European–Mediterranean Regional Centroid Moment Tensor catalog: Solutions for years 2003 and 2004

doi:10.1016/j.pepi.2007.05.004

Physics of the Earth and Planetary Interiors

Volume 164, Issues 1–2, 14 September 2007, Pages 90-112

https://doi.org/10.1016/j.pepi.2007.05.004 Get rights and content

Abstract

We present an update, for years 2003 and 2004, of the European– Mediterranean Regional Centroid Moment Tensor (RCMT) catalog that we maintain since 1997. This update adds 177 new solutions to the database, relating to moderate-magnitude ( $4.5 \leq M < 5.5$ ) earthquakes. About 30% of our new solutions also appear in the global CMT catalog: comparison of the two independent determinations generally shows very good agreement. Within the time span covered, the most noticeable seismic sequences occurred in Northern Africa (Boumerdes, Algerian coast in 2003 and Al Hoceima, Morocco in 2004) and in Southern Greece and Dodecanese region (August 2003 and 2004). The complete RCMT catalog for the European and Mediterranean region now covers 8 years, and contains about 600 solutions.

Introduction

The Mediterranean region is the seat of widespread deformation and seismicity. The tectonics is mainly driven by convergence between Africa and Eurasia, but it is complicated by processes, like back-arc extension, that make it difficult to fully understand the underlying dynamics. Seismic events are distributed in relatively wide belts, but only seldom reach large magnitudes. Mapping seismic deformation through source mechanisms therefore requires also modeling earthquakes with moderate energy. These earthquakes are unfortunately also important because, due to the building characteristics, they can often cause damage.

This paper presents the continuation of our effort to create and maintain a coherent database of seismic moment tensor solutions for intermediate magnitude earthquakes occurring in the European and Mediterranean regions. This effort is intended to complement the global (formerly Harvard) CMT catalog (Dziewonski et al., 1981, Dziewonski et al., 2001, Ekström et al., 2005; http://www.globalcmt.org/), with events with regional significance for the specific area. Previous reports Pondrelli et al., 2002, Pondrelli et al., 2004 presented 420 seismic source mechanisms for years 1997–2002 with magnitude ranging from 4.0 to 5.5, outlined the method, based on an extension of the global CMT technique to fitting fundamental mode surface waveforms with intermediate to long period, and also provided comparisons with global CMT determinations of source mechanisms for the largest earthquakes analysed. The Regional CMT (RCMT) catalog is also available on the Worldwide Web at http://www.ingv.it/seismoglo/RCMT.

This is the third report of our activity. We present moment tensor solutions for 177 events that occurred in our study region in the years 2003 and 2004, along with some statistics illustrating the database which now covers 8 years and includes almost 600 solutions. We also briefly comment on a few events of 2003 and 2004 of particular interest.

Section snippets

Seismic moment tensors for 2003 and 2004

We compute seismic moment tensors using an inversion algorithm based on the original CMT method (Dziewonski et al., 1981), that also models intermediate period surface waves recorded at regional distances (Arvidsson and Ekström, 1998). Fundamental mode Rayleigh and Love waves account for the largest amplitudes in seismograms recorded in this range, and the RCMT method is then able to also model earthquakes with moderate magnitudes—often as low as 4.0. At intermediate periods we have to account

Events of interest

As in previous reports of the European–Mediterranean catalog Pondrelli et al., 2002, Pondrelli et al., 2004, we include here a description of a few seismic sequences and swarms that are of interest because of the size or location of the earthquake, or because of the damage that was caused. It is, however, beyond the scope of this paper to provide a complete seismotectonic interpretation of each event.

During 2003 and 2004, a number of interesting seismic sequences occurred in the Mediterranean

Conclusions

This paper adds 177 new Regional Centroid Moment Tensor solutions for years 2003 and 2004 to the European–Mediterranean catalog, which now lists 598 solutions for the time period 1997–2004. The main statistical features of the new data set are similar to those described in the previous reports. The most significant quantity indicators – e.g. the numbers of RCMTs computed yearly, the lowest magnitude for which an RCMT is computed – show slight but continuous improvement over the years, a

Acknowledgements

We thank MedNet, ORFEUS-VEBSN, GEOFON and IRIS for online waveform archives and all their seismographic network maintenance groups. Without their work we would not be able to produce our results. Comments from an anonymous reviewer greatly improved our manuscript. Maps and focal mechanisms have been plotted with GMT (Wessel and Smith, 1998).

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Short communicationEuropean–Mediterranean Regional Centroid Moment Tensor catalog: Solutions for years 2003 and 2004

Abstract

Introduction

Section snippets

Seismic moment tensors for 2003 and 2004

Events of interest

Conclusions

Acknowledgements

Tectonophys.

Earth Planet. Sci. Lett.

Phys. Earth Planet. Inter.

Earth Plan. Sci. Lett.

Tectonophysics

Tectonophysics

Phys. Earth Planet. Int.

Phys. Earth Planet. Int.

Phys. Earth Planet. Int.

Global CMT analysis of moderate earthquakes MW≥4.5 using intermediate period surface waves

Bull. Seismol. Soc. Am.

Earthquakes in Switzerland and surrounding regions during 2004

Eclogae Geol. Helv.

An innovative cartographic concept—the geodynamic map of the Mediterranean

EPISODES

The 14 August 2003 Lefkada Island (Greece) earthquake: Focal mechanisms of the mainshock and of the aftershock sequence

J. Seismol.

The 2003 Boumerdes, Algeria earthquake: regional moment tensor analysis

Geophys. Res. Lett.

The 21 May 2003 Zemmouri (Algeria) earthquake Mw 6.8: relocation and aftershock sequence analysis

Geophys. Res. Lett.

NT4.1.1, un catalogo parametrico di terremoti di area italiana al di sopra della soglia del danno

Slip distribution of the 2003 Boumerdes-Zemmouri earthquake, Algeria, from teleseismic, GPS, and coastal uplift data

Geophys. Res. Lett.

Aegean and surrounding regions complex multiplate and the continuum tectonics in a convergent zone

Geol. Soc. Amer. Bull.

Determination of earthquake source parameters from waveform data for studies of global and regional seismicity

J. Geophys. Res.

Short communication
European–Mediterranean Regional Centroid Moment Tensor catalog: Solutions for years 2003 and 2004

Global CMT analysis of moderate earthquakes $M_{W} \geq 4.5$ using intermediate period surface waves