Crust and Upper Mantle Seismic Anisotropy Variations from the Coast to
Inland in Central and Southern Mexico
Jorge Castillo1*, Xyoli Pérez-Campos2, Raúl Valenzuela2, Allen Husker2 and Luca Ferrari3
APPENDIX A: ANISOTROPIC COMPONENT CHARACTERIZATION FOR
NON-HORIZONTAL LAYERS
Taking into account the previously established behavior and periodicity of RFs in nonhorizontal layers, we perform a non-linear curve fitting of the form
æ 2p t
ö
u(t) = A cos ç
-j ÷+ C
è T
ø
,
to the picked Ps phases of interest. In this expression, A is the dimension of the
phenomena described by the cosine function, T is the period, j is the initial phase and C
is the value at which fitted function is centered in time. For our purposes, j is of
particularly interest since it describes the initial position of the cosine wave in t = 0 . In
other words, it allows us to determine if the cosine function is either advanced or delayed
with regard of the reference signal, translating in the direction in which the Ps phases are
arriving earlier in time. However, before describing the general tendency of the arrivals of a
given discontinuity, it is necessary to remove the influence of the preceding Ps phases.
Figure A1 shows the general process of characterization of the azimuthal variation for the
continental crust, upper oceanic crust and lower oceanic crust beneath one station; it is
important to notice the 360º periodicity with late arrivals coming from the northern
geographic quadrants, which is in accordance with the geometry of the slab.
Once the fast azimuth directions are obtained, the RFs are rotated to the fast/slow
coordinate system, defined by the initial phase of the cosine fit, and the shear wave splitting
is quantified through a cross-correlation computation. For this estimation, we employ a
time window of 0.5 s around each RF to ensure the inclusion of the Ps phase of interest in
both the fast and slow components of motion, and consider the time delay that results in the
maximum or minimum coefficient of the cross-correlation function as the appropriate
splitting measure of the two movement components. This last procedure is performed under
the same principle previously mentioned, in which it is necessary to estimate the time delay
for a given discontinuity and compensate the splitting effect for the proceeding phase. To
ensure the validity of the parameters, we only consider shear wave splitting measurements
when the waveforms of the fast/slow components are similar and the delay time is coherent
(Figure A2). This characterization scheme was implemented to the first 13 stations of the
MASE array, where the RF preliminary analysis clearly revealed an inclination in the
medium.
FIGURE CAPTIONS
Figure A1. Radial and tangential RFs of station PLAY (left). The color of the RFs
indicates its backazimuth geographic quadrant (light blue is NE, blue is SE, green is SW
and red is NW). The dashed lines over the RFs represent the continental crust (green),
upper oceanic crust (blue) and lower oceanic crust (red) pulses. Characterization process of
the timing variations of the analyzed Ps phases (right). The color format is the same as in
Figure A1 (left). The fitted curve parameters were obtained using a grid search algorithm
for all coherent values of A , T , j and C . The j values for the analyzed phases of this
station are: 205º, 157º and 183º, progressively.
Figure A2. Example of used and discarded RFs rotated to the fast/slow system from which
reliable measurements of d t were obtained for the different Ps phases analyzed in station
PLAY. The dashed red lines represent the splitting between the two phases.
FIGURES
Figure A1
Figure A2
APPENDIX B: ANISOTROPY PARAMETERS
For tables B1-B4, the  parameter is the fast polarization direction (measured clockwise
from the north) and the t parameter is the time delay between the fast and slow polarized
shear waves. The  and t values are the parameters standard error estimates. Uncertainty
values for the grid search algorithm were obtained by the 95% bootstrap confidence
interval and by the bootstrap standard error for the particle motion analysis and crosscorrelation procedure results. A total of 200 repetitions were used for such processes.
Stations in which a single set of reliable parameters was possible to obtain are marked with
an asterisk.
For Table B4, the  parameter is the fast polarization direction (measured clockwise from
the north) and the t parameter is the time delay between the fast and slow polarized shear
waves. The and t values are uncertainties of the SKS-wave study of Rojo (2012). As
reference, the stations in which a single set of SKS-wave parameters were obtained are
marked with an asterisk.
Table B1 Average anisotropy parameters for the continental crust.
