Seismic Attenuation Structure beneath Harrat Lunayyir, northern Arabian shield

Thursday, 18 December 2014
Nassir Saad Al-Arifi1, Sami El khrepy1,2, Ivan Koulakov3 and I Sychev4, (1)King Saud University, Riyadh, Saudi Arabia, (2)National Research Institute of Astronomy and Geophysics, NRIAG, seismology, Cairo,helwan, Egypt, (3)IPGG SB RAS, Novosibirsk, Russia, (4)Trofimuk Institute of Petroleum Geology and Geophysics SB RAS, Prospekt Koptyuga, 3, 630090, Novosibirsk, Russian Federation, Prospekt Koptyuga, RI, Russia
A Strong earthquake swarm occurred in Harrat Lunayyir northern Arabian shield 60km from the northern Red Sea coast during the year 2009. In this work we present the seismic attenuation tomography model beneath Harrat Luaiyyer. The earthquake data set recorded at Harrat Luaiyyer during 2009 swarm is used in the model calculations. The tomography inversion uses the envelope shape of the S wave seismograms from over 300 strong events (M > 3.5). The resulting attenuation structures appear to be consistent with the distribution of seismic velocities. The obtained 3-D attenuation model distinguishes the low-attenuation zones down to 5 km depth corresponding to the rigid basaltic cover. At greater depths, we detect a high-attenuation anomaly coinciding with the main seismicity cluster. We propose that this zone corresponds to the upper part of the conduit area ascending from deeper magma sources. According to the distributions of local events, fluids and melts from this conduit appear to reach a depth of 2 km, but were not able to reach the surface and cause the eruption in 2009.