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