From a series of fault-plane solutions of earthquakes in any one area, it is possible to determine the tectonic displacement of that area by a least squares solution. This method has been applied to the areas marginal to the Northwest Pacific Ocean. It turns out that the directions of the tectonic displacement in the Kurile Islands, Honshu, the Marianas Islands, and the Philippines are more or less parallel: the direction is approximately N 14° W. This is a rather startling result: it appears that the whole Northwest Pacific Ocean is moving en bloc with regard to its margin. A determination of the motion for Sakhalin gives an entirely different direction (N 36° E), which is an indication that the tectonic motion of Sakhalin is unrelated to that of the Pacific Ocean.

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