Update on RCA Broadband Hydrophone Data Availability, File Formats, and Directory Structure

As part of continuing OOI data process improvements, the RCA Data and OOI Software Development Teams have been working closely to expand data availability and improve data file consistency for six Broadband Hydrophones (HYDBBs) located at Axial Base (2), Slope Base (2), and Oregon Offshore (1) and Shelf (1) sites. Additional details are available on these study sites and instruments at these links.

A system update will go live at 17:00 UTC June 7, 2023 and will affect all HYDBB data posted on the Raw Data Archive server after that date.  In the near future, the updates will also be applied to historical HYDBB files previously posted on the Raw Data.

OOI HYDBB data are currently provided to the public on the OOI Raw Data Archive server as MiniSEED-formatted files (extension “.mseed”). This lossless, compressed format is a subset of the Standard for the Exchange of Earthquake Data (SEED) that is in extensive use for archiving and serving seismological data (see IRIS). The HYDBB MiniSEED files are served on the Raw Data Archive in daily subdirectories organized by year and month for each of the sites:

• Axial Seamount – Axial Base
  1. Seafloor HYDBB at 2607 m water depth
  2. Water Column Mooring HYDBB (~200 m below sea surface)

• Continental Margin – Slope Base
  1. Seafloor HYDBB at 2908 m water depth
  2. Water Column Mooring HYDBB (~200 m below sea surface)

• Continental Margin – Oregon Offshore
  1. Seafloor HYDBB at 581 m water depth

• Continental Margin – Oregon Shelf
  1. Seafloor HYDBB at 81 m water depth

Once the system update goes live on June 7, all HYDBB data posted on the Raw Data Archive server after this date will have the following enhancements:

• Currently, only HYDBB data arriving at the OOI data repository in near real-time are provided to the public in the daily subdirectories, updated at nominal 5-min intervals. After the system update, data arriving at the OOI repository after Navy review will also be made available on the Raw Data Archive. These delayed and previously publicly unavailable data will be provided as analogously named MiniSEED datafiles but in separate subdirectories named “addendum” under each daily directory.

• Each individual MiniSEED file will include HYDBB data over fixed 5 min timespans, starting at 00:00 UTC and repeated at subsequent 5 min intervals (beginning at 00:05, 00:10 UTC, etc.). If no data are available for a specific 5 min timespan, the datafile will not be created. Any gaps in the data stream during each 5 min timespan are accounted for by the use of the multi-trace extension of the MiniSEED file format construct, which allows multiple temporal segments within a single file. Previously, each HYDBB file on the Raw Data Archive contained only a single continuous trace of data. An example Python toolbox for accessing/processing such MiniSEED data is available, with additional information on the ObsPy open-source project here.

This change in file construction will allow for more efficient access and delivery of HYDBB data, particularly when there are small and frequent gaps in the data streams which can lead to excessive file fragmentation, as was often the case with these data before this system update.

If you have any questions, please contact the OOI HelpDesk or post your question on the public OOI Discourse Forum.