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1.
Since late 2002, a continuous automatic monitoring network is operating in Tuscany, Central Italy, to investigate the geochemical response of selected aquifers to local seismic activity. The monitoring is aimed at identifying possible earthquake geochemical precursors. The network is currently constituted by six stations, all equipped with sensors for the measurement of temperature, pH, redox potential, electrical conductivity, CO2 and CH4 dissolved concentration, that have been installed in the areas of highest seismic risk of the region. By combining geochemical data gathered from the automatic station of Gallicano (Garfagnana, Northern Tuscany), and obtained via chemical analyses of spring water samples collected during periodic field surveys in the area surrounding this station, the most significant aspects of the deep fluid circulation paths feeding the Gallicano thermo-mineral system have been investigated, and the geochemical baseline of the Gallicano spring defined. The CO2 continuous signal recorded by the Gallicano automatic station has been then processed over the period 2003–2013 in the search for anomalies possibly related to local seismic activity. A substantial anomaly in CO2 content has been observed at Gallicano in conjunction with the Alpi Apuane earthquake (M = 5.2) of 21 June 2013.  相似文献   

2.
Rapid sample preparation and measurement protocols for optically stimulated luminescence (OSL) dating have been investigated as a method of increasing the throughput of samples (e.g. Roberts et al. 2009). Here, we investigate the potential of dating samples treated using only hydrochloric acid (HCl) for providing accurate range-finder ages for quartz. The equivalent dose (De) is underestimated for older samples using a standard single-aliquot regenerative-dose (SAR) protocol, but measurement of the post-IR OSL signal (e.g. Roberts and Wintle, 2003) provides De estimates within 15% of the ‘target fully prepared De’ for two-thirds of samples. The application of a standardised growth curve (SGC) is also investigated. For these dune samples, the most efficient preparation and measurement procedure from which accurate De estimates can be obtained is treatment with HCl-only, measurement of the natural and regenerative post-IR OSL signal, and calculation using a region-independent SGC. A slightly longer protocol incorporating an additional preparation stage of heavy liquid density separation can be used to improve De estimates in samples where feldspar-contamination is thought to be particularly problematic. In practice, these time savings of days to weeks in the preparation and measurement protocols mean that a large number of samples can first be rapidly treated with HCl, the post-IR blue OSL signal measured using a shortened double-SAR protocol, and De calculated by applying an independent SGC before then deciding which samples require full preparation and measurement, rather than the inefficiency of committing time and resources to all samples if this is unnecessary for the context of a particular suite of samples. The potential of this rapid preparation and measurement protocol is discussed in relation to sand dune dating studies.  相似文献   

3.
A new continuous monitoring system has been developed for the measurement of volcanic gas from the steam well located 3 km north from the summit of Izu-Oshima volcano, Japan. After removing the water vapor using three sequential dehydration methods, CO2 and SO2 contents are measured using IR sensors, and O2 and H2 using a zirconia sensor and a semiconductor sensor, respectively. This system has been in operation without any significant trouble for 3 years.The dehydrated volcanic gas from the well consists of a mixture of CO2, O2 and N2. A decreasing trend of the CO2 content was observed from 1995 to 1998 together with a decrease of volcanic activity. Seasonal changes have also been observed in CO2 and O2 contents, CO2 being higher and O2 lower in summer, which suggests larger contribution of magmatic components in summer. While changes in short-term variation in CO2 and O2 are influenced by atmospheric pressure changes; the CO2 content correlates inversely with atmospheric pressure unlike O2 with some hours delay. In contrast, the H2 content increased intermittently up to 1200 ppm one to several hours after a sudden drop in the atmospheric pressure and without any apparent correlation with seasonal changes.This system allows us to study temporal variation in chemical composition of volcanic gas during quiescent periods of volcanic activity of Izu-Oshima volcano, and might help us detect anomalous changes before future eruptive events.  相似文献   

