Historical seismicity of the Jordan Dead Sea Transform region and seismotectonic implications

Abstract

Based on all available files, catalogs, and previous compilations, it is found that96 historical earthquakes (M≥6.0) were felt along the Jordan Dead Sea Transform region during the last 2,000 years. More than 50 % of these occurred in the form of sequences and swarms that lasted for different periods, some of which were volcanic related. The largest assigned magnitude is 7.6 with 667 years recurrence period, while the maximum possible future magnitude is 7.8±0.2 with 1,000± 80 years recurrence period. Quiescent periods, with a duration of up to 200 and 400 years and characterized by reduced levels of seismicity, are punctuated by active periods of tens of years when a few large earthquakes occurred. The historical seismic- ity indicates that all tectonic elements of the study region are presently active. Our results indicate that previous studies over- estimate the level of seismicity in this region. Not less than 25 earthquakes, most of which had M≥7.0, are erroneously related to the transform. It is probable that most of these are located within the East Mediterranean region and/or along intraplate faults, rather than the Jordan Dead Sea Transform. This is evidenced by (i) frequency-magnitude results, (ii) moderate- large East Mediterranean tsunamis, (iii) an apparent higher seismicity of the northernmost three segments compared with the southern three, (iv) relatively high annual seismic slip rate as calculated from the compiled historical seismicity, and (v) overdependence of some previous compilations on secondary rather than primary sources. The revised historical seismicity impliesanannual seismic sliprateofabout 0.68cm/year,which indicates that not less than 30 % of the tectonic movements along the regional structures of the study region are aseismic. This is in agreement with results obtained from pre-historic and instrumental data.