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An Initial Dense Seismic Array Study of Magmatic System Structure and Seismicity of the Three Sisters Volcanic Complex

Description: 

The Three Sisters volcanic complex of central Oregon is classified as a Very High Threat system, with geodetic evidence for ongoing multi-decadal surface deformation, lava flows as young as ~1600 years, and Holocene eruptions of compositions ranging from basaltic andesite to rhyolite. Yet, there is little knowledge of the 3-D distribution of middle to upper crustal magma storage and microseismicity beneath this multi-vent volcanic complex located within the High Cascades graben. Observational seismology has been limited by the need for minimal impact in a large federal Wilderness. An array of about 240 low-impact three-component nodal seismometers from Summer 2024 is providing the first local imaging and microseismicity perspectives on the Three Sisters magmatic system. Ambient noise surface wave tomography of shear velocity in the middle-to-upper crust, local seismicity detected by deep learning models, and teleseismic receiver function results will be presented. Seismicity and structure identified in the study will be compared with swarm activity detected by the regional network in 2001 and available geodetic constraints. Based on erupted compositions and geodesy we hypothesize that upper crustal magma storage is more likely in the southern portion of the complex, near South Sister volcano. The results will also serve as a case study on the potential of a low-impact nodal array deployed largely on foot in Wilderness for an initial evaluation of modern seismic structure and activity at an understudied high threat volcanic system.

Session: Innovative Applications of Seismic Nodal Technology for Hazard Mitigation and Earth System Monitoring [Poster]

Type: Poster

Date: 4/15/2025

Presentation Time: 08:00 AM (local time)

Presenting Author: Brandon

Student Presenter: No

Invited Presentation: 

Poster Number: 15

Authors