USGS Body-Wave Moment Tensor Solution
OFF W COAST OF NORTHERN SUMATRA
13/05/02 19:40:52.50 Epicenter: 2.741 91.565 MW 5.4 USGS MOMENT TENSOR SOLUTION Depth 16 No. of sta: 29 Moment Tensor; Scale 10**17 Nm Mrr= 0.16 Mtt=-1.42 Mpp= 1.27 Mrt= 0.14 Mrp=-0.17 Mtp=-0.86 Principal axes: T Val= 1.55 Plg= 8 Azm= 73 N 0.13 81 272 P -1.68 3 164 Best Double Couple:Mo=1.6*10**17 NP1:Strike=209 Dip=82 Slip= 4 NP2: 118 86 172
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.