Fault location and source process of the Boumerdes, Algeria, earthquake inferred from geodetic and strong motion data

Abstract

The Boumerdes earthquake occurred on a fault whose precise location, offshore the Algerian coast, was unknown. Geodetic data are used to determine the absolute position of the fault. The fault might emerge at about 15 km offshore. Accelerograms are used to infer the space‐time history of the rupture using a two‐step inversion in the spectral domain. The observed strong motion records agree with the synthetics for the fault location inferred from geodetic data. The fault plane ruptured for about 18 seconds. The slip distribution on the fault indicates one asperity northwest of the hypocenter with maximum slip amplitude about 3 m. This asperity is probably responsible for most of the damage. Another asperity with slightly smaller slip amplitude is located southeast of the hypocenter. The rupture stops its westward propagation close to the Thenia fault, a structure almost perpendicular to the main fault.

DIRDOP: a directivity approach to determining the seismic rupture velocity vector

“…In the last 10 s, the rupture propagates at an average velocity of 5.4 ± 1.81 km/s but in the opposite direction (γ = 264 ± 22 • ; segment D2). The bilaterality of the rupture was also reported by Yagi (2003), Delouis et al (2004), Semmane et al (2005), and Belabbès et al (2009). Yagi (2003 found an asymmetric bilateral rupture that mainly propagated 30 km to the southwest and 20 km to the northeast.…”

“…Delouis et al (2004), by joint inversion of teleseismic waveforms and global positioning system (GPS) data, estimate two slip zones, on both sides (NE and SW) of the hypocenter, and low rupture velocity (2.4 km/s in NE section and 1.9 km/s in SW section). Semmane et al (2005), using an inversion analysis of strong-motion and GPS data, fixed the fault orientation (USGS CMT), and the slip distribution result also reveals the two patches of a bilateral rupture. Belabbès et al (2009) studied the surface deformation associated with the May 21, 2003 Zemmouri (Algeria) earthquake by inversion of InSAR, coastal uplift, and GPS data and found two rupture sections on both sides of the epicenter.…”

The large Algerian earthquakes (267 A.D.-2017)

“…This model was precised later by several authors (Semmane et al, 2005;Belabbes et al, 2009, Beldjoudi, 2017 to integrate all measurements carried out in this region. This earthquake displays the first south dipping active fault along the margin ( figure.…”

Searching for the seafloor signature of the 21 May 2003 Boumerdès earthquake offshore central Algeria

“…More recently, the Algerian coastal zone, an area representing the limit between the African and Eurasian plates, has also undergone several events of sufficient magnitude to trigger large gravity effects testified by submarine cable breaks in the deep basin in 1954 (Heezen and Ewing, 1955), 1980(ElRobrini et al, 1985(Carter et al, 2009. In particular, the 2003 Mw 6.8 Boumerdès earthquake was one of the most devastating historical seismic events in the western Mediterranean and generated significant gravity flows recognized by numerous submarine cable breaks at the foot of the margin and in the deep Algerian basin, leading to a nearly complete stop of all telecommunication exchanges in Algeria for about 48 h. However, most of the studies on the impacts of the 2003 Boumerdès event were carried out on land Bounif et al, 2004;Delouis et al, 2004;Semmane et al, 2005), whereas little attention has been paid until now to its effects and signatures offshore.…”