Abstract
In order to study teleseismic arrivals times across the Ladoga-Bothnian Bay zone, a proposed suture zone that separates the Karelian region (2.7 Ga) from the Svecofennian region (1.8 Ga), a seismic array of 22 event recorders was deployed along the SVEKA profile in Central Finland. The P-travel-time delays are shown to vary by less than ± 0.2 s along the profile and consistent delay patterns are observed for the various earthquakes. The travel-time delays delineate zones that appear to correlate with different geological terrains. A 2-D inversion of the data yields a tomographic image of the crust and lithosphere across the Ladoga-Bothnian Bay zone where 1% velocity variations are resolved. The southwestern Proterozoic crust is slower (0.15 s) than the northeastern Archean crust, in agreement with a relatively thinner (about 6 km) Archean crust. A subcrustal lower-velocity ( − 0.8 %) dome-like structure is present beneath the Kuhmo block (northern part of the profile) and is bordered by a southwest-dipping higher-velocity ( + 0.8 %) body that seems to connect to the surface trace of the Kuhmo-Suomussalmi Greenstone belt.
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