Seismic structure changes beneath Redoubt Volcano during the 2009 eruption inferred from local earthquake tomography

Abstract

We present seismic velocity models of the area beneath Redoubt Volcano (Alaska) corresponding to two time periods, before and after the strong eruption that occurred in March 2009. The calculations were based on tomographic inversion of P and S arrival time data recorded by 19 stations using the local earthquake tomography code LOTOS. We performed thorough analysis of the results based on synthetic tests in each of the time periods that allow real-time variations in structure to be distinguished from artifacts caused by changes in the observation system configurations. In the resulting images corresponding to the period before the eruption, the summit area is characterized by higher values of both P and S velocities and moderate values of the Vp/Vs ratio. This may correspond to the rigid igneous rocks composing the body of the volcano that lack significant liquid content. In the second episode corresponding to the time of the eruption, the P velocity remained high, whereas the S velocity became very low. The anticorrelation of P and S anomalies in the summit area produced a Vp/Vs ratio as high as 2.2, which is seen down to 2-3 km depth. This indicates presence of mobile phase at shallow depth beneath the volcano, which can be either in the form of partial melt or fluid-saturated rocks.

Evolution of the Magma Conduit Beneath the Galeras Volcano Inferred From Repeated Seismic Tomography

“…Observing the results of the P and S wave velocity anomalies in the supporting information shows that this anomaly is associated with high P and low S wave anomalies. Note that the same feature is observed in many other volcanoes throughout the world, such as Nevado del Ruiz (Vargas et al, 2017), Bezymianny (Ivanov et al, 2016), and Redoubt (Kasatkina et al, 2014). In the cases of volcano-related structures, this pattern can be explained by the fact that the P wave velocity is most sensitive to the composition of the rocks, whereas the S wave velocity is strongly affected by the presence of liquid phases.…”

Fault‐Associated Magma Conduits Beneath Volcán de Colima Revealed by Seismic Velocity and Attenuation Tomography Studies

“…The area of volcanic edifices of the Volcán de Colima and Nevado de Colima at 5‐km depth appears to be associated with a high‐velocity anomaly with the diameter of ~8 km centered with Nevado del Colima. Such high‐velocity anomalies associated with volcano summits are fairly typical features observed in many different volcanoes, such as Popocatepetl (Kuznetsov & Koulakov, ) and Redoubt (Kasatkina et al, ). This might be related to the fact that the volcano is mostly composed of lava flows having more rigid integral properties than volcanoclastic deposits on the volcano's flanks.…”

Breathing of the Nevado del Ruiz volcano reservoir, Colombia, inferred from repeated seismic tomography

“…In recent years, several authors have investigated time variations of seismic structure beneath active areas using repeated tomographic inversions131415. Results are typically derived from the same calculations performed over different time intervals and hence may be affected by artefacts due to changes of data coverage.…”