GO_3D_OBS: A 3D Subduction-Zone Benchmark Model for Assessing Acquisition Footprint and 3D 

Effects in Crustal-Scale Seismic Imaging 

Prof.  Andrzej Górszczyk

Institute of Geophysics of the Polish Academy of 

Sciences in Warsaw 

2026.06.24（星期三）11:00，理科二号楼 2821 

摘要： 

Detailed reconstruction of deep crustal structures using active-source seismic methods remains challenging due to sparse acquisition geometries, incomplete subsurface illumination, and the inherent 3D nature of wave propagation. Academic marine surveys are commonly conducted with 2D layouts of OBSs, yet recorded wavefields travel along fully 3D paths. This mismatch introduces acquisition footprint and out-of-plane 3D effects that can significantly bias velocity model building and FWI, particularly at crustal s       cale s where seismic waves propagate over hundreds of kilometers. 

To address these limitations, we introduce GO_3D_OBS, a high-resolution 3D crustal-scale geomodel inspired by the geology of the Nankai Trough subduction zone. The model spans 175 km × 100 km × 30 km and integrates complex structural features within a viscoelastic isotropic parameterization. Discretized on a uniform Cartesian grid with 25 m spacing (approximately 33.6 billion degrees of freedom), the model poses substantial high-performance computing challenges for forward simulations and inverse problems. We describe the workflow used to construct the model, including 2D structural building blocks, their 3D projection, stochastic heterogeneities, and physical parameterization. 

Using realistic wavefield simulations, we evaluate the imprint of acquisition geometry and 3D wave propagation on seismic data and on the results of velocity model building. Polarization analysis and synthetic inversion experiments demonstrate how out-of-plane propagation distorts 2D imaging and may lead to erroneous velocity reconstructions in complex geological environments. We further explore strategies to mitigate these effects by coupling optimized acquisition geometries with fully 3D FWI. 

GO_3D_OBS provides an open-access benchmark for the geophysical community to assess acquisition footprint, investigate 3D effects, and design next-generation crustal-scale seismic experiments, particularly long-offset OBS surveys aimed at high-resolution imaging of the deep crust.