single direction. In the deep zone, between 5.5 and 10 km, P axes define a wheel-spoke pattern pointing radially away from the center of the aseismic zone. The 459 fault plane solutions were inverted for stress tensor parameters using the algorithm of Gephart and Forsyth. The inversion of the whole data set revealed that faulting was not produced by a uniform stress distribution. The subdivision of the zone into smaller volumes significantly reduced misfit and confidence areas of the solutions, whereas temporal subdivision of the sample did not lead to significant improvements in terms of stress uniformity. We suggest that the inhomogeneous stress field is consistent with a varying pressure source originating from the inferred crustal magma chamber and a thin conduit extending above it.
Appears in Collections:Annals of Geophysics

Files in This Item:
File Description SizeFormat 
02.pdf6.42 MBAdobe PDFView/Open
Show full item record

Page view(s)

81
Last Week
0
Last month
checked on Jun 22, 2017

Download(s)

231
checked on Jun 22, 2017

Google ScholarTM

Check