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

Substantial terrestrial gas emissions, such as carbon dioxide (CO2), 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 CO2 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 CO2, and Syabru-Bensi Hydrothermal System (SBHS, Central Nepal) with metamorphic CO2. At both sites, radon fluxes reach exceptionally high values (> 10 Bq m-2 s-1) systematically associated with large CO2 fluxes (> 10 kg m-2 day-1). The significant radon‒CO2 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‒CO2 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.

Effects of dwarfing allele sd1-d originating from 'Dee-geo-woo-gen' and its tall alleles SD1-in and SD1-ja on morphological characteristics concerning dry-matter production and photosynthesis on the genetic background of indica-rice IR36.

sd1-d has been utilized to develop short-culmed indica varieties adaptable to higher fertilizer-applications. Its tall alleles SD1-in and SD1-ja are harbored in indica and japonica subspecies, respectively. SD1-in possesses a higher effect on elongating culm than SD1-ja. The sd1-d of indica IR36 was substituted with SD1-in or SD1-ja through recurrent backcrossing with IR36, and two tall isogenic lines ("5867-36" and "Koshi-36") were developed. IR36, 5867-36 and Koshi-36 were grown in a paddy field, and the effects of sd1-d, SD1-in and SD1-ja on morphological characteristics concerning dry-matter production and photosynthesis were compared mutually. sd1-d diminished dry weight of total brown rice/m2 and total dry matter weights, but enhanced harvest indexes, compared with SD1-in. In IR36, shorter lengths of the first (flag) to third leaves, and more panicle-bearing stems, caused by sd1-d, compared with SD1-in-carrying 5867-36, and erect first leaves, not caused by sd1-d, could construct the canopy structure appropriate for obtaining a high rate of photosynthesis at an optimum LAI. Koshi-36 could be used for a mid-mother line to develop indica varieties adaptable to middle and low fertilizer-applications, due to higher effect of SD1-ja on yielding ability, compared with that of sd1-d, no breaking-type lodging, and resistances to diseases and pests.

Effects of tall alleles SD1-in and SD1-ja to the dwarfing allele sd1-d originating from 'Dee-geo-woo-gen' on yield and related traits on the genetic background of indica IR36 in rice.

sd1-d originating from 'Dee-geo-woo-gen' has been utilized to develop short-culmed indica varieties adaptable to higher fertilizer-application. Its tall alleles SD1-in and SD1-ja are harbored in indica and japonica subspecies, respectively. The sd1-d of indica IR36 was substituted with SD1-in or SD1-ja by recurrent backcrossing with IR36, and two tall isogenic lines ("5867-36" and "Koshi-36") were developed. IR36, 5867-36 and Koshi-36 were grown in a paddy field in three years, and yield and related traits were measured, the effects of SD1-in and SD1-ja on yielding ability and related characteristics were examined on the genetic background of IR 36. SD1-in decreased panicle number per m2 but increased spikelet number per panicle, ripened-grain percentage and 1000-grain weight, compared with sd1-d, resulting in the increase of yield. The increase of 1000-grain weight by SD1-in, caused by the increases of length, width and thickness of grain, was due to the increases of the length and width of lemma. SD1-ja did not significantly affect yield, mainly because the decrease of panicle number per m2 was compensated by the enlarged 1000-grain weight owing to the increase of lemma length. Serious lodging was observed in long-culmed 5867-36, suggesting that sd1-d is indispensable for indica breeding programs.

Author Correction: Widespread ground motion distribution caused by rupture directivity during the 2015 Gorkha, Nepal earthquake.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Responses of earliness and lateness genes for heading to different photoperiods, and specific response of a gene or a pair of genes to short day length in rice.

BACKGROUND: Heading time is an important trait for regional and seasonal adaptabilities in rice, and is controlled by genetic factors in relation with environmental factors, mainly day length and temperature. The following genes controlling heading were examined for their responses to six different environmental conditions involving different day lengths using five early near-isogenic lines (NILs) of T65-R and three late NILs of T65wx: two earliness genes, Ef1 and Efx controlling basic vegetative phase (BVG), and m-Ef1, the enhancer to the former gene; and two lateness genes, Se1-pat(t) and se-pat controlling photo-sensitivity and BVG, respectively. T65-R and T65-T were different accessions of Taichung 65. T65wx is a NIL of T65-T carrying wx. RESULTS: The five early NILs of T65-R were in the order of ER50 (Ef1, Efx, m-Ef1) < ER40 (Ef1, m-Ef1) ≤ ER20 (Ef1, Efx) < ER1 (Ef1) ≤ ER21 (Efx) < T65-R regarding days to heading (DTH) under two spring-sowing and one summer-sowing paddy field (PF) conditions. The three late NILs of T65wx were in the order of LF3 (Se1-pat(t)) ≤ LF2 (Se1-pat(t), se-pat) ≤ T65wx < LF1 (se-pat) under two short-day conditions (10-h photoperiod condition with artificial-light and natural short-day condition from autumn to winter). The NILs and T65wx were in the order of T65wx < LF3 < LF1 < LF2 under the two spring-sowing PF (long day) conditions. T65-R (Ac-ef1) was 2.8 or 5.1 days earlier in DTH than T65-T (ac-ef1) under the two spring-sowing PF conditions. However, T65-R was 19 and 10 days earlier than T65-T under the two short-day conditions. CONCLUSIONS: Earliness gene(s) and their combinations reduced DTH regardless of photoperiod lengths. Se1-pat(t) increased DTH under long-day conditions but decreased it under short-day conditions, while se-pat elongated DTH under both short-day and long-day conditions indicating that se-pat is responsible for BVG. The se-pat increased DTH by adding its effect over that of Se1-pat(t) under long-day conditions. However, this increasing effect of DTH by se-pat was almost completely masked when it coexisted with Se1-pat(t) under the short-day conditions. Notably, the response of Ac-ef1 to day length was found to delay heading under the short-day conditions.

