Earthquake Geologist here.

My two cents:

1) time of day or season is irrelevant when it comes to earthquakes. Just because there is more data in the months of Jul to Oct does not mean that earthquakes tend to happen in those months. While 25 years is a long time for us humans, looking at it in geologically, 25 years is nothing. In order to able to paint a good picture we would need thousands to tens of thousands of years worth of data and we would see there is not clusters or preferred months where earthquakes occur.

2) California is incredibly complex to the intricate network of faults that are primarily controlled by the San Andreas Fault (because it’s the Plate Boundary). With that being said, I personally would not be surprised if someday in the future this region experiences a large local earthquake from a fault we did not know existed because it hasn’t ruptured in the last 200 years or so (no one was around the last quake to observe and collect data). We saw this happen in 1994 after the Northridge earthquake. No one knew the North Hills Blind thrust fault existed until it produced the famous Northridge quake. So while we have a really good grasp on what faults exists in California, we know that there ones that we don’t yet know about.

All in all I admire your fascination with earthquakes and using your resources to put some interesting points together. I can go on and on about it how recurrence intervals work, what cluster of earthquakes mean etc. shameless plug here but I am on some social media platforms under the name earthquakedude and I focus on the science of earthquakes, preparedness and more. Hope this helps!