Abstract
The Dead Sea fault system and its branching faults represent one of the most tectonically active regions in the Middle East. The present investigation emphasis on the recent earthquake swarm, which occurred at the end of 2003 and extended to the middle of July 2004 with critical examination on the strongest event of 11th Feb. 2004. The present study examines the location of the strongest events (Dec. 31st, 2003; February 11th, 2004 and March, 15th, 2004) and correlates them with the various tectonic elements in the Dead Sea basin. The source mechanism of the three events is also examined. The focal mechanism and the depth of the events were obtained from the motion of the P waves. The fault plan solution of the main event (11th Feb.), indicates that the rupture propagated down dip, where the motion was initiated mainly as a normal component with slight strike-slip movement. At the same time, the analyses of the aftershocks during the subsequent two weeks show that the source mechanism is the same as that of the main event. The source mechanism of the event, which occurred at Dec. 31st and March, 15th indicates that the movements were initiated as left-lateral strike-slip motion with a slight normality. The seismic energy appears to have migrated from the south to the north during the period of Dec., 31 up to March, 12, where the seismic energy has a migration character to the southern block of the eastern side of the Dead Sea after March, 12, which lead the seismic event to occur in March, 15. Therefore, another relatively major event occurred in July, 8, 2005 as predicted.
Highlights
The Dead Sea earthquake occurred on February, 11th, 2004 at 0815 UTC at 31.694° N, 35.581° E, at a depth of about 21 km, as declared by the Jordan Seismological Observatory (JSO) at the Natural Resources Authority, Jordan
These observations are in agreement with the geological and geophysical evidences[4,7,12,14,15,24,25] and the source mechanism of the strongest events recorded during the present earthquake swarm
The source mechanism of the event, which occurred at Dec. 31st, 2003 and March, 15th (March, 16th, local time, Jordan) indicated that the movements were initiated as left-lateral strike-slip motion with slightly normal motion (Fig. 9 and 10)
Summary
The Dead Sea earthquake occurred on February, 11th, 2004 at 0815 UTC at 31.694° N, 35.581° E, at a depth of about 21 km, as declared by the Jordan Seismological Observatory (JSO) at the Natural Resources Authority, Jordan. The sagging process in the Dead Sea indicates that the upper crust has lost its foundation over a wider area than just the deepest part of the basin, Fig. 9: Fault solution (focal mechanism) of the seismic events of Dec. 31st, 2003. The east-west faults (such as Zarqa Ma’in, Swaqa and Hasa) show the maximum displacement near the major rift faults This situation became very complicated around the Dead Sea basin due to the large depth of the basin (8.5 km), salt tectonic, horizontal movement and basin subsidence. The signal were recorded from these event had a clear phases of P waves (for example Fig. 7, shows the P waves recorded from the main shock: Mc = 4.9) This record was used to calculate the depth to the focal point of the earthquakes. The main shock (Mc=4.9) was caused by normal component with slight strike-slip motion (Fig. 9), where the two others shock were caused by strike-slip motion with slight normal motion (Fig. 8 and 10)
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