Apparent weekly and daily earthquake periodicities in the western United States, and evolution of Wadi Kubbania in Egypt.

摘要

The dissertation consists of two separate sections. The first section is on apparent daily and weekly periodicities in earthquake occurrence in the western United State. Analysis of Apparent Seismicity Rate (ASR) in the western United States confirmed the existence of prominent spectral peaks with a period of 1 and 7 days. The number of recorded earthquakes on Sundays for the duration of 1963-2008 is about 5% higher than that on weekdays, and, more significantly, there is a 9% increase of ASR in the early morning compared with that in the middle of the days. Significant similarities between the spatial distributions of the weekly and daily variations suggest that the two types of variations have the same sources and both originate from periodic variations in cultural noise that lead to periodic variations in the detectability of the seismic networks.;The second section of the dissertation reports results from an active-source seismic experiment conducted in southern Egypt. The ancient Nile River (pre-Eonile) is believed to have flowed west-northwest from the Red Sea Hills due to the Nubian uplift in the Eastern Desert. It continued over Wadi Abu Subeira in the Eastern Desert and across the modern Nile to the Western Desert over the valley known today as Wadi Kubbania. This study addresses two hypotheses. The first hypothesis advocates that Wadi Kubbania was a morphologically incised valley of the pre-Eonile River where uplift of the Nubian swell may have forced rapid erosion forming Wadi Kubbania. The second hypothesis argues that Wadi Kubbania is a northwest trending graben formatted as a result of regional tectonic effects of the rifting of the Red Sea and the associated uplift in form of graben structure prior to the flowing of the pre-Eonile River. Analysis of seismic refraction data indicated that the Wadi Kubbania formed as a result of tectonic events.