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1. Mantle earthquakes in the Himalayan collision zone

   https://doi.org/10.1130/G46378.1  

   Schulte-Pelkum, Vera; Monsalve, Gaspar; Sheehan, Anne F.; Shearer, Peter; Wu, Francis; Rajaure, Sudhir (June 2019, Geology)

   Abstract Earthquakes are known to occur beneath southern Tibet at depths up to ∼95 km. Whether these earthquakes occur within the lower crust thickened in the Himalayan collision or in the mantle is a matter of current debate. Here we compare vertical travel paths expressed as delay times between S and P arrivals for local events to delay times of P-to-S conversions from the Moho in receiver functions. The method removes most of the uncertainty introduced in standard analysis from using velocity models for depth location and migration. We show that deep seismicity in southern Tibet is unequivocally located beneath the Moho in the mantle. Deep seismicity in continental lithosphere occurs under normally ductile conditions and has therefore garnered interest in whether its occurrence is due to particularly cold temperatures or whether other factors are causing embrittlement of ductile material. Eclogitization in the subducting Indian crust has been proposed as a cause for the deep seismicity in this area. Our observation of seismicity in the mantle, falling below rather than within the crustal layer with proposed eclogitization, requires revisiting this concept and favors other embrittlement mechanisms that operate within mantle material. 

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2. Evidence for Large Amounts of Brown Carbonaceous Tarballs in the Himalayan Atmosphere

   https://doi.org/10.1021/acs.estlett.0c00735  

   Yuan, Qi; Xu, Jianzhong; Liu, Lei; Zhang, Aoxing; Liu, Yanmei; Zhang, Jian; Wan, Xin; Li, Mengmeng; Qin, Kai; Cong, Zhiyuan; et al (January 2021, Environmental Science & Technology Letters)

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3. The stop-start control of seismicity by fault bends along the Main Himalayan Thrust

   https://doi.org/10.1038/s43247-021-00153-3  

   Sathiakumar, Sharadha; Barbot, Sylvain (May 2021, Communications Earth & Environment)

   Abstract The Himalayan megathrust accommodates most of the relative convergence between the Indian and Eurasian plates, producing cycles of blind and surface-breaking ruptures. Elucidating the mechanics of down-dip segmentation of the seismogenic zone is key to better determine seismic hazards in the region. However, the geometry of the Himalayan megathrust and its impact on seismicity remains controversial. Here, we develop seismic cycle simulations tuned to the seismo-geodetic data of the 2015M_w7.8 Gorkha, Nepal earthquake to better constrain the megathrust geometry and its role on the demarcation of partial ruptures. We show that a ramp in the middle of the seismogenic zone is required to explain the termination of the coseismic rupture and the source mechanism of up-dip aftershocks consistently. Alternative models with a wide décollement can only explain the mainshock. Fault structural complexities likely play an important role in modulating the seismic cycle, in particular, the distribution of rupture sizes. Fault bends are capable of both obstructing rupture propagation as well as behave as a source of seismicity and rupture initiation. 

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4. Climatic and anthropogenic drivers of a drying Himalayan river

   https://doi.org/10.5194/hess-26-375-2022  

   Penny, Gopal; Dar, Zubair A.; Müller, Marc F. (January 2022, Hydrology and Earth System Sciences)

   Abstract. Streamflow regimes are rapidly changing in many regions of the world. Attribution of these changes to specific hydrological processes and their underlying climatic and anthropogenic drivers is essential to formulate an effective water policy. Traditional approaches to hydrologic attribution rely on the ability to infer hydrological processes through the development of catchment-scale hydrological models. However, such approaches are challenging to implement in practice due to limitations in using models to accurately associate changes in observed outcomes with corresponding drivers. Here we present an alternative approach that leverages the method of multiple hypotheses to attribute changes in streamflow in the Upper Jhelum watershed, an important tributary headwater region of the Indus basin, where a dramatic decline in streamflow since 2000 has yet to be adequately attributed to its corresponding drivers. We generate and empirically evaluate a series of alternative and complementary hypotheses concerning distinct components of the water balance. This process allows a holistic understanding of watershed-scale processes to be developed, even though the catchment-scale water balance remains open. Using remote sensing and secondary data, we explore changes in climate, surface water, and groundwater. The evidence reveals that climate, rather than land use, had a considerably stronger influence on reductions in streamflow, both through reduced precipitation and increased evapotranspiration. Baseflow analyses suggest different mechanisms affecting streamflow decline in upstream and downstream regions, respectively. These findings offer promising avenues for future research in the Upper Jhelum watershed, and an alternative approach to hydrological attribution in data-scarce regions. 

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5. Differences between the central Andean and Himalayan orogenic wedges: A matter of climate

   https://doi.org/10.1016/j.epsl.2023.118216  

   DeCelles, Peter G.; Carrapa, Barbara (August 2023, Earth and Planetary Science Letters)