An Earthquake Generates Three Kinds of Waves: Surface Waves (L-Waves)

Multiple Choice

An earthquake generates three kinds of waves: surface waves (L-waves) , which are the slowest and weakest, shear (S) waves, which are transverse waves and carry most of the energy, and pressure (P) waves, which are longitudinal waves and are the fastest. People do not generally feel the P waves, but animals seem to be sensitive to them. Take the density of the material through which these waves travel to be 2.0 × 10³ kg/m³, the Young's modulus to be 9.8 × 10¹⁰ N/m², and the shear modulus to be 3.2 × 10¹⁰ N/m². A person reports that her dog started barking 30 seconds "before the earthquake." Approximately how far away was the origin of the earthquake?

A) 180 km
B) 280 km
C) 140 km
D) 90 km
E) 360 km