Figure 2 - uploaded by John J. Sánchez
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1. Map of Mount Pinatubo. Contours represent meters above sea level; contour interval is 300 m. Black triangle at the center marks the location of the vent. Stars mark the locations of the pre-15 June 1991 seismograph stations. Solid black circles show epicenters of pre-eruption earthquakes. Solid black squares mark the locations of the post-15 June 1991 seismograph stations. White circles show epicenters of post-eruption M D > 0.73 earthquakes used for the b-value mapping. Magnitude is proportional to symbol size. A-A and B-B indicate the locations of cross sections shown in 4.
Source publication
A compilation of research papers in volcano seismology is presented: 1) to study the configuration of magma systems beneath volcanoes, 2) to describe unexpected effects of the shaking from a regional earthquake on volcanic systems, and 3) to integrate seismicity investigations into a conceptual model for the magma system of a volcano. This work was...
Citations
... An intracaldera cinder and spatter cone with a summit height of 2156 m has been the source of all historical eruptions which have been largely Strombolian in character producing local tephra falls and lava flows confined to the summit caldera (Miller et al., 1998). Seismic activity at MV is characterized by background occurrence of volcano-tectonic (VT) earthquakes and periods of unrest when the LP events and tremor dominate (Sánchez, 2005). ...
... The values of f increase as time progresses. A similar long-term trend in values of f for LP events at MV was reported by Sánchez (2005). The lowest values of f are estimated from LP events and tremor-like LP events recorded during episodes of abundant steaming from the intracaldera cone. ...
Ambient noise interferometry has become an increasingly popular tool for monitoring active volcanoes. We apply this method to investigate seven past eruptive periods at Veniaminof volcano, Alaska. Two of the largest eruptions studied show seismic velocity changes associated with preeruptive, coeruptive, and posteruptive volcanic processes. We develop and implement new analysis techniques to determine how seismic velocity changes at Veniaminof are distributed with depth. Spatiotemporal examination of these seismic velocity changes reveals evidence for the distribution of magma storage and the timescale at which magmatic fluids intrude into and reside within these storage regions in the months preceding eruption. We conduct the depth analysis using data recorded on a single seismometer. The same analysis could be applied to any volcano monitored by at least one seismometer in order to detect magmatic activity indicative of impending eruption, specifically the intrusion and migration of magmatic fluids into the volcanic system.
In 2005 a repeat GPS campaign was conducted at 12 sites on Mt.Veniaminof Volcano and the surrounding region. A previous survey in 2002 provided initial locations for the sites. The deformation that occurred in the three years between the two surveys consist of ∼2–4 cm of displacement caused by the northwest convergence of the Pacific and North America Plates and ∼0.5–1 cm displacements caused by a deep intrusion that may be associated with eruptive activity in 2003–2005. The site velocities are corrected for compression using a pre-existing model for a locked subduction zone and the residuals modeled with volcanic sources in homogeneous and layered material. Although the data are fit equally well by several source models, we nevertheless gain important information about the deformation source. The best fitting models have depths that range from 3 to 17 km.
Mt. Veniaminof, Alaska Peninsula, is a stratovolcano with a summit ice-filled caldera containing a small intracaldera cone
and active vent. From January 2 to February 21, 2005, Mt. Veniaminof erupted. The eruption was characterized by numerous small
ash emissions (VEI 0 to 1) and accompanied by low-frequency earthquake activity and volcanic tremor. We have performed spectral
analyses of the seismic signals in order to characterize them and to constrain their source. Continuous tremor has durations
of minutes to hours with dominant energy in the band 0.5–4.0Hz, and spectra characterized by narrow peaks either irregularly
(non-harmonic tremor) or regularly spaced (harmonic tremor). The spectra of non-harmonic tremor resemble those of low-frequency
events recorded simultaneously with surface ash explosions, suggesting that the source mechanisms might be similar or related.
We propose that non-harmonic tremor at Mt. Veniaminof results from the coalescence of gas bubbles while low-frequency events
are related to the disruption of large gas pockets within the conduit. Harmonic tremor, characterized by regular and quasi-sinusoidal
waveforms, has duration of hours. Spectra containing up to five harmonics suggest the presence of a resonating source volume
that vibrates in a longitudinal acoustic mode. An interesting feature of harmonic tremor is that frequency is observed to
change over time; spectral lines move towards higher or lower values while the harmonic nature of the spectra is maintained.
Factors controlling the variable characteristics of harmonic tremor include changes in acoustic velocity at the source and
variations of the effective size of the resonator.