4.
Data on the distribution of fCO2 were obtained during a cruise in the Aegean Sea during February 2006. The fCO2 of surface water (fCO2sw) was lower than the atmospheric fCO2 (fCO2atm) throughout the area surveyed and ΔfCO2 values varied from ?34 to ?61 μatm. The observed under-saturation suggests that surface waters in the Aegean represent a sink for atmospheric CO2 during the winter of 2006. Higher fCO2sw values were recorded in the ‘less warm’ and ‘less saline’ shallow northernmost part of the Aegean Sea implying that the lower seawater temperature and salinity in this area play a crucial role in the spatial distribution of fCO2sw.A first estimate of the magnitude of the air–sea CO2 exchange and the potential role of the Aegean Sea in the transfer of atmospheric CO2 was also obtained. The air–sea CO2 fluxes calculated using different gas transfer formulations showed that during February 2006, the Aegean Sea absorbs atmospheric CO2 at a rate ranging from ?6.2 to ?11.8 mmol m?2 d?1 with the shipboard recorded wind speeds and at almost half rate (?3.5 to ?5.5 mmol m?2 d?1) with the monthly mean model-derived wind speed. Compared to recent observations from other temperate continental shelves during winter period, the Aegean Sea acts as a moderate to rather strong sink for atmospheric CO2.Further investigations, including intensive spatial and temporal high-resolution observations, are necessary to elucidate the role of the Aegean Sea in the process of transfer of atmospheric CO2 into the deep horizons of the Eastern Mediterranean.  相似文献   

5.
With some special adaptations the technique of matrix isolation followed by detection through electron paramagnetic resonance (EPR) can also be used for the measurement of atmospheric radical concentrations. A light weight cryogenic sampling device has been constructed. It uses condensation of atmospheric CO2 or H2O at 77 K for matrix formation and trapping of the radicals. The sampler has been flown on a balloon for stratospheric sampling. First data on stratospheric, HO2 and NO2 at 32 km altitude have been obtained on a flight on 8 August 1976 and will be reported.  相似文献   

6.
Earthquake early warning systems have been developed to help minimize the loss of life and other damages resulting from catastrophic earthquakes. In the past several decades, these systems have evolved to function using a variety of methodologies. This study introduces an onsite system developed from a correlation between the precursor measurement (Pd3) and the peak ground acceleration (PGV) from 780 historical earthquake events recorded in Taiwan, Japan and South California. The study analyzes and integrates the uncertainty of the onsite system, establishing the statistical relationship between the PGV forecast, the Pd3 precursor, and the exceedance probability (PE). A method is presented for forecasting the PGV by scaling the Pd3. Furthermore, this study also suggests a decision-making model to determine whether or not the early warning notification should be issued, based on factors such as the uncertainty of the early warning system, the magnitude of the precursor, and warning recipient characteristics.  相似文献   

7.
Accurate modeling of storage of carbon dioxide (CO2) in heterogeneous aquifers requires experiments of the capillary pressure as function of temperature and pressure. We present a method with which static drainage and imbibition capillary pressures can be measured continuously as a function of saturation at various temperature (T) and pressure (P) conditions. The measurements are carried out at (T, P) conditions of practical interest. Static conditions can be assumed as small injection rates are applied. The capillary pressure curves are obtained for the unconsolidated sand–distilled water–CO2 system. The experimental results show a decrease of drainage and imbibition capillary pressure for increasing CO2 pressures and pronounced dissolution rate effects for gaseous CO2. Significant capillary pressure fluctuations and negative values during imbibition are observed at near critical conditions. The measurement procedure is validated by a numerical model that simulates the experiments.  相似文献   

8.
The NASA/Goddard Space Flight Center two-dimensional (GSFC 2D) photochemical transport model has been used to study the influence of thermospheric NO on the chemical balance of the middle atmosphere. Lower thermospheric NO sources are included in the GSFC 2D model in addition to the sources that are relevant to the stratosphere. A time series of hemispheric auroral electron power has been used to modulate the auroral NO production in the auroral zone. A time series of the Ottawa 10.7-cm solar flux index has been used as a proxy to modulate NO production at middle and low latitudes by solar EUV and soft X-rays. An interhemispheric asymmetry is calculated for the amounts of odd nitrogen in the polar stratosphere. We compute a <∼3% enhancement in the odd nitrogen (NOy=N, NO, NO2, NO3, N2O5, BrONO2, ClONO2, HO2NO2, and HNO3) budget in the north polar stratosphere (latitude > 50°) due to thermospheric sources, whereas we compute a <∼8% enhancement in the NOy budget in the south polar stratosphere (latitude > 50°).  相似文献   

