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1.
Soil H2 and CO2 surveys were carried out along seven active faults and around the aftershock region of the 2000 Tottori-ken Seibu earthquake in Japan. Diffuse CO2 effluxes were also measured along one fault and around the 2000 aftershock region. The results show highly variable H2 concentration in space and time and it seems that the maximum H2 concentration at each active fault correlates with fault activity as exemplified by the time of the latest big earthquakes. Even though observed H2 concentrations in four faults were markedly lower than those collected previously in the latter half of the 1970s, it is evident that the higher H2 concentrations in this study are due to the addition of the fault gases. Comparing the chemical composition of trapped gases (H2: 5–20% and CO2/H2: 0.5–12) in fractured rocks of drill cores bored at the Nojima fault, a soil gas sample with the highest H2 concentration showed large amounts of the trapped fault gas, diluted with atmospheric component. The profile experiment across a fracture zone at the Yamasaki fault showed higher H2 concentrations and lower CO2/H2 ratios as was observed in soil gas from the fracture zone. A few days after the 2000 Tottori-kei Seibu earthquake, no CO2 effluxes related to the occurrence of earthquakes were observed at the aftershock region. However, only above the epicenter zone, relatively high H2 concentrations in soil gases were observed.  相似文献   

2.
Soil temperature and gas (CO2 concentration and flux) have been investigated at Merapi volcano (Indonesia) during two inter-eruptive periods (2002 and 2007). Precise imaging of the summit crater and the spatial pattern of diffuse degassing along a gas traverse on the southern slope are interpreted in terms of summit structure and major caldera organization. The summit area is characterized by decreasing CO2 concentrations with distance from the 1932 crater rim, down to atmospheric levels at the base of the terminal cone. Similar patterns are measured on any transect down the slopes of the cone. The spatial distribution of soil gas anomalies suggests that soil degassing is controlled by structures identified as concentric historical caldera rims (1932, 1872, and 1768), which have undergone severe hydrothermal self-sealing processes that dramatically lower the permeability and porosity of soils. Temperature and CO2 flux measurements in soils near the dome display heterogeneous distributions which are consistent with a fracture network identified by previous geophysical studies. These data support the idea that the summit is made of isolated and mobile blocks, whose boundaries are either sealed by depositional processes or used as pathways for significant soil degassing. Within this context, self-sealing both prevents long-distance soil degassing and controls heat and volatile transfers near the dome. A rough estimate of the CO2 output through soils near the dome is 200–230 t day−1, i.e. 50% of the estimated total gas output from the volcano summit during these quiescent periods. On Merapi’s southern slope, a 2,500 m long CO2 traverse shows low-amplitude anomalies that fit well with a recently observed electromagnetic anomaly, consistent with a faulted structure related to an ancient avalanche caldera rim. Sub-surface soil permeability is the key parameter that controls the transfer of heat and volatiles within the volcano, allowing its major tectonic architecture to be revealed by soil gas and soil temperature surveys.  相似文献   

3.
Two stations monitoring concentrations of carbon dioxide and radon in soil gas (Oldřišská and Novy Kostel) and one station monitoring flow of carbon dioxide at a mofette (Soos) have been operated in the area of the West Bohemian earthquake swarms. We present preliminary results obtained on the base of four-year observations. We found that data are not influenced considerably by barometric pressure. Although the CO2 concentration varies greatly, the long-term trends at stations Oldřišská and Novy Kostel are similar, which indicates that the CO2 flow is controlled by common geogenic processes. Also temporal trends of CO2 and Rn concentrations in soil gas at individual stations are analogous. We found diurnal variations of both CO2 concentration in soil gas and the CO2 flow at mofettes due to the earth tides. A response to tides of semi-diurnal period is insignificant in CO2 concentration and only weak in the CO2 flow. We also examined possible pre-seismic, co-seismic and post-seismic effects of the intensive 2008 earthquake swarm on the CO2 concentration at Oldřišská and Novy Kostel, and on the CO2 flow at Soos. However, all potential indications were insignificant and there has not been proven any influence of the swarm on the CO2 concentration as well as on the CO2 flow. Nevertheless, a gradual decrease of amplitudes of diurnal variations before the swarm and the lowest amplitudes during the swarm is a noteworthy phenomenon, which might indicate the strain changes of the rock associated with earthquake swarm.  相似文献   

