The seismic moment tensor is a complete description of the earthquake size and source geometry. The Centroid Moment Tensor (CMT) is a reliable method for calculating moment tensors (Dziewonski et al., 1981; Dziewonski and Woodhouse, 1983; Dziewonski et al., 2000) based on fitting long period surface waves and ideally suited to study global seismicity. We use instead a modified algorithm (modeling intermediate-period surface waves) to compute Regional CMTs (RCMT; Arvidsson and Ekström, 1998; Ekström et al., 1998) for moderate-magnitude events, that are not well recorded at a global scale. Our main product is a routinely updated catalog of seismic moment tensors for the Euro-Mediterranean region.
The Alpine Mediterranean region is characterized by complex active tectonics, connected to the convergence between Africa and Eurasia, but also to the motion of several microplates, producing a wide range of tectonic regimes. The relevance of the RCMT Catalog therefore also lies in the contribution that it can give to the understanding of the active tectonics.
Seismicity in the Mediterranean area is rather diffuse, in may areas characterized by moderate energy release. Moderate-magnitude events are therefore particularly important because more widely spread than the relatively few larger-magnitude earthquakes. Small or moderate events are difficult to model at teleseismic distance with the classical Centroid Moment Tensor (CMT) method, owing to the low signal-to-noise ratio of the long period body waves used. The inversion of intermediate period surface waves recorded at regional distance, as done in RCMTs, allows instead to compute moment tensors also for these events with reliability comparable to the standard CMT analysis.
We compute Regional Centroid Moment Tensors (RCMT) routinely since 1997 for earthquakes, with magnitude approximately betweeen 4.5 and 5.5, occurring in the Euro-Mediterranean region (see also Morelli et al., 1998; Pondrelli et al., 1999 and 2001), and we maintain a catalog of solutions. Our catalog occasionally also lists events with magnitude as low as 4.0, in cases where the station distribution is particularly favorable. All data can be downloaded at the European-Mediterranean RCMT site or from this CD. The catalog generally does not include larger events, which can instead be found in the global CMT Catalog maintained at Harvard. The European-Mediterranean Regional Centroid Moment Tensor Catalog is a joint project between scientists from Istituto Nazionale di Geofisica e Vulcanologia (Rome, Italy) and Harvard University (Cambridge, MA, USA).
Please reference these data as:
Pondrelli, S., A. Morelli, G. Ekström, S. Mazza, E. Boschi, and A. M. Dziewonski, 2002, European-Mediterranean regional centroid-moment tensors: 1997-2000, Phys. Earth Planet. Int., 130, 71-101.
Pondrelli S., A. Morelli, and G. Ekström, 2004, European-Mediterranean Regional Centroid Moment Tensor catalog: solutions for years 2001 and 2002, Phys. Earth Planet. Int, 14, 127-147.
Arvidsson, R., Ekström, G., 1998. Global CMT analysis of moderate earthquakes Mw > 4.5 using intermediate period surface waves. Bull. Seismol. Soc. Am. 88, 1003Ü1013.
Dziewonski, A.M., Chou, T.A., Woodhouse, J.H., 1981. Determination of earthquake source parameters from waveform data for studies of global and regional seismicity. J. Geophys. Res. 86, 2825-2852.
Dziewonski, A.M., Woodhouse, J.H., 1983. An experiment in the systematic study of global seismicity; centroid moment tensor solutions for 201 moderate and large earthquakes of 1981. J. Geophys. Res. 88, 3247-3271.
Dziewonski, A.M., Ekström, G., Maternovskaya, N.N., 2000. Centroid-moment tensor solutions for October-December 1999. Phys. Earth Planet. Inter. 121, 205-221.
Ekström, G., Morelli, A., Boschi, E., Dziewonski, A.M., 1998. Moment tensor analysis of the central Italy earthquake sequence of September-October 1997. Geophys. Res. Lett. 25, 1971-1974.
Morelli, A., Ekström, G., Olivieri, M., 2000. Source properties of the 1997-1998 Central Italy earthquake sequence from inversion of long-period and broad-band seismograms. J. Seismol. 4, 365-375.
Pondrelli, S., Ekström, G., Morelli, A., Primerano, S., 1999. Study of source geometry for tsunamigenic events of the Euro-Mediterranean area. In: International Conference on Tsunamis. UNESCO Books, Paris, pp. 297-307.
Pondrelli, S., Ekström, G., Morelli, A., 2001. Seismotectonic re-evaluation of the 1976 Friuli, Italy, seismic sequence. J. Seismol. 5, 73-83.