The seismicity of the 2009 Redoubt eruption

Abstract

Redoubt Volcano erupted in March 2009 following 6 months of precursory seismic activity. The 4.5-monthlong eruptive sequence was accompanied by phreatic and magmatic explosions, periods of steady dome growth, lahars, seismic swarms, extended episodes of volcanic tremor and changes in the background seismicity rate. This study presents a seismic chronology of the eruption and places it in context with the variety of other geological and geophysical data that were recorded during the eruptive period. We highlight 6 notable seismic swarms, 3 of which preceded large explosions. The swarms varied from an hour to several days in duration, and contained tens to over 7000 earthquakes. Many of the swarms were dominated by low frequency type earthquakes that contained families of repeating events. Seismic tremor varied considerably in frequency, amplitude and duration during the eruption with distinct characteristics accompanying different types of volcanic activity. The explosion signals during March 23-24 were the most energetic, and the explosions on March 26-29 contained proportionally more low frequency energy (0.033-0.3 Hz). Two seismic stations were particularly well-suited to recording lahars that flowed down the Drift River valley. Data from these stations showed that lahars were generated by the majority of the explosion events, as well as during the continuous eruptive activity on March 29 when no large explosions occurred. We also examine the seismicity which occurred outside of the explosion and swarm episodes, and find several families of repeating VT earthquakes which begin shortly before the April 4 explosion and that continue through May 2009, locating between 3 and 6 km below sea level.

Character, mass, distribution, and origin of tephra-fall deposits from the 2009 eruption of Redoubt Volcano, Alaska—Highlighting the significance of particle aggregation

“…Integration of field observations and laboratory analyses of tephra-fall and other deposits of the 2009 eruption of Redoubt Volcano is critical to interpreting the origins of the fall deposits. Close coordination with researchers who studied other aspects of the eruption (e.g., Bull and Buurman, 2013;Coombs et al, 2013;Buurman et al, 2013;Waythomas et al, 2013) allowed for consistent identification and characterization of all eruptive products. Evidence used to interpret deposit origin includes: (1) duration of plume generation and plume height, (2) volume of fall deposits, (3) componentry of fragmental deposits, (4) grain-size data, (5) contemporaneous volcanic activity, (6) seismicity, (7) infrasound pressure-sensor signals, and (8) gas and steam emissions.…”

“…Deposit characteristics and geophysical data however, suggest that events 9-18 mark a change in eruptive character, somewhat distinct from earlier events and from the final event on April 4. Buurman et al (2013) report a change in the character of seismicity prior to the explosive events 9-18 beginning with a very energetic swarm of earthquakes on March 26. Individual explosions were accompanied by lower frequency seismicity compared to events 1-6 which is consistent with the short duration explosions and high plume heights (Table 1).…”

Volcano Seismology: Detecting Unrest in Wiggly Lines

“…Green and Neuberg 2006) and Redoubt volcano (e.g. Buurman et al 2013). Using precursory seismicity and the FFM, Salvage and Neuberg (2016) graphical representation of the FFM is depicted by the linear regression (it is assumed that a ¼ 2 for simplicity) and the forecasted timing of failure can be read off the x-axis at the point where the linear regression crosses it.…”

A phase coherence approach to identifying co-located earthquakes and tremor

“…12(a) shows a seismogram from the last hour prior to the eruption, with more than 100 visible earthquakes. Most of the earthquakes have similar waveforms and arrival times (Buurman et al 2013;Hotovec et al 2013). Hotovec et al (2013) therefore interpreted the earthquakes as the repeated rupture of a single patch.…”