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Modelling Wavefield Complexity for Submarine DAS Data From Santorini (Greece)

Description: 

Distributed Acoustic Sensing (DAS) with existing telecommunication cables has contributed significantly to the seismological exploration of difficult-to-access regions such as the ocean bottom. In contrast to the relative simplicity of deployment of a DAS interrogator on dark fibres, the data can be challenging to analyse and interpret, particularly in geophysically complex areas, as the wavefield becomes much more complex. In our study focused on the region around Santorini in the Aegean Sea, we interrogated a 45 km long dark fibre extending from Santorini along the ocean bottom to the neighbouring island of Ios from mid-October to mid-December 2021. This region is of great geophysical interest because of its historical and recent seismic and volcanic activity, especially along the Kolumbo volcanic chain. Alongside the anthropogenic noise on Santorini, we directly observe the time-variable primary and secondary microseisms along the submarine section of the cable, the latter inducing slow-moving Scholte waves. Throughout the experiment, we recorded 1021 seismic events with varying strengths and locations.

To better understand the complex wavefield in the region, we take advantage of the latest developments in DAS wave propagation modelling using the spectral-element solver Salvus. We run simulations with varying levels of complexity, from a simple layered model to the inclusion of topography, bathymetry, and a heterogeneous velocity model. Furthermore, the fully complex model allows us to perform backpropagation with the aim of locating seismic events near the Kolumbo volcanic chain. The simulations with varying complexity and backpropagations for four different earthquakes highlight the complicated wavefield in the region and the challenges of recovering a source location, even when all complexities are taken into account.

Session: Advancing Seismology with Distributed Fiber Optic Sensing [Poster Session]

Type: Poster

Date: 5/3/2024

Presentation Time: 08:00 AM (local time)

Presenting Author: Jonas

Student Presenter: Yes

Invited Presentation: 

Authors