Two seismic stations and

PHYSICS · Multi-part · Fermi University Physics · Oscillations, Waves & Acoustics · Earth, Climate & Energy Physics · Seismology, tectonics and geodynamics

Bending, Ringing, Breaking and Flowing, Ch Elastic waves in a solid and at its surface

Problem

Two seismic stations

A

and

B

120\,\mathrm{km}

apart along a straight line, record the same shallow earthquake in crust that behaves as a Poisson solid (

\nu=0.25

) with longitudinal speed

c_L=6.0\,\mathrm{km\,s^{-1}}

. Station

A

measures an S-P delay of

14.0\,\mathrm{s}

; station

B

, farther from the epicentre, measures a delay of

28.6\,\mathrm{s}

. ((a)) Find the transverse wave speed

c_T

from

\nu

and

c_L

. ((b)) Find the distance from each station to the epicentre. ((c)) Assuming the epicentre lies on the line through

A

and

B

extended beyond

A

(order: epicentre, then

A

, then

B

), check whether the two distances found are consistent with the

120\,\mathrm{km}

station separation, and state where the epicentre lies relative to the stations.

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