Surface Wave Magnitude
Ms = log (A/T) + 1.66 log D + 3.3
A is the maximum ground amplitude in micrometers (microns) of the vertical component of the surface wave within the period range 18 <= T <= 22.
T is the period in seconds.
D is the distance in geocentric degrees (station to epicenter) and 20 <= D <= 160.
No depth corrections are applied, and Ms magnitudes are not generally computed for depths greater than 50 kilometers.
Magnitude Ms Magnitude Ms
5 6 7 8 5 6 7 8
Distance (degrees) Ground Motion Amplitude (microns) for T = 20 s Log of Ground Motion Amplitude (microns) for T = 20 s
20 6.939373 69.39373 693.9373 6939.373 0.84132 1.84132 2.84132 3.84132
30 3.540044 35.40044 354.0044 3540.044 0.549009 1.549009 2.549009 3.549009
40 2.195889 21.95889 219.5889 2195.889 0.34161 1.34161 2.34161 3.34161
50 1.516142 15.16142 151.6142 1516.142 0.18074 1.18074 2.18074 3.18074
60 1.120209 11.20209 112.0209 1120.209 0.049299 1.049299 2.049299 3.049299
70 0.867296 8.672958 86.72958 867.2958 -0.06183 0.938167 1.938167 2.938167
80 0.694865 6.948653 69.48653 694.8653 -0.1581 0.841901 1.841901 2.841901
90 0.571462 5.714621 57.14621 571.4621 -0.24301 0.756987 1.756987 2.756987
100 0.479767 4.797666 47.97666 479.7666 -0.31897 0.68103 1.68103 2.68103
110 0.409561 4.095606 40.95606 409.5606 -0.38768 0.612318 1.612318 2.612318
120 0.354478 3.544779 35.44779 354.4779 -0.45041 0.549589 1.549589 2.549589
130 0.310373 3.103731 31.03731 310.3731 -0.50812 0.491884 1.491884 2.491884
140 0.274446 2.744463 27.44463 274.4463 -0.56154 0.438457 1.438457 2.438457
150 0.244748 2.447476 24.47476 244.7476 -0.61128 0.388719 1.388719 2.388719
160 0.219883 2.198826 21.98826 219.8826 -0.65781 0.342191 1.342191 2.342191
Magnitude Ms Magnitude Ms
5 6 7 8 5 6 7 8
Distance (degrees) Ground Motion Velocity (microns/s) for T = 20 s Log of Ground Motion Velocity (microns/s) for T = 20 s
20 2.178963 21.78963 217.8963 2178.963 0.33825 1.33825 2.33825 3.33825
30 1.111574 11.11574 111.1574 1111.574 0.045938 1.045938 2.045938 3.045938
40 0.689509 6.895092 68.95092 689.5092 -0.16146 0.83854 1.83854 2.83854
50 0.476068 4.760685 47.60685 476.0685 -0.32233 0.677669 1.677669 2.677669
60 0.351746 3.517455 35.17455 351.7455 -0.45377 0.546229 1.546229 2.546229
70 0.272331 2.723309 27.23309 272.3309 -0.5649 0.435097 1.435097 2.435097
80 0.218188 2.181877 21.81877 218.1877 -0.66117 0.33883 1.33883 2.33883
90 0.179439 1.794391 17.94391 179.4391 -0.74608 0.253917 1.253917 2.253917
100 0.150647 1.506467 15.06467 150.6467 -0.82204 0.17796 1.17796 2.17796
110 0.128602 1.28602 12.8602 128.602 -0.89075 0.109248 1.109248 2.109248
120 0.111306 1.113061 11.13061 111.3061 -0.95348 0.046519 1.046519 2.046519
130 0.097457 0.974571 9.745714 97.45714 -1.01119 -0.01119 0.988814 1.988814
140 0.086176 0.861762 8.617615 86.17615 -1.06461 -0.06461 0.935387 1.935387
150 0.076851 0.768508 7.685076 76.85076 -1.11435 -0.11435 0.885648 1.885648
160 0.069043 0.690431 6.904313 69.04313 -1.16088 -0.16088 0.83912 1.83912