Surface wave radiation pattern and source mechanism of the September 1, 1962, Iran earthquake

Surface waves recorded at stations surrounding the Iran earthquake of September 1, 1962, were Fourier-analyzed; the amplitudes have been corrected for instrumental response, geometric spreading, and absorption and are presented as a function of azimuth and frequency. The patterns thus derived are compared with theoretical radiation patterns for different source types, orientation of motion vectors, and other parameters. It is found that the source of the Iran earthquake can be represented as a double couple equivalent to a sinistral reverse shear fault with strike N 80°W, dip 78° to the southwest, slip angle 63° and a depth of 11 km. This solution agrees well with the conclusion obtained from a first motion study. It is remarkable that solutions obtained over such a wide frequency range conform to each other.