Attenuation of high-frequency P and S waves in south and southeast Tehran using blast data

The attenuation of P and S waves caused by quarry blasts in south and southeast Tehran was estimated using the extended coda-normalization method. The analysis used 230 seismic events from quarry blasts recorded in a range of 3–50 km using a network of 13 seismic stations. To estimate the frequency-dependent Q-value, the seismograms were band-pass filtered at the central frequencies (fi) of 1, 1.5, 2, 2.5, 3, 3.5, 4, 5, 6, 7, 8, 10 and 12 Hz using a phaseless eight-pole Butterworth band pass filter with a bandwidth of fi/√2 to fi√2. We showed that geometrical spreading exponent value (γ) is a variable depending on the propagation distance. The attenuation parameters were: Qp−1=(100±6) ×10−3 (f−1±0.07) and Qs−1=(73±2)×10−3 (f−1.06±0.03) indicating that the strong frequency dependency of Qp−1and Qs−1can propose heterogeneity of the medium. The ratio of Qp−1/Qs−1 obtained in this study is larger than unity and less than 2 for the entire frequency range. Also, Qs≥Qpindicates that the region is composed of half-saturated rocks.

► Estimation of Q (attenuation) performed for quarry blasts in southeast Tehran, Iran. ► Extended coda-normalization method used for 230 events. ► Stronger attenuation observed for P waves than for S waves in 1–12 Hz. ► Higher attenuation for the blast observed than for earthquake data in Iran.