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SUMMARY:Seismic tomography from ocean bottom seismometers  - Maria Tsekhmi
 strenko - University College London
DTSTART:20221012T150000Z
DTEND:20221012T160000Z
UID:TALK180350@talks.cam.ac.uk
CONTACT:Yihe Xu
DESCRIPTION:This presentation will have three parts. I will start with som
 e (preliminary) results from two ocean bottom seismometer (OBS) experiment
 s (UPFLOW and RHUM-RUM). I will additionally introduce an ongoing project 
 using OBS data and machine learning. \n\nThe UPFLOW project\, funded by th
 e European Research Council (2021-2026)\, is an off-shore experiment in th
 e Azores-Madeira-Canary region. We recovered 49 (out of 50) OBS in August 
 and September 2022. Here\, I will show various waveforms\, spectrograms an
 d data quality analysis from the recovered OBS data.\n\nMy second topic wi
 ll cover the preliminary results of a variational autoencoder (VAE) archit
 ecture to denoise seismic waveforms to extract more information than previ
 ously possible. Data from OBS are inherently more challenging than their l
 and counterpart because of their noisy environment (e.g. microseismic nois
 es). Additionally\, anthropogenic (e.g.\, ships) and animal noise (e.g.\, 
 Whales) contribute to complex noise signals that can make it challenging t
 o use traditional filtering methods (e.g.\, broadband or Gabor filters).\n
 \nFinally\, I will present results from the RHUM-RUM (2012-2016) experimen
 t where for 13 months 57 OBS were deployed around the hotspot island of La
  Réunion. I present a 3-D P-wave tomography model supplemented by a globa
 l data set of P-diffracted measurements and a selection of ISC picks. \n\n
 We observe the Large Low-Velocity Province (LLVP) rising 800 km above the 
 CMB\, forming a cusp beneath South Africa. A low-velocity branch undulates
  obliquely from this cusp region towards the uppermost mantle beneath La R
 éunion. The La Réunion’s connection to the lower mantle seems to be mo
 re complex than previously envisioned. The deep-mantle connections of the 
 Afar and Kerguelen hotspots emerge from the same LLVP cusp beneath South A
 frica and extend towards the surface through tilted low-velocity branches.
  
LOCATION:Wolfson Lecture Theatre
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