Direction of Faulting in the Deep-Focus Spanish Earthquake of March 29, 1954

An earthquake of magnitude 7.1 occurred off the south coast of Spain on March 29, 1954. The earthquake was remarkable in that it had a focal depth of about 650 km; no earthquake with focal depth greater than normal is known to have occurred in this area previously.

Using methods already established but here reviewed, the mechanism at the focus is investigated. The method defines two planes, without determining which is the fault. There are thus two possibilities. Under the first possibility the fault is approximately vertical and strikes north-south. The movement is vertical, such that the eastern side of the fault rises with respect to the western side. Under the second possibility the fault is approximately horizontal, and the movement is also horizontal, the material above the focus moving due east (that is, in the sense of the earth's rotation) with respect to the material below the focus.