Study of calibration function for surface wave magnitude of DK1 seismographs

ＳｔｕｄｙｏｆｃａｌｉｂｒａｔｉｏｎｆｕｎｃｔｉｏｎｆｏｒｓｕｒｆａｃｅｗａｖｅｍａｇｎｉｔｕｄｅｏｆＤＫ１ｓｅｉｓｍｏｇｒａｐｈｓＦＥＮＧＸＵＥ（薛峰）ＹＯＮＧＺＨＡＯ（赵永）ＣｅｎｔｅｒｆｏｒＡｎａｌｙｓｉｓａｎｄＰｒｅｄｉｃｔｉｏｎ，Ｓｔａｔ...     

Source parameters of bohai earthquake, July 18, 1969 and yongshan earthquake, May 11, 1974 determined by synthetic seismograms of teleseismic P waves

The source parameters of the Bohai Sea earthquake, July 18, 1969 and Yongshan, Yunnan earthquake, May 11, 1974 were determined by full — wave theory synthetic seismograms of teleseismic P waves. P+pP+sP wereform were calculated with WKBJ approximation and real integral paths. One — dimensional unilateral, finite propagation source was also considered. By trail — and — error in comparing the theoretical seismograms with the observational ones of WWSSN stations, the source parameters were obtained as follow: for Bohai earthquake, φ=195°, δ=85°, λ=65°,M _o=0.9×10¹⁹Nm,L=59.9km.V _R=3.5km/s, ∧ _R =160°; for Yongshan earthquake, φ=240°, δ=80°, ∧=150°,M _o=1.3×10¹⁸Nm,L=48.8km,V _R=3km/s, ∧ _R =−10°, where φ is strike, δ dip angle, λ slip angle,M _o seismic moment,L rupture length,V _R rupture propagation speed. As III type fractures the faulting propagated along the fault planes, and ∧ _R is the angle from the strike to the propagation direction. Yongshan earthquake showed complexity in its focal process, having four sub—ruptures during the first 60 seconds. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 1–8, 1991.     

Morphology and causes of the Weddell Sea anomaly

The zone of anomalous diurnal variations in foF2, which is characterized by an excess of nighttime foF2 values over daytime ones, has been distinguished in the Southern Hemisphere based on the Intercosmos-19 satellite data. In English literature, this zone is usually defined as the Weddell Sea anomaly (WSA). The anomaly occupies the longitudes of 180°–360° E in the Western Hemisphere and the latitudes of 40°–80° S, and the effect is maximal (up to ∼5 MHz) at longitudes of 255°–315° E and latitudes of 60°–70° S (50°–55° ILAT). The anomaly is observed at all levels of solar activity. The anomaly formation causes have been considered based on calculations and qualitative analysis. For this purpose, the longitudinal variations in the ionospheric and thermospheric parameters in the Southern Hemisphere have been analyzed in detail for near-noon and near-midnight conditions. The analysis shows that the daytime foF2 values are much smaller in the Western Hemisphere than in the Eastern one, and, on the contrary, the nighttime values are much larger, as a result of which the foF2 diurnal variations are anomalous. Such a character of the longitudinal effect mainly depends on the vertical plasma drift under the action of the neutral wind and ionization by solar radiation. Other causes have also been considered: the composition and temperature of the atmosphere, plasma flows from the plasmasphere, electric fields, particle precipitation, and the relationship to the equatorial anomaly and the main ionospheric trough.     

Estimate of seasonal changes in the intensity of the infrared atmospheric system of molecular oxygen

On the basis of measurements of the intensity of 1.58-μm emissions of the Infrared Atmospheric System of molecular oxygen (IRAO₂) conducted at the Zvenigorod scientific station of the Institute of Atmospheric Physics of the Russian Academy of Sciences (φ = 55.7°N, λ = 36.8°E), seasonal variations are estimated for various solar zenith angles. Their amplitude has the maximum value at the solar zenith angles χ _S ∼ 105–110°. It decreases at χ _S ∼ 125–130° and tends to zero at χ _S ∼ 80–85°. The comparison of currently measured values of the 1.58-μm emission intensity of the Infrared Atmospheric System of molecular oxygen with published data on the intensity of this emission obtained in 1961–1966 reveals their decrease over approximately 50 years. This fact is in good agreement with similar behavior of the emission intensity of atomic oxygen (557.7 nm) over the period considered.     

