JOURNAL OF GEOPHYSICAL RESEARCH

Supporting Information for ”Interseismic Coupling1

on the Main Frontal Thrust”2

DOI: 10.1002/3

V. L. Stevens1

and JP Avouac1,2

Contents of this file4

1. Tables S1 to S2.5

2. Figures S1 to S7.6

Additional Supporting Information (Files uploaded separately)7

1. Dataset S1 - GPS Data used in the Inversion.8

2. Dataset S2 - Electronic data for coupling map of Figure 1.9

3. Dataset S3 - Electronic data for stress rate map of Figure 2b.10

Corresponding author: V. L. Stevens, Geological and Planetary Sciences, California Institute

of Technology, Pasadena, CA 91125, USA. (vstevens@caltech.edu)

1Geological and Planetary sciences,

California Institute of Technology,

Pasadena, California, USA.

2Bullard Laboratories, Cambridge

University, Cambridge, Cambridgeshire UK.

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X - 2V L STEVENS AND JP AVOUAC: INTERSEISMIC COUPLING ON THE MAIN HIMALAYAN THRUST

Introduction Here we show extra figures relating to data, model set-up, resolution and11

residuals.12

References

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rich, M. Thomas, K. Chanard, S. N. Sapkota, S. Rajaure, P. Shrestha, L. Ding, and14

M. Flouzat (2012), Convergence rate across the nepal himalaya and interseismic cou-15

pling on the main himalayan thrust: Implications for seismic hazard, J. Geophys. Res.,16

117 (B4).17

Berthet, T., J.-F. Ritz, M. Ferry, P. Pelgay, R. Cattin, D. Drukpa, R. Braucher, and18

G. Hetnyi (2014), Active tectonics of the eastern himalaya: New constraints from the19

first tectonic geomorphology study in southern bhutan, Geology, 42 (5), 427–430, doi:20

10.1130/G35162.1.21

Bollinger, L., S. N. Sapkota, P. Tapponnier, Y. Klinger, M. Rizza, J. Van der Woerd,22

D. R. Tiwari, R. Pandey, A. Bitri, and S. Bes de Berc (2014), Estimating the return23

times of great himalayan earthquakes in eastern nepal: Evidence from the patu and24

bardibas strands of the main frontal thrust, Journal of Geophysical Research: Solid25

Earth, 119 (9), 7123–7163, doi:10.1002/2014JB010970.26

Burgess, W. P., A. Yin, C. S. Dubey, Z.-K. Shen, and T. K. Kelty (2012), Holocene short-27

ening across the main frontal thrust zone in the eastern himalaya, Earth and Planetary28

Science Letters, 357358 (0), 152 – 167, doi:http://dx.doi.org/10.1016/j.epsl.2012.09.040.29

Colchen, M. (1999), The thakkholamustang graben in nepal and the late cenozoic ex-30

tension in the higher himalayas, Journal of Asian Earth Sciences, 17 (56), 683 – 702,31

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V L STEVENS AND JP AVOUAC: INTERSEISMIC COUPLING ON THE MAIN HIMALAYAN THRUSTX - 3

doi:http://dx.doi.org/10.1016/S1367-9120(99)00037-1.32

Gan, W., P. Zhang, Z.-K. Shen, Z. Niu, M. Wang, Y. Wan, D. Zhou, and J. Cheng (2007),33

Present-day crustal motion within the tibetan plateau inferred from gps measurements,34

J. Geophys. Res., 112 (B8), B08,416–.35

Kundu, B., R. K. Yadav, B. S. Bali, S. Chowdhury, and V. K. Gahalaut (2014), Oblique36

convergence and slip partitioning in the nw himalaya: Implications from gps measure-37

ments, Tectonics, 33 (10), 2013–2024, doi:10.1002/2014TC003633.38

Lav, J., and J. P. Avouac (2000), Active folding of fluvial terraces across the siwaliks hills,39

himalayas of central nepal, Journal of Geophysical Research: Solid Earth, 105 (B3),40

