Fwd: [SIO GP Seminars] FRIDAY 3PM: Seth Moran, CVO, USGS

[Robin Matoza]

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> From: Robin Matoza <rmatoza at ucsd.edu>
> Date: May 1, 2007 6:30:27 PM PDT
> To: gp-seminars at sio.ucsd.edu
> Subject: [SIO GP Seminars] FRIDAY 3PM: Seth Moran, CVO, USGS
>
> Geophysics Seminar Announcement-
>
> ========================
>
> Friday, May 4th, 3:00 PM
>   (refreshments served at 2:45 PM)
>   Munk Conference Room
>
> Seth Moran, Cascades Volcano Observatory (CVO), USGS
>
> "Seismogenesis during the 2004-2007 eruption of Mount St. Helens"
>
> =====================
>
>
> ABSTRACT
> The ongoing eruption of Mount St. Helens (MSH) has been highly  
> seismogenic but remarkably benign, with only six explosions  
> accompanying the continuous extrusion of a lava dome. The lack of  
> explosions, coupled with development of platforms for remotely  
> deploying instruments, has made it reasonably safe for scientists  
> to deploy seismometers, cameras, GPS receivers, tiltmeters, and  
> other instruments at short distances from the vent, in some cases  
> as close as 100m. One phenomenon that has motivated much research  
> is the extrusion of a fault-gouge-covered lava dome, a fact that  
> has lead to speculation that much of the seismicity accompanying  
> the eruption has been generated by stick-slip processes along the  
> conduit walls (Iverson and others, 2006; Harrington and Brodsky,  
> 2007). This speculation has been bolstered by observations of  
> earthquakes occurring in conjunction with 10-minute-long tilt  
> events, suggesting that at least a subset are responding to  
> stresses caused by extrusion. Deployments of time-lapse cameras at  
> various locations within 500m of the vent have been primarily  
> designed to capture sub-cm-level motion of the extruding lava dome  
> to investigate the relationship between dome motion and earthquake  
> occurrence. The close-in cameras have so far failed to capture  
> individual slips, however, and recent results from a temporary  
> broadband deployment indicate that a significant fraction of MSH  
> earthquakes may be generated by a collapsing crack (Waite and  
> others, 2007). However, more distant cameras placed on the crater  
> rim have recorded whole-scale slumping of the dome following larger  
> earthquakes and, in one remarkable several-day-long sequence, the  
> sticking-and-slipping of a large segment of the lava dome in  
> association with several M > 3 earthquakes (this sequence motivated  
> an earthquake prediction that proved successful, although the  
> methodology is unfortunately not exportable outside the MSH  
> crater). Thus at this stage there is no single model that can  
> adequately relate all geophysical and geologic observations to the  
> problem of seismogenesis at MSH.
>
>
> References:
>
> Iverson, R.M., Dzurisin, D., Gardner, C.A., Gerlach, T.M., Lahusen,  
> R.G., Lisowski, M., Major, J.J., Malone, S.D., Messerich, J.A.,  
> Moran, S.C., Pallister, J.S., Qamar, A.I., Schilling, S.P., and  
> Vallance, J.W., 2006, Dynamics of seismogenic volcanic extrusion at  
> Mount St. Helens in 2004-2005: Nature, v. 444, p. 439-443.
>
> Harrington, R.M., and Brodsky, E.E., 2007, Volcanic hybrid  
> earthquakes that are brittle-failure events: Geophysical Research  
> Letters, v. 34, no. L06308, p. 4.
>
> Waite, G.P., Chouet, B., and Dawson, P.B., 2007, Eruption dynamics  
> at Mount St. Helens imaged from inversion of broadband waveforms:  
> Interaction of the shallow magmatic and hydrothermal systems (abs),  
> Seismological Research Letters, v. 78 (2), p. 245..
> _______________________________________________
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