If the differences in the time of arrival of each wave is measured, the distance can be calculated. The more the difference in their time of arrival, the more the distance and this distance can be in any direction. If distance is used as the radius on the circle that will mean that the disturbance must have taken place on the circle.
If you place a telephone call to two people with similar measurements about this same event at different places, then their circles can be transfered to your own map, the point of intersection of this 3 circles is the location of disturbance.
