Surface-wave Magnitude Distance Factor
Distance 1.66 log10(distance) bsdist table
(degrees)
20 2.159709793
21 2.194884029
22 2.22842165
23 2.260468208
24 2.291150661
25 2.320580414
26 2.348855758
27 2.376063849
28 2.402282332
29 2.427580677
30 2.452021283
31 2.475660412
32 2.498548964
33 2.52073314
34 2.542255002
35 2.563152954
36 2.583462151
37 2.603214862
38 2.62244077
39 2.641167248
40 2.659419586
41 2.677221202 Dark line (Series1):
42 2.694593822 The equation for MS inlcudes the distance term 1.66 log10 (distance) and is valid from 20 to 130 degrees.
43 2.711557636
44 2.728131443 Colored line (Series2):
45 2.744332773 The table values in column C are used for distance greater than 130 degrees.  The table takes into
46 2.760178001 account the increase in amplitude as the surface waves converge at 180 degrees.
47 2.775682444
48 2.790860454 For distance between 20 and 130 degrees:  MS = log10 (amp/t) + 1.66*log10(distance) + 3.3
49 2.805725493 For distance greater than 130 and up to 180 degrees: MS = log10(amp/t) + bsdist(int(distance - 129.5)) + 3.3
50 2.820290207 (t is the period, which should be between 18 and 22 seconds.)
51 2.834566492
52 2.84856555
53 2.862297944
54 2.875773641
55 2.889002065
56 2.901992125
57 2.91475226
58 2.927290469
59 2.939614339
60 2.951731076
61 2.963647526
62 2.975370205
63 2.986905312
64 2.998258757
65 3.009436172
66 3.020442933
67 3.031284172
68 3.041964795
69 3.052489491
70 3.062862746
71 3.073088859
72 3.083171944
73 3.093115948
74 3.102924655
75 3.112601697
76 3.122150563
77 3.131574604
78 3.14087704
79 3.150060972
80 3.159129378
81 3.168085131
82 3.176930995
83 3.185669633
84 3.194303615
85 3.202835417
86 3.211267429
87 3.219601959
88 3.227841236
89 3.235987411
90 3.244042566
91 3.252008711
92 3.259887793
93 3.267681695
94 3.275392237
95 3.283021185
96 3.290570247
97 3.298041079
98 3.305435286
99 3.312754423
100 3.32
101 3.32717348
102 3.334276285
103 3.341309793
104 3.348275343
105 3.355174236
106 3.362007736
107 3.368777071
108 3.375483434
109 3.382127987
110 3.388711857
111 3.395236145
112 3.401701918
113 3.408110216
114 3.414462053
115 3.420758415
116 3.427000262
117 3.43318853
118 3.439324132
119 3.445407956
120 3.451440868
121 3.457423715
122 3.463357319
123 3.469242485
124 3.475079997
125 3.480870622
126 3.486615105
127 3.492314177
128 3.49796855
129 3.503578919
130 3.509145965
131 3.514670351 3.49
132 3.520152726 3.5
133 3.525593724 3.5
134 3.530993965 3.5
135 3.536354056 3.51
136 3.541674588 3.51
137 3.546956141 3.51
138 3.552199283 3.51
139 3.557404568 3.52
140 3.562572539 3.52
141 3.567703727 3.52
142 3.572798652 3.52
143 3.577857822 3.52
144 3.582881737 3.53
145 3.587870884 3.53
146 3.592825741 3.53
147 3.597746776 3.53
148 3.602634448 3.53
149 3.607489206 3.54
150 3.61231149 3.54
151 3.617101733 3.54
152 3.621860356 3.54
153 3.626587775 3.54
154 3.631284397 3.54
155 3.635950619 3.54
156 3.640586833 3.54
157 3.645193423 3.54
158 3.649770764 3.54
159 3.654319226 3.54
160 3.658839171 3.54
161 3.663330954 3.54
162 3.667794924 3.53
163 3.672231423 3.53
164 3.676640788 3.53
165 3.681023347 3.52
166 3.685379426 3.52
167 3.689709342 3.52
168 3.694013408 3.52
169 3.69829193 3.51
170 3.702545209 3.51
171 3.706773543 3.51
172 3.710977222 3.5
173 3.715156531 3.49
174 3.719311752 3.47
175 3.723443161 3.44
176 3.727551029 3.41
177 3.731635622 3.39
178 3.735697204 3.34
179 3.739736031 3.29
180 3.743752358 3.19