The 2010 Beni-Ilmane, Algeria, earthquake sequence: statistical analysis, source parameters, and scaling relationships

Abstract

Source parameters were estimated for the 18 largest events (MD ≥ 4) of the 2010 Beni-Ilmane earthquake sequence (north-central Algeria) using data recorded by permanent broadband seismic stations of the Algeria Digital Seismic Network (ADSN). Displacement spectra of P and S waves were estimated using a Brune seismic source model to compute spectral parameters. Spectra were corrected to account for path effects and near-surface attenuation. The average seismic moments estimated from P and S wave spectra ranged from 5.5 × 1014 to 1.6 × 1017 N m, with a logarithmic mean M0(S)/M0(P) ratio of 0.96. Source radii ranged from 735 to 2266 m with an average r(S)/r(P) value of 0.99. Stress drops varied from 0.2 to 11 MPa with an average Δσ(S)/Δσ(P) ratio of 1.08. Corner frequencies (fc) vary from 0.8 to 2.4 Hz, and moment magnitudes (Mw) range from 3.8 to 5.4. Scaling relations of seismic moments, source radii, and stress drops indicate that events with M0 ≥ 2 × 1016 N m have stress drops that are generally constant, while the stress drops of earthquakes with M0 < 2 × 1016 N m decrease with decreasing seismic moment. The source parameters of the 1960 Melouza (now Beni-Ilmane) moderate earthquake are also estimated from these scaling relationships. Finally, we find low b and γ values in the Gutenberg–Richter and gamma function laws. The seismic sequence is discussed in the context of the active tectonics of the Beni-Ilmane fault system.