Holocene tephrochronology record of large explosive eruptions in the southernmost Patagonian Andes

For regionally widespread Holocene tephra layers in southernmost Patagonia, correlations based on both chemical and chronological data indicate their derivation from five large-volume (>1 km³) explosive eruptions of four different volcanoes in the southernmost Andes. Bulk-tephra and tephra-glass major and trace-element chemistry and Sr isotopic ratios unambiguously distinguish different source volcanoes, and imply that two of the regionally widespread tephra (MB₁ and MB₂) were derived from Mt. Burney (52°S), one (R₁) from Reclus (51°S), one (A₁) from Aguilera (50°S) and one (H₁) from Hudson volcano (46°S). The H₁ tephra derived from the Hudson volcano, which is located at the southern end of the Andean Southern Volcanic Zone (SVZ; 33–46°S), contains distinctive greenish andesitic glass with FeO > 4.5 wt.% and TiO₂ > 1.2 wt.%. In contrast, rhyolitic glass in tephra derived from the eruptions of Mt. Burney, Reclus and Aguilera volcanoes, which are located in the Andean Austral Volcanic Zone (AVZ; 49–55°S), is clear and transparent and has significantly lower FeO and TiO₂. Tephra derived from these three AVZ volcanoes all contain plagioclase, orthopyroxene, minor clinopyroxene and amphibole. Biotite occurs only in the Aguilera A₁ tephra, which also has the highest bulk-tephra and tephra-glass K₂O and Rb contents. Averages of new and published ¹⁴C ages determined on organic material in soil and sediment samples above and below these tephra constrain the uncalibrated ¹⁴C age of the R₁ eruption of Reclus volcano to 12,685 ± 260 years BP, the MB₁ and MB₂ eruptions of Mt. Burney to 8,425 ± 500 and 3,830 ± 390 years BP, the Hudson H₁ eruption to 6,850 ± 160 years BP, and the A₁ eruption of Aguilera volcano to 3,000 ± 100 years BP. The volume of the largest of these eruptions, H₁ of the Hudson volcano, is estimated as >18 km³. The volume of the Reclus R₁ eruption is estimated at >10 km³, the Aguilera A₁ eruption at between 4 and 9 km³, and the younger Mt. Burney MB₂ eruption at ≥2.8 km³. The volume of the older MB₁ Mt. Burney eruption is the least well constrained, but must have been larger than the younger MB₂ eruption. The data indicate that the frequency of explosive activity of volcanic centers in the AVZ is lower than in the southern SVZ.     

SSQ-1 Digital Tape Recording Horizontal Pendulum Tiltmeter

The SSQ-1 Digital Tape Recording Horizontal Pendulum Tiltmeter is an instrument of high sensitivity to detect the changes of ground tilt. It uses a quartz horizontal pendulum held by Z?llner bifilar suspension to sense vertical displacement, the eddy-current transducer on the pendulum converts its displacements into electric signals. Then a microcomputer is used for data acquisition and printing as well as digit tape recording. And at the same time, a filtering pen recorder is used for visible recording. The scale value of the instrument is calibrated by computer using the known tilt angle of the bulging plate — mercury cup. The scale value is 0.3–0.5 m(″)/mV. The following are the testing results for the earth tide observation obtained from the east-west component at Baijiatan Seismic Station, Beijing: r(O₁): 0.6490±0.0179 α(O₁): −3.83°±1.58° r(K₁): 0.8049±0.0128 α(K₁): 1.40°±0.90° r(M₂): 0.6699±0.0040 α(M₂): −0.27°±0.34° r(S₂): 0.7316±0.0075 α(S₂): 2.83°±0.58° r(M₃): 0.8497±0.0964 α(M₃): 1.61°±6.51° The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,15, 353–359, 1993. In this work also participated Mr. Huai-Wen PAN and Wei-Jin ZHANG. And we here give special thanks to Yun-Zao XI, Qin-Wen XI, Bo-Xong TANG, Yi-Hui CHEN and An-Xu WU for their kind help in the development and test of the instrument. This paper is translated by Mr. Zhong ZHENG.     

