The Spike Mystery

For at least 2 years I have a spike that appears occasionally. Usually in the late afternoon (4p to 6p local time), but I have seen a few in the pre-dawn hours. It will occur for a few days and then go away for a few months.

I think I researched it on the RS forums long ago and came to the conclusion that it was some type of expansion near the shake and never followed up here. Recently, I have talked to other shakers with similar experiences, but different setups. So, I thought I would ask the RS team what their thoughts are on these signatures.

I have attached my latest spikes. The previous spike I noted occurred 3 months ago. The first set is from yesterday and were smaller. The second set is from just a little later in the day today and larger. Oh yeah, they seem to come in pairs.

My vault temp in the past 24 hours has only varied by 0.4F. The Shake is powered by POE and is connected to a line interactive UPS.


Chino Hills, Ca

It is quite a mistery indeed Steve.

From a first glance it seems that this phenomenon could be caused by some kind of spurious and random RF interference (at least from it’s appearance on the trace and spectra viewers).

However what you describe (thanks for all the details) could indicate something different. Maybe @ivor could provide his opinion on this, and other Shakers too, to try to solve this mystery.

I have had spikes similar to @scaron on my RS4D in the early morning as well. I’ll see if I can find it. I’ve also had larger spikes but they have another signature and were a complete other issue.
Edit: Was not able to find my spike/blip.
Edit 2: Something I’ve also noticed is that some spikes just dip down, and others dip both up and down.
Another thing I noticed is that on my accelerometer channel (ENZ) I noticed I have this “Permanent Dip” not sure if it’s related at all though as the other spikes have been on the Geophone (ENZ) channel. See the picture below for the “Perma-dip”.

You can also see my “Perma-dip” on my Live Stream at the bottom right.

Adding some additional information. I went back to my logs and pulled a list of false alarms I noted as these types of spikes. This is since 2019. This is when I started using WinSDR with the 4D and would alarm based on STA/LTA ratio. So, the spike list is incomplete. I only have from 2019 and if the spike did not trigger the alarm, I did log it.

I have also attached a .csv file with this information:

This is the largest spike based on the STA/LTA ratio. 10/12/2019

spikes.csv (802 Bytes)

Chino Hills, Ca

Do the spikes in raw counts indicate sensor saturation?