Coseismic deformation of the May 21st, 2003, M w = 6.8 Boumerdes earthquake, Algeria, from GPS measurements

International audienceOn May 21st, 2003, a M w = 6.8 earthquake struck the central part of northern Algeria causing extensive damage in the Boumerdes area, 40 km east of Algiers. It is among the largest events to occur in the western Mediterranean over the past 25 years. We present GPS measurements of horizontal coseismic displacements that provide new constraints on the rupture geometry. Modeling the data with a uniform dislocation on a rectangular fault in an elastic half‐space, we find that the rupture occurred on a reverse fault dipping 42°S, with its upper edge 6 km offshore and lower edge 4 km inland. The amplitude distribution of the coseismic displacements indicates that the rupture did not reach the surface, at least in its western part, and ended to the west around 3.4°E. Offshore faults like that of the Boumerdes earthquake could account for part of the Africa‐Eurasia relative plate motion in the western Mediterranean and represent a significant seismic threat for Algeria

Shallow afterslip following the 2003 May 21, M<SUB>w</SUB> = 6.9 Boumerdes earthquake, Algeria

International audienceWe investigated post-seismic deformation following the 2003 May 21, Mw = 6.9 Boumerdes, Algeria, earthquake using surface displacements from six continuous Global Positioning System sites that operated in the epicentral area for 2.5 yr following the event. We find up to 4 cm of cumulative horizontal displacement during that time period, with a time-dependence well fit by a logarithmic decay. Post-seismic deformation appears to continue at all sites after the 2.5-yr observation period, with rates on the order of 1 cmyr-1 or less. The data is consistent with shallow afterslip (0-5 km) and shows no evidence for afterslip downdip of the coseismic rupture. The data is poorly explained by viscoelastic relaxation in the lower crust or upper mantle, or by poroelastic rebound. The concentration of afterslip adjacent to and updip of the coseismic rupture, at least in the western half of the fault, suggests that afterslip is driven by coseismic stresses. The correlation between the depth of afterslip and that of the sedimentary wedge along the Algerian margin, while coseismic slip occurs in deeper basement rocks, suggests (1) that post-seismic deformation may also involve folding and (2) that spatial variations in frictional properties along the fault correlate with the type of rocks involved

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

Geophysical Research Letters, v. 31, p. L18607, 2004. http://dx.doi.org/10.1029/2004GL020687International audienc

Strong Algerian earthquake strikes near capital city

International audienceOn 21 May 2003, a damaging earthquake of Mw 6.8 struck the region of Boumerdes 40 km east of Algiers in northern Algeria (Figure 1). The main shock, which lasted ∼36–40 s, had devastating effects and claimed about 2300 victims, caused more than 11,450 injuries, and left about 200,000 people homeless. It destroyed and seriously damaged around 180,000 housing units and 6000 public buildings with losses estimated at $5 billion. The main shock was widely felt within a radius of ∼400 km in Algeria. To the north, the earthquake was felt in southeastern Spain, including the Balearic Islands, and also in Sardinia and in southern France