Fecal carriage of Extended Spectrum β-Lactamases (ESBL) Producing Escherichia coli and Klebsiella spp. among School Children in Pokhara, Nepal

Extended-spectrum β-lactamases (ESBL) producing microbes in recent years have been a major problem in developing countries like Nepal, with limited treatment options. This study aimed to determine the prevalence of ESBL producing E. coli and Klebsiella spp. in school children in Pokhara, Nepal. The study was conducted from June to October, 2015 at the microbiology laboratory of Manipal Teaching Hospital, Pokhara, Nepal. Antibiotic Susceptibility Test (AST) was done after isolation and identification of bacterial isolates. Then, presence of ESBL enzymes in E. coli and Klebsiella spp. were tested by combination disc diffusion test using cefotaxime and ceftazidime alone and with clavulanic acid. Out of total 309 school children, 211 (68%) bacterial isolates were detected from stool samples. Among them, E. coli and Klebsiella spp. were detected in 97 (46%) and 39 (19%) stool samples respectively. Bacteria isolated from 14 (5%) stool samples were multi-drug resistant (MDR) positive. After applying combined disk method, 88 (29%) isolates were found to be ESBL producer. Emerging prevalence rate of ESBL producing E. coli and Klebsiella spp. are major problem in medical history. Therefore, rapid need of surveillance for effective management of such MDR-strain is required

Pre- and post-seismic deformation related to the 2015, M_w 7.8 Gorkha earthquake, Nepal

We analyze time series from continuously recording GPS stations in Nepal spanning the pre- and post-seismic period associated to the M_w7.8 Gorkha earthquake which ruptured the Main Himalayan Thrust (MHT) fault on April 25th, 2015. The records show strong seasonal variations due to surface hydrology. After corrections for these variations, the time series covering the pre- and post-seismic periods do not show any detectable transient pre-seismic displacement. By contrast, a transient post-seismic signal is clear. The observed signal shows southward displacements consistent with afterslip on the MHT. Using additional data from stations deployed after the mainshock, we invert the time series for the spatio-temporal evolution of slip on the MHT. This modelling indicates afterslip dominantly downdip of the mainshock rupture. Two other regions show significant afterslip: a more minor zone updip of the rupture, and a region between the mainshock and the largest aftershock ruptures. Afterslip in the first ~ 7 months after the mainshock released a moment of [12.8 ± 0.5] × 10^(19) Nm which represents 17.8 ± 0.8% of the co-seismic moment. The moment released by aftershocks over that period of time is estimated to 2.98 × 10^(19) Nm. Geodetically observed post-seismic deformation after co-seismic offset correction was thus 76.7 ± 1.0% aseismic. The logarithmic time evolution of afterslip is consistent with rate-strengthening frictional sliding. According to this theory, and assuming a long-term loading velocity modulated on the basis of the coupling map of the region and the long term slip rate of 20.2 ± 1.1 mm/yr, afterslip should release about 34.0 ± 1.4% of the co-seismic moment after full relaxation of post-seismic deformation. Afterslip contributed to loading the shallower portion of the MHT which did not rupture in 2015 and stayed locked afterwards. The risk for further large earthquakes in Nepal remains high both updip of the rupture area of the Gorkha earthquake and West of Kathmandu where the MHT has remained locked and where no earthquake larger than M_w7.5 has occurred since 1505

Pre- and post-seismic deformation related to the 2015, M_w 7.8 Gorkha earthquake, Nepal

We analyze time series from continuously recording GPS stations in Nepal spanning the pre- and post-seismic period associated to the M_w7.8 Gorkha earthquake which ruptured the Main Himalayan Thrust (MHT) fault on April 25th, 2015. The records show strong seasonal variations due to surface hydrology. After corrections for these variations, the time series covering the pre- and post-seismic periods do not show any detectable transient pre-seismic displacement. By contrast, a transient post-seismic signal is clear. The observed signal shows southward displacements consistent with afterslip on the MHT. Using additional data from stations deployed after the mainshock, we invert the time series for the spatio-temporal evolution of slip on the MHT. This modelling indicates afterslip dominantly downdip of the mainshock rupture. Two other regions show significant afterslip: a more minor zone updip of the rupture, and a region between the mainshock and the largest aftershock ruptures. Afterslip in the first ~ 7 months after the mainshock released a moment of [12.8 ± 0.5] × 10^(19) Nm which represents 17.8 ± 0.8% of the co-seismic moment. The moment released by aftershocks over that period of time is estimated to 2.98 × 10^(19) Nm. Geodetically observed post-seismic deformation after co-seismic offset correction was thus 76.7 ± 1.0% aseismic. The logarithmic time evolution of afterslip is consistent with rate-strengthening frictional sliding. According to this theory, and assuming a long-term loading velocity modulated on the basis of the coupling map of the region and the long term slip rate of 20.2 ± 1.1 mm/yr, afterslip should release about 34.0 ± 1.4% of the co-seismic moment after full relaxation of post-seismic deformation. Afterslip contributed to loading the shallower portion of the MHT which did not rupture in 2015 and stayed locked afterwards. The risk for further large earthquakes in Nepal remains high both updip of the rupture area of the Gorkha earthquake and West of Kathmandu where the MHT has remained locked and where no earthquake larger than M_w7.5 has occurred since 1505

