Summary Data from a new deep‐penetration seismic reflection line (LISA cruise 1995), onland seismic recording (LISA) and marine ESPs (expanding spread profiles, CROC II cruise 1981) are integrated to study the crustal structure of the north Ligurian basin. The correlation of these different seismic data, located along an Antibes–Ile Rousse transect, provides accurate information on the nature of the crust. On the Provençal margin, the multichannel seismic (MCS) profile LISA01 shows a major step in the basement. This structure is associated with a crustal change, corresponding to the ocean boundary. On the Corsica margin, we do not observe such a structure and the ocean boundary is constrained by magnetic anomalies. These anomalies are identical to those observed on the Provençal margin above the main basement structure. On the MCS line, the Messinian salt and the bottom water multiple obscure the crustal image below 7 s two‐way traveltime (TWTT). Nevertheless, the ESPs provide information about the crust below 7 s TWTT. These ESPs were reprocessed and analysed by matching traveltime and amplitude variations in the X–T and τ–p domains. The main result is the identification of a transitional zone on the continental margin (Provençal and Corsica margin) characterized by a layer with velocities of 7.2–7.3 km s−1 in the lower crust. Recordings from land stations on the Corsica margin define the geometry of this layer. In the centre of the basin, the oceanic crust is about 6 km thick. From the Corsica margin to the centre of the basin, the Moho depth decreases from 18 to 13 km. The velocity model deduced from offshore data is consistent with the ESP velocity model and MCS line LISA01. The combined analysis of these data allows us to propose a new boundary of the oceanic crust in the north Ligurian basin.

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Summary Stacking methods applied to wide arrays of long period stations provide a powerful tool to investigate the physical properties of the upper mantle by means of higher modes. In this paper, the UC‐diagram technique of Cara (1976) is applied to a subset of records first used by Nolet (1975, 1976) to determine the dispersion of higher Rayleigh modes in western Europe. For the fundamental and first higher modes, the phase velocities found in the present study are very similar to those first obtained by Nolet (1976) but the second made exhibits slightly higher velocities in the period range 35–55 s. As a consequence, the low density channel proposed by Nolet (1977) under western Europe is no longer necessary to explain the higher mode data and further investigation will be necessary to obtain more details in the density distribution with depth. A new set of higher Love mode phase velocities has been also obtained in western Europe. As it has already been observed for the fundamental mode in several parts of the world, the phase velocities found here for the first and second higher modes are too large compared to those predicted by the models fitting the Rayleigh mode data. It is very difficult to interpret both the Love and Raylcigh wave data in terms of isotropic S velocity distribution and an anisotropy of the elastic parameters of the upper mantle is probable under western Europe. Another wide continental region, northern Eurasia, is investigated from higher Rayleigh mode phase velocities measured for the path between northern Japan and western European stations. A nearly constant 4.5–4.6 km s−1S velocity is required by these data in the uppermost 200 km of the upper mantle. Unlike the higher mode data obtained for the central and eastern United States by Cara (1978) or for western Europe in this paper, no wide low velocity channel is necessary to explain the higher mode data in this large arca.

Seismological Research Letters, vol. 80, n°6, pp. 977-984, 2009International audienceWe report results from a six-month seismological experiment in the area of the eastern Polochic-Motagua fault system (Guatemala) designed to both characterize the present seismicity and bring some constraints on the lithospheric structure. The seismic activity occurs in the upper 15 km of the crust, on the Polochic and the Motagua faults as well as in a NS-trending graben south of the Motagua fault and within the active folds north of the Polochic fault. From receiver function analysis the Moho discontinuity is found at about 35 km depth north of the Polochic fault and south of the Motagua fault, while the region in between is characterized by a 4-to-6-km thinner crust or by a 6–7% decrease of the Vp/Vs ratio

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