Question

at what time did the p wave arrive?
helena, montana
8:07
8:06
8:08
8:09
8:10
8:11

Explanation:

Step1: Identify P - wave arrival

In a seismogram, the P - wave (primary wave) is the first wave to arrive. Looking at the seismogram for Helena, Montana, the first set of waves (the P - waves) start at 8:07.

Answer:

8:07