India‐Sunda Plate Motion, Crustal Deformation, and Seismic Hazard in the Indo‐Burmese Arc

Abstract

Plate motion along the Indo‐Burmese Arc (IBA), strain accommodation in the Indo‐Burmese wedge, status of active convergence and seismic vulnerability in the outer wedge, is a matter of concern due to the large population density in northeast India, Bangladesh, and Myanmar. In the present study, we have constrained the India‐Sunda plate motion by estimating the Euler pole using updated GPS observations from the region. Our estimated India‐Sunda relative plate motion at a point on the blind megathrust (24°N and 90°E) in Bangladesh constrains India‐Sunda relative motion at ~37 mm/year oriented along N11°E. This motion is partitioned among three major active units, namely, the Sagaing Fault (~18 mm/year), Churachandpur‐Mao Fault (~17 mm/year), and the blind megathrust (~7 mm/year), from west to east of the IBA, respectively. Our estimate of convergence across the blind megathrust is significantly lower than that estimated earlier. Due to large scatter in the data close to the updip edge of the blind megathrust, it is not certain whether it is accommodated through shallow creep or in stick‐slip manner, thus leading to uncertainty in the seismic hazard in this densely populated region.

Modelling the seismic potential of the Indo-Burman megathrust

“…We will show later on that the shortening occurs here by seismic moment release in the IBD. This result is similar to one modelled by Panda et al 5 .

Figure 3 Changes of the modeled interseismic velocities across the Indo-Burman arc as simulated in three experiments.

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“…Recent observations from the Indian, Myanmar and Bangladesh GPS networks 3 , 4 suggest that the shortening rate across the Burma plate is 12–24 mm/y and 13–17 mm/y, respectively. Based on the relative motion of India and the undeformed Sundaland block, Panda et al 5 found that convergence across the blind megathrust (~ 7 mm/y) is significantly lower than previously thought 3 , 4 . They exclude the influence of the toroidal flow from Eastern Tibet, which induces additional arc-normal motion of ~ 10 mm/y in the non-rigid Shan Plateau.…”

“…The region is modelled as a system of rigid crustal blocks separated by thin visco-elastic faults, which move in response to external tectonic and basal motions. Several static block models were recently developed 3 – 5 to study the capability of the Indo-Burman megathrust of generating great earthquakes. The basic principles of elastic dislocation models 3 – 5 differ significantly from those of the BAFD model.…”

“…Several static block models were recently developed 3 – 5 to study the capability of the Indo-Burman megathrust of generating great earthquakes. The basic principles of elastic dislocation models 3 – 5 differ significantly from those of the BAFD model. The advantage of our dynamic model is that it simulates both slow tectonic motions and earthquake sequences.…”

Sinking Slab Stress and Seismo‐Tectonics of the Indo‐Burmese Arc: A Reappraisal

“…Unlike the passive seismic observations, space‐geodetic solutions provide precise control over the plate‐kinematics. Present‐day geodetic estimates show that the Indian plate converges, with respect to Sunda, toward E with an estimated rate of 37 mm/yr at N and E (Mallick et al., 2019; Panda et al., 2020; Steckler et al., 2016). Initial kinematic space geodetic solutions (Vigny et al., 2003), based on a sparse and spatially restricted data set, gave indications of ample amount of IBA wedge deformation.…”