Project Details
Projekt
Generation and Destruction of Lithosphere in the Ligurian Sea
Applicants
Dr. Dietrich Lange; Dr. Martin Thorwart
Subject Area
Geophysics
Term
from 2017 to 2023
Project identifier
Deutsche Forschungsgemeinschaft (DFG) - Project number 365287383
The convergence of the Africa and the Eurasia plates and the recent evolution of the western Mediterranean-Alpine area has built a puzzle of basins (such as the Ligurian Sea) and ranges. The Ligurian sea is a key location due to its complex geodynamic setting characterized by pronounced variations in crustal nature and thickness. The deep structure is characterized by the transition from the western Alpine orogen to the Apennine system and change in subduction polarity. Beneath the Ligurian Sea the Alpine front subducts to the East while beneath the Apennine eastward subduction and subduction rollback advancing to the NW occurs. In particular for larger depths (>20 km) no seismological imaging using OBS data was carried out and the knowledge of the deep structure in the Ligurian sea is mostly inferred from land data observations or from very large-scale tomography studies. In order to image the lithospheric structure we propose to use the data from 33 broadband Ocean Bottom Seismometer (OBS) stations from the LOBSTER deployment in the Ligurian Sea and adjacent landstations. The OBS stations form the marine component of the AlpArray installed within the framework of the SPP 4D-MB and will be installed in May/June 2017 in the Ligurian sea for a period of ~11 months. We propose seismological ambient noise cross correlation techniques in order to estimate empirical Green functions between the receivers. The extracted group velocities of the Rayleigh waves will be complemented with Rayleigh wave phase velocity dispersion curves from distant earthquakes in order to enhance the quality of the dataset for the inversion of a 3D shear velocity model. The shear wave velocity model will be used to discriminate between previously hypothesed nature of the basin center such as serpentinized, typical oceanic crust or underplated material. In particular, the geometry of the oceanic crust in the basin is of special interest in relation with the major geodynamic events that shaped it.The current seismicity rate is in the Ligurian Sea is modest with magnitude 4-4.5 events with an approximate period of 2-3 years. Despite the moderate seismicity level destructive earthquakes occurred in the region in historical times such as the Imperia earthquake 1897 in the centre of the basin (Mw 6.3-7.5) with at least 600 casualties. The LOBSTER OBS network will allow for the first time precise determination of seismic moment release with homogenous resolution down to small magnitude events (Ml 1-2) resulting in the identification of active faults and their seismogenic depths involved in current basin opening. Current locations and properties of active faults are poorly known and a thorough analysis of the local seismicity will enlighten the shallow geology and possibly the stress regime (from focal mechanisms) in the Ligurian basin.
DFG Programme
Priority Programmes
