USGS Centroid Moment Solution
OFF W COAST OF NORTHERN SUMATRA
12/04/11 08:38:35.72 Epicenter: 2.350 93.039 MW 8.6 USGS CENTROID MOMENT TENSOR 12/04/11 08:39:32.59 Centroid: 2.244 93.100 Depth 40 No. of sta: 61 Moment Tensor; Scale 10**21 Nm Mrr= 0.40 Mtt=-5.39 Mpp= 4.98 Mrt= 1.74 Mrp=-1.57 Mtp=-6.31 Principal axes: T Val= 8.55 Plg=15 Azm= 64 N -0.08 74 267 P -8.47 6 155 Best Double Couple:Mo=8.5*10**21 NP1:Strike=201 Dip=75 Slip= 6 NP2: 109 84 165
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.
