Double-couple earthquake source: symmetry and rotation
Abstract
We consider statistical analysis of double-couple (DC) earthquake focal mechanism orientation. The symmetry of DC changes with its geometrical properties, and the number of 3-D rotations one DC source can be transformed into another depends on its symmetry. Four rotations exist in a general case of DC with the nodal-plane ambiguity, two transformations if the fault plane is known and one rotation if the sides of the fault plane are known. The symmetry of rotated objects is extensively analysed in statistical crystallographic texture studies, and we apply their results to analysing DC orientation. We consider theoretical probability distributions which can be used to approximate observational patterns of focal mechanisms. Uniform random rotation distributions for various DC sources are discussed, as well as two non-uniform distributions: the rotational Cauchy and von Mises-Fisher. We discuss how parameters of these rotations can be estimated by a statistical analysis of earthquake source properties in global seismicity. We also show how earthquake focal mechanism orientations can be displayed on the Rodrigues vector space.
- Publication:
-
Geophysical Journal International
- Pub Date:
- August 2013
- DOI:
- 10.1093/gji/ggt156
- arXiv:
- arXiv:1207.5079
- Bibcode:
- 2013GeoJI.194.1167K
- Keywords:
-
- Probability distributions;
- Earthquake source observations;
- Computational seismology;
- Statistical seismology;
- Fractures and faults;
- Physics - Geophysics;
- Mathematical Physics;
- Statistics - Applications
- E-Print:
- 40 pages, 14 figures, 1 table