Radon and carbon dioxide around remote Himalayan thermal springs

Additional radon and carbon dioxide flux measurement profiles

Effective radium concentration across the Main Central Thrust in the Nepal Himalayas

International audienceEffective radium concentration (EC Ra) of 622 rock samples from 6 different sites in the Nepal Himalayas was measured in the laboratory using radon accumulation experiments. These sites, located from Lower Dolpo in Western Nepal to Eastern Nepal, are divided into 9 transects which cut across the Main Central Thrust zone (MCT zone) separating low-grade meta-morphic Lesser Himalayan Sequence (LHS) units to the south and higher-grade metamorphic Greater Himalayan Sequence (GHS) units to the north. This boundary remains difficult to define and is the subject of numerous debates. EC Ra values range from 0.03 ± 0.03 to 251.6 ± 4.0 Bq kg À1 , and appear to be representative of the formation and clearly related to the local lithology. For example, for the Upper Trisuli and Langtang Valleys site in Central Nepal, the most studied place with 350 available EC Ra values, LHS rocks are characterized by a mean value of 5.3 ± 1.3 Bq kg À1 while GHS rocks of Formations I and II show significantly lower values with a mean value of 0.69 ± 0.11 Bq kg À1 , thus leading to a LHS/GHS EC Ra ratio of 7.8 ± 2.2. This behavior was systematically confirmed by other transects (ratio of 7.9 ± 2.2 in all other sites), with a threshold EC Ra value, separating LHS from GHS, of 0.8 Bq kg À1 , thus bringing forward a novel method to characterize, within the MCT shear zone, which rocks belong to the GHS and LHS units. In addition, Ulleri augen gneiss, belonging to LHS rocks, occurred in several transects and were characterized by high EC Ra values (17.9 ± 4.3 Bq kg À1), easy to distinguish from the GHS gneisses, characterized by low EC Ra values at the bottom of the GHS, thus providing a further argument to locate the MCT. The measurement of EC Ra data, thus, provides a cost-effective method which can be compared with neodymium isotopic anomalies or estimates of the peak metamorphic temperature. This study, therefore, shows that the measurements of EC Ra provides additional information to discriminate different geological formations, and can be particularly useful in areas where geology mapping is not straightforward or still remains controversial

Tectonic significance of the 2021 Lamjung, Nepal, mid-crustal seismic cluster

International audienceSince the Mw 7.9 Gorkha earthquake of April 25, 2015, the seismicity of central and western Nepalese Himalaya has been monitored by an increasing number of permanent seismic stations. These instruments contribute to the location of thousands of aftershocks that occur at the western margin of the segment of the Main Himalayan Thrust (MHT) that ruptured in 2015. They also help to constrain the location of seismic clusters that originated at the periphery of the fault ruptured by the Gorkha earthquake, which may indicate a migration of seismicity along the fault system. We report here a seismic crisis that followed the Lamjung earthquake, a moderate Mw 4.7 event (ML 5.8, MLv 5.3) that occurred on May 18, 2021, about 30 km west of the Gorkha earthquake epicenter at the down-dip end of the locked fault zone. The study of the hypocentral location of the mainshock and its first 117 aftershocks confirms mid-crustal depths and supports the activation of a 30-40° dipping fault plane, possibly associated with the rupture of the updip end of the MHT mid-crustal ramp. The cluster of aftershocks occurs near the upper decollement of the thrust system, probably in its hanging wall, and falls on the immediate northern margin of a region of the fault that has not been ruptured since the 1344 or 1505 CE earthquake. The spatio-temporal distribution of the first 117 aftershocks shows a typical decrease in the associated seismicity rate and possible migration of seismic activity. Since then, the local seismicity has returned to the pre-earthquake rate and careful monitoring has not revealed any large-scale migration of seismicity towards the locked fault segments

Postseismic deformation following the April 25, 2015 Gorkha earthquake (Nepal): Afterslip versus viscous relaxation

International audienceThe postseismic deformation consecutive to the April 25, 2015 Gorkha earthquake (Mw 7.9) is estimated in this paper based on a cGNSS network installed prior to the earthquake and supplemented by 6 cGNSS stations installed after the main shock. Postseismic displacement are obtained from daily time series corrected for interseismic deformation and seasonal variations. The maximum postseismic displacement is found north of the rupture area, where locally it reached 100 mm between the date of the earthquake and late 2016. The postseismic deformation affects the northern part of the rupture area but not the southern part, along the southern part of the Main Himalayan Thrust (MHT). Three hypotheses for the mechanisms controlling postseismic deformation are tested through numerical simulations of the postseismic time series: (i) viscous relaxation, (ii) afterslip, or (iii) a combination of these two mechanisms. We can exclude postseismic deformation controlled by viscous relaxation of a thick deformation zone along the northern and lower flat of the MHT. However, it is impossible to discriminate between postseismic deformation controlled by either afterslip along the MHT (northern part of the rupture zone, crustal ramp, and lower flat of the MHT) or a combination of afterslip along the MHT (northern part of the rupture zone, crustal ramp) and viscous relaxation controlled by a thin (∼3–4 km thick) low-viscosity body centered on the lower flat of the MHT. The occurrence of afterslip along the northern part of the upper flat of the MHT and its longitudinal variations have been established thanks to the densification of GNSS network by our team presented in this paper

