Evidence of the 1762 Arakan and Prior Earthquakes in the Northern Sunda Subduction

The objective of this dissertation is to understand the seismic hazard associated with Arakan segment of the northern Sunda subduction along SE Bangladesh. In order to do that, it is necessary to document geologic evidence for the 1762 Arakan earthquake and prior events, to help estimate the recurrence interval (repeat time) for that earthquake. Historical records described that the 1762 earthquake caused extensive damage along the Arakan segment of the Sunda subduction system. But the geologic evidence for the earthquake farther north is necessary to better understand its associated seismic hazard to the densely populated nation of Bangladesh. This dissertation presents the results obtained from U/Th dating of the dead and live coral microatolls including their elevations measured by high precision GPS from the Saint Martin’s Island, DEM analysis and elevation of terraces from Teknaf coast and fault dislocation modeling based on the data obtained from the Saint Martin’s Island and Teknaf. Coral microatolls from Saint Martin’s island documents the evidence of the 1762 and prior earthquakes. The U/Th ages documents strong evidence of microatoll die offs related to the 1762 earthquake. The \u3e2 m elevation difference between the dead microatolls and present-day living corals suggest that the microatolls died due to the coseismic uplift of 1762 Arakan earthquake. This dissertation also provides evidence for two additional earthquakes taking place in ~700 and ~1140 C.E. which suggests an earthquake recurrence interval of ~500 years. Geomorphic studies documented three terraces along the coast of Teknaf. Several marine terraces have been previously documented along the west coast of Myanmar. The youngest of these terraces has been correlated to the coseismic uplift of 1762 Arakan along the Myanmar coast. The terraces along the coast of Teknaf are characterized by flat to semi-flat surfaces followed by sharp topographic rises. DEM (Digital Elevation System) analysis and GPS (Global Positioning System) survey documented 2 to 3 terraces. Among these three, the youngest terrace is possibly linked to the 1762 Arakan Earthquake but the ages have not been verified. Modeling using the data obtained from Saint Martin’s Island, Teknaf and other published articles (for the west coast of Teknaf) suggest a fault dipping at 10-15° to the northeast. The result of coseismic slip inversion shows 15 - 25 m of reverse slip along the Arakan rupture segment, which was accommodated by the upper plate failure. Based on our results from coral microatolls, terraces and the modeling study, this dissertation suggests that this segment of the Arakan collision zone has the potential to cause a future earthquake of Mw\u3e8 which can produce a devastating effect to the inhabitants of Bangladesh, Myanmar and Eastern India

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

Deltas, the low-lying land at river mouths, are sensitive to the delicate balance between sea level rise, land subsidence and sedimentation. Bangladesh and the Ganges-Brahmaputra Delta (GBD) have been highlighted as a region at risk from sea-level rise, but reliable estimates of land subsidence have been limited. While early studies suggested high rates of relative sea-level rise, recent papers estimate more modest rates. Our objective is to better quantify the magnitude, spatial variability, and depth variation of sediment compaction and land subsidence in the lower GBD to better evaluate the processes controlling them and the pattern of relative sea level rise in this vulnerable region. We combine subsidence and compaction estimates from hand-drilled tube wells and historic sites (1–5 mm/y), GNSS and river gauges (4–8 mm/y) and RSET-MH and borehole vertical strainmeters (9–10 mm/y) in SW Bangladesh. The differences between the different types of measurements reflect the different timescales, spatial distribution and depth sensitivity of the different observations. Rates are lower for times >300y providing data on the timescale of compaction. We also observe differences related to the degree to which different devices measure shallow and deep subsidence. Higher values reflect a greater component of subsidence from young shallow deposits from soil compaction and organic matter degradation. Thus, we observe different rates for different environments and physical settings. These differences indicate that in planning adaptation for rising sea level, hard construction with a solid foundation may experience different subsidence rates than open fields or reclaimed land with recent natural or anthropogenic sedimentation. Significance statement: Land subsidence increases the impact of sea level rise. We combine six different types of measurements that examine land subsidence in coastal Bangladesh. The results show that causes of subsidence, including compaction of the sediments varies both spatially and with depth, and that compaction and organic matter degradation from young shallow deposits is a significant contribution to subsidence. This suggests that hard construction with a solid foundation, such as buildings and embankments, may experience a lower subsidence rates than open fields or reclaimed land with recent natural or anthropogenic sedimentation

Chemical and environmental vector control as a contribution to the elimination of visceral leishmaniasis on the Indian subcontinent: cluster randomized controlled trials in Bangladesh, India and Nepal

