an Entity references as follows:
Travel Time (in Seismology) means time for the seismic waves to travel from the focus of an earthquake through the crust to a certain seismograph station. Travel-time curve is a graph showing the relationship between the distance from the epicenter to the observation point and the travel time. Travel-time curve is drawn when the vertical axis of the graph is the travel time and the horizontal axis is the epicenter distance of each observation point.