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Acoustic Detection of Volcanic Gas Seeps Using Underwater Distributed Acoustic Sensing.

Description: 

Volcanic gases are a main trigger of explosive eruptions. The largest amounts, however, are emitted through passive and non-eruptive degassing during quiescence. The presence of a large body of water near or on a volcano provides an underexploited opportunity to investigate passive volcanic degassing through non-conventional means. For example, naturally occurring underwater bubbles are powerful sound sources as they scatter and refract the underwater sound field. Contrary to subaerial settings, the acoustic detection of bubbles is, therefore, straightforward in aquatic environments, and degassing rates can be tracked at high temporal resolution (~kHz) before mixing and dilution in the atmosphere. Yet, seismo-acoustic approaches using hydrophones have mostly been deployed in non-volcanic areas.
In this contribution, we present results gathered using a Distributed Acoustic Sensing (DAS) interrogator at the Laacher See volcanic lake in Germany, where bubbles seep due to volcanic activity. We deployed a 500-m underwater fiber-optic cable connected to the interrogator over 48h. DAS data allowed us to detect and analyze plentiful bubble acoustic signals in various areas of the lake. This work demonstrates the sensitivity of fiber-optic cables to degassing events and its potential for monitoring underwater volcanic emissions or Carbon Capture and Storage (CCS) operations with great accuracy and over wide-spread areas.

Session: Advances in Marine Seismoacoustics

Type: Oral

Date: 4/18/2023

Presentation Time: 02:00 PM (local time)

Presenting Author: Zack Spica

Student Presenter: No

Invited Presentation: No

Authors