Research

Frictional, viscous and plastic deformation over the earthquake cycle

We combine long-term folding models with earthquake sequence simulations to study how permanent deformation along the fault (as fault slip) and permanent deformation in the bulk (off-fault deformation) occur during the earthquake cycle and work together to build geologic structures.


  • Mallick, R., Bürgmann, R., Johnson, K., & Hubbard, J. (2021). A unified framework for earthquake sequences and the growth of geological structure in fold-thrust belts. Link to paper

  • Hubbard, J. & Mallick, R. (2021). An overlooked hazard can cause damage weeks after an earthquake strikes. Link to article

We are also interested in understanding the interplay between aseismic (localized and distributed creep) and seismic slip over the entire earthquake cycle. This is a problem that combines geodesy, continuum mechanics and rock deformation experiments to understand what approximations of constitutive relations of the lithosphere-asthenosphere system are relevant over what spatial and temporal scales. The goal is to determine what we can infer about the Earth's interior using surface observations.

  • Meade, B. J., Mallick, R. & Carrero-Mustelier, E. (2022). Kinematic representations of linear and power-law viscoelastic deformation through the earthquake cycle. Link to paper

  • Mallick, R., Lambert, V. R. & Meade, B. J. (2022) On the choice and implications of rheologies that maintain kinematic and dynamic consistency over the entire earthquake cycle. Link to paper

Slow Slip Events
Fault friction and geodetic observations

Using force balance equations that govern the mechanics of the interseismic period of the earthquake cycle and optimization methods to fit geodetic data in a subduction zone setting, we developed a novel method for inferring the coupling ratio on shallow megathrusts. This new technique stays true to the governing mechanics of subduction while significantly reducing the problem of low resolution near the trench. We can also use this concept to test the validity of our assumptions when we have sufficient data, as we demonstrated in Sumatra by discovering what is possibly the longest ever Slow Slip Event (SSE) ever recorded - we estimate it lasted over 30 years! This means that the megathrust was in a state of stress release for three decades - a highly unexpected finding!.

  • Mallick, R., Meltzner, A. J., Tsang, L. L. H., Lindsey, E. O., Feng, L., and Hill, E. M. (2021); Long-lived shallow slow-slip events on the Sunda megathrust. Link to paper

  • Lindsey, E., Mallick, R., Hubbard, J., Bradley, K., Almeida, R., Moore, J. D. P., Burgmann, R., Hill, E. M. (2021); Slip rate deficit and earthquake potential on shallow megathrust. Link to paper

  • Almeida, R., Lindsey, E. O., Bradley, K., Hubbard, J., Mallick, R., & Hill, E. M. (2018). Can the Up-Dip Limit of Frictional Locking on Megathrusts be Detected Geodetically? Quantifying the Effect of Stress Shadows on Near-Trench Coupling. Link to paper

  • Mallick, R., Lindsey, E. O., Feng, L., Hubbard, J., Banerjee, P., & Hill, E. M. (2019). Active convergence of the India-Burma-Sunda plates revealed by a new continuous GPS network. Link to paper

  • Mallick, R., Hubbard, J. A., Lindsey, E. O., Bradley, K. E., Moore, J. D. P., Ahsan, A., Khorshed Alam, A. K. M., Hill, E. M. (2020). Subduction initiation and the rise of the Shillong Plateau. Link to paper

Tectonics of Indo-Burma, Himalaya and surrounding regions

In Bangladesh and Myanmar, the Indian plate collides against the Burma Plate in an oblique manner and creates a ~500 km wide, remarkably flat accretionary prism along with a number of strike-slip features. We are trying to understand -

  1. How continental blocks respond to imposed oblique convergence?

  2. When can we treat continental deformation as elastic blocks with inelastic deformation localised on faults (leading to slip episodes such as earthquakes)?

  3. Under what conditions can we approximate continental tectonics as a distributed deformation problem with negligible localisation/faulting?

  4. Which faults accommodate this inter-plate motion, and what are their slip rates?

  5. What section of the faults here are locked and accumulating elastic strain?

Shillong Plateau

To the north, we are also interested in the rise of the Shillong Plateau. Along with quantifying the fault geometry and the modern slip rate of the Dauki Thrust which drives this uplift, we compare modern geodetic observations with long-term uplift recorded in geomorphological and thermochronological observations. There is a discrepancy in the uplift rates calculated from these two different timescales, which we attribute to possible subduction initiation of the Surma Basin (the footwall block). This might be the first ever observation of passive margin subduction initiation in the Cenozoic!

Himalayas

The Himalayas are possibly the most magnificent natural laboratory to study continental tectonics. We found that the interseismic locked-creeping transition seems to follow the location of a mid-crustal ramp along the entire Nepal Himalaya. This suggests that geometrical features, like ramps and flats, may control where earthquakes start and stop.

  • Lindsey, E. O., Almeida, R., Mallick, R., Hubbard, J., Bradley, K., Tsang, L. L. H., et al. (2018). Structural Control on Downdip Locking Extent of the Himalayan Megathrust. Link to paper

Earthquake source seismology

In addition to studying the processes that lead up to and follow earthquakes (interseismic and postseismic phenomena), we also study the earthquake rupture process. Most of our work on earthquakes are related to events off the coast of Sumatra, Indonesia.

Each event tells us something interesting about the way the Earth's lithosphere deforms.

  • Morgan, P. M., Feng, L., Meltzner, A. J., Mallick, R., & Hill, E. M. (2020). Diverse Slip Behavior of the Banyak Islands Subsegment of the Sunda Megathrust in Sumatra, Indonesia. Link to paper

  • Mallick, R., Parameswaran, R. M., & Rajendran, K. (2017). The 2005 and 2010 Earthquakes on the Sumatra–Andaman Trench: Evidence for Post‐2004 Megathrust Intraplate Rejuvenation. Link to paper

  • Mallick, R., & Rajendran, K. (2016). The 2014 Mw 6.1 Bay of Bengal, Indian Ocean, Earthquake: A Possible Association with the 85° E Ridge. Link to paper

  • Parameswaran, R. M., Natarajan, T., Rajendran, K., Rajendran, C. P., Mallick, R., Wood, M., & Lekhak, H. C. (2015). Seismotectonics of the April–May 2015 Nepal earthquakes: An assessment based on the aftershock patterns, surface effects and deformational characteristics. Link to paper