A large-scale concentric pattern of deformation was observed between 1994 and 2000 centered on
Uturuncu Volcano, Bolivia from satellite geodetic surveys. A reconnaissance investigation took place
1-6 April 2003 to see if there were other signs of volcanic unrest. A single component vertical, T=1.0
s seismometer, was placed at five sites for periods up to 14 hours. Persistent low level earthquake
activity was observed at all locations. The events were very similar to each other and had distinct P
waves (T= 0.1 s) and clear S waves. Events at each station had similar S-P times, suggesting that they
came from one source. Using bootstrapping methods we determine this to be from the NW flank
close to the center of deformation. Several events with different S-P times and different waveforms
suggest that two other sources exist within the volcanic edifice. The rates of M=0.5 to 1.5 earthquakes
varied from 0 to 13 per half hour, with a mean rate of 2.6 events per hour. This is a surprisingly high
rate for a dormant stratovolcano. The sources were shallow (3-4 km), although the velocity structure
is not well known. We also examined data from IRIS station PNEG for November to December 1996.
These data show rates of 0-3 small events per day on the south flank of Uturuncu. Thus there exist at
least four sources of events near the volcano. The recent unrest manifested by ground deformation,
thermal activity and seismicity indicates that an active magmatic system may still be present.