1994-2004 El Hüseyma (Fas) depremleri: Eşlenik faylanmanın SAR interferometrisi ile tayini.

We study the two North African earthquakes, May 26, 1994 (Mw=6.0) and February 24, 2004 (Mw=6.4) earthquakes that affected the Al Hoceima region of northern Morocco with the available In-SAR data collected from both the ascending and descending orbits. Being the strongest earthquakes ever to be recorded instrumentally in the region, the analysis of the earthquakes has an important role in the tectonics of the region. The Rif Cordillera belong to the E-W trending thrust-and-fold system of north Africa that results from the collision between Africa and Eurasia. The system includes the Tell Atlas mountain ranges of Algeria and Tunisia along the Mediterranean coast to the east, and forms a collision tectonics strip along the African-Eurasian plate boundary. The ongoing shortening rate between the two plates decreases towards the west from 6.3 to 2.3 mm/yr from Sicily to northern Morocco. The seismicity along the boundary is rather complex and varies significantly from west to east. The Al Hoceima sequence indicate that the Rif is being deformed under a strike-slip tectonic regime. However adjacent regions in northern Algeria to the east and the Gulf of Cadiz to the west are subject to thrust faulting. Neotectonic features of the Rif consist of the major Nekor and Jebha, NESW trending left-lateral strike slip faults accompanied by N-S trending normal faults that form a graben-like structure east of Al Hoceima and a conjugate network of relatively small NW-SE and NE-SW strike-slip faults. The transpressive tectonics and existence of a complex fault network with different types of faulting in the Rif probably reflect the rapidly changing local tectonic regime with block rotations during the Neogene and Quaternary. Several strong earthquakes are known to have occurred in the historical times. The exact location, kinematics and relationships between the 1994 and 2004 earthquakes are poorly known since neither of them produced surface ruptures. Using Synthetic Aperture Radar interferometry (InSAR) we mapped the surface displacement field of the two earthquakes to characterize their seismic source parameters. The availability of ascending and descending interferograms for both earthquakes allows us to constrain their rupture parameters with high confidence. We used European Space Agency's (ESA) ERS and Envisat SAR data, respectively. While the ERS Level-0 (raw) SAR data were processed using the JPL ROI̱PAC software, the Envisat Level-1 (single-look) ASAR data were processed using DORIS SAR processing software, and precise satellite orbits from Delft University. The effect of topography which depends on the perpendicular separation between orbital trajectories is removed from the interferograms using the SRTM 3-arc-second (∼90 m) posting digital elevation model. The interferograms were also filtered using a weighted power spectrum technique. We modelled the manually unwrapped fringes derived from the processed interferograms by using slip inversions on triangular fault patches instead of commonly used rectangular ones which enabled us to use nonplanar more realistic fault models for the earthquakes. … [ABSTRACT FROM AUTHOR]