9.
In this paper, we discussed the influence of the initial tectonic stress on the relative measurement value of the ground stress when a long cylindrical straingauge is used in the viscoelastic media. We simulate the whole system consisting of the stratum, cement ring and the straingauge cylinder with a three-layer-medium model and obtain the solution of radial displacement on the inner wall of the straingauge under the action of initial tectonic stress by using the correspondence principle. The result showes: 1) The influence of initial stress making of the radial displacement on the inner wall of the straingauge increases gradually with time at a gradually reduced rate and tends to a certain value eventually; 2) The principal stress with a magnitude of [C 0+C 1 exp (?ω 1t)+C 2 exp (?w 2 t]σ 10 in the opposite direction of initial stress will be superimposed to the measuring result of stress change without considering the initial stress. whereC 0,C 1,C 2 andω 1,ω 2 are related only to the mechanical property of the stratum,σ i0 (i=1, 2) are the two principal components of the initial tectonic stress. It is pointed out that the initial tectonic stress affects obviously on the measurement of the relative change of ground stress in the cases of soft strata and high initial stress.  相似文献   

10.
In January 1989 we observed submarine eruptions on the summit of Macdonald volcano during a French-German diving programme with the IFREMER submersible Cyana. Gas-streaming of large amounts of CH4, CO2 and SO2 from summit vents, inferred from water column anomalies and observed by submersible, was accompanied on the sea surface by steam bursts, turbulence, red-glowing gases, and black bubbles comprising volcanic ash, sulphur and sulphides. Chloride depletion of water sampled on the floor of an actively degassing summit crater suggests either boiling and phase separation or additions of magmatic water vapour. Submersible observations, in-situ sampling and shipboard geophysical and hydrographic measurements show that the hydrothermal system of this hotspot volcano is distinguished by the influence of magmatic gases released from its shallow summit.  相似文献   

11.
The melting curves of the fluorides ZnF2 and NiF2 (rutile structure), CaF2, SrF2 and BaF2 (fluorite structure), and of the fluoroberyllates Na2BeF4 and Li2BeF4 have been studied at pressures ? 40 kbar by differential thermal analysis in a piston-cylinder high-pressure device. The initial slopes (dTm/dP)0 of these melting curves are respectively 7.2, 5.8, 16.7, 15.2, 15.7, 15.1 and <0°C/kbar. A new Li2BeF4 polymorph, apparently of the olivine structure type, is stable at pressures > 10 kbar and its melting curve has an average slope of ～6.7°C/kbar. These new data and those for SiO2, BeF2, GeO2, LiF and MgF2, recently studied by Jackson, are combined with existing data for elements, ionic compounds and silicates to assess the influence of crystal structure, molar volume and the nature of interatomic bonding on the initial slopes of melting curves. It is found that the entropy of fusion (ΔSm) is primarily a function of crystal structure while the volume change on fusion (ΔVm) is controlled by crystal molar volume within each isostructural series. Such systematics have recently facilitated estimation of the initial slopes of the melting curves of periclase and stishovite. New and existing melting data for silicates and their analogues have been analysed and a systematic dependence of (dTm/dP)0 on SiO2 concentration has been demonstrated. Possible implications of this trend for partial melting of upper-mantle garnet lherzolite are illustrated. Finally, the use of the traditional silicate-germanate and oxide-fluoride modelling schemes is reviewed in the light of information from this present study.  相似文献   

