Synthesis of the distribution of subsidence of the lower Ganges-Brahmaputra Delta, Bangladesh

Steckler, M. S.; Oryan, Bar; Wilson, Carol; Grall, C.; Nooner, S. L.; Mondal, D. R.; Akhter, S. H.; DeWolf, Scott; Goodbred, S. L.

doi:10.1016/j.earscirev.2021.103887

Cited by 38 publications

(45 citation statements)

References 83 publications

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“…Finally, our analysis did not include vertical rates measured near large concentrations of population, such as Dhaka, and within the GBD as water pumping and subsidence due to sediment compaction, among other reasons, overshadow the vertical tectonic signature (e.g., Grall et al., 2018; Morris et al., 2003; Steckler et al., 2022).…”

Section: Gnss Rates In the Indo‐burma Subduction Zonementioning

confidence: 99%

New GNSS and Geological Data From the Indo‐Burman Subduction Zone Indicate Active Convergence on Both a Locked Megathrust and the Kabaw Fault

et al. 2023

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The Indo‐Burma subduction zone is a highly oblique subduction system where the Indian plate is converging with the Eurasian plate. How strain is partitioned between the Indo‐Burma interface and upper plate Kabaw Fault, and whether the megathrust is a locked and active zone of convergence that can generate great earthquakes are ongoing debates. Here, we use data from a total of 68 Global Navigation Satellite System (GNSS) stations, including newly installed stations across the Kabaw Fault and compute an updated horizontal and vertical GNSS velocity field. We correct vertical rates for fluctuating seasonal signals by accounting for the elastic response of monsoon water on the crust. We model the geodetic data by inverting for 11,000 planar and non‐planar megathrust fault geometries and two geologically viable structural interpretations of the Kabaw Fault that we construct from field geological data, considering a basin‐scale wedge‐fault and a crustal‐scale reverse fault. We demonstrate that the Indo‐Burma megathrust is locked, converging at a rate of 11.6±5.4 $11.6\pm 5.4$ mm/yr, and capable of hosting >8.2 Mw megathrust events. We also show that the Kabaw Fault is locked and accommodating strike‐slip motion at a rate of 8.4±3.0 $8.4\pm 3.0$ mm/yr and converging at a rate of 5.7±4.1 $5.7\pm 4.1$ mm/yr. Our interpretation of the geological, geophysical, and geodetic datasets indicates the Kabaw Fault is a crustal‐scale structure that actively absorbs a portion of the convergence previously ascribed to the Indo‐Burma megathrust. This reveals a previously unrecognized seismic hazard associated with the Kabaw Fault and slightly reduces the estimated hazard posed by megathrust earthquakes in the region.

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Section: Gnss Rates In the Indo‐burma Subduction Zonementioning

confidence: 99%

New GNSS and Geological Data From the Indo‐Burman Subduction Zone Indicate Active Convergence on Both a Locked Megathrust and the Kabaw Fault

et al. 2023

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“…Flood‐dominant tides then advect suspended river‐plume sediments back onshore to form a vast muddy tidal delta plain sustained by a dense network of channels and intertidal platform (Allison et al., 1998; Rogers et al., 2013). The resulting stratigraphy is mud‐dominated and faces higher rates of subsidence due to natural compaction and exacerbated by anthropogenic activities (Allison et al., 2003; Atker et al., 2016; Auerbach et al., 2015; Grall et al., 2018; Rogers et al., 2013; Steckler et al., 2022). Recent studies (Islam & Gnauck, 2008; Passalacqua et al., 2013) divided the study area into four geomorphic regions: active, tidally active, mature, and paleo‐delta (Figure 1a).…”

Section: Stratigraphic Setting and Context Of The Study Areamentioning

confidence: 99%

Predicting Subsurface Architecture From Surface Channel Networks in the Bengal Delta