Influence of Atmospheric Solar Radiation Absorption on Photodestruction of Ions at D-Region Altitudes of the Ionosphere

The influence of atmospheric solar radiation absorption on the photodetachment, dissociative photodetachment, and photodissociation rate coefficients (photodestruction rate coefficients) of O^?, Cl^?, O₂ ^?, O₃ ^?, OH^?, NO₂ ^?, NO₃ ^?, O₄ ^?, OH^?(H₂O), CO₃ ^?, CO₄ ^?, ONOO^?, HCO₃ ^?, CO₃ ^?(H₂O), NO₃ ^?(H₂O), O₂ ⁺(H₂O), O₄ ⁺, N₄ ⁺, NO⁺(H₂O), NO⁺(H₂O)₂, H⁺(H₂O) _n for n = 2–4, NO⁺(N₂), and NO⁺(CO₂) at D-region altitudes of the ionosphere is studied. A numerical one-dimensional time-dependent neutral atmospheric composition model has been developed to estimate this influence. The model simulations are carried out for the geomagnetically quiet time period of 15 October 1998 at moderate solar activity over the Boulder ozonesonde. If the solar zenith angle is not more than 90° then the strongest influence of atmospheric solar radiation absorption on photodestruction of ions is found for photodissociation of CO₄ ^? ions when CO₃ ^? ions are formed. It follows from the calculations that decreases in the photodestruction rate coefficients of ions under consideration caused by this influence are less than 2 % at 70 km altitude and above this altitude if the solar zenith angle does not exceed 90°.     

A one-dimensional modeling study of the diurnal cycle in the equatorial Atlantic at the PIRATA buoys during the EGEE-3 campaign

A one-dimensional model is used to analyze, at the local scale, the response of the equatorial Atlantic Ocean under different meteorological conditions. The study was performed at the location of three moored buoys of the Pilot Research Moored Array in the Tropical Atlantic located at 10° W, 0° N; 10° W, 6° S; and 10° W, 10° S. During the EGEE-3 (Etude de la circulation océanique et de sa variabilité dans le Golfe de Guinee) campaign of May–June 2006, each buoy was visited for maintenance during 2 days. On board the ship, high-resolution atmospheric parameters were collected, as were profiles of temperature, salinity, and current. These data are used here to initialize, force, and validate a one-dimensional model in order to study the diurnal oceanic mixed-layer variability. It is shown that the diurnal variability of the sea surface temperatures is mainly driven by the solar heat flux. The diurnal response of the near-surface temperatures to daytime heating and nighttime cooling has an amplitude of a few tenths of degree. The computed diurnal heat budget experiences a net warming tendency of 31 and 27 W m⁻² at 0° N and 10° S, respectively, and a cooling tendency of 122 W m⁻² at 6° S. Both observed and simulated mixed-layer depths experience a jump between the nighttime convection phase and the well-stabilized diurnal water column. Its amplitude changes dramatically depending on the meteorological conditions occurring at the stations and reaches its maximum amplitude (~50 m) at 10° S. At 6° and 10° S, the presence of barrier layers is observed, a feature that is clearer at 10° S. Simulated turbulent kinetic energy (TKE) dissipation rates, compared to independent microstructure measurements, show that the model tracks their diurnal evolution reasonably well. It is also shown that the shear and buoyancy productions and the vertical diffusion of TKE all contribute to the supply of TKE, but the buoyancy production is the main source of TKE during the period of the simulation.     

Water exchange between the subpolar and subtropical North Pacific in an OGCM

The water exchange between the subpolar and subtropical gyres of the North Pacific is demonstrated by the simulation of chlorofluorocarbon (CFC) using an ocean general circulation model. The simulated CFC concentration in the North Pacific is in good agreement with observations. The water exchange is clearly illustrated by the tongues of CFC concentration. The subpolar waters with high CFC are transported southward into the eastern subtropical gyre, whereas the subtropical waters with low CFC are transported northward into the western subpolar gyre. The simulated exchange transport along 42°N in the layer of σθ< 26.8 indicates that the northward mass transport is about 15 Sv (1 Sv = 106 m3·s-1) west of 165°E, and about 5 Sv between 175°W and 150°W. The southward mass transport is about 5 Sv between 165°E and 175°W, and about 2 Sv east of 150°W.     

