Fig. 6

PDE catalog projected onto source-type diagrams. Mechanisms for 35,403 events in the USGS Preliminary Determination of Epicenters (PDE) catalog, from February 1981 to July 2013, are shown after projection onto each source-type diagram. There are 19,808 events with deviatoric mechanisms, including 310 DC events. For these comparison plots, we use normalized diagrams, where DC, ±CLVD, and ±ISO correspond to \(\left( {0, 0} \right)\), \(\left( {0, \pm 1} \right)\), and \(\left( { \pm 1, 0} \right)\), respectively. Only parts of diagram with the horizontal range −1 to 1 and the vertical range −0.25 to 0.25 are shown. a Cubic projection diagram \(\left( {\tilde{u}, \tilde{v}} \right)\). b Hexagonal bi-pyramid projection diagram \(\left( {\tilde{\tau }, \tilde{k}} \right)\). c Modified hexagonal bi-pyramid projection diagram \(\left( {\tilde{T}, \tilde{k}} \right)\). d Conjugate hexagonal bi-pyramid projection diagram \(\left( {\tilde{\eta }, \tilde{\xi }} \right)\). e Spherical equirectangular projection diagram \(\left( {\tilde{\gamma }, \tilde{\delta }} \right)\). f Spherical orthogonal projection diagram \(\left( {\tilde{R}, \tilde{\zeta }} \right)\). g Modified spherical orthogonal projection diagram \(\left( {\tilde{r}, \tilde{s}} \right)\). (h) Spherical azimuthal projection diagram \(\left( {\tilde{p}, \tilde{q}} \right)\). i Spherical cylindrical projection diagram \(\left( {\tilde{\gamma }, \tilde{\zeta }} \right)\). j Modified spherical cylindrical projection diagram \(\left( {\tilde{a}, \tilde{b}} \right)\). k Spherical cylindrical orthogonal projection diagram \(\left( {\tilde{\chi }, \tilde{\zeta }} \right)\). l Percentile diagram \(\left( {\tilde{\epsilon }, \tilde{v}} \right)\). m Modified percentile diagram \(\left( {\tilde{c}, \tilde{v}} \right)\)