Question

3. Earthquake warning system A typical earthquake produces two types of seismic waves. P ("primary" seismic waves are longitudinal waves that move through the earth's upper crust with speed anywhere from 3 km/s to 5 km/s (the exact speed depends on the local composition of the earth's crust). S ("secondary") waves are transverse waves that move slower than P waves. The S-wave speed is typically about 60% less than the P-wave speed in any given material. The map below shows the Cascadia subduction zone (white line) just off the coast of Oregon. In the next 50 years, there is a 30% chance that a very large earthquake will occur with an epicenter on this white line. Washington Mount Rainier Mount Adams ount St ns Mount Hood Newport Corvallis Newberry Volcano Crater Lake Oregon a) Assume there is an earthquake centered on the Cascadia subduction zone directly west of Corvallis. Estimate the time delay between the arrival of P waves and the arrival of S waves in Corvallis. Give a range of possible time delays Sense making: Is this time delay long enough for our class to evacuate Weniger Hall before the arrival of S waves? (S waves are more destructive than P waves). b) Rather than rely on P waves as a warning system, what about using standard telecommunication technology? Imagine there was a P-wave sensor in Newport that "instantly" sent a warning to Corvallis (signals can't go faster than the speed of light). Estimate the time delay between triggering the sensor and the arrival of S waves in Corvallis

Answer 1