Abstract

Earthquake data from temporary passive experiments acquired between 2002 and 2007 in the northern main Ethiopian rift (NMER) and Afar rift of Ethiopia have provided an opportunity to study the efficiency of Lg wave propagation in that region. High‐quality horizontal component broadband seismological data from earthquakes with magnitudes larger than 3.0 were band‐passed at a center frequency of 1 Hz to calculate Q using two methods. The coda normalization method was used to calculate the Lg wave Q (QLg), and the energy flux model was used to calculate intrinsic and scattering Q, denoted by QI and QS, respectively. High QI values between 700 and 900 seen in the center of the NMER and in eastern Afar coincide with Pliocene fissural basalts located there. QS values are between 200 and 300 within the center of the NMER and in eastern Afar, where both regions are severely dissected by faults. QI values are the lowest in northern Afar (200–400), where Pliocene‐Recent sediments and Quaternary magmatic segments cover the area. While fissures and cracks in the rift serve as scatterers, movement of fluids and partial melts within them intrinsically absorb seismic energy. Both QI and QS values are between 400 and 700 in the western Ethiopian plateau, indicating the importance of both scattering and intrinsic attenuation mechanisms there. Average results from both methods agreed that values for Lg wave Q for NMER and Afar are within the range of about 147–220, a common range of values for many active tectonic regions of the world.

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