(a) Seismographs measure the arrival times of earthquakes with a precision of 0.100 s. To get the distance to the epicenter of the quake, they compare the arrival times of S- and P-waves, which travel at different speeds. If S- and P-waves travel at 4.00 and 7.20 km/s, respectively, in the region considered, how precisely can the distance to the source of the earthquake be determined? (b) Seismic waves from underground detonations of nuclear bombs can be used to locate the test site and detect violations of test bans. Discuss whether your answer to (a) implies a serious limit to such detection. (Note also that the uncertainty is greater if there is an uncertainty in the propagation speeds of the S- and P-waves.)

A tsunami is a sort of pulse or “wave packet” consisting ofseveral crests and troughs that become dramaticallylarge as they enter shallow water at the shore. Supposea tsunami of wavelength 235 km and velocity 550 km/htravels across the Pacific Ocean. As it approaches Hawaii,people observe an unusual decrease of sea level in theharbors. Approximately how much time do they have torun to safety? (In the absence of knowledge and warning,people have died during tsunamis, some of them attractedto the shore to see stranded fishes and boats.)

The intensity of an earthquake wave passing through the Earth is measured to be 3.0 × 106 J/m2 at a distance of 48 km from the source. Sketch the situation.  A) What was the intensity when it passed a point only 6.0 km from the source? B) At what rate did energy pass through an area of 2.0 m2 at 6.0 km?