STATION
QUEM
CEME
EL30
EL40
XALT
PLAY
XOLA
TICO
CARR
ACAH
MAZA*
PETA
UICA*
ELPO*
ZURI*
PLAT
HUIT
VEVI
PLLI
XALI
MAXE*
TONA
SATA
ZACA*
TEPO
CIEN*
BUCU
PALM
SAFE
CASA
AMAC
PUIX
SJVH
ATLA
TEMI
JIUT
CUNO
LAT. (º)
16.94
16.97
17.00
17.05
17.10
17.12
17.16
17.17
17.21
17.36
17.44
17.48
17.52
17.59
17.65
17.70
17.74
17.82
17.87
18.00
18.05
18.10
18.24
18.26
18.30
18.41
18.47
18.52
18.55
18.58
18.60
18.63
18.66
18.75
18.83
18.87
18.98
LON. (º)
-99.82
-99.81
-99.78
-99.76
-99.71
-99.67
-99.62
-99.54
-99.51
-99.47
-99.46
-99.46
-99.49
-99.51
-99.52
-99.54
-99.48
-99.56
-99.57
-99.55
-99.59
-99.56
-99.51
-99.53
-99.52
-99.47
-99.41
-99.43
-99.42
-99.38
-99.39
-99.32
-99.26
-99.22
-99.24
-99.20
-99.24
 (º)
 (º)
t (s)
t (s)
42
42
38
74
11
25
32
107
118
167
113
53
160
146
139
146
150
144
127
142
121
131
146
131
143
76
59
71
116
37
39
15
20
29
148
32
41
8
13
6
5
6
8
4
14
5
6
9
10
18
10
7
11
8
14
6
8
5
1
7
13
2
3
7
3
9
6
0.1
0.18
0.11
0.12
0.12
0.15
0.12
0.1
0.13
0.16
0.13
0.17
0.21
0.1
0.11
0.12
0.1
0.12
0.17
0.18
0.22
0.16
0.11
0.1
0.09
0.16
0.16
0.23
0.24
0.17
0.16
0.14
0.16
0.16
0.21
0.14
0.15
0.03
0.02
0.01
0.04
0.03
0.05
0.03
0.05
0.03
0.06
0.05
0.04
0.01
0.04
0.02
0.03
0.05
0.06
0.09
0.01
0.03
0.06
0.04
0.02
0.01
0.04
0.02
0.02
0.04
0.02
Table B1 Continuation
STATION
CHIC*
TONI*
TEPE*
CIRE
MULU*
ESTA
COAC*
TONN*
TECA
SALU
TIZA
ECID*
PSIQ
KM67
SAPE
SUPA*
PASU
MIMO*
SAPA*
VEGU
ATOT
SABI
NOGA
AGBE
VENA
SAME
ELBA*
MOJO
TIAN
MOLA
PEMU*
OCOL
CIRI
TEMP*
LAT. (º)
19.09
19.21
19.27
19.39
19.44
19.49
19.61
19.69
19.70
19.74
19.82
19.87
19.90
19.96
19.99
20.03
20.08
20.14
20.15
20.22
20.29
20.32
20.39
20.43
20.47
20.53
20.56
20.63
20.73
20.78
20.83
20.85
21.40
21.52
LON. (º)
-99.15
-99.15
-99.14
-99.16
-99.13
-99.11
-99.07
-99.04
-98.98
-98.97
-98.92
-98.93
-98.91
-98.88
-98.86
-98.81
-98.79
-98.68
-98.61
-98.64
-98.70
-98.66
-98.66
-98.63
-98.67
-98.64
-98.62
-98.62
-98.63
-98.72
-98.76
-98.74
-98.36
-98.38
 (º)
 (º)
t (s)
t (s)
101
156
140
126
118
40
59
27
122
43
126
150
84
121
54
54
39
114
53
140
130
132
97
53
37
112
119
125
134
54
44
156
14
9
18
12
16
11
8
14
8
11
11
6
8
8
3
10
7
5
6
8
14
4
6
-
0.25
0.2
0.17
0.2
0.2
0.19
0.21
0.34
0.26
0.19
0.18
0.2
0.1
0.19
0.1
0.23
0.19
0.12
0.23
0.22
0.16
0.14
0.11
0.19
0.27
0.15
0.11
0.18
0.26
0.2
0.14
0.19
0.1
0.05
0.12
0.05
0.07
0.07
0.02
0.03
0.05
0.03
0.04
0.02
0.05
0.03
0.04
0.05
0.04
0.03
0.03
0.01
0.04
0.01
0.01
-
Tabla B2 Average anisotropy parameters for the upper oceanic crust.
