USGS Centroid Moment Solution
OFF W COAST OF NORTHERN SUMATRA
12/04/11 10:43:10.76 Epicenter: 0.829 92.434 MW 8.2 USGS CENTROID MOMENT TENSOR 12/04/11 10:43:50.29 Centroid: 0.921 92.488 Depth 43 No. of sta: 36 Moment Tensor; Scale 10**21 Nm Mrr= 0.45 Mtt=-1.30 Mpp= 0.85 Mrt= 0.21 Mrp=-0.84 Mtp=-1.63 Principal axes: T Val= 2.15 Plg=26 Azm= 63 N 0.05 63 231 P -2.20 5 331 Best Double Couple:Mo=2.2*10**21 NP1:Strike=200 Dip=75 Slip= 23 NP2: 104 68 164
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.
