Halliday, Resnick & Walker — Waves–II: Problem 74

The average density of Earth’s crust 10 km beneath the continents is \(2.7 \text{ g/cm}^3\). The speed of longitudinal seismic waves at that depth, found by timing their arrival from distant earthquakes, is \(5.4 \text{ km/s}\). Find the bulk modulus of Earth’s crust at that depth. For comparison, the bulk modulus of steel is about \(16 \times 10^{10} \text{ Pa}\).