Average Attenuation of 0.7–5.0 Hz Lg Waves and Magnitude Scale Determination for the Region Bounding the Western Branch of the East African Rift
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Date
1998
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Abstract
The investigation of L G attenuation characteristics in the region bounding the western branch of the East African rift system using digital recordings from a seismic network located along the rift between Lake Rukwa and Lake Malawi is reported. A set of 24 recordings of L G waves from 12 regional earthquakes has been used for the determination of anelastic attenuation, QLg , and regional body‐wave magnitude, MbLg , scale. The events used have body‐wave magnitudes, Mb , between 4.6 and 5.5, which have been determined teleseismically and listed in ISC bulletins. The data were time‐domain displacement amplitudes measured at 10 different frequencies (0.7–5.0 Hz). QLg and its frequency dependence, Η, in the region can be represented in the form QLg = (186.2 ± 6.5) F (0.78±0.05). This model is in agreement with models established in other active tectonic regions. The L G‐wave‐based magnitude formula for the region is given by MbLg = log A + (3.76 ± 0.38) log D − (5.72 ± 1.06), where A is a half‐peak‐to‐peak maximum amplitude of the 1 s L G wave amplitude in microns and D is the epicentral distance in kilometres. Magnitude results for the 12 regional earthquakes tested are in good agreement with the ISC body‐wave magnitude scale.
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http://gji.oxfordjournals.org/content/134/3/818.short
Keywords
Attenuation, Mb magnitude, MbLg magnitude, Q Lg
Citation
Ferdinand, R.W., 1998. Average attenuation of 0.7-5.0 Hz Lg waves and magnitude scale determination for the region bounding the western branch of the East African Rift. Geophysical Journal International, 134(3), pp.818-830.