The normalization of passive source ocean bottom seismometer data

<p indent="0mm">Seismic records obtained from ocean-bottom seismometers (OBSs) are vital for understanding the deep structure of the ocean floor, predicting submarine earthquakes, and exploring deep resources of the ocean floor. The standardization and normalization of OBS data are necessary to ensure their credibility and facilitate their use in various applications. Having a unified OBS data standard will also make it easier for research groups and departments to share data, advance efforts to link marine and land station seismic data, and reduce costs and delays associated with data format inconsistencies. Additionally, it will support the development of efficient and accurate data processing and analysis software, thereby enhancing the utility of seismic data. Furthermore, a unified data standard could elevate the performance of seafloor seismic monitoring networks and improve our ability to predict and respond to earthquakes. In summary, the standardization of OBS data is crucial for ensuring data quality, increasing data-sharing efficiency, and maximizing their utility. However, efforts to standardize and normalize OBS data have been significantly hindered by technical bottlenecks and the complexity of marine environments. Moreover, there are substantial differences between OBS and land station seismic records due to clock drift and azimuthal deviations. Therefore, studies focused on the standardization and normalization of OBS data are of utmost importance. This work proposes two key processes for the standardization and normalization of OBS data to ensure their reliability and usability. We suggest establishing a comprehensive OBS data preprocessing and correction system by first designing a unified data format, coordinate system, and quality indicators to standardize the OBS data, followed by temporal and azimuth corrections. By using a unified data format, coordinate system, and quality indicators to standardize OBS data, information obtained under different conditions from different instruments can be made comparable and consistent through a preprocessing procedure. For instance, data headers could be stored in the miniSEED format, while attached XML files could store basic data and data quality information. Additionally, the coordinates of each instrument should be converted to a standard coordinate system to improve data consistency and reliability. By analyzing the effects of clock drift and azimuthal ambiguities on data accuracy, we propose methods for temporal and azimuth corrections. Temporal corrections can be performed by syncing the OBS’s clock to that of the global positioning system and then using ambient noise cross-correlation functions to further reduce temporal errors. Azimuth corrections can be done by analyzing the polarization and direction of propagation of seismic waves using various methods, and then cross-validating the results to improve the accuracy and reliability of OBS data. The standardization and normalization procedures established in this work for OBS data will be beneficial for high-precision earthquake relocation, accurate travel-time tomography, and precise waveform inversion. Additionally, they will provide reliable information that could serve as the foundation for systematic geophysical studies. Reliable, valid, and standardized OBS data will also improve the utilization of seafloor seismic data and profoundly influence studies on the deep structure of the Earth’ oceans. Standardization and normalization of OBS data will allow researchers to address the growing need for cross-referencing data across multiple domains. With a focus on overcoming existing challenges, this work aims to set a precedent for future marine geophysical research. Furthermore, the establishment of a unified OBS data framework will promote international collaboration, allowing researchers from different countries to contribute to and benefit from shared data repositories.