[SIO GP Seminars] Paul Segall, Stanford U, Intrusions, Eruptions, Silent Slip Events, and Triggered Earthquakes

[Matt Wei]

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FRIDAY, Mar. 2, 3:00 PM
(refreshments served at 2:45 PM)
Munk Conference Room

Paul Segall
Stanford University

"Intrusions, Eruptions, Silent Slip Events, and Triggered  
Earthquakes: Lessons
from monitoring an active volcano with possible application to mega- 
thrust earthquakes"

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Abstract:

A decade of continuous GPS monitoring on Kilauea volcano has recorded  
several dike intrusions, 8 hours of deformation prior to a short- 
lived eruption, continuous seaward sliding of the volcano’s south  
flank, and a sequence of slow slip events.  The slow slip events  
displace the south flank seaward ~1 cm over 1-2 days.  Four events  
are clear in GPS data in 1998, 2000, 2003, and 2005, although smaller  
events may have occurred.  Depths of slow events are difficult to  
constrain based on surface deformation measurements alone. Kilauea  
slow events, however,  are associated with swarms of small quakes.    
In 2005, the swarm follows the onset of GPS displacement, making the  
quakes “coshocks” and aftershocks of the otherwise silent  
earthquakes. The temporal evolution of the quakes is consistent with  
stressing caused by slip, implying that the quakes are triggered. The  
focal depths of 7–8 km, constrain the slow slip to be at comparable  
depths, since they must fall in zones of positive Coulomb stress  
change. Triggered quakes are similarly located in other slow events,  
in areas of background seismicity, suggesting that their locations  
are controlled by structural or material heterogeneity.

Slow slip events, accompanied by non-volcanic tremor, have been  
observed in a number of convergent plate boundaries where young  
oceanic lithosphere is subducting, and may be ubiquitous in such  
environments.  A few examples of swarm seismicity associated with  
slow slip have been reported, possibly similar to the triggered  
events observed on Kilauea. I will discuss the possibility that such  
events can be used as a means to gauge the stress level in megathrust  
zones with potential applications for hazard warning.

Have a good day.

Matt

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Meng Wei ( Matt )
Institute of Geophysics and Planetary Physics
Scripps Institution of Oceanography
University of California, San Diego
La Jolla, CA 92093-0225
mwei at ucsd.edu
(858) 822-4347
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