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WP4: Seafloor Signal Separation and Noise Removal

This WP applies advanced signal processing techniques to separate signal/noise sources and tests the use of a new rotational sensor.

Objectives

Increase sensitivity to low-frequency seismological signals (normal modes, teleseisms…)

Tasks

Number Title Responsable Status Project Management
T4.1 Reducing horizontal noise using a rotational seismometer @WayneCrawford, Frederic not started Page
T4.2 Signal separation/removal techniques Ker, @WayneCrawford not started  
T4.3 Separating seismological and biological signals Ker, Duval not started  

Deliverables

Number Title Due Date Status
D4.1 Report on rotational seismometer integration in BBOBS M12 not started
D4.2 Open source software for noise separation and removal M24-48 not started
D4.3 Catalog of seafloor noise sources M36 not started
D4.3 Scientific articles M24-48 not started

Details

Task 4.1: Reducing horizontal noise using a rotational seismometer

We will investigate reducing seafloor horizontal noise levels using the iXblue blueSeis-1C rotational seismometer. This task is divided into sequential subtasks:

  1. Conception. Mechanical analysis of integration of blueSeis-1C into INSU-IPGP BBOBS;
  2. Manufacturing: Construction of blueSeis-1C and modified BBOBS parts
  3. Installation of the rotational seismometer in a BBOBS
  4. Calibration table evaluation. Using iXblue’s state of the art 3-axis calibration table
  5. Analysis of results. Compare calibration table tests with predicted noise level improvements. Modify installation and retest if needed
  6. Near-shore test: Deployment offshore Brest to validate instrument and obtain high-current data
  7. At-sea test. Leverage yearly month-long expeditions by the OBS team to the deep seafloor Lucky Strike volcano. We will request a 1-day cruise extension for summer 2023 or 2024
  8. Analysis and scientific article.

Task 4.2: Signal processing techniques for signal separation and noise removal

This task will be run in collaboration between IPGP and IFREMER with the support of a postdoctoral researcher specialised in signal analysis/processing and a broad group of signal processing experts from ESIEE, iXBlue, GEO3BCN and GIPSA-Lab.

Task 4.3: Separating seismological and biological signals

We will develop an approach to separate simultaneous seismological and whale call signals in the shared frequency band around 20 Hz, including the challenging chorus footprint (Bouffaut et al., 2018). We will use recently developed signal deconvolution/restoration techniques (SPOQ) using sparse non-convex norm-ratio penalties (Cherni et al., 2020) to characterise the overlapping signals using robust statistical measures (moments and moment ratios) to enhance their differences and assist their separation.

Risks:

Task 4.1 risks are 1) inability to integrate the rotational seismometer into the BBOBS seismometer sphere or 2) less horizontal noise reduction than predicted. These risks will be evaluated in the first 2-5 subtasks, before the major cost and personnel items are engaged. The risk of the technique not working is low, as the relation between horizontal signal and rotational measurements has already been demonstrated for a less sensitive rotational seismometer using the same technology [Bernauer et al., 2018].

Task 4.2 is relatively low risk: We know the existing methods very well and have identified weaknesses that we can improve on. We will quantify improvements, limitations and benefits using synthetic and measured data.

Task 4.3 is high-risk, high-reward. It uses few resources and failure has no impact on other tasks.