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GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L06305, doi:10.1029/2004GL022038, 2005

The 2003 Boumerdes, Algeria earthquake: Regional moment tensor analysis

Jochen Braunmiller

Swiss Seismological Service, Institute of Geophysics, Eidgenössische Technische Hochschule Zürich, Zurich, Switzerland


Fabrizio Bernardi

Swiss Seismological Service, Institute of Geophysics, Eidgenössische Technische Hochschule Zürich, Zurich, Switzerland


Abstract

We used regional broadband seismograms to determine seismic moment tensors for the destructive May 21, 2003 Boumerdes (Algeria) Mw = 7.0 earthquake and its larger aftershocks. Fully automatic inversions using near-real time data provided solutions for seven Mw ≥ 4.7 events within 90 minutes after event occurrence. After adding off-line data, we manually obtained 30 solutions (Mw ≥ 3.8) from May 2003 to January 2004. All have shallow source depths (6–21 km). The median P-axis orientation (338°) of 24 thrust and four strike-slip events is consistent with Africa-Eurasia plate motion (330°). The main shock hypocenter at 8–10 km depth at the coastline and its shallow southward dip (25° ± 5°) puts the fault surface trace 15–20 km offshore, consistent with documented seafloor deformation at the base of the continental slope. A main shock rupture length of about 50 km is deduced from first day aftershocks and location of strike-slip events. The strike-slip events probably define the western rupture end and indicate a left-step of main convergence. Fault strike variability of thrust events suggests fault orientation changes and possibly fault segmentation.

Received 19 November 2004; accepted 18 February 2005; published 18 March 2005.

Index Terms: 7215 Seismology: Earthquake source observations (1240); 7230 Seismology: Seismicity and tectonics (1207, 1217, 1240, 1242); 8123 Tectonophysics: Dynamics: seismotectonics; 8150 Tectonophysics: Plate boundary: general (3040).

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Citation: Braunmiller, J., and F. Bernardi (2005), The 2003 Boumerdes, Algeria earthquake: Regional moment tensor analysis, Geophys. Res. Lett., 32, L06305, doi:10.1029/2004GL022038.