Geophysical Research Letters
Supporting Information for
Complicated rupture process of the Mw 7.0 intraslab strike-slip earthquake in the Tohoku
region on 10 July 2011 revealed by near-field pressure records
Tatsuya Kubota1，Ryota Hino1, Daisuke Inazu2, Yoshihiro Ito3, Takeshi Iinuma4
1) Graduate
2) UTokyo
3) Disaster
4) I
School of Science, Tohoku University, Sendai, Japan
Ocean Alliance, The University of Tokyo, Tokyo, Japan
Prevention Research Institute, Kyoto University, Uji, Japan
Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
Contents of this file
Text S1
Figures S1 to S6
Table S1
Introduction
Text S1 is the description of the assignment of the unit source used in the tsunami waveform
inversion. Figure S1 shows the comparisons of the low-pass filtered waveform that was used to
determine the optimum cutoff. A schematic illustration of assignment of the unit source used in
the tsunami waveform inversion is shown in Figure S2. The trade-off relationship used to
determine the smoothing weight in the tsunami source inversion is shown in Figure S3. A
schematic of the unknown parameters in the grid search is shown in Figure S4. The result of the
grid-search assuming a fault striking NW–SE (NS model) is shown in Figure S5. Figure S6 is the
result of the grid-search assuming uneven Mo between two fault planes. Table S1 shows the
search range for the unknown parameters in the grid-search analysis.
1
Text S1.
In the tsunami waveform calculation, we used the pyramid-like-shaped unit source expressed
by the following form:
æ x - x0 öæ y - y0 ö
h0 ( x, y) = ç1÷ç1÷,
10 øè
10 ø
è
x0 -10 < x < x0 +10(km) ,
y0 -10 < y < y0 +10(km)
where η0(x, y) denotes the displacement of each unit source at the grid point (x, y) and (x0, y0) is
the center of the unit source. The schematic illustration of the unit source is shown in Figure S3.
Each unit source has the size of 20 km × 20 km, and is distributed with an interval of 10 km.
2
Figure S1. Comparison of low-pass filtered waveforms with several cutoff periods, de-tided
waveform (light gray), and 60 s moving averaged waveform (dark gray). Cutoff parameters for
the filter [Saito, 1978] were as = 5.0 and ap = 0.5, and as shown in upper right legend. In the
analysis, cutoff parameters of Tp = 100 s and Ts = 20 were used (red lines).
3
Figure S2. Schematic illustration of the unit source used in the tsunami waveform calculation.
Upper figure is the top view. Each cell is enclosed by computational grids. Numerals in cells
show the given amount of uplift. Lower figure is the side view. Each unit source overlaps with
next ones by 10 km in length.
4
Figure S3. Trade-off curve between smoothing weight of initial sea surface height inversion
and RMS misfit between observed and calculated waveforms. Because of the large curvature
around 100 in the smoothing weight, we used a smoothing weight of one in the tsunami
waveform inversion.
5
Figure S4. Schematic image of the unknown parameters in the grid-search. The origin of the
fault lengths and widths (reference point) is defined as the epicenter for the fault model of 65°
strike, or as the location of the CMT solution for the 330° fault model. The optimum solution is
sought in the range of the parameters shown in Table S1.
6
Figure S5. Result of grid search assuming fault striking NW–SE (NS model). (b) Vertical profile
along A–A’ and (c) B–B’ line in Figure S4a. Red line denotes optimum fault. Black lines show top
100 solutions of grid search. Thick black curved line denotes plate boundary [Ito et al., 2005]. (d)
Histograms of model parameters. (e) Histogram of L/W ratios.
7
Figure S6. Result of grid search assuming uneven moment between the two faults. The best-fit
model with moment ratio of 2:1 between the EW and NS faults. (a) Initial sea surface height
distribution. (b) Vertical profile along A–A’, and (c) B–B’ lines in (a). (d) Histograms of model
parameters. (e) Histogram of L/W ratios.
8
Table S1. Search range of the grid-search
Conjugate model
Model
Strike [°]a
EW model
NS model
65
NS fault
65
330
0 – 30
150 – 180
330
60 – 90
b
Dip [°]
Rake [°]b
EW fault
0 – 30
150 – 180
L1 [km]c,d
˗40 – 0
˗20 – 0
˗25 – ˗10
L2 [km]c,d
0 – 40
0 – 15
5 – 15
W1 [km]c,d,e
˗30 – ˗5
˗30 – ˗5
˗30 – ˗5
W2 [km]c,d,e
0–5
0–5
0–5
Slip amount [m] Adjusted to Mo = 3.96 × 1020 Nm with rigidity of 40 GPa.
aStrike
angle is fixed to the Global CMT focal mechanism.
bInterval of dip and rake angle parameters is 5°.
cInterval of parameters L1, L2, W1, and
W2 is 5 km.
fault length L and width W are defined as L2˗L1 and W2˗W1, respectively.
eThe total width W and depth of the fault is constrained to be equal.
dTotal
9