2012年江苏高邮、宝应交界MS4.9地震发震断层参数测定

基于一维单侧有限移动震源模式,根据地震波传播过程中的多普勒效应,分别利用P波和S波拐角频率的方位变化,反演2012年7月20日江苏高邮、宝应交界MS4.9地震的发震断层面参数。P波和S波拐角频率的反演结果一致显示:本次地震的断层面破裂方向为232°左右,破裂面呈NE-SW向;地震马赫数v/c为0.2左右,平均破裂速度小于S波速度,破裂长度较短,为0.2~0.3km左右。破裂面方位与震源机制解、宏观烈度调查和余震精定位的研究结果具有一致性,结合震区周边的地质构造背景,分析认为滁河断裂很可能是高邮、宝应交界MS4.9地震的发震构造。     

Evolution of erythemal and total shortwave solar radiation in Valladolid,Spain: Effects of atmospheric factors

Erythemal ultraviolet (UVER; 280–400 nm) and total shortwave (SW; 305–2800 nm) solar irradiances were recorded from 2000 to 2009 in Valladolid, Spain. UVER and SW values under cloudless conditions are simulated by radiative transfer (TUV 4.6) and empirical models. These model estimations are tested with experimental measurements showing a great agreement (root mean square error around 7%). The aerosol effect on UVER irradiance is determined through a model study. UVER radiation and total ozone column (TOC) temporal evolutions show a negative relationship. TOC accounts for 80% of UVER variance and its radiation amplification factor is 1.1 at zenith of 65°. Cloud effects on solar radiation are shown and quantified by the cloud modification factor. Moreover the enhancement effect cases are analysed. SW radiation proves more sensitive to clouds than UVER. Clouds are seen to attenuate and enhance solar radiation by up to 93% and 22% in the UVER range, respectively.     

Radio emission spectrum from an interplanetary shock front

The characteristics of low-damping high-frequency waves in hot magnetized solar and stellar coronal plasmas under the conditions when the electron gyrofrequency ω_He is equal to or higher than the electron plasma frequency ω_pe have been analyzed using the numerical solution of the dispersion equation. It is shown that the wave branches corresponding to the Z mode and ordinary waves approach each other when the magnetic field increases and become almost indistinguishable in a wide frequency range at all angles between the wave vector and magnetic field. A branch with anomalous dispersion appears at angles close to 90°. A new interpretation of broadband pulsations and spikes is suggested on the basis of the results.     

Properties of electric turbulence in the polar cap ionosphere

Small-scale (scales of ∼0.5–256 km) electric fields in the polar cap ionosphere are studied on the basis of measurements of the Dynamics Explorer 2 (DE-2) low-altitude satellite with a polar orbit. Nineteen DE-2 passes through the high-latitude ionosphere from the morning side to the evening side are considered when the IMF z component was southward. A rather extensive polar cap, which could be identified using the ɛ-t spectrograms of precipitating particles with auroral energies, was formed during the analyzed events. It is shown that the logarithmic diagrams (LDs), constructed using the discrete wavelet transform of electric fields in the polar cap, are power law (μ ∼ s ^α). Here, μ is the variance of the detail coefficients of the signal discrete wavelet transform, s is the wavelet scale, and index α characterizes the LD slope. The probability density functions P(δE, s) of the electric field fluctuations δE observed on different scales s are non-Gaussian and have intensified wings. When the probability density functions are renormalized, that is constructed of δE/s ^γ, where γ is the scaling exponent, they lie near a single curve, which indicates that the studied fields are statistically self-similar. In spite of the fact that the amplitude of electric fluctuations in the polar cap is much smaller than in the auroral zone, the quantitative characteristics of field scaling in the two regions are similar. Two possible causes of the observed turbulent structure of the electric field in the polar cap are considered: (1) the structure is transferred from the solar wind, which is known to have turbulent properties, and (2) the structure is generated by convection velocity shears in the region of open magnetic field lines. The detected dependence of the characteristic distribution of turbulent electric fields over the polar cap region on IMF B _y and the correlation of the rms amplitudes of δE fluctuations with IMF B _z and the solar wind transfer function (B _y ² + B _z ²)^1/2sin(θ/2), where θ is the angle between the geomagnetic field and IMF reconnecting on the dayside magnetopause when IMF B _z < 0, together with the absence of dependence on the IMF variability are arguments for the second mechanism.     

