ORIGINAL ARTICLE Relative location and source mechanism of inland earthquakes in Northern Egypt Ahmed A. Badawy & A. AL-Werr & Sh. M. Ali Received: 7 November 2012 / Accepted: 10 June 2013 # Springer Science+Business Media Dordrecht 2013 Abstract We have relocated 259 inland earthquakes in northern Egypt using the double-difference hypocenter technique. Among this dataset we are able to determine source mechanisms of 200 events using P-wave polari- ties and amplitude ratios as well. The studied earthquakes have been recorded by the Egyptian National Seismolog- ical Network from October 1997 to December 2006 with local magnitude (M L ) varies between 1.5 and 5.0. Three earthquake dislocations have been defined namely: Dahshour, southeast Beni-Suef, and Cairo-Suez district. Earthquake activities tend to occur in clusters along the first dislocation (Dahshour) however, relatively scattered along the second (southeast Beni-Suef) and the third (Cairo-Suez district) dislocations. At Dahshour disloca- tion three distinct clusters have been distinguished. Source mechanism solutions of Dahshour earthquakes displayed normal faulting with a strike-slip component to strike-slip faulting with a minor normal dip-slip com- ponent. Most of earthquake focal mechanism orientations are varying from NE-SW to NW-SE. The fault plane solutions of Beni-Suef earthquakes represented normal faulting with a strike-slip component. If the NNW-SSE striking plane has been chosen to be the actual fault plane, some solutions would indicated normal faulting with a sinistral strike-slip motion and other reflect normal faulting with a dextral strike-slip component. The fault plane solutions of Cairo-Suez district earthquakes are compatible with E-W to ENE-WSW striking normal fault with a dextral strike-slip motion. Keywords Relative location . HypoDD . Source mechanisms . Inland earthquakes . Brittle–ductile transition . Northern Egypt 1 Introduction Egypt is characterized by moderate earthquake activity related to the relative motion between African, Arabian, and Eurasian plates (Badawy 1996, 1998; Badawy and Horvath 1999a, b, c). Outside this relatively active zone, inland or intra-plate seismic active dislocations (e.g., Dahshour, southeast Beni-Suef, and Cairo-Suez district) are also reported (Badawy 2005a, b; Abou Elenean 2007). These inland earthquake dislocations are impor- tant because they greatly expand the region of possible seismic hazard. Their role in tectonics is poorly under- stood, owing to their complexity, and therefore, it is of great importance to study source mechanisms and depths of the small-to-moderate size earthquakes. Despite the fact that the earthquake activity in northern Egypt is relatively moderate, the seismic risk is considerably high. This is due to the fact that most of earthquakes take place near over-populated cities and villages, coupled with the little awareness of knowledge and dealing with geo-hazard problems, in particular, earthquakes. J Seismol DOI 10.1007/s10950-013-9378-z A. A. Badawy (*) : S. M. Ali Seismology Division, National Research Institute of Astronomy and Geophysics, 11421, Helwan, Egypt e-mail: ahmedbadawy@Yahoo.com A. AL-Werr Geophysics Department, Faculty of Sciences, Ain Shams University, Cairo, Egypt