HR: 09:45h
AN: V41B-08 [Abstracts]
TI: Analysis of Seismicity Related to the December 2002 - February 2003 Eruptions at Popocatepetl Volcano, Mexico
AU: * Quezada-Reyes, A
EM: aida@ssn.ssn.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, UNAM. Circuito
de Institutos, Ciudad Universitaria, Mexico, DF 04510, Mexico
AU: Valdes-Gonzalez, C
EM: carlosv@ollin.igeofcu.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, UNAM. Circuito
de Institutos, Ciudad Universitaria, Mexico, DF 04510, Mexico
AU: Lesage, P
EM: lesage@ollin.igeofcu.unam.mx
AF: Universidad Nacional Autonoma de Mexico, Instituto de Geofisica, UNAM. Circuito
de Institutos, Ciudad Universitaria, Mexico, DF 04510, Mexico
AU: Lesage, P
EM: lesage@ollin.igeofcu.unam.mx
AF: Institut de Recherche pour le Developpement, LGIT - Universite de Savoie 73376 Le
Bourget-du-Lac, France
AB:
Since its reactivation in 1994 Popocatepetl Volcano has undergone several activity stages, some of which
comprise cycles of intrusion, extrusion and destruction of a lava dome. Popocatepetl has produced up to several
tens of daily long-period (LP) events and several volcanic tremor episodes, along with a few volcano-tectonic
earthquakes. A lava dome was extruded on May 2002 and subsequently destroyed by 19 explosions from
December 2002 to February 2003. The seismicity accompanying the destruction of the lava dome was dominated
by long-period (LP) events and a mix of harmonic and spasmodic tremor. We analysed the seismity related to
this explosive phase and classified the majority of LP events into three families according to their frequency
content. Most of the LP events are characterized by a dominant frequency near 2 Hz throughout the eruptive
period. Many events also exhibited a low-amplitude short-period (SP) phase ocurring a few seconds before the
LP signal. The SP signal was not observed without the LP event, although several events occurred in the absence
of the precursory signal. We also found a notably decrease of LP events activity prior to December 18, 2002 and
February 14 to 28, 2003 explosive episodes.
Three different types of tremor lasting from a few minutes to several hours were also observed: spasmodic,
harmonic and a very low-amplitude pulse-like type of tremor, the latter occurring on November 11, 12 and 30 with
a duration of about 120 minutes each.
Harmonic tremor episodes lasted from a few minutes to a few hours and there was no tremor occurrence days
before the explosive events. Tremor spectra display a fundamental frequency which can vary in the range 0.6-1.3
Hz within a one-hour-long series of tremor. Similar observations are obtained for the peak spacing of the
harmonic tremor spectra.
These variations may reflect short-term fluctuations of the acoustic properties of the source while no long-term
evolutions of the LP sources are detected prior the dome destruction.
The seismic activity at Popocatepetl Volcano from December 2002 to February 2003 differs from that observed
prior to the December 2000 dome destruction. In contrast, a similar behavior was observed prior to the eruptive
activity of November and December, 1998 and that of January 2001. This analysis could be useful to determine
and/or understand a the variability of the volcano behavior prior to intense activity and therefore, to forecast more
accurately future possible eruptive scenarios.
DE: 7280 Volcano seismology (8419)
DE: 8419 Volcano monitoring (7280)
SC: Volcanology, Geochemistry, and Petrology [V]
MN: 2007 Joint Assembly