<p>Abstract</p> <p>Background</p> <p>Bangladesh, India and Nepal are working towards the elimination of visceral leishmaniasis (VL) by 2015. In 2005 the World Health Organization/Training in Tropical Diseases launched an implementation research programme to support integrated vector management for the elimination of VL from Bangladesh, India and Nepal. The programme is conducted in different phases, from proof-of-concept to scaling up intervention. This study was designed in order to evaluate the efficacy of the three different interventions for VL vector management: indoor residual spraying (IRS); long-lasting insecticide treated nets (LLIN); and environmental modification (EVM) through plastering of walls with lime or mud.</p> <p>Methods</p> <p>Using a cluster randomized controlled trial we compared three vector control interventions with a control arm in 96 clusters (hamlets or neighbourhoods) in each of the 4 study sites: Bangladesh (one), India (one) and Nepal (two). In each site four villages with high reported VL incidences were included. In each village six clusters and in each cluster five households were randomly selected for sand fly collection on two consecutive nights. Control and intervention clusters were matched with average pre-intervention vector densities.</p> <p>In each site six clusters were randomly assigned to each of the following interventions: indoor residual spraying (IRS); long-lasting insecticide treated nets (LLIN); environmental management (EVM) or control. All the houses (50-100) in each intervention cluster underwent the intervention measures. A reduction of intra-domestic sand fly densities measured in the study households by overnight US Centres for Disease Prevention and Control light trap captures (that is the number of sand flies per trap per night) was the main outcome measure.</p> <p>Results</p> <p>IRS, and to a lesser extent EVM and LLINs, significantly reduced sand fly densities for at least 5 months in the study households irrespective of type of walls or whether or not people shared their house with cattle. IRS was effective in all sites but LLINs were only effective in Bangladesh and India. Mud plastering did not reduce sand fly density (Bangladesh study); lime plastering in India and one Nepali site, resulted in a significant reduction of sand fly density but not in the second Nepali site.</p> <p>Conclusion</p> <p>Sand fly control can contribute to the regional VL elimination programme; IRS should be strengthened in India and Nepal but in Bangladesh, where vector control has largely been abandoned during the last decades, the insecticide treatment of existing bed nets (coverage above 90% in VL endemic districts) could bring about an immediate reduction of vector populations; operational research to inform policy makers about the efficacious options for VL vector control and programme performance should be strengthened in the three countries.</p

Locked and loading megathrust linked to active subduction beneath the Indo-Burman Ranges

The Indo-Burman mountain rangesmarkthe boundary between the Indian and Eurasian plates, north of the Sumatra–Andaman subduction zone. Whether subduction still occurs along this subaerial section of the plate boundary, with 46mm/yr of highly oblique motion, is contentious. About 21mm/yr of shear motion is taken up along the Sagaing Fault, on the eastern margin of the deformation zone. It has been suggested that the remainder of the relative motion is taken up largely or entirely by horizontal strike-slip faulting and that subduction has stopped. Here we present GPS measurements of plate motions in Bangladesh, combined with measurements from Myanmar and northeast India, taking advantage of a more than 300 km subaerial accretionary prism spanning the Indo-Burman Ranges to the Ganges–Brahmaputra Delta. They reveal 13–17mm/yr of plate convergence on an active, shallowly dipping and locked megathrust fault. Most of the strike-slip motion occurs on a few steep faults, consistent with patterns of strain partitioning in subduction zones. Our results strongly suggest that subduction in this region is active, despite the highly oblique plate motion and thick sediments. We suggest that the presence of a locked megathrust plate boundary represents an underappreciated hazard in one of the most densely populated regions of the world

An assessment of the accuracy of the VGOS geodetic products

American Geophysical Union (AGU) Fall Meeting, 13-17 December 2021, New OrleansThe next-generation VLBI system called VGOS (VLBI Global Observing System) is now operational. A network of 8 VGOS stations has been observing bi-weekly since 2019 under the auspices of the International VLBI Service for Geodesy and Astrometry (IVS) for the creation of standard geodetic products. Moreover, a subset of 2-4 of those VGOS stations has also been observing, starting in 2020, in a VLBI Intensives-like mode to assess the feasibility of earth¿s rotation (UT1) estimation using VGOS. Intensives are VLBI observations that are run on a daily basis using a single baseline, for instance, between Kokee Park Geophysical Observatory, Hawaii, and Wettzell Observatory, Germany, with the goal of near-real time monitoring of UT1. We will describe the VGOS observations, correlation, post-processing, and preliminary geodetic results, including UT1. We will compare the VGOS estimates to estimates from legacy VLBI and other geodetic techniques such as GNSS, when and where possible, to draw some conclusions on the precision and accuracy of the VGOS estimate

The Parkinson’s Disease-Associated H50Q Mutation Accelerates α‑Synuclein Aggregation <i>in Vitro</i>

α-Synuclein (α-Syn) aggregation is directly linked with Parkinson’s disease (PD) pathogenesis. Here, we analyzed the aggregation of newly discovered α-Syn missense mutant H50Q <i>in vitro</i> and found that this mutation significantly accelerates the aggregation and amyloid formation of α-Syn. This mutation, however, did not alter the overall secondary structure as suggested by two-dimensional nuclear magnetic resonance and circular dichroism spectroscopy. The initial oligomerization study by cross-linking and chromatographic techniques suggested that this mutant oligomerizes to an extent similar to that of the wild-type α-Syn protein. Understanding the aggregation mechanism of this H50Q mutant may help to establish the aggregation and phenotypic relationship of this novel mutant in PD