UPLFOW ocean bottom seismometers data: preliminary performance report

<p><span data-preserver-spaces="true">We present preliminary results from the UPFLOW (Upward mantle flow from novel seismic observations;&#160;</span><em>https://upflow-eu.github.io/</em><span data-preserver-spaces="true">) project and associated large-scale amphibian experiment. The UPFLOW project, funded by the European Research Council (2021-2026), led a passive seismology large-scale experiment in the Azores-Madeira-Canary region starting in July 2021 and ending in September 2022.&#160;</span></p> <p><span data-preserver-spaces="true">We recovered 49 (out of 50) OBSs deployed in a ~1,000&#215;2,000 km² area and with an average station spacing of ~150-200 km. Most instruments have three-component wideband seismic sensors (Trillium compact OBS version with a corner period of 120 s) and broadband hydrophones (type HTI-01 and HTI-04-PCA/ULF) with a corner period of typically 100 seconds. Three different designs of OBS frames were used LOBSTER, NAMMU and DUNE. We achieved data recovery rates of ~90-100% in 37 stations and ~50% in 6 stations, with only 7 stations being faulty, highly problematic or lost.&#160;</span></p> <p><span data-preserver-spaces="true">We present various illustrative examples of seismic waveforms, spectrograms and data quality analysis from the recovered OBS data. Systematic probability power spectra density (PPSD) plots for all stations and over the whole deployment show a marked improvement in the quality of the long-period data (T>~30s) compared to previous experiments.&#160;</span></p> <p><span data-preserver-spaces="true">We analyse the data performance as a function of the three models of OBS, recorder and seismometer types. Additionally, we present initial results from: (i) noise correlation analysis to quantify the clock skew during the deployment; (ii) estimation of horizontal component rotation angles from teleseismic data (body and surface waves); and, (iii) tilt and compliance analysis.&#160;</span></p> <p><span data-preserver-spaces="true">Finally, we present an initial set of ~6000 multi-frequency body-wave travel time measurements generated with the UPFLOW OBS data and show a glimpse of preliminary body wave tomographic models built with this new dataset.</span></p>