A seismograph records the arrivals of a P-wave at 11:13 am. If the earthquake occurred 4,000 km from the recording station, when did the earthquake occur
If a seismograph records the arrivals of a P-wave at 11:13 am and the earthquake occurred 4,000km from the recording station, then the earthquake occurred at 11:06am!
Attached is an example of a GIF to calculate the travel time of a P-wave for a given epicenter. The given distance from epicenter to the recording station in this case is 4000 km. The Y-axis in the GIF attachment represents the time travel time while the X-axis represents the epicenter distance (× 10³ km). The idea here is to go to the epicenter distance on the x-axis and go up to the correct curve. You can then go over to the y-axis and determine the travel time. The answer will be 7 minutes from the epicenter to the recording station
