USGS WPhase Moment Solution
OFF W COAST OF NORTHERN SUMATRA
12/ 4/11 8:38:38.00 Epicenter: 2.348 93.072 MW 8.6 USGS/WPHASE CENTROID MOMENT TENSOR 12/ 4/11 8:38:38.00 Centroid: 2.248 92.872 Depth 25 No. of sta:109 Moment Tensor; Scale 10**21 Nm Mrr= 1.25 Mtt=-5.99 Mpp= 4.74 Mrt= 1.34 Mrp=-0.63 Mtp=-7.03 Principal axes: T Val= 8.40 Plg= 9 Azm= 63 N = 1.14 79 271 P = -9.54 4 154 Best Double Couple:Mo=9.0*10**21 NP1:Strike=199 Dip=80 Slip= 3 NP2: 108 87 170
The figure above shows a visual representation of the style of faulting (focal mechanism)
derived from the estimated moment tensor.
Shaded areas show quadrants of the focal sphere in which the P-wave first-motions
are away from the source, and unshaded areas show quadrants
in which the P-wave first-motions are toward the source.
The dots represent the axis of maximum compressional strain
(in black, called the "P-axis")
and the axis of maximum extensional strain (in white, called the "T-axis")
resulting from the earthquake.
