Quantification of OBS source offset effects on first-arrival travel times and crustal velocity modeling: A case study from the Arctic JASMInE expedition

Accurate crustal velocity modeling from Ocean Bottom Seismometer (OBS) data requires precise travel-time measurements, which may be affected by spatial offsets between seismic sources and OBS profiles. In this study, we quantitatively assess the influence of seismic source offsets on first-arrival travel times and crustal structure modeling accuracy, with application and validation using field data from the 2021 Joint Arctic Scientific Middle-ocean ridge Insight Expedition (JASMInE) conducted along the Gakkel Ridge in the Arctic Ocean. The results show that for the typical crustal structure of the Gakkel Ridge, when the seismic source offset is less than 4 km and the source-receiver offset exceeds 6 km, the induced travel-time error (∆t) remains below 120 ms—within acceptable limits for reliable crustal forward and inverse modeling. Statistical analysis of the JASMInE dataset indicates an average seismic source offset of 2.5 ± 1.5 km. The impact of this offset is primarily confined to source-receiver offset 10 km is recommended to minimize the travel-time errors. Travel-time errors due to seafloor variations are <50 ms (equivalent to ~0.175 km Moho depth variation), whereas combined effects of seafloor and lateral crustal variations near magmatic centers can reach 140 ms, corresponding to <0.5 km Moho depth uncertainties. Overall, the uncertainties remain within a reasonable range. These results validate the robustness of the JASMInE-derived 2D crustal velocity model and offer quantitative guidance for seismic source deployment and data interpretation in polar challenging environment.