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Detection, Characterization and Interpretation of Diverse Seismic Signals in Submarine Hotspot-ridge Interaction Settings

Description: 

Ocean bottom seismometers (OBS) placed on mid-ocean ridges record a broad spectrum of signals that originate from diverse solid Earth processes and other sources, including whale calls, anthropogenic activity (e.g., ship noise, air guns), and ocean noise. Detection, discrimination, and characterization of these signals is challenging because of their complexity and because they are often recorded concurrently. This is especially true in periods leading up to and during eruptions when local OBS data are inundated with seismic events. Furthermore, phase conversions and reverberations complicate the interpretation of seismic phases. Here we show examples from the East Pacific Rise at 9°50’N and from Axial Seamount, an active submarine volcano on the Juan de Fuca Ridge which last erupted in April 2015. We focus on the 7-station, cabled OOI OBS network at Axial where we employ an extensive suite of methods to automatically detect and characterize events from various sources in near real-time: kurtosis, machine learning and waveform cross-correlation for event detection as well as polarity, phase arrival and delay time measurement; inversion and grid search for absolute hypocenter location; double-difference for precise relative location. In addition, we use unsupervised machine learning to characterize time-dependent variations in spectrograms to effectively discriminate between different source origins and types of brittle failure. This allows us, for example, to monitor precursory mixed frequency earthquakes which were observed before the 2015 eruption, or impulsive seafloor events that track lava flow during eruptions. Analysis of the ambient noise over 7-years reveals a long‐term trend of decreasing velocity during rapid inflation, followed by an increase in velocities leading up to the next eruption. These complementary observations, when combined and interpreted together with results from active source seismics, lead to significant improvement of our understanding of the structure, mechanics, and dynamics of this hotspot-ridge system, and help forecast the timing of Axial’s next, imminent eruption.

Session: ESC-SSA Joint Session:Seismology in the Global Oceans: Advances in Methods and Observations - I

Type: Oral

Date: 4/15/2025

Presentation Time: 05:00 PM (local time)

Presenting Author: Felix

Student Presenter: No

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