Khan

Ahmed

et al. 2023

JGR Earth Surface

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In the Bengal Delta, more than 150 million inhabitants rely on groundwater as their primary source of water due to its accessibility and lower risk of microbial contamination compared to surface water (Bangladesh Bureau of Statistics, 2011). However, 27.5 million people are drinking groundwater with high levels of geogenic arsenic in the shallow Abstract Groundwater is the primary source of water in the Bengal Delta but contamination threatens this vital resource. In deltaic environments, heterogeneous sedimentary architecture controls groundwater flow; therefore, characterizing subsurface structure is a critical step in predicting groundwater contamination. Here, we show that surface information can improve the characterization of the nature and geometry of subsurface features, thus improving the predictions of groundwater flow. We selected three locations in the Bengal Delta with distinct surface river network characteristics-the lower delta with straighter tidal channels, the mid-delta with meandering and braided channels, and the inactive delta with transitional sinuous channels. We used surface information, including channel widths, depths, and sinuosity, to create models of the subsurface with object-based geostatistical simulations. We collected an extensive set of lithologic data and filled in gaps with newly drilled boreholes. Our results show that densely distributed lithologic data from active lower and mid-delta are consistent with the object-based models generated from surface information. In the inactive delta, metrics from object-based models derived from surface geometries are not consistent with subsurface data. We further simulated groundwater flow and solute transport through the object-based models and compared these with simulated flow through lithologic models based only on variograms. Substantial differences in flow and transport through the different geologic models show that geometric structure derived from surface information strongly influences groundwater flow and solute transport. Land surface features in active deltas are therefore a valuable source of information for improving the evaluation of groundwater vulnerability to contamination. Plain Language SummaryThe structure of groundwater aquifers affects how groundwater and contaminants move through them. In deltas, dynamic river networks are responsible for depositing sediments that ultimately form subsurface aquifers. Therefore, the characteristics of the surface river channel network should provide information about the structure of the subsurface. We tested this idea using a large set of sedimentary data from the Bengal Basin. We created models of the subsurface based on the surface network and showed that the subsurface data reflect the model characteristics in deltas that are actively depositing sediment. Using these subsurface models as input for groundwater flow models, we showed that incorporating this surface information is important for being able to predict how contaminants move in groundwater.XU ET AL.

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“…The purpose of the subsidence superstation is to integrate multiple methods to monitor subsidence at a single site-something that has to date rarely happened. Notable exceptions are recent studies in the Venice Lagoon (Zoccarato & Da Lio, 2021) and the Ganges-Brahmaputra Delta (Steckler et al, 2022). Here, we build on this work by means of a dedicated experiment where multiple instruments are located at the same site.…”

Section: 1029/2022jf006718mentioning

confidence: 99%

“…Nevertheless, the most recent assessment report of the Intergovernmental Panel on Climate Change (IPCC‐AR6; Fox‐Kemper et al., 2021) indicates low to medium confidence in projections of vertical land motion (including glacial isostatic adjustment) and stresses the need for more detailed studies at the regional scale. Despite numerous recent efforts to better understand the processes that contribute to coastal subsidence, progress has been hindered by the fact that different measurement techniques sometimes produce seemingly conflicting results (e.g., Brown & Nicholls, 2015; Frederick et al., 2019; Steckler et al., 2022), presenting an obstacle to disentangling subsidence drivers. For example, even separating the effect of anthropogenic processes (e.g., groundwater vs. hydrocarbon extraction) may be challenging (Candela & Koster, 2022).…”

Section: Introductionmentioning

confidence: 99%

Novel Integration of Geodetic and Geologic Methods for High‐Resolution Monitoring of Subsidence in the Mississippi Delta

et al. 2022

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Coastal lowlands and river deltas, which rise less than 10 m above sea level, are particularly vulnerable to the climate-change effects forecast for the 21st century and beyond, including the threat of inundation by accelerating sea-level rise and increases in the severity of tropical storm surges. Most large deltas are receiving insufficient sediment to maintain themselves (Giosan et al., 2014). These threats coincide with a worldwide surge in human population in coastal areas. Coastal population centers include multiple megacities, whose inhabitants exceed 10 million. Many of these coastal megacities are located on river deltas that are also hubs and hot spots for agriculture, fisheries, transportation, and hydrocarbon production. Most deltas are subsiding, in many cases at rates exceeding the rate of sea-level rise (e.g.,

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Synthesis of the distribution of subsidence of the lower Ganges-Brahmaputra Delta, Bangladesh

Cited by 38 publications

References 83 publications

New GNSS and Geological Data From the Indo‐Burman Subduction Zone Indicate Active Convergence on Both a Locked Megathrust and the Kabaw Fault

New GNSS and Geological Data From the Indo‐Burman Subduction Zone Indicate Active Convergence on Both a Locked Megathrust and the Kabaw Fault

Predicting Subsurface Architecture From Surface Channel Networks in the Bengal Delta

Novel Integration of Geodetic and Geologic Methods for High‐Resolution Monitoring of Subsidence in the Mississippi Delta

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