Geochemical model of a magmatic–hydrothermal system at the Lastarria volcano, northern Chile

Lastarria volcano (25°10′ S, 68°31′ W; 5,697 m above sea level), located in the Central Andes Volcanic Zone (northern Chile), is characterized by four distinct fumarolic fields with outlet temperatures ranging between 80°C and 408°C as measured between May 2006–March 2008 and April–June 2009. Fumarolic gasses contain significant concentrations of high temperature gas compounds (i.e., SO₂, HCl, HF, H₂, and CO), and isotopic ratios (³He/⁴He, δ¹³C–CO₂, δ¹⁸O–H₂O, and δD–H₂O) diagnostic of magmatic gas sources. Gas equilibria systematics, in both the H₂O-H₂-CO₂-CO-CH₄ and alkane–alkene C₃ system, suggest that Lastarria fumarolic gasses emanate from a superheated vapor that is later cooled and condensed at relatively shallow depths. This two-stage process inhibits the formation of a continuous aquifer (e.g., horizontal liquid layer) at relatively shallow depth. Recent developments in the magmatic gas system may have enhanced the transfer and release of heat causing shallow aquifer vaporization. The consequent pressure increase and aquifer vaporization likely triggered the inflation events beginning in 2003 at the Lastarria volcano.     

Measurements of solar ultra violet radiation on the Tibetan Plateau and comparisons with discrete ordinate method simulations

Measurements of both broadband and spectral UV radiation have been carried out at Lhasa (29°40′N, 91°08′E, 3648 m above sea level) on the Tibetan Plateau, using a moderate bandwidth filter instrument (NILUV) and a Fixed Imaging Compact Spectrometer (FICS). In this paper, the erythemal UV dose rates deduced from broadband measurements during the period from 1 July 1996 to 10 December 1997 are presented. The observed highest erythemal UV dose rate is 500 (or 458) mW/m² in July 1996 (or 1997), and the corresponding daily erythemal UV dose can reach up to 7.60 (or 7.00) kJ/m² and 9.18 (or 8.96) kJ/m², respectively, for the monthly mean and the monthly maximum. Comparisons with the UV levels at other locations at similar latitudes show that both the monthly mean and monthly maximum erythemal UV doses at Lhasa can be higher by a factor of 1.3–1.5 than those at San Diego (32°05′N, 117°1′W) in summer (from May to August), and exceed the corresponding values at Perth (32°0′S, 115°8′E) in the southern hemisphere summer (from November to February) by a factor of 1.2–1.4. Comparisons of both the broadband measurements and spectral measurements with the outputs of a discrete ordinate method (DOM) radiative transfer model have also been conducted. The results from the comparisons of broadband measurements with model outputs show that a 15, 11 and 10% agreement may be achieved around solar noon (with solar zenith angle smaller than 60°), respectively, for global irradiances in the 305, 320 and 340 mm channels, whilst the corresponding agreements are about 8 and 4% for the erythemal UV dose rate and the 340–305 nm ratio, respectively. The comparisons of the measured spectral irradiance with model calculations indicate that large discrepancies may appear at wavelengths shorter than 310 nm and longer than 380 nm. However, a 10% agreement may be generally achieved in UVA for solar zenith angle lower than 55°C. The corresponding agreement is about 20 and 5%, respectively, for UVB and the erythemal UV dose rate.     

