Joint Inversion of Surface Wave Dispersion and Receiver Functions for Crustal and Uppermost Mantle Structure in the Chukchi Borderland

The Arctic Craton has traditionally been regarded as a long-stable, ancient continental nucleus. The Chukchi Borderland (CB), as part of this craton, is generally interpreted as a fragment of thinned continental crust. Investigating the sedimentary layer and the velocity structure of the deep crust and upper mantle beneath the CB provides critical insights into the destruction mechanisms of the Arctic Craton lithosphere. This study constructed the shallow S-wave velocity structure of the CB by extracting and inverting ambient noise surface wave dispersion from passive-source data recorded by six recovered ocean-bottom seismometers during the 11th Chinese National Arctic Research Expedition. Combined with receiver function results, a joint inversion provided a high-resolution S-wave velocity model of the crust–upper mantle beneath each station. The depth of each geosphere structure, discontinuities, and low-velocity zones was determined. The results indicate that the sedimentary sequence beneath the stations may comprise two distinct layers: 1) muddy sediments composed of glacial debris mixed with marine clay, and 2) sandy sediments formed from glacial scour products. The study delineates the fine-scale velocity structure of the crustal and upper mantle in the investigated area through ambient noise surface wave dispersion and joint inversion methodology, providing novel constraints on the velocity structure of the CB. The origins of crustal thinning were analyzed from the perspective of sedimentary layer characteristics, revealing that the formation and distribution patterns of sedimentary environments may create localized zones of brittle fracture. These structural features, together with the low-velocity zones, manifest regional extensional processes that further facilitate crustal thinning.