12.
The structure, configuration, dynamics, and solar sources of the near-Earth MHD disturbance of the solar wind on November 20, 2003, is considered. The disturbances of October 24 and November 22 after flares from the same AR 10484 (10501) are compared. The velocity field in the leading part of the sporadic disturbance is for the first time studied in the coordinate system stationary relative to the bow shock. A possible scenario of the physical processes in the course of this solar-terrestrial storm is discussed in comparison with the previously developed scenario for the storm of July 15, 2000. It has been indicated that (1) the near-Earth disturbance was observed at the sector boundary (HCS) and in its vicinities and (2) the disturbance MHD structure included: the complicated bow shock, wide boundary layer with reconnecting fields at a transition from the shock to the magnetic cloud, magnetic cloud with a magnetic cavity including packed substance of an active filament, and return shock layer (supposedly). It has been found out that the shock front configuration and the velocity field are reproduced at an identical position of AR and HCS relative to the Earth on November 20 and 24. It has been indicated that the maximal magnetic induction in the cloud satisfied the condition B m = (8πn 1 m p)1/2(D ? NV1), i.e., depended on the dynamic impact on the cloud during all three storms [Ivanov et al., 1974]. When the disturbance was related to solar sources, the attention has been paid to the parallelism of the axes of symmetry of the active filament, transient coronal hole, coronal mass ejection, zero line of the open coronal field (HCS), and the axis of the near-Earth magnetic cloud: the regularity previously established in the scenario of the storm of July 15, 2000 [Ivanov et al., 2005]. It has been indicated that the extremely large B m value in the cloud of October 20 was caused by a strong suppression of the series of postflare shocks reflected from the heliospheric streamer.  相似文献   

13.
The ion microprobe at Johnson Space Center has been calibrated for in situ water determinations on a 10-μm scale over the range 0.2 wt.% H2O to 1.8, 6.8, and 3.7 wt.%, for basaltic, albitic, and rhyolitic glasses, respectively. The basalt glass calibration curve differs substantially from those of albite and rhyolite glasses, indicating a need to carefully match composition and/or melt structure between H2O standards and unknowns.A value for the diffusivity of water as a function of concentration and time has been calculated from water diffusion profiles measured in rhyolite glasses prepared at 850°C and 700 barsPt(H2O) [1]. Transient diffusion into a semi-infinite medium is described by the equation:?(φ/2)?¸/?φ=?(Dw?¸/?φ)/?φ #x003B8;=1, φ=0, θ→ 0, θ→∞, wherex =distance from the cylinder edge,t =time,C0 =initial concentration,Cs =concentration at the edge,C =concentration at x,θ = C ? C0/Cs ? C0,φ = x/t1/2, andDw =diffusivity of water. An iterative technique has been used to calculate solutions to the diffusion equation as a function ofDw [2]. Comparison of these solutions with the ion probe data indicate that, for0.2wt.% ≤ C ≤ 3.7wt.%H2O,Dw can be described by an exponential function of θ, of the formDw = D0exp(bθ), withD0 (i.e.,Dw at 0.2%) = (0.8?2.2) × 10?8 cm2/s and2 ≤ b ≤ 4.  相似文献   

14.
Repeat times of strong shallow mainshocks have been determined by the use of instrumental and historical data for 68 seismogenic sources in the Aegean and surrounding area (34°N–43°N, 18°E–30°E). For 49 of these sources at least two interevent times (three mainshocks) are available for each source. By using the repeat times for these 49 sources the following relation has been determined: $$\log T_t = 0.36M_{\min } + 0.35M_p + a$$ whereT t is the repeat time, measured in years,M p the surface wave magnitude of the preceding mainshock,M min the magnitude of the smallest earthquake considered and “a” parameter which varies from source to source. A multilinear correlation coefficient equal to 0.89 was determined for this relation. By using the same repeat times for the 49 seismogenic sources, the following relation has been determined between the magnitude,M f , of the following mainshock andM min andM p . $$M_f = 0.95M_{\min } - 0.49M_p + m$$ wherem is a constant which varies from source to source. A multilinear correlation coefficient equal to 0.80 was found for this relation. The model expressed by these two relations is represented by a scheme of a time variation of stress under constant tectonic loading. In this scheme, the maximum stress values during the different seismic cycles fluctuate around a value, τ1, in a relatively narrow stress interval, expressing the high correlation coefficient of the relation between LogT andM p . On the contrary, the minimum stress values fluctuate around a value, τ2, in a much broader stress interval. However, each of these minimum stress values becomes lower or higher than τ2 if the previous one is higher or lower than τ2, respectively, expressing the negative correlation betweenM f andM p .  相似文献   

