Volcanic terrains are actively avoided for submarine infrastructure projects as they represent significant challenges in terms of geohazard risk and non-standard soil/rock conditions. We present data from a unique front end engineering design (FEED) pipeline route assessment that crossed a submarine volcanic terrain over a section of the pipeline corridor. Through integration of multiple geo-datasets, the site was effectively characterised providing confidence in the emplacement and depositional history of the volcanic terrain such that engineering design could progress. The volcanic terrain studied is present between 100 m and 120 m below seafloor and was subjected to a range of dynamic depositional environments throughout its history due to sea level regression during the Quaternary. The relationship between dynamic sea level change and volcanic eruptive history is defined across the terrain by morphological features such as an ashfall plateau with an associated palaeocoastline, infilled volcanic collapse structures and a very shallow marine to subaerial eruptive centre. These morphological features were imaged at surface by multibeam echo sounder bathymetry at a horizontal resolution of 1 m, and in the subsurface by chirp and sparker sub-bottom profiler with vertical resolutions between 0.1 m and 5 m. Through the integration of these geophysical data with geological core samples and sedimentary dating results, a geological model of the area for 'recent' volcanic episodes was devised and is presented as part of this paper. The importance of integration of all datasets (geotechnical, geophysical, geological and engineering) is even more pronounced when investigating non-standard sites. Particularly where multiple lines of evidence are required to assess the risk posed by adverse ground conditions and geohazards to installation of submarine infrastructure.
Osama Safaqah, Xuan Nhan Pham, Quang Chung Dam, Chris A. Smith, Lorraine O'Leary, Chris Steven and Jason Goh
Keywords: site characterisation, volcano, pipeline
Publisher: DFI