# Putting ocean bottom seismometer data in Résif

Wayne C. Crawford, Olivier Dewée, Rima Bouazzouz, David Wolyniec

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Wayne C. Crawford, Olivier Dewée, Rima Bouazzouz, David Wolyniec. Putting ocean bottom seismometer data in Résif. Rencontres scientifiques et techniques RESIF 2019, Nov 2019, Biarritz, France. hal-02415321

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Submitted on 17 Dec 2019

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Distributed under a Creative Commons Attribution 4.0 International License
# Putting ocean bottom seismometer data in RESIF

Wayne Crawford¹ (crawford@ipgp.fr), Olivier Dewee², Rima Bouazzouz³ and David Wolyniec³

1: Institut de Physique du Globe de Paris, Marine Geosciences Team, 1 rue Jussieu, 75238 Paris Cedex 5, France

2: INSU Division Technique, UPS 855, 1 Place Aristide Briand, 92195 Meudon Cedex, France

3: RESIF Data center, ISTERRE, Université Grenoble Alpes, CS40700, 38058 Grenoble Cedex 9

Orfeus

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université
PARIS
DIDEROT

INSTITUT DE PHYSIQUE DU GLOBE DE PARIS

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Université de Paris

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## Overview

Few ocean bottom seismometer experiments are currently available on EIDA data centers, in part because of the difficulty of preparing their data and metadata for data centers, including:

- Non-standard dataloggers which are unreferenced in the Nominal Response Library (NRL) and which have non-standard data formats

- The inability to synchronize the sensor clock with GPS while at the seafloor

- A lack of standards for OBS-specific parameters

We present a 3-part, harmonized approach to simplify data/metadata preparation and standardize the output using FAIR principles:

1) **Standards for OBS data and metadata**

2) Software to prepare OBS datafiles for EIDA

3) Software and «information files» to prepare metadata for EIDA

## 1) Standards

Standards have been proposed through FDSN Working Group 5 (Mobile Instrumentation) and SERA Deliverable 4.2. The principal standards are:

- **SEED «Data quality» codes:**

- 'D': no time correction applied

- 'Q': time correction applied and fully specified in the miniSEED header.

- **Channel naming:**

- Horizontal channels should be called '1' and '2', with '1' corresponding geometrically to 'N'. and '2' to 'W'

- Geophone vertical channels (positive downward) should be named '3'

- **Channel azimuths/dips** in StationXML:

- '1' has azimuth = 0.0, uncertainty = 180.0

- '2' has azimuth = 90.0, uncertainty = 180.0

- 'Z' has dip = -90.0

- '3' has dip = 90.0

- 'H' (hydrophone) has dip=

- -90.0 if a positive voltage corresponds to a positive pressure

- 90.0 if a positive voltage corresponds to a negative pressure.

- **Comments**

- Processing steps (clock correction, leap seconds...) should be specified in comments. Clock corrections should be specified as absolute dates, not «slew» or «drift» as the polarity of these latter are ambiguous.

## 2) Preparing data: SDPCHAIN

Programs to transform obs data into time-corrected SeisComp3 Data Structure (SDS), while creating a Provenance file. The software works on uncorrected miniSEED files (considered the primary «standard» output of OBS parks).

**mscat**: concatenate miniSEED files

**msdrift**: apply a clock drift correction

**msleap**: add a leap-second correction

**ms2sds**: convert miniSEED file(s) to SeisComp3 Data Structure

**sdp-process**: run a Unix command-line program and appends the provenance file.

This package is not yet ready for distribution, but interested parties can obtain it and help us evaluate and upgrade it.

### Example SDPCHAIN Provenance file (JSON format)

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## Where to find the files:

**Standards:**

**SERA deliverable**: http://www.sera-eu.org/en/Dissemination/deliverables/, then D4.2

**Latest proposal**: http://www.ipgp.fr/~crawford/Documents/OBS_data_standards.pdf

**obsinfo**: https://pypi.org/project/obsinfo/ and https://github.com/WayneCrawford/obsinfo

**SDPCHAIN**: write to crawford@ipgp.fr or olivier.dewee@cnrs.fr