Ps‐P Tomography of a Midcrustal Magma Reservoir Beneath Cleveland Volcano, Alaska

Abstract

Seismic tomography of the crust is an essential tool for studying the three-dimensional structure of magmatic plumbing systems feeding active volcanoes, but it is often limited in resolution by the absence of deep local seismicity. Teleseismic receiver functions can be used to illuminate local structural variations, but typically do not account for the effects of three-dimensional velocity heterogeneities. Here we harness the complementary strengths of both techniques by processing Ps-P delay times derived from teleseismic receiver functions in a tomographic S wave inversion. Using our inversion technique, we produce the first tomographic crustal velocity model beneath Cleveland Volcano, identifying a vertically extensive high V P /V S anomaly beneath the volcano that likely signifies a middle-to-lower crustal magma reservoir. The observation is the first of its kind in the central Aleutians, illustrating the potential of our technique to advance our understanding of crustal magmatic systems without broad seismic networks or distributed local seismicity. Plain Language Summary Detailed models of magma pathways and storage regions beneath volcanoes are critical for our understanding of the dynamics of volcanic systems and their long-term hazard to society, but there is often a large gap in these images in the lower crust. With this study, we fill that gap at Cleveland Volcano in the central Aleutians, Alaska, by using seismic waves generated at the crust-mantle interface. These waves traverse the entire crust before reaching seismic stations on the volcano, allowing us to infer relative variations in seismic velocity in the crust. With this technique, we produce an image of a low velocity anomaly directly beneath the volcano that reaches from the volcano through the entire crustal column that represents an extensive network of stored magma, rock, and/or volatiles. This network is likely what supplies Cleveland Volcano's persistent activity. Our new technique has the potential to help fill similar imaging gaps beneath other volcanoes.

Magma‐Fluid Interactions Beneath Akutan Volcano in the Aleutian Arc Based on the Results of Local Earthquake Tomography

“…Seismic tomography is an efficient tool to reveal the geometry of magmatic feeding systems that has been successfully used to explore many volcanoes throughout the world. For example, volcanoes of the Aleutian Arc and Alaska have been investigated in a number of tomographic studies, such as those of Mount Spurr (Koulakov et al, 2013(Koulakov et al, , 2018Power et al, 1998), Mount Redoubt (Benz et al, 1996;Kasatkina et al, 2014), Katmai Group (Murphy et al, 2014), Okmok (Ohlendorf et al, 2014), Augustine (Syracuse et al, 2011), Atka (Koulakov et al, 2020), Makushin (Lanza et al, 2020), and Cleveland (Portner et al, 2020), and each of them shed light on the magma feeding processes of these specific cases. It should be noted that most volcanoes are in some sense unique and not similar to others.…”

Trends in volcano seismology: 2010 to 2020 and beyond

“…Ambient noise tomography studies, often in conjunction with other methods, have imaged the S-wave structure under volcanoes (Lin et al 2014;Kiser et al 2016;Ulberg et al 2020), where S-wave travel times are sparse in the seismic catalog (Nagaoka et al 2012;Jaxybulatov et al 2014;Flinders and Shen 2017;Heath et al 2018;Green et al 2020;Miller et al 2020). Towards the end of the 2010-2019 decade Janiszewski et al (2020) and Portner et al (2020) have illuminated the mid and lower crust of volcanoes using receiver functions within sparse networks. Advances in time-dependent (4D) tomography (Koulakov et al 2013;Vargas et al 2017;Koulakov and Vargas 2018) have revealed temporal changes in the ratio between the p-wave velocity and s-wave velocity, which have been interpreted as relating to magma storage and transport structures.…”