4.
Soil CO2 concentration data were collected periodically from July 2001 to June 2005 from sampling site grids in two areas located on the lower flanks of Mt. Etna volcano (Paternò and Zafferana Etnea–Santa Venerina). Cluster analysis was performed on the acquired data in order to identify possible groups of sites where soil degassing could be fed by different sources. In both areas three clusters were recognised, whose average CO2 concentration values throughout the whole study period remained significantly different from one another. The clusters with the lowest CO2 concentrations showed time-averaged values ranging from 980 to 1,170 ppm vol, whereas those with intermediate CO2 concentrations showed time-averaged values ranging from 1,400 to 2,320 ppm vol, and those with the highest concentrations showed time-averaged values between 1,960 and 55,430 ppm vol. We attribute the lowest CO2 concentrations largely to a biogenic source of CO2. Conversely, the highest CO2 concentrations are attributed to a magmatic source, whereas the intermediate values are due to a variable mixing of the two sources described above. The spatial distribution of the CO2 values related to the magmatic source define a clear direction of anomalous degassing in the Zafferana Etnea–Santa Venerina area, which we attribute to the presence of a hidden fault, whereas in the Paternò area no such oriented anomalies were observed, probably because of the lower permeability of local soil. Time-series analysis shows that most of the variations observed in the soil CO2 data from both areas were related to changes in the volcanic activity of Mt. Etna. Seasonal influences were only observed in the time patterns of the clusters characterised by low CO2 concentrations, and no significant interdependence was found between soil CO2 concentrations and meteorological parameters. The largest observed temporal anomalies are interpreted as release of CO2 from magma batches that migrated from deeper to shallower portions of Etna’s feeder system. The pattern of occurrence of such episodes of anomalous gas release during the observation period was quite different between the two studied areas. This pattern highlighted an evident change in the mechanism of magma transport and storage within the volcano’s feeder system after June 2003, interpreted as magma accumulation into a shallow (<8 km depth) reservoir.  相似文献   

5.
We describe analytical details and uncertainty evaluation of a simple technique for the measurement of the carbon isotopic composition of CO2 in volcanic plumes. Data collected at Solfatara and Vulcano, where plumes are fed by fumaroles which are accessible for direct sampling, were first used to validate the technique. For both volcanoes, the plume-derived carbon isotopic compositions are in good agreement with the fumarolic compositions, thus providing confidence on the method, and allowing its application at volcanoes where the volcanic component is inaccessible to direct sampling. As a notable example, we applied the same method to Mount Etna where we derived a δ13C of volcanic CO2 between −0.9 ± 0.27‰ and −1.41 ± 0.27‰ (Bocca Nuova and Voragine craters). The comparison of our measurements to data reported in previous work highlights a temporal trend of systematic increase of δ13C values of Etna CO2 from ~ −4‰, in the 1970’s and the 1980’s, to ~ −1‰ at the present time (2009). This shift toward more positive δ13C values matches a concurrent change in magma composition and an increase in the eruption frequency and energy. We discuss such variations in terms of two possible processes: magma carbonate assimilation and carbon isotopic fractionation due to magma degassing along the Etna plumbing system. Finally, our results highlight potential of systematic measurements of the carbon isotopic composition of the CO2 emitted by volcanic plumes for a better understanding of volcanic processes and for improved surveillance of volcanic activity.  相似文献   