15.
The geomagnetic and auroral response to the variations in the solar wind dynamic pressure (Pd) are investigated in the periods of positive values of the IMF B z component. It is shown that the growth of Pd results in the intensification of luminosity along the auroral oval and in the poleward expansion of the poleward boundary of luminosity (PBL) in the nightside part of the oval by ～7° in latitude at a velocity of ～0.5 km/s and is accompanied by an enhancement of the DP2-type current system. A decrease in Pd, accompanied by an abrupt reversal of the IMF B y polarity from positive to negative, results in an enhancement of the westward electrojet and in a poleward shift of PBL and electrojet center. The conclusion has been made that the available three types of auroral response to Pd variations differ in the azimuthal velocity of the luminosity region or particle precipitation along the auroral oval: V 1 ～ 30–40 km/s, V 2 ～ 10, and V 3 ～ 1 km/s.  相似文献   

16.
The hardware complex that was produced by OOO Polynom, Khabarovsk, for registration of the level, temperature, and electrical conductivity of ground water in wells and meteorological parameters (atmospheric pressure, air temperature) at a measurement frequency from 5 min to 1 h is described. The equipment is installed in the wells of Kamchatka and has been used for several years to register variations caused by earthquakes in the parameters of ground waters. Different variations in measured parameters of ground waters due to strong earthquakes of February 28, 2013, M W = 6.8 and May 24, 2013, M W = 8.3 are registered with this equipment in wells YuZ-5 and E-1. The registered variations and their systematization are described taking into account the mechanisms of a seismic impact on the state of the well–water-saturated rock system.  相似文献   

17.
A preliminary study of b value of rocks with two kinds of structural models has been made on the base of a new acoustic emission recording system. It shows that b value of the sample decreases obviously when the sample with compressive en echelon faults changes into a tensile one after interchange occurs between stress axis σ 1 and σ 2. A similar experiment is observed when the sample with tensile en echelon faults changes into that with a bend fault after two segments of the en echelon fault linking up. These facts indicate that the variation of b value may contain the information of the regional dominant structural model. Therefore, b-value analyses could be a new method for studying regional dominant structural models.  相似文献   

18.
A series of undrained cyclic direct simple shear tests, which used a soil container with a membrane reinforced with stack rings to maintain the K0 condition and integrated bender elements for shear wave velocity measurement, were performed to study the liquefaction characteristics of gap-graded gravelly soils with no fines content. The intergrain state concept was employed to categorize gap-graded sand–gravel mixtures as sand-like, gravel-like, and in-transition soils, which show different liquefaction characteristics. The testing results reveal that a linear relationship exists between the shear wave velocity and the minor fraction content for sand–gravel mixtures at a given skeleton void ratio of the major fraction particles. For gap-graded gravelly sand, the gravel content has a small effect on the liquefaction resistance, and the cyclic resistance ratio (CRR) of gap-graded gravelly sands can be evaluated using current techniques for sands with gravel content corrections. In addition, the results indicate that the current shear wave velocity (Vs) based correlation underestimates the liquefaction resistance for Vs values less than 160 m/s, and different correlations should be proposed for sand-like and gravel-like gravelly soils. Preliminary modifications to the correlations used in current evaluations of liquefaction resistance have thus been proposed.  相似文献   

19.
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20.
—A comparison of isoplanatic angles θ 0 derived from (1) balloon-borne in situ measurements of the index of refraction structure constant (C n 2) profiles and (2) ground-based optical measurements of stellar intensity fluctuations using an isoplanometer is presented. Concurrent data taken over a six-day period in the spring of 1986 show reasonably good agreement between the mean values determined by the two methods. Comparisons in light of meteorological conditions suggest an isoplanatic angle behavior consistent with the Kelvin-Helmholtz instability where the best correlation was found between the optically-measured isoplanatic angle and the layer-averaged wind shear. Differences between the two measurement methods are largest for isoplanometer azimuth angles perpendicular to the balloon trajectory and for lower values of mean shear.  相似文献   

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