Throw a rock into a pond or lake and watch the waves rippling out in all directions from the point of impact. Just as this impact sets waves in motion on a quiet pond, so an earthquake generates seismic waves that radiate out through the Earth earthquake.usgs.gov/learn/topics/seismology... Earthquake Travel Time Information and Calculator
Use a Calculator and generate a listing of phase arrival times at YOUR seismic station neic.usgs.gov/neis/travel_times/ Measuring and Predicting Earthquakes
The Richter scale, was developed by Charles F. Richter in 1934. It used a formula based on amplitude of the largest wave recorded on a specific type of siemometer https://socratic.org/earth-science/earthquakes/mea...