6.
At present, using Eddy Covariance (EC) method to estimate the “true value” of carbon sequestration in terrestrial ecosystem arrests more attention. However, one issue is how to solve the uncertainty of observations (especially the nighttime CO2 flux data) appearing in post-processing CO2 flux data. The ratio of effective and reliable nighttime EC CO2 flux data to all nighttime data is relatively low (commonly, less than 50%) for all the long-term and continuous observation stations in the world. Thus, the processing method of nighttime CO2 flux data and its effect analysis on estimating CO2 flux annual sums are very important. In this paper, the authors analyze and discuss the reasons for underestimating nighttime CO2 flux using EC method, and introduce the general theory and method for processing nighttime CO2 flux data. By analyzing the relationship between nighttime CO2 flux and air fraction velocity u*, we present an alternate method, Average Values Test (AVT), to determine the thresholds of fraction velocity (u*c) for screening the effective nighttime CO2 flux data. Meanwhile, taking the data observed in Yucheng and Changbai Mountains stations for an example, we analyze and discuss the effects of different methods or parameters on nighttime CO2 flux estimations. Finally, based on the data of part ChinaFLUX stations and related literatures, empirical models of nighttime respiration at different sites in ChinaFLUX are summarized.  相似文献   

7.
We present an uncertainty analysis of ecological process parameters and CO2 flux components (R eco, NEE and gross ecosystem exchange (GEE)) derived from 3 years’ continuous eddy covariance measurements of CO2 fluxes at subtropical evergreen coniferous plantation, Qianyanzhou of ChinaFlux. Daily-differencing approach was used to analyze the random error of CO2 fluxes measurements and bootstrapping method was used to quantify the uncertainties of three CO2 flux components. In addition, we evaluated different models and optimization methods in influencing estimation of key parameters and CO2 flux components. The results show that: (1) Random flux error more closely follows a double-exponential (Laplace), rather than a normal (Gaussian) distribution. (2) Different optimization methods result in different estimates of model parameters. Uncertainties of parameters estimated by the maximum likelihood estimation (MLE) are lower than those derived from ordinary least square method (OLS). (3) The differences between simulated Reco, NEE and GEE derived from MLE and those derived from OLS are 12.18% (176 g C·m−2·a−1), 34.33% (79 g C·m−2·a−1) and 5.4% (92 g C·m−2·a−1). However, for a given parameter optimization method, a temperature-dependent model (T_model) and the models derived from a temperature and water-dependent model (TW_model) are 1.31% (17.8 g C·m−2·a−1), 2.1% (5.7 g C·m−2·a−1), and 0.26% (4.3 g C·m−2·a−1), respectively, which suggested that the optimization methods are more important than the ecological models in influencing uncertainty in estimated carbon fluxes. (4) The relative uncertainty of CO2 flux derived from OLS is higher than that from MLE, and the uncertainty is related to timescale, that is, the larger the timescale, the smaller the uncertainty. The relative uncertainties of Reco, NEE and GEE are 4%−8%, 7%−22% and 2%−4% respectively at annual timescale. Supported by the National Natural Science Foundation of China (Grant No. 30570347), Innovative Research International Partnership Project of the Chinese Academy of Sciences (Grant No. CXTD-Z2005-1) and National Basic Research Program of China (Grant No. 2002CB412502)  相似文献   

8.
Lake Albano (Alban Hills volcanic complex, Central Italy) is located in a densely populated area near Rome. The deep lake waters have significant dissolved CO2 concentrations, probably related to sub-lacustrine fluid discharges fed by a pressurized CO2-rich reservoir. The analytical results of geochemical surveys carried out in 1989–2010 highlight the episodes of CO2 removal from the lake. The total mass of dissolved CO2 decreased from ∼5.8 × 107 kg in 1989 to ∼0.5 × 107 kg in 2010, following an exponential decreasing trend. Calculated values of both dissolved inorganic carbon and CO2 concentrations along the vertical profile of the lake indicate that this decrease is caused by CO2 release from the epilimnion, at depth <9 m, combined with (1) water circulation at depth <95 m and (2) CO2 diffusion from the deeper lake layers. According to this model, Lake Albano was affected by a large CO2 input that coincided with the last important seismic swarm at Alban Hills in 1989, suggesting an intimate relationship between the addition of deep-originated CO2 to the lake and seismic activity. In the case of a CO2 degassing event of an order of magnitude larger than the one that occurred in 1989, the deepest part of Lake Albano would become CO2-saturated, resulting in conditions compatible with the occurrence of a gas outburst. These results reinforce the idea that a sudden CO2 input into the lake may cause the release of a dense gas cloud, presently representing the major volcanic threat for this densely populated area.  相似文献   

