برآورد رابطه بسامد ضريب كيفيت امواج برشي در دشت لرستان با استفاده از شتابنگاشت هاي زلزله درب آستانه (2006)

Estimation of Attenuation Function for Shear Waves Phase in Lorestan Province by Using Darb-e-Astane Earthquake (2006) Acceleration Data

In general, seismic attenuation is caused bya combination of both scattering and intrinsic mechanisms. Scattering redistributes wave energy within the medium but does not remove energy from the overall wave field. In contrast, intrinsic attenuation mechanisms convert wave energy to heat through friction, viscosity, and thermal relaxation processes. The frequency-domain spectral decay method is employed to estimate frequency dependence value ofQs. We used foreshock, main-shock and afiershock of Darb-c-Astane earthquake acceleration data with magnitude of 5.1, 6.1 and 4.9 for estimation at 1.5, 3, 6,12 and 24 Hz central frequencies, respectively. The estimated average frequeney dependence shear wave quality factor gives the relation Q, ~(l 09:!:6)1" jʹQ 081. Shear wave quality factor are increasing from 156 to 592 at frequency band of 1-2 Hz and 16-32 Hz, respectively. The QOvalue with frequency for this area is similar to those obtained for similar tectonically active regions in the world.