Imaging the P-Wave Velocity Structure of Arctic Subsea Permafrost Using Laplace-Domain Full-Waveform Inversion

摘要

Climate change in the Arctic has recently become a major scientific issue, and detailed information on the degradation of subsea permafrost on continental shelves in the Arctic is critical for understanding the major cause and effects of global warming, especially the release of greenhouse gases. The subsea permafrost at shallow depths beneath the Arctic continental shelves has significantly higher P-wave velocities than the surrounding sediments. The distribution of subsea permafrost on Arctic continental shelves has been studied since the 1970s using seismic refraction methods. With seismic refraction data, the seismic velocity and the depth of the upper boundary of subsea permafrost can be determined. However, it is difficult to identify the lower boundary and the internal shape of permafrost. Here, we present two-dimensional P-wave velocity models of the continental shelf in the Beaufort Sea by applying the Laplace-domain full-waveform inversion method to acquired multichannel seismic reflection data. With the inverted P-wave velocity model, we identify anomalous high seismic velocities that originated from the subsea permafrost. Information on the two-dimensional distribution of subsea permafrost on the Arctic continental shelf area, including the upper and lower bounds of subsea permafrost, are presented. Also, the two-dimensional P-wave velocity model allows us to estimate the thawing pattern and the shape of subsea permafrost structures. Our proposed P-wave velocity models were verified by comparison with the previous distribution map of subsea permafrost from seismic refraction analyses, geothermal modeling, and well-log data.