9.
Use of eddy covariance (EC) techniques to map the spatial distribution of diffuse volcanic CO2 fluxes and quantify CO2 emission rate was tested at the Horseshoe Lake tree-kill area on Mammoth Mountain, California, USA. EC measurements of CO2 flux were made during September–October 2010 and ranged from 85 to 1,766 g m−2 day−1. Comparative maps of soil CO2 flux were simulated and CO2 emission rates estimated from three accumulation chamber (AC) CO2 flux surveys. Least-squares inversion of measured eddy covariance CO2 fluxes and corresponding modeled source weight functions recovered 58–77% of the CO2 emission rates estimated based on simulated AC soil CO2 fluxes. Spatial distributions of modeled surface CO2 fluxes based on EC and AC observations showed moderate to good correspondence (R 2 = 0.36 to 0.70). Results provide a framework for automated monitoring of volcanic CO2 emissions over relatively large areas.  相似文献   

10.
Observations of CO2 concentration at a mountaintop in the Colorado Rockies in summer show a large diurnal variability with minimum CO2 concentrations found between 10:00 and 18:00 MST. Simulations are performed with a mesoscale model to examine the effects of atmospheric structure and large-scale flows on the diurnal variability. In the simulations initialized without large-scale winds, the CO2 minimum occurs earlier compared to the observations. Upslope flows play an important role in the presence of this early (pre-noon) minimum while the timing and magnitude of the minimum depend only weakly on the temperature structure. An increase in large-scale flow has a noticeable impact on the diurnal variability with a more gradual decrease in daytime CO2 concentration, similar to summer-averaged observations. From the idealized simulations and a case study, it is concluded that multi-scale flows and their interactions have a large influence on the observed diurnal variability.  相似文献   

11.
There are well coherences between annual averaged air temperatures at every meteorological station along the Qinghai-Xizang railway, and its 10-year moving average correlation coefficient is 0.92. Thus, the regional averaged annual mean temperature series along the Qinghai-Xizang railway (Trw) from 1935 to 2000 are constructed. The investigation is suggested that: Trw had significant responses to the 5-year lagged sunspot cycle length (SCL) and 15-year lagged concentration of atmospheric carbon dioxide (CO2), and the correlation coefficients between them are -0.76 (SCL) and 0.88 (CO2), respectively. The future SCL is predicted by the model of average generated function constructed with its main cycles of 76a, 93a, 108a, 205a and 275a. The result shows that the SCL would be becoming longer in the first half of the 21st century, and then it could be becoming shorter in the second half of the 21st century. Based on the natural change of SCL and the effect of double CO2 concentration, inrw in the 21st century is forecasted. It could warm up about 0.50°C in the first half of the 21st century compared with the last decade of last century. The mean maximum air temperature could be likely about 0.20°C in July and from 0.40°C to 1.10°C in January. The annual air temperature difference would likely reduce 0.3–1.00°C. The probability of above predictions ranges from 0.64 to 0.73.  相似文献   

