USGS/SLU Regional Moment Solution
12/12/03 21:40:18.74 Epicenter: 39.625 23.335 MW 4.1 USGS/SLU REGIONAL MOMENT TENSOR Depth 7 No. of sta: 18 Moment Tensor; Scale 10**15 Nm Mrr= 0.04 Mtt= 1.46 Mpp=-1.50 Mrt=-0.84 Mrp=-0.20 Mtp=-0.52 Principal axes: T Val= 1.90 Plg=24 Azm=187 N -0.23 63 39 P -1.67 13 283 Best Double Couple:Mo=1.8*10**15 NP1:Strike=234 Dip=83 Slip= 154 NP2: 327 64 8
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.