A direct evidence for high carbon dioxide and radon-222 discharge in Central Nepal

International audienceGas discharges have been identified at the Syabru–Bensi hot springs, located at the front of the High Himalaya in Central Nepal, in the Main Central Thrust zone. The hot spring waters are characterized by a temperature reaching 61 °C, high salinity, high alkalinity and δ13C varying from + 0.7‰ to + 4.8‰. The gas is mainly dry carbon dioxide, with a δ13C of − 0.8‰. The diffuse carbon dioxide flux, mapped by the accumulation chamber method, reached a value of 19 000 g m− 2day− 1, which is comparable with values measured on active volcanoes. Similar values have been observed over a two-year time interval and the integral around the main gas discharge amounts to 0.25 ± 0.07 mol s− 1, or 350 ± 100 ton a− 1. The mean radon-222 concentration in spring water did not exceed 2.5 Bq L− 1, exponentially decreasing with water temperature. In contrast, in gas bubbles collected in the water or in the dry gas discharges, the radon concentration varied from 16 000 to 41 000 Bq m− 3. In the soil, radon concentration varied from 25 000 to more than 50 000 Bq m− 3. Radon flux, measured at more than fifty points, reached extreme values, larger than 2 Bq m− 2s− 1, correlated to the larger values of the carbon dioxide flux. Our direct observation confirms previous studies which indicated large degassing in the Himalaya. The proposed understanding is that carbon dioxide is released at mid-crustal depth by metamorphic reactions within the Indian basement, transported along pre-existing faults by meteoric hot water circulation, and degassed before reaching surface. This work, first, confirms that further studies should be undertaken to better constrain the carbon budget of the Himalaya, and, more generally, the contribution of mountain building to the global carbon balance. Furthermore, the evidenced gas discharges provide a unique natural laboratory for methodological studies, and appear particularly important to study as a function of time, especially in relation to the seismic activity. For this purpose, the observed high radon-222 flux is a particularly interesting asset. Indeed, while the relationship between radon and carbon dioxide needs to be better understood, radon measurements, using the available radon sensors, constitute a powerful tool for robust and cost effective long term monitoring

Radon signature of CO2 flux constrains the depth of degassing: Furnas volcano (Azores, Portugal) versus Syabru-Bensi (Nepal Himalayas)

International audienceAbstract Substantial terrestrial gas emissions, such as carbon dioxide (CO 2 ), are associated with active volcanoes and hydrothermal systems. However, while fundamental for the prediction of future activity, it remains difficult so far to determine the depth of the gas sources. Here we show how the combined measurement of CO 2 and radon-222 fluxes at the surface constrains the depth of degassing at two hydrothermal systems in geodynamically active contexts: Furnas Lake Fumarolic Field (FLFF, Azores, Portugal) with mantellic and volcano-magmatic CO 2 , and Syabru-Bensi Hydrothermal System (SBHS, Central Nepal) with metamorphic CO 2 . At both sites, radon fluxes reach exceptionally high values (> 10 Bq m −2 s −1 ) systematically associated with large CO 2 fluxes (> 10 kg m −2 day −1 ). The significant radon‒CO 2 fluxes correlation is well reproduced by an advective–diffusive model of radon transport, constrained by a thorough characterisation of radon sources. Estimates of degassing depth, 2580 ± 180 m at FLFF and 380 ± 20 m at SBHS, are compatible with known structures of both systems. Our approach demonstrates that radon‒CO 2 coupling is a powerful tool to ascertain gas sources and monitor active sites. The exceptionally high radon discharge from FLFF during quiescence (≈ 9 GBq day −1 ) suggests significant radon output from volcanoes worldwide, potentially affecting atmosphere ionisation and climate

Large-scale organization of carbon dioxide discharge in the Nepal Himalayas

International audienceGaseous carbon dioxide (CO 2) and radon-222 release from the ground was investigated along the Main Central Thrust zone in the Nepal Himalayas. From 2200 CO 2 and 900 radon-222 flux measurements near 13 hot springs from western to central Nepal, we obtained total CO 2 and radon discharges varying from 10 À3 to 1.6 mol s À1 and 20 to 1600 Bq s À1 , respectively. We observed a coherent organization at spatial scales of ≈ 10 km in a given region: low CO 2 and radon discharges around Pokhara (midwestern Nepal) and in the Bhote Kosi Valley (east Nepal); low CO 2 but large radon discharges in Lower Dolpo (west Nepal); and large CO 2 and radon discharges in the upper Trisuli Valley (central Nepal). A 110 km long CO 2-producing segment, with high carbon isotopic ratios, suggesting metamorphic decarbonation, is thus evidenced from 84.5°E to 85.5°E. This spatial organization could be controlled by geological heterogeneity or large Himalayan earthquakes