STATION
QUEM
CEME
EL30
EL40
XALT
PLAY
XOLA
TICO
CARR
ACAH
MAZA*
PETA
UICA
ELPO*
ZURI
PLAT
HUIT
VEVI
PLLI
XALI
MAXE
TONA
SATA
ZACA
TEPO
CIEN
BUCU
PALM
SAFE
CASA
AMAC
PUIX
SJVH
ATLA
LAT. (º)
16.94
16.97
17.00
17.05
17.10
17.12
17.16
17.17
17.21
17.36
17.44
17.48
17.52
17.59
17.65
17.70
17.74
17.82
17.87
18.00
18.05
18.10
18.24
18.26
18.30
18.41
18.47
18.52
18.55
18.58
18.60
18.63
18.66
18.75
LON. (º)
-99.82
-99.81
-99.78
-99.76
-99.71
-99.67
-99.62
-99.54
-99.51
-99.47
-99.46
-99.46
-99.49
-99.51
-99.52
-99.54
-99.48
-99.56
-99.57
-99.55
-99.59
-99.56
-99.51
-99.53
-99.52
-99.47
-99.41
-99.43
-99.42
-99.38
-99.39
-99.32
-99.26
-99.22
 (º)
 (º)
t (s)
t (s)
29
7
1
49
89
157
174
180
157
134
113
117
40
29
154
154
126
39
157
37
43
35
35
114
132
106
100
139
71
71
40
48
20
80
5
12
6
6
8
5
6
13
7
5
2
10
8
5
3
7
9
9
7
8
11
7
10
2
10
14
3
6
9
5
9
6
0.19
0.1
0.1
0.17
0.13
0.13
0.13
0.19
0.1
0.14
0.12
0.16
0.13
0.04
0.19
0.1
0.14
0.14
0.17
0.14
0.14
0.18
0.22
0.24
0.12
0.21
0.19
0.13
0.18
0.1
0.22
0.21
0.22
0.2
0.03
0.04
0.02
0.04
0.03
0.04
0.06
0.04
0.03
0.04
0.03
0.03
0.06
0.02
0.06
0.01
0.02
0.05
0.02
0.02
0.01
0.03
0.06
0.03
0.03
0.06
0.01
0.04
0.09
0.02
0.03
0.03
Table B3 Average anisotropy parameters for the lower oceanic crust.
STATION
QUEM
CEME
EL30
EL40
XALT
PLAY
XOLA
TICO
CARR
ACAH
MAZA
PETA
UICA
ELPO*
ZURI
PLAT
HUIT
VEVI
PLLI
XALI
MAXE
TONA
SATA
ZACA
TEPO
CIEN
BUCU
PALM
SAFE
CASA
AMAC*
PUIX
SJVH
ATLA
LAT. (º)
16.94
16.97
17.00
17.05
17.10
17.12
17.16
17.17
17.21
17.36
17.44
17.48
17.52
17.59
17.65
17.70
17.74
17.82
17.87
18.00
18.05
18.10
18.24
18.26
18.30
18.41
18.47
18.52
18.55
18.58
18.60
18.63
18.66
18.75
LON. (º)
-99.82
-99.81
-99.78
-99.76
-99.71
-99.67
-99.62
-99.54
-99.51
-99.47
-99.46
-99.46
-99.49
-99.51
-99.52
-99.54
-99.48
-99.56
-99.57
-99.55
-99.59
-99.56
-99.51
-99.53
-99.52
-99.47
-99.41
-99.43
-99.42
-99.38
-99.39
-99.32
-99.26
-99.22
 (º)
 (º)
t (s)
t (s)
138
161
154
139
82
3
43
132
113
164
143
145
122
141
120
129
85
120
137
158
121
136
132
34
58
71
127
71
146
134
160
146
127
128
5
7
6
8
8
9
4
11
6
4
6
4
4
5
10
5
7
2
7
15
8
9
5
14
13
16
10
11
8
7
15
7
12
0.15
0.14
0.16
0.22
0.17
0.11
0.1
0.11
0.11
0.22
0.24
0.14
0.25
0.12
0.14
0.16
0.16
0.11
0.13
0.19
0.11
0.24
0.16
0.27
0.09
0.2
0.21
0.13
0.21
0.14
0.16
0.21
0.16
0.14
0.02
0.03
0.03
0.02
0.04
0.01
0.03
0.02
0.02
0.03
0.02
0.04
0.03
0.04
0.05
0.05
0.04
0.03
0.03
0.04
0.02
0.01
0.04
0.04
0.03
0.03
0.01
0.02
0.02
0.05
0.04
0.03
0.03
Table B4 Anisotropy parameters for the upper mantle.