Statistical testing of the relation between burst of aftershocks and strong earthquakes

According to geological tectonics and seismic activites this paper devided North China (30°–45°N, 105°–130°E) into four areas. We analyzed the North China earthquake catalogue from 1970 to 1986 (from 1965 to 1986 for Huabei, the North China, plain region) and identified forty-two bursts of aftershock. Seven of them occurred in aftershock regions of strong earthquakes and seventeen of them in the seismic swarm regions. The relation between strong earthquakes with the remaining eighteen bursts of aftershocks has been studied and tested statistically in this paper. The result of statistical testing show that the random probabilityp of coincidence of bursts of aftershock with subsequent strong earthquakes is less than six percent. By Xu’sR scoring method the efficacy of predicting strong earthquake from bursts of aftershock is estimated greater than 39 percent. Following the method proposed in the paper we analyzed the earthquake catalogue of China from 1987 to June, 1988. The results show that there was only one burst of aftershock occurred on Jan. 6, 1988 withM=3.6 in Xiuyan of Northeast China. It implicates that a potential earthquake withM _S⩽5 might occur in one year afterwards in the region of Northeast China. Actually on Feb. 25, 1988 an earthquake withM _S=5.3 occurred in Zhangwu of Northeast China. Another example is Datong-Yanggao shock on October 18, 1989 which is a burst of aftershock. Three hours after an expected shock withM =6.1 took place in the same area. Two examples above have been tested in practical prediction and this shows that bursts of aftershocks are significant in predicting strong earthquakes. The Chinese version of this paper appeared in the Chinese edition ofActa Seismologica Sinica,13, 273–280, 1991. Part of earthquake catalogue is from Jinbiao Chen, Peiyan Chen and Quanlin Li.     

Modelling the peak of the ionospheric E-layer

Calculations with a full time-varying model are used to study changes in the height and density of the E-layer peak, caused by known changes in the neutral atmosphere. Agreement with mean observed values of N_mE requires an increase of 10% in calculated ion densities, and an increase of 33% in the solar-maximum EUV model at λ<150 Å. At a fixed site, changes with the solar zenith angle χ agree well with the simple Chapman theory during most of the daylight hours. Simple modifications to the Chapman equations give improved accuracy near sunrise and sunset. When corrected for changes in χ, model results for summer and equinox show a decrease in the peak density N_mE at increasing latitudes. The overall change agrees well with experimental data, as summarised in the IRI model. Known changes in the neutral atmosphere also reproduce the increase in N_mE in winter, at latitudes up to 30°. The continuing increase at higher winter latitudes, in the IRI model, requires a major reduction in NO densities in winter. A suitable compromise is suggested. Equations fitted to the model results then provide a simpler and better behaved replacement for the IRI equations. Calculations at night show that known sources of ionisation, largely from starlight, can produce observed peak densities using current chemistry. There is an appreciable change with latitude, as starlight production increases in the southern hemisphere. The improbably large solar cycle change built into the IRI model, at night, cannot be reproduced and is not found in recent data. A new, simpler model is suggested. Changes in zenith angle and atmospheric composition cause the peak height (h_mE) to vary between 105 and 120 km, as a function of time, latitude, season and solar flux. These changes are approximated by simple equations that should be definitely preferable over the single, fixed height used in the IRI models.     

The importance of cross-calibration and protecting water temperature sensors against direct solar radiation heating in hydrological studies

ABSTRACT

Water temperature monitoring is important in many scientific studies. This study compares three models of water temperature sensors (Vemco Minilog II, HOBO TidbiT and HOBO Pendant) to test the importance of: (1) using cross-calibration to minimize relative errors, (2) using cross-calibration to improve on the accuracy of less accurate sensors, and (3) protecting sensors against direct solar radiation heating. The results show that when the same sensor models are cross-calibrated, the relative error can be reduced (Vemco: 0.01°C; HOBO TidbiT: 0.02°C; and HOBO Pendant: 0.07°C). Cross-calibration can also improve less accurate sensors (HOBO TidbiT and Pendant) to similar accuracies of Vemco (±0.1°C). Finally, no evidence of solar radiation heating was observed for Vemcos (unprotected); however, HOBO TidbiT and Pendant showed heating up to 2°C (maximum). When HOBO TidbiT and Pendant are shielded (flow-through system), heating is no longer an issue.     

