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Small Earthquakes Matter for Triggering Volcanic Unrest

Description: 

The occurrence of large earthquakes often inspires questions about their potential to trigger volcanic unrest. Most prior studies that address these questions focus on case studies of a single earthquake and its impact on a specific eruption or on changes in eruptive activity at all volcanoes within a certain distance. Instead of this earthquake-centric strategy we take a novel volcano-centered approach, in which we compare volcanic activity at a single volcano with a calculated, continuous time series of stress changes due to all potentially impactful earthquakes. This approach accounts for the facts that the amplitudes of stress changes from small to large earthquakes are comparable within near-field distances, which roughly scale with earthquake source dimensions, and that the numbers of earthquakes increases as magnitude decreases. We assume any stress change smaller than typical, ever-present, tidal values of ~0.01 MPa may be neglected, and consider spatial decays consistent with earthquake-generated static, quasi-static, and dynamic stress changes. Noting that stresses may relax over time, particularly in volcanic systems, we also consider a range of temporal decay rates, and we remove earthquakes close to the volcano that are likely to be driven by the magmatic system itself.

Our approach is general, and we have tested it on the Turrialba, Costa Rica and Redoubt, Alaska volcanoes, which have different tectonic settings and eruptive styles. Turrialba has been persistently active since 2010, while Redoubt has had two short-lived eruptive phases within decades of quiescence. Although we calculate stress changes using a very simple model, preliminary results for a range of plausible models show the summed stresses from smaller earthquakes closer to a volcano may be more perturbing than the stress from a single or a few larger more distant earthquakes, particularly if considering dynamic stress changes. Connecting earthquake-generated stress changes with volcanic unrest may be more complex than previously thought.

Session: Multidisciplinary Approaches for Volcanic Eruption Forecasting - I

Type: Oral

Date: 5/2/2024

Presentation Time: 02:15 PM (local time)

Presenting Author: Joan

Student Presenter: No

Invited Presentation: 

Authors