Geodynamics Of Azores-tunisia (pageoph Topical Volumes)

The following four papers deal with the seismicity and seismotectonic of the region. Carrilho et al. present the first results of GEOALGAR, a project initiated in 2000 to monitor the seismic activity in the Algarve region (southern Portugal). In this paper results of the relocation of epicenters and determination of fault plane solutions are presented. The new epicentral locations show a more organized spatial distribution which could indicate a possible correlation with some known tectonic features. Fault plane solutions are predominantly of strike-slip motion consistent with a horizontal compression in the NW-SE to NNW-SSE direction. The paper by Yelles-Chaouche et al. presents a detailed study of the 22 December, 1999 earthquake at Ain Temouchent (northwest Algeria) of magnitude 5. 7. The earthquake caused serious damage in the town of Ain Teemouchent with 25 casualties and 25000 people left homeless. Intensity map, surface features and the focal mechanism, based on wave form analysis, are shown. The mechanism corresponds to reverse fault motion with planes striking NNE-SSW resulting from horizontal compression in the NW-SE direction. This corresponds to the general mechanism found for Algeria earthquakes. Buforn et al. present a study of the characteristics of the plate boundary between Africa and Iberia, from west of Cape San Vicente to Algeria, using seismicity and source mechanism data. The region is divided into three areas which manifest different characteristics. Front Matter....Pages i-vi Introduction....Pages 473-476 Rapid Exhumation in the Alpine Belt of the Betic-Rif (W Mediterranean): Tectonic Extrusion....Pages 477-487 The Alpine Rif Belt (Morocco): A Case of Mountain Building in a Subduction-Subduction-Transform Fault Triple Junction....Pages 489-519 Recent Tectonic Deformations and Stresses in the Frontal Part of the Rif Cordillera and the Saïss Basin (Fes and Rabat Regions, Morocco)....Pages 521-540 Recent Tectonic Structures in a Transect of the Central Betic Cordillera....Pages 541-563 Neogene Through Quaternary Tectonic Reactivation of SW Iberian Passive Margin....Pages 565-587 GEOALGAR Project: First Results on Seismicity and Fault-plane Solutions....Pages 589-606 The Ain Temouchent (Algeria) Earthquake of December 22 nd , 1999....Pages 607-621 Seismic Sources on the Iberia-African Plate Boundary and their Tectonic Implications....Pages 623-646 Calibration of Local Magnitude M L in the Azores Archipelago Based on Recent Digital Recordings....Pages 647-659 Geodetic Measurements of Crustal Deformation in the Western Mediterranean and Europe....Pages 661-681 Recent Geodetic Results in the Azores Triple Junction Region....Pages 683-699 New Palaeomagnetic Data from the Betic Cordillera: Constraints on the Timing and the Geographical Distribution of Tectonic Rotations in Southern Spain....Pages 701-722 The Azores-Tunisia region is formed by the western part of the plate boundary between Eurasia and Africa. This plate boundary presents a complex nature due to its proximity to the pole of rotation of the African plate. This condition produces crustal extensions and normal faulting at the Azores archipelago, transcurrent motion with strike slip faulting at the center part of the Azores-Gibraltar fault and at the eastern end, from the Gulf of Cadiz to Tunisia, plate convergence with reverse faulting. In this last part, the collision of Iberia with northern Morocco produces complex phenomena with intermediate depth and deep earthquakes and an extensional regime at the Alboran sea. Recently, new evidence has been gathered in this region based on observations from geology, geodesy, mainly through GPS measurements, seismology, especially with the installation of broad-band stations, and other fields of geophysics, such as paleomagnetism and gravimetry