Persistent CO2 emissions and hydrothermal unrest following the 2015 earthquake in Nepal.

Fluid-earthquake interplay, as evidenced by aftershock distributions or earthquake-induced effects on near-surface aquifers, has suggested that earthquakes dynamically affect permeability of the Earth's crust. The connection between the mid-crust and the surface was further supported by instances of carbon dioxide (CO2) emissions associated with seismic activity, so far only observed in magmatic context. Here we report spectacular non-volcanic CO2 emissions and hydrothermal disturbances at the front of the Nepal Himalayas following the deadly 25 April 2015 Gorkha earthquake (moment magnitude Mw = 7.8). The data show unambiguously the appearance, after the earthquake, sometimes with a delay of several months, of CO2 emissions at several sites separated by > 10 kilometres, associated with persistent changes in hydrothermal discharges, including a complete cessation. These observations reveal that Himalayan hydrothermal systems are sensitive to co- and post- seismic deformation, leading to non-stationary release of metamorphic CO2 from active orogens. Possible pre-seismic effects need further confirmation.

Widespread ground motion distribution caused by rupture directivity during the 2015 Gorkha, Nepal earthquake.

The ground motion and damage caused by the 2015 Gorkha, Nepal earthquake can be characterized by their widespread distributions to the east. Evidence from strong ground motions, regional acceleration duration, and teleseismic waveforms indicate that rupture directivity contributed significantly to these distributions. This phenomenon has been thought to occur only if a strike-slip or dip-slip rupture propagates to a site in the along-strike or updip direction, respectively. However, even though the earthquake was a dip-slip faulting event and its source fault strike was nearly eastward, evidence for rupture directivity is found in the eastward direction. Here, we explore the reasons for this apparent inconsistency by performing a joint source inversion of seismic and geodetic datasets, and conducting ground motion simulations. The results indicate that the earthquake occurred on the underthrusting Indian lithosphere, with a low dip angle, and that the fault rupture propagated in the along-strike direction at a velocity just slightly below the S-wave velocity. This low dip angle and fast rupture velocity produced rupture directivity in the along-strike direction, which caused widespread ground motion distribution and significant damage extending far eastwards, from central Nepal to Mount Everest.

Temporal signatures of advective versus diffusive radon transport at a geothermal zone in Central Nepal.

Temporal variation of radon-222 concentration was studied at the Syabru-Bensi hot springs, located on the Main Central Thrust zone in Central Nepal. This site is characterized by several carbon dioxide discharges having maximum fluxes larger than 10 kg m(-2) d(-1). Radon concentration was monitored with autonomous Barasol™ probes between January 2008 and November 2009 in two small natural cavities with high CO(2) concentration and at six locations in the soil: four points having a high flux, and two background reference points. At the reference points, dominated by radon diffusion, radon concentration was stable from January to May, with mean values of 22 ± 6.9 and 37 ± 5.5 kBq m(-3), but was affected by a large increase, of about a factor of 2 and 1.6, respectively, during the monsoon season from June to September. At the points dominated by CO(2) advection, by contrast, radon concentration showed higher mean values 39.0 ± 2.6 to 78 ± 1.4 kBq m(-3), remarkably stable throughout the year with small long-term variation, including a possible modulation of period around 6 months. A significant difference between the diffusion dominated reference points and the advection-dominated points also emerged when studying the diurnal S(1) and semi-diurnal S(2) periodic components. At the advection-dominated points, radon concentration did not exhibit S(1) or S(2) components. At the reference points, however, the S(2) component, associated with barometric tide, could be identified during the dry season, but only when the probe was installed at shallow depth. The S(1) component, associated with thermal and possibly barometric diurnal forcing, was systematically observed, especially during monsoon season. The remarkable short-term and long-term temporal stability of the radon concentration at the advection-dominated points, which suggests a strong pressure source at depth, may be an important asset to detect possible temporal variations associated with the seismic cycle.