Is Southern California's San Andreas Fault the Hole in Mogi's Donut?

john's picture

In 1969 the famous Japanese seismologist Kiyoo Mogi (1929-) wrote a paper entitled:  "Some Features of Recent Seismic Activity in and near Japan.  Activity before and after Great Earthquakes."  Published in the Bulletin of the Earthquake Research Institute, Japan [1], it described patterns of smaller earthquakes that precede great earthquakes. 

In the paper, Mogi made the important observation that "In the period of several to twenty years just before a great event, the area where the great event occurs is abnormally calm and its surrounding wide areas becomes markedly active (the foreshock activity in the broad sense).  Withe the great event, the above mentioned doughnut pattern of the seismic activity disappears and then the area in and near the focal region of the great earthquake becomes active (the aftershock activity in the broad sense)."

Is this pattern occurring around the San Andreas fault in southern California?  While not a strict quantitative description of activity, the Mogi donut idea is a useful concept for characterizing qualitatively the behavior of major earthquakes in southern California during the last 30 years or so.  It is in fact striking that in the last 70 years  little or no activity has been observed on the San Andreas fault that last broke in the great earthquake of 1857.  In contrast, large and major earthquakes have occurred on faults that surround the San Andreas in the past several decades.  Moreover, the section of the San Andreas fault from the Salton Sea to Cajon Pass has also shown little or no activity as long as instrumental observations have been made with seismographs. 

Geologic observations along the San Andreas fault document a record of great earthquakes at regular intervals of some 150 to 200 or so years.  When will the donut hole be filled?

[1] Mogi's paper can be found online at:


Jeffery Mercier's picture

Your blog is truly deserving and revealing. I am also the biggest fan of your bestessay reviews blog. Your every post, every article is truly amazing and amusing and we enjoyed a lot to read out all the stuff. Keep posting like this and never lose the spirits. Good luck for the bright future.

academic writing service
marthawilson710's picture

The figure above provides a good view of the long term change in probability, but what about the short term, say, over the past weeks and months? survival games online

Risk Alert