STATION
QUEM
CEME
EL30
EL40
XALT
PLAY
XOLA
TICO
CARR
ACAH
MAZA
PETA
UICA
ELPO
ZURI
PLAT
HUIT
VEVI
PLLI
XALI
MAXE
TONA
SATA
ZACA
TEPO
CIEN
BUCU
PALM
SAFE
CASA
AMAC
PUIX
SJVH
ATLA
TEMI
JIUT
CUNO
LAT. (º)
16.94
16.97
17.00
17.05
17.10
17.12
17.16
17.17
17.21
17.36
17.44
17.48
17.52
17.59
17.65
17.70
17.74
17.82
17.87
18.00
18.05
18.10
18.24
18.26
18.30
18.41
18.47
18.52
18.55
18.58
18.60
18.63
18.66
18.75
18.83
18.87
18.98
LON. (º)
-99.82
-99.81
-99.78
-99.76
-99.71
-99.67
-99.62
-99.54
-99.51
-99.47
-99.46
-99.46
-99.49
-99.51
-99.52
-99.54
-99.48
-99.56
-99.57
-99.55
-99.59
-99.56
-99.51
-99.53
-99.52
-99.47
-99.41
-99.43
-99.42
-99.38
-99.39
-99.32
-99.26
-99.22
-99.24
-99.20
-99.24
 (º)
 (º)
42
48
17
34
21
47
37
20
12
26
1
3
4
30
27
22
20
23
4
10
7
7
3
8
10
3
1
8
3
1
2
3
28
41
43
45
31
8
5
9
6
11
14
7
11
14
6
9
8
8
18
7
6
10
6
11
8
7
7
9
8
10
8
7
8
10
14
9
14
13
8
8
7
28
t (s)
0.62
0.76
1.01
0.9
0.51
0.72
0.77
0.52
0.87
1.16
0.98
0.88
1.18
0.59
1.03
0.94
0.9
0.8
1.06
0.87
0.83
0.94
0.68
0.74
1.08
0.57
0.53
0.54
0.73
0.56
0.48
0.45
0.18
0.6
1.22
0.97
0.75
t (s)
0.20
0.10
0.20
0.25
0.20
0.20
0.10
0.25
0.20
0.10
0.20
0.20
0.15
0.20
0.10
0.15
0.15
0.10
0.20
0.10
0.10
0.15
0.10
0.10
0.10
0.15
0.10
0.10
0.15
0.10
0.10
0.65
0.10
0.25
0.40
0.40
0.45
Table B4 Continuation
STATION
CHIC
TONI*
TEPE*
CIRE*
MULU*
ESTA
COAC*
TONN*
TECA
SALU
TIZA
ECID*
PSIQ
KM67
SAPE
SUPA
PASU
MIMO
SAPA
VEGU
ATOT
SABI*
NOGA
AGBE
VENA
SAME
ELBA
MOJO
TIAN
MOLA
PEMU
OCOL
CIRI*
TEMP*
LAT. (º)
19.09
19.21
19.27
19.39
19.44
19.49
19.61
19.69
19.70
19.74
19.82
19.87
19.90
19.96
19.99
20.03
20.08
20.14
20.15
20.22
20.29
20.32
20.39
20.43
20.47
20.53
20.56
20.63
20.73
20.78
20.83
20.85
21.40
21.52
LON. (º)
-99.15
-99.15
-99.14
-99.16
-99.13
-99.11
-99.07
-99.04
-98.98
-98.97
-98.92
-98.93
-98.91
-98.88
-98.86
-98.81
-98.79
-98.68
-98.61
-98.64
-98.70
-98.66
-98.66
-98.63
-98.67
-98.64
-98.62
-98.62
-98.63
-98.72
-98.76
-98.74
-98.36
-98.38
 (º)
58
20
28
43
47
179
167
179
170
14
161
167
171
164
173
168
7
162
3
168
165
165
163
175
161
174
161
29
161
180
174
17
152
144
 (º)
59
41
34
73
44
33
18
30
15
13
12
46
15
12
6
13
9
16
76
20
23
63
16
16
21
4
8
14
61
7
21
49
58
46
t (s)
0.72
1.16
0.55
0.73
0.77
1.26
2.1
1.87
1.48
1.4
1.52
1.37
1.29
1.28
1.26
1.44
1.12
1.35
0.88
0.39
0.41
0.97
0.85
0.83
0.34
0.89
0.9
0.39
0.56
1.1
1.58
0.65
0.72
0.37
t (s)
0.75
0.50
0.40
1
1.05
0.95
1.20
1.65
0.65
0.45
0.45
1.05
0.70
0.60
0.20
0.60
0.40
0.75
2
0.25
0.20
0.90
0.45
0.40
0.30
0.10
0.20
0.30
0.95
0.25
1.00
1.10
0.55
0.30