Latitudinal patterns of export production recorded in surface sediments of the Chilean Patagonian fjords (41–55°S) as a response to water column productivity

The Chilean Patagonian fjords region (41–56°S) is characterized by highly complex geomorphology and hydrographic conditions, and strong seasonal and latitudinal patterns in precipitation, freshwater discharge, glacier coverage, and light regime; all of these directly affect biological production in the water column. In this study, we compiled published and new information on water column properties (primary production, nutrients) and surface sediment characteristics (biogenic opal, organic carbon, molar C/N, bulk sedimentary δ¹³C_org) from the Chilean Patagonian fjords between 41°S and 55°S, describing herein the latitudinal pattern of water column productivity and its imprint in the underlying sediments. Based on information collected at 188 water column and 118 sediment sampling sites, we grouped the Chilean fjords into four main zones: Inner Sea of Chiloé (41° to ～44°S), Northern Patagonia (44° to ～47°S), Central Patagonia (48–51°S), and Southern Patagonia (Magellan Strait region between 52° and 55°S). Primary production in the Chilean Patagonian fjords was the highest in spring–summer, reflecting the seasonal pattern of water column productivity. A clear north–south latitudinal pattern in primary production was observed, with the highest average spring and summer estimates in the Inner Sea of Chiloé (2427 and 5860 mg C m^?2 d^?1) and Northern Patagonia (1667 and 2616 mg C m^?2 d^?1). This pattern was closely related to the higher availability of nutrients, greater solar radiation, and extended photoperiod during the productive season in these two zones. The lowest spring value was found in Caleta Tortel, Central Patagonia (91 mg C m^?2 d^?1), a site heavily influenced by glacier meltwater and river discharge loaded with glacial sediments. Biogenic opal, an important constituent of the Chilean fjord surface sediments (Si_OPAL ～1–13%), reproduced the general north–south pattern of primary production and was directly related to water column silicic acid concentrations. Surface sediments were also rich in organic carbon content and the highest values corresponded to locations far away from glacier influence, sites within fjords, and/or semi-enclosed and protected basins, reflecting both autochthonous (water column productivity) and allochthonous sources (contribution of terrestrial organic matter from fluvial input to the fjords). A gradient was observed from the more oceanic sites to the fjord heads (west–east) in terms of bulk sedimentary δ¹³C_org and C/N ratios; the more depleted (δ¹³C_org ?26‰) and higher C/N (23) values corresponded to areas close to rivers and glaciers. A comparison of the Chilean Patagonian fjords with other fjord systems in the world revealed high variability in primary production for all fjord systems as well as similar surface sediment geochemistry due to the mixing of marine and terrestrial organic carbon.     

Evolution of fluid geochemistry at the Turrialba volcano (Costa Rica) from 1998 to 2008

Turrialba (10°02′N, 83°45′W) is a 3,349-m high stratovolcano belonging to the Holocene “Cordillera Central” volcanic belt of Costa Rica. The summit consists of three EW-oriented craters (East, Central, and West). Since its last eruptive phase (1864–1866), the Central and West craters have displayed modest fumarolic activity, with outlet temperatures clustering around 90°C. In 2001, seismic swarms, ground deformation, and increasing fumarolic activity occurred. From 2005 to 2008, new fumarolic vents opened between and within the Central and West craters, and along the western and southwestern outer flanks of the volcanic edifice. These physical changes were accompanied by a drastic modification in the gas chemistry that can be divided in three stages: (1) hydrothermal (from 1998 to autumn 2001), characterized by the presence of H₂O, CO₂, H₂S, and, to a very minor extent, HCl and HF; (2) hydrothermal/magmatic (autumn 2001–2007), with the appearance of SO₂ and a significant increase of HCl and HF; and (3) magmatic-dominated (2007–2008), characterized by increased SO₂ content, SO₂/H₂S > 100, and temperatures up to 282°C. Accordingly, gas equilibrium in the CO₂-CH₄-H₂ system suggests a progressive evolution of the deep fluid reservoir toward higher temperatures and more oxidizing conditions. The chemical–physical modifications of Turrialba in the last decade can be interpreted as part of a cyclic mechanism controlling the balance between the hydrothermal and the magmatic systems. Nevertheless, the risk of rejuvenation of the volcanic activity cannot be excluded, and an appropriate seismic, ground deformation, and geochemical monitoring program is highly recommended. Turrialba lies at a distance of 35 and 15 km from San José and Cartago, respectively, the two largest cities in Costa Rica.