So Japan just had another 5.6 today close to the southern zone, and there has been a bit of increased seismic activity closer Tokyo in the last month
I started looking into some historical seismicity, kind of in follow up to the situation there, and after having spent so much time on it in
2011/2012. I came across a USGS map that proved to be kind of interesting, because I found a spot along the southern zone that appears to be locked.
In other words, there hasn't been a big quake there in recorded history, at all. Here's a crop I did from that map, and the black arrow I drew in
points towards this "hole" of no major activity:
Now that is only through 2007, but still, I don't believe anything major happened there during the aftershock activity after the 9+. And even with a
recent historical seismicity since 1990, you can still see a small hole there:
Historical Seismicity since 1990
So while there have been some smaller ones close, that little hole there could be the locked point.
These latest line of quakes running north to south seem to be occurring along a depth transition boundary.
So that region, for all anyone knows could have some pretty serious stress accumulated over thousands of years.
I went back and pulled the last 30 days of quake activity at USGS, and that looks like this:
And what is kind of interesting (at least to me), is there seems to be two lines of recent quakes, that appear to be converging on that very area! I
have prepped a pic:
The black arrow is pointing to the zone, and also represents the general direction of pressure from the pacific plate- which is getting subducted. The
red lines indicate the general trending lines of quakes, showing where they converge- and the blue star to me represents where I feel there could
possibly be another whopper. Or in that general area. Maybe not today or tomorrow, but if we keep getting bigger quakes from this point in the high
5's or 6's or so in that area- sorry but gonna have to sound the alarm again.
With all the stress redistribution that occurred from the 9+, and continuing pressure from the pacific plate, that spot has got to be ripe to give way
sometime in the future. And who knows when. And even though that southern zone it is supposedly a transform boundary, and not a subduction zone, it
didn't save Tokyo back in 1923- when a big quake nearly leveled the place, and sent a tsunami into Tokyo bay. And that one is still a mystery to me,
because tsunamis are usually generated from thrust type, subduction zone quakes.
But anyway, just some food for thought. In the case of Santa Cruz Islands, I spotted trouble
before the 8.0
because of foreshock activity that was abnormal.
In this case, it may be because of noticing patterns and historical lack of big seismicity in that blue star area. But I am not liking the way those
lines seem to be converging. Those quakes on those lines all represent stress releases adjacent to that locked area, that seems to be holding out. And
so there is even MORE stress being put on this area now.
The question is, how much longer can it hold out? The unreleased stress there has got to be enormous by now!
edit on Tue Feb 19th 2013 by
TrueAmerican because: (no reason given)