5735–5770, doi:10.1029/1999JB900292.41

Mugnier, J., P. Huyghe, P. Leturmy, and F. Jouanne (2003), Episodicity and rates of42

thrust-sheet motion in the himalayas (western nepal), AAPG Mem., 82, 1–24.43

Parkash, B., R. Rathor, P. Pati, R. Jakhmola, and S. S. (2011), Convergence rates along44

the himalayan frontal thrust inferred from terraces at chandidevi temple hill, hardwar,45

northwestern himalaya, Curr Sci, 100, 1426 – 1432.46

Styron, R., M. Taylor, and K. Okoronkwo (2010), Database of active structures from the47

indo-asian collision, Eos, Transactions American Geophysical Union, 91 (20), 181–182,48

doi:10.1029/2010EO200001.49

Thakur, V., M. Joshi, D. Sahoo, N. Suresh, R. Jayangondapermal, and A. Singh (2014),50

Partitioning of convergence in northwest sub-himalaya: estimation of late quaternary51

uplift and convergence rates across the kangra reentrant, north india, International52

Journal of Earth Sciences, 103 (4), 1037–1056, doi:10.1007/s00531-014-1016-7.53

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X - 4 V L STEVENS AND JP AVOUAC: INTERSEISMIC COUPLING ON THE MAIN HIMALAYAN THRUST

Vernant, P., R. Bilham, W. Szeliga, D. Drupka, S. Kalita, A. K. Bhattacharyya, V. K.54

Gaur, P. Pelgay, R. Cattin, and T. Berthet (2014), Clockwise rotation of the brahma-55

putra valley relative to india: Tectonic convergence in the eastern himalaya, naga hills,56

and shillong plateau, Journal of Geophysical Research: Solid Earth, 119 (8), 6558–6571,57

doi:10.1002/2014JB011196.58

Wesnousky, S. G., S. Kumar, R. Mohindra, and V. C. Thakur (1999), Uplift and con-59

vergence along the himalayan frontal thrust of india, Tectonics, 18 (6), 967–976, doi:60

10.1029/1999TC900026.61

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V L STEVENS AND JP AVOUAC: INTERSEISMIC COUPLING ON THE MAIN HIMALAYAN THRUST X - 5

Table S1. Long term slip rates from geomorphic studies and modelled here

Lon Slip Rate (cm/yr) Uncertainty Modelled Modelled Reference

Slip Rate (cm/yr) Uncertainty

76.0 13.3 0.8 14.6 1.5 Thakur et al. [2014]

77.5 11.9 3.1 17.1 1.7 Wesnousky et al. [1999]

78.1 10.8 2.2 17.1 1.7 Parkash et al. [2011]

82 .0 19 6.0 19.3 1.2 Mugnier et al. [2003]

85.3 21 1.5 19.7 1.6 Lav and Avouac [2000]

85.8 18.2 6 19.7 1.6 Bollinger et al. [2014]

90.3 20.8 8.8 17.4 1.2 Berthet et al. [2014]

92.5 23 6.2 20.2 2.0 Burgess et al. [2012]

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X - 6 V L STEVENS AND JP AVOUAC: INTERSEISMIC COUPLING ON THE MAIN HIMALAYAN THRUST

Table S2. Rotation Poles with respect to India for the Sikkim/Shillong and

Bhutan/Assam Blocks of this study, and the Shillong and Assam Blocks in the study

of Vernant et al. [2014].

Block Lon Lat Rotation Rate Study

Assam 88.1 26.6 -1.13 this study

Shillong 87.1 25.6 -0.62 this study

Assam 87.8 26.8 -1.13 Vernant et al. [2014]

Shillong 88.8 26.4 -1.15 Vernant et al. [2014]

Longitude (°E)74 76 78 80 82 84 86 88 90 92 94 96

Latit

ude

(°N

)

25

26

27

28

29

30

31

32

33

34

Continuous GPS10 mm/yr

Campaign GPS10 mm/yr

InSAR data-3, 0, +3 mm LOS/yr

Leveling data1, 3, 6 mm uplift/yr

Figure S1. Location of data used in the inversion. Arrows show velocities relative to

India (as defined by Ader et al. [2012]) determined from continuous (green) and campaign

(black) GPS data. Ellipses show the uncertainties at the 67% confidence level. The blue

circles are InSAR data. The magenta circles are leveling data. The thick red line is the

simplified geometry of the MHT used in the model. Country borders are marked in grey.

