An earthquake 45 km from a city produces P and S waves that...

Name: Problem 7, Chapter 15: College Physics: A Strategic Approach
Uploaded: 2020-11-06T06:42:32-08:00
Duration: 1 min 40 s
Channel: Sheh Lit Chang
Description: An earthquake 45 km from a city produces P and S waves that travel outward at 5000 and 3000 m/s, respectively. Once city residents feel the shaking of the P wave, how much time do they have before the S wave arrives?

An earthquake 45 km from a city produces P and S waves that travel outward at 5000 and 3000 m/s, respectively. Once city residents feel the shaking of the P wave, how much time do they have before the S wave arrives?

Key Concepts

Unit Conversion in Kinematics

Unit conversion is an important aspect in kinematics and physics problems involving motion, ensuring that all measurements are consistent. In problems involving distances and speeds, converting units such as kilometers to meters is essential when the speeds are given in meters per second. This consistency avoids calculation errors and ensures accurate results when applying fundamental equations of motion.

Secondary Waves (S Waves)

S waves, or secondary waves, are slower than P waves and follow after them. These shear waves can only travel through solid materials and typically cause more pronounced ground shaking. The delay between the arrival of P and S waves is critical for seismic analysis and for triggering early warning systems in earthquake-prone areas.

Time Difference Calculation

The time difference calculation involves determining how much later one wave (typically the slower S wave) arrives relative to the other (the faster P wave). This is done by computing the travel time of each wave over the same distance using the formula time = distance/speed, and then subtracting the P wave travel time from the S wave travel time. This time difference is important for triggering timely responses such as safety protocols or early warning systems.

Seismic Waves

Seismic waves are energy waves generated by disturbances such as earthquakes. They propagate through the Earth's interior and along its surface, carrying energy from the source to distant locations. Understanding these waves is crucial in seismology for determining the location and magnitude of earthquakes, as well as for designing structures that can withstand seismic activity.

Primary Waves (P Waves)

P waves, or primary waves, are the fastest type of seismic waves and are the first to be detected by seismographs following an earthquake. They are compressional waves that travel through both solid and liquid materials in the Earth. Their higher speeds allow them to be used as early indicators of an earthquake, providing a brief warning before the arrival of slower waves.

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