12.
The source parameters of the M W = 7.6 Olyutorskii earthquake were estimated using the moments of the slip rate function with degrees 1 and 2. The moments were estimated from broadband P-wave records at 52 stations of the worldwide network. The first step was to find a function S(t) for each station; this function is an apparent source time function, i.e., the P-wave slip as radiated by the source toward a station under consideration. The method of empirical Green’s functions was used to estimate S(t). The next step was to calculate the moments of S(t) of degrees 1 and 2 over time and to set up relevant equations to be solved by least squares for the unknown source moments. The horizontal linear source was used as a nonparametric model for calculating the source moments. Haskell’s parametric model was used for further interpretation of the source moments. The resulting estimates are as follows: the source centroid was 13–25 km southwest of the epicenter, the source was 105–120 km long, the source strike was 222°–228°, the rupture velocity was 2.7–3.0 km/s, and the total radiation duration was 24–27 s. These estimates indicate a bilateral rupture dominated by a southwestward sense of rupture propagation. The source characteristics are consistent with the aftershock area geometry and with the focal mechanism, as well as with surface breakage as observed by geologists in the field.  相似文献   

13.
Deterioration of air quality as a result of rapid eco- nomic development in the Yangtze River Delta (YRD) has attracted much scientific and public attention[1―7]. To explore the air quality of a region, measurement of pollutants in locations reflecting the “background” atmospheric conditions of the region is essential. The Regional Baseline Air Quality Monitoring Station of the Chinese Academy of Meteorological Sciences (CAMS) at Lin’an is located in such an area in Zhe- jiang Pro…  相似文献   

14.
—The development of the digital seismic network in the Azores Archipelago during recent years made it possible to obtain the amplitudes (waveform) of recorded motion in a large set of stations. With this new data, maximum amplitudes of the Wood Anderson seismograph are computed, for each station/component, which, together with epicentral distances, allows for the estimation of local magnitude M L . We used data recorded in 8 digital permanent three-component stations, with inter-stations distances up to 300 km, in the period June 1998 – June 2000, corresponding to a set of 1315 events with magnitude (M L or M D ) 2<M<5.8 and epicenters located in the Azores region, to estimate the coefficients of the equation to compute M L , as well as to determine the corrections to be applied to each station. The new set of parameters, formed by attenuation coefficients and station corrections, were introduced in the calculations of the M L , leading to smaller dispersions in the analyzed dataset. We also conclude that the attenuation in the first 150 km is similar to the California values, although higher for longer distances.  相似文献   

15.
The global rate of fossil fuel combustion continues to rise, but the amount of CO2 accumulating in the atmosphere has not increased accordingly. The causes for this discrepancy are widely debated. Particularly, the location and drivers for the interannual variability of atmospheric CO2 are highly uncertain. Here we examine links between global atmospheric CO2 growth rate (CGR) and the climate anomalies of biomes based on (1986–1995) global climate data of ten years and accompanying satellite data sets. Our results show that four biomes, the tropical rainforest, tropical savanna, C4 grassland and boreal forest, and their responses to climate anomalies, are the major climate-sensitive CO2 sinks/sources that control the CGR. The nature and magnitude by which these biomes respond to climate anomalies are generally not the same. However, one common influence did emerge from our analysis; the extremely high CGR observed for the one extreme El Niño year was caused by the response of the tropical biomes (rainforest, savanna and C4 grassland) to temperature.  相似文献   

16.
We have derived, evaluated, and compared two empirical methods for computing duration magnitude M D from 25 short-period vertical component stations of the Northern Morocco Seismic Network (NMSN). M D has been scaled to IGN (Insituto Geograpfico National, Spain) body-wave magnitude (mb IGN ), using a set of 479 shallow (less than 30 km) earthquakes recorded from March 1992 to February 2001, with 2.5 ≤ mb IGN ≤ 5.4. In the first approach: Individual Network Calibration, we determined an individual M D formula for each station. In the second approach: Global Network Calibration, we used a single relationship to compute M Dij (from the jth observation for the i-th earthquake) magnitudes at 25 selected stations as: M Dij = − 0.14 +1.63 log10 ij )+0.031(Δij)+cSta j . Residuals (M Dij − mb IGN ) for both techniques were thereafter deduced. Comparison between the two approaches provided the principal results: (1) The mean correlation between estimated magnitude; M Dij and reference magnitude; mb IGN is about 89.9% for the individual calibration method, and near 95% for global calibration method in which station corrections cSta j were introduced, (2) Residuals (M Dij − mb IGN ) are relatively large, and are ranging between − 0.60 and 0.60 magnitude units, for the individual calibration method, whereas they vary in the range − 0.38 to 0.40, for the global calibration method with corrections; cSta j . (3) A random distribution of residuals (M Dij − mb IGN ) is observed for each station in the case of the individual approach. Thus, the resulting average of these residuals is almost equal to zero. Using a global calibration without corrections results in negative residuals for a group stations and positive residuals for another an group indicating respectively that sites corresponding to these groups have a tendency to underestimate, or overestimate observed magnitude values.  相似文献   

