ESTIMATION OF SOURCE PARAMETERS AND Q FROM ACCELERATION RECORDED IN THE VATNAFJOLL EARTHQUAKE IN SOUTH ICELAND

The earthquake in Vatnafjoll, 25 May 1987 (M = 5.8), was the largest e arthquake in south Iceland since 1912 (M = 7), and it was one of the f irst earthquakes recorded on a local network of strong-motion accelera tion recorders. In this study, the strong-motion records are used to o btain an estimate of the source parameters and the attenuation of high -frequency waves. The source parameters are obtained by fitting the da ta by a dislocation source model combined with an exponential model fo r the attenuation. The root-mean-squared acceleration is also estimate d and compared to predicted values using the source parameters. The so urce parameters estimated here (M-0 = 8.2 x 10(24) dyn-cm, r = 4.6 km, Delta sigma = 38 bars, Delta u = 36 cm, T-d = 3 sec) and estimated mo ment magnitude (M-w = 5.9) agree well with values obtained previously from teleseismic waves and strain-meter data. Estimates of path-averag ed crustal shear-wave quality factors give results in the range Q = 12 8 to 425, and kappa = 0.05 sec for the spectral decay parameter, confi rming recent measurements of higher crustal Q for this region than in earlier studies.