= *Earthquakes. The elastic moduli of the material in the earth's crust vary but repre- sentative values for granite are B 40 GPa and SM = 25 GPa. The density of granite is about 2.7 103 kg/m. (The speed of sound in air is about 340 m/s and the density of air is 1.29 kg/m.) (a) What is the speed of longitudinal and transverse seismic waves in granite? (b) A P-wave is detected by a seismometer three seconds before the S-wave is detected. How far from the epicenter is the seismometer? (c) What is the characteristic impedance of P-waves in granite? (d) What is the characteristic impedance of sound waves in air? (e) When the P-wave reaches the surface of the earth, what is the reflection coeffi- cient for the displacement? (Assume normal incidence.)