Seismicity, arrival time delays of the seismic phases and slowness characteristics study in Abu Dabbab area, Egypt

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Abstract

The temporal variations of seismicity from the Abu Dabbab area, 25 km west of the Red Sea coast, are collected from the Egyptian national seismic network (ENSN), which has magnified the detection capability in that area to ML < 1 earthquakes. These data show a sequence of the micro earthquake swarm during 2003–2011. This area has experienced larger shocks up to M = 6 during the 20th century and its seismicity is concentrated in a narrow spatial volume.
We analyze the digital waveform data of about 1000 seismograms, recorded by portable network of 10 vertical component seismographs that are employed in a temporary survey experiment in the Abu Dabbab area in 2004, and the results indicate: firstly, there are similar waveform seismograms, which are classified into three groups. In each group a master event is identified. Then, the arrival time delays of the P and S phases (Δtp and Δts, respectively) are measured between the master event and its slave events. Δtp and Δts range between −0.01 and 0.02 s, respectively. These values are used to relocate the studied events. Secondly, the slowness vector (Δs) in 3-dimensional pattern, which is estimated using the genetic algorithms, is found Δsx = 0.0153, Δsy = 0.00093 and Δsz = 0.2086 s/km in the three spatial coordinates (X, Y and Z), respectively. These analyses demonstrate the inhomogeneities within the upper crust of the study area. Also, Δs shows little dependence of lateral distances and reasonably high slowness along the depth extent, which is consistent with the seismic velocity structure variations.

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NRIAG Journal of Astronomy and Geophysics
Volume 2, Issue 2
December 2013
Pages 234-242

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