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V L STEVENS AND JP AVOUAC: INTERSEISMIC COUPLING ON THE MAIN HIMALAYAN THRUST X - 7

Longitude (°E)74 76 78 80 82 84 86 88 90 92 94 96

Latit

ude

(°N

)

25

26

27

28

29

30

31

32

33

34

ASSAM

YG

SHILLONG

DS

TH

KC

Figure S2. The model setup. The red line shows the simplified surface trace of the

fault, and the grid shows the discretization used in this model. The dashed black lines are

the boundaries between different regions of uniform long term slip rate. The blue lines

show the edges of the two blocks for which rotation poles are found. The red dashed lines

show the rough location of major grabens. KC = Kaurik Changdu rift [Kundu et al.,

2014]. TH = Thakkola graben [Colchen, 1999]. DS = Dingjie-Sehnza fault zone [Gan

et al., 2007]. YG = Yadong-Gulu rift [Gan et al., 2007]. Thinner red/brown lines show

faults from Styron et al. [2010].

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X - 8 V L STEVENS AND JP AVOUAC: INTERSEISMIC COUPLING ON THE MAIN HIMALAYAN THRUST

78 80 82 84 86 88 90 92 94

30

32

34

Longitude (ºE)

La

titu

de

(ºN

)

13.3 ± 1.7

20.9 ± 1.9

17.6 ± 0.919.4 ± 1.4

20.2 ± 1.1

18.5 ± 1.8

0 1

Coupling

0.5

74 76

26

28Continuous GPS

Campaign GPS

Model

10 mm/yr INDIA ASSAMSHILLONG

Figure S3. Same as Figure 2, except with the poles of Vernant et al. [2014] imposed

and not solved for.

74 76 78 80 82 84 86 88 90 92 94 96

26

28

30

32

34

Longitude (ºE)

La

titu

de

(ºN

)

0 1

Coupling

0.5

Figure S4. Same as Figure 3a, except with uniform weighting of the Laplacian. The

coupling model is thus not regulated by the seismicity.

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V L STEVENS AND JP AVOUAC: INTERSEISMIC COUPLING ON THE MAIN HIMALAYAN THRUST X - 9

74 76 78 80 82 84 86 88 90 92 94 96

26

28

30

32

34

Longitude (ºE)

La

titu

de

(ºN

)

28

28

29

mm

-3

0

3

-1

-2

1

2

84 86

Continuous GPS

Campaign GPS

10 mm/yr

Figure S5. Residuals to the GPS data, with uncertainy ellipses. Campaign measure-

ments are in red, and continuous measurements in green. The inset shows the residuals

of the InSAR and leveling data.

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X - 10V L STEVENS AND JP AVOUAC: INTERSEISMIC COUPLING ON THE MAIN HIMALAYAN THRUST

74 76 78 80 82 84 86 88 90 92 94 96

26

28

30

32

34

Longitude (ºE)

La

titu

de

(ºN

)

15 25 40 8060

Resolution, km

InSAR point

Leveling point

Campaign GPS station

Continuous GPS station

Figure S6. Resolution on each patch of the fault. The resolution here is the character-

istic size of the smallest inhomogeneities of coupling which could in principle be resolved,

given the spatial distribution and uncertainties of the measurements. The figure is sat-

urated at a resolution of 80 km, as above this value we assume there is no resolution

on the corresponding patch, and so slip on this patch is just determined by slip on the

neighbouring patches. See Ader et al. [2012] for details of the calculation. The location

of data points used to find the resolution are also shown.

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Latitude (°N)30 30.5 31 31.5 32 32.5

Ele

vatio

n, k

mM

odel

ed U

plift

Rat

e, m

m/y

r

-1

0

1

2

3

4

5

675°E

Latitude (°N)28 28.5 29 29.5 30 30.5

Ele

vatio

n, k

mM

odel

ed U

plift

Rat

e, m

m/y

r

-1

0

1

2

3

4

5

680°E

Latitude (°N)26.5 27 27.5 28 28.5 29

Ele

vatio

n, k

mM

odel

ed U

plift

Rat

e, m

m/y

r

-1

0

1

2

3

4

5

685°E

Latitude (°N)26.5 27 27.5 28 28.5 29

Ele

vatio

n, k

mM

odel

ed U

plift

Rat

e, m

m/y

r

-1

0

1

2

3

4

5

690°E

Figure S7. Smoothed elevation (red) compared with modelled uplift rates (blue) at

different longitudes. Profile locations are shown in Figure 5 of the main text.

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