For the last few weeks on our bicycle rides along the Holmes County Trail we have noticed, first, a lot of survey markers and flags, and second, a little later, a small tracked drilling rig. The first day I saw the rig, I also saw an Amish farmer plowing a nearby field. When I came back on my return trip, the farmer was giving his horses a rest and had walked over to the Trail. I stopped and asked him what all the drilling and survey work was for. They were running a seismic exploration for deep oil deposits.
Then late last week I began seeing strong impulsive signals showing up on my seismograph. Sharp impulsive signals are indicative of local disturbances as their higher frequency components die out quickly with distance (making them no longer sharp and impulsive). These signals showed up around 8:00 pm or early in the morning. I assume that these were the seismic sources being detonated and were done at that time to minimize the number of people on the Trail when they set off the buried charges. Another one is showing up this evening as I write.
So I share a seismogram with natural and manmade seismicity in the same view.