On September 21st 2004 an M l = 4.0 earthquake took place in the Eastern Pyrenees, widely felt in the region and producing slight damage at the epicenter zone. It happened at the same area of the 1428 destructive earthquake (I o = IX EMS-98) (Olivera et al., 2004). At present, the area is characterized by a continued, moderate seismicity, with a few events of magnitude close to 4 reported in the last decades. For this recentmost event, the gauge made with the permanent regional seismological network located the hypocenter at 42.34o N, 2.17oE and 4 Km depth (www.icc.es/sismes). In the following two days the permanent network registered about 120 aftershocks, three of which were felt again in the epicentral zone.

Seminario Internacional Complutense. Workshop on Fracture Dynamics: Theory and Applications to Earthquakes. In Honour of Prof. A. Udias.