17.
On 27 February 2007, a new eruption occurred on Stromboli which lasted until 2 April. It was characterized by effusive activity on the Sciara del Fuoco and by a paroxysmal event (15 March). This crisis represented an opportunity for us to refine the model that had been developed previously (2002–2003 eruption) and to improve our understanding of the relationship between the magmatic dynamics of the volcano and the geochemical variations in the fluids. In particular, the evaluation of the dynamic equilibrium between the volatiles (CO2 and SO2) released from the magma and the corresponding fluids discharged from the summit area allowed us to evaluate the level of criticality of the volcanic activity. One of the major accomplishments of this study is a 4-year database of summit soil CO2 flux on the basis of which we define the thresholds (low–medium–high) for this parameter that are empirically based on the natural volcanological evolution of Stromboli. The SO2 fluxes of the degassing plume and the CO2 fluxes emitted from the soil at Pizzo Sopra la Fossa are also presented. It is noteworthy that geochemical signals of volcanic unrest have been clearly identified before, during and after the effusive activity. These signals were found almost simultaneously in the degassing plume (SO2 flux) and in soil degassing (CO2 flux) at the summit, although the two degassing processes are shown to be clearly different. The interpretation of the results will be useful for future volcanic surveillance at Stromboli.  相似文献   

18.
A new modified magnitude scale M S (20R) is elaborated. It permits us to extend the teleseismic magnitude scale M S (20) to the regional epicenter distances. The data set used in this study contains digital records at 12 seismic stations of 392 earthquakes that occured in the northwest Pacific Ocean in the period of 1993–2008. The new scale is based on amplitudes of surface waves of a narrow range of the periods (16–25 s) close to the period of 20 s, for distances of 80–3000 km. The digital Butterworth filter is used for processing. On the basis of the found regional features concerning distance dependence for seismic wave attenuation, all the stations of the region have been subdivided into two groups, namely, “continental” and “island-arc.” For each group of stations, its own calibration function is proposed. Individual station corrections are used to compensate for the local features.  相似文献   

19.
The relationship between the critical frequency of the F 2 layer and the atmospheric characteristics has been obtained in a general form. It has been shown that this relation makes it possible to sufficiently accurately describe the daytime values of foF2 while comparing them with the observed monthly median values. Such comparisons were performed, first, for the data of measurements in Irkutsk using the DPS-4 digital ionosonde in 2003–2006 and, second, based on the annual variations in the noon foF2 values at 24 stations of the Northern Hemisphere in 1984. The calculations were performed using the MSIS-86 thermospheric model [Hedin, 1987].  相似文献   

20.
Carbon dioxide (CO2) capture and geologic storage has been postulated as one possible method to stabilize the atmospheric concentration of CO2 by injecting and storing it in deep geologic formations. This issue paper analyzes the viability of capture and geologic storage of becoming an effective method to aid in stabilizing the atmospheric concentration of CO2. It is herein shown that such viability is contingent on overcoming major obstacles that are hydrogeological, technical, and economic in nature. Our analysis indicates that capture and geologic storage is likely to have negligible success in reducing the atmospheric buildup of CO2 in the coming decades. The magnitude of the anthropogenic emissions of CO2 indicates that a transition of the world economy away from reliance on fossil fuels might be the only path to stabilize its atmospheric concentration.  相似文献   

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