Mark first arrivals in the following seismograph record. there is a clear break in slope, so it means you are dealing with a 2-layer case. use a metric ruler to measure times, because precision is going to make a big difference. the first arrival for the 800 m geophone happens to be at 800 ms. once you have measured your times use excel to plot your data, like you did in question 3, to calculate seismic velocities and depth to the interface. (l6pts) 800 ms geophone distance (m)