Question Constellation Sign up for free AQA · GCSE · Physics · Higher
Seismic Arrival-Time Delay with Distance
A seismometer is a device that detects earthquakes. P-waves travel at a known speed between an earthquake and a seismometer. S-waves travel at a slower speed than P-waves. A P-wave and an S-wave from the earthquake arrive at the seismometer at different times.
Describe the relationship between the distance from the earthquake to the seismometer and the time between the P-wave and the S-wave arriving.
Write your answer first. You can study the marking guidance whenever you need it.
Study the marking See what earns credit and compare it with a full-mark answer.
Marking points
- 1 States that increasing distance increases the arrival-time difference.
- 2 Identifies the relationship as directly proportional for full credit.
Full-mark answer
The time gap increases as the distance increases, and the distance is directly proportional to the time between the P-wave and S-wave arrivals.
Why this answer loses marks
The arrival-time gap gets bigger.
That gives the trend only; the second marking point requires the precise directly proportional relationship.