This paper supplements Seismicity of the earth (Gutenberg and Richter, 1941). Additional epicenters for shallow and deep earthquakes are reported. Sixty-four great earthquakes are now identified for 1904–1943, and 201 major earthquakes for 1922–1943. New maps are given. Relative seismicity of active regions is discussed quantitatively (shallow shocks only). The Pacific belt has about 80 per cent and the trans-Asiatic zone about 10 per cent of the general activity. Earthquakes, volcanism, and gravity anomalies are discussed in their geographical and dynamical relation to structural arcs of Pacific type. These must be maintained by persistent processes in which subcrustal currents play a part.

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