Fault-Plane Solution
Fault-Plane Solution : A simplified geometric-mathematical way of presenting an earthquake fault and the direction of slip on it, using circles with two intersecting curves for the two potential fault planes that look like "beach balls" (see Fig. 3.33 ??? in this Manual). A fault-plane solution is found by an analysis using stereographic projection or its mathematical equivalent to determine the attitude of the causative fault and its direction of slip from the radiation pattern of seismic waves using earthquake records at many stations. The most common analysis uses the direction of first motion of P-wave onsets and yields two possible orientations for the fault rupture and the direction of seismic slip. Other techniques use in addition the polarization of teleseismic S waves and/or amplitude ratios between P and S waves. From these data, inferences can be made concerning the principal axes of stress in the region of the earthquake. The principal stress axes determined by this method are the compressional axis (also called the P-axis, i.e. the axis of greatest compression, or s1), the tensional axis (also known as the T-axis, i.e., the axis of least compression, or s3), and the intermediate axis (s2). See also focal mechanism
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