Shake table tests of suspended ceilings to simulate the observed damage in the M_s 7.0 Lushan earthquake,China

Severe damage to suspended ceilings of metal grids and lay-in panels was observed in public buildings during the 2013 Ms7.0 Lushan earthquake in China. Over the past several years, suspended ceilings have been widely used practice in public buildings throughout China, including government offices, schools and hospitals. To investigate the damage mechanism of suspended ceilings, a series of three-dimensional shake table tests was conducted to reproduce the observed damage. A full-scale reinforced concrete frame was constructed as the testing frame for the ceiling, which was single-story and infilled with brick masonry walls to represent the local construction of low-rise buildings. In general, the ceiling in the tests exhibited similar damage phenomena as the field observations, such as higher vulnerability of perimeter elements and extensive damage to the cross runners. However, it exhibited lower fragility in terms of peak ground/roof accelerations at the initiation of damage. Further investigations are needed to clarify the reasons for this behavior.     

云南漾濞6.4级地震公共建筑的震害特征

2021年5月21日云南漾濞发生6.4级地震,成为继2014年6.5级鲁甸地震和6.6级景谷地震之后云南省内时隔7年的又一次震级大于6级的破坏性地震。漾濞地震虽然与鲁甸地震在震级、震源深度和震源机制等方面均较相似,但漾濞地震震中附近的地面运动强度远不及鲁甸地震,且漾濞县的抗震设防烈度远高于鲁甸;相应地,漾濞地震对抗震设防建筑造成的破坏也远轻于后者。本文首先通过比较这三次地震震中附近的强震记录的反应谱,并结合公共建筑的震后应急评估结果,说明漾濞地震和鲁甸地震中公共建筑破坏程度的显著差异。进而以位于漾濞县城的两栋钢筋混凝土公共建筑为例,介绍此次地震中砌体填充墙和吊顶等典型非结构构件的震害。     

Seismic damage to structures in the <Emphasis Type="Italic">M</Emphasis><Subscript>s</Subscript>6.5 Ludian earthquake

On 3 August 2014, the Ludian earthquake struck northwest Yunnan Province with a surface wave magnitude of 6.5. This moderate earthquake unexpectedly caused high fatalities and great economic loss. Four strong motion stations were located in the areas with intensity V, VI, VII and IX, near the epicentre. The characteristics of the ground motion are discussed herein, including 1) ground motion was strong at a period of less than 1.4 s, which covered the natural vibration period of a large number of structures; and 2) the release energy was concentrated geographically. Based on materials collected during emergency building inspections, the damage patterns of adobe, masonry, timber frame and reinforced concrete (RC) frame structures in areas with different intensities are summarised. Earthquake damage matrices of local buildings are also given for fragility evaluation and earthquake damage prediction. It is found that the collapse ratios of RC frame and confined masonry structures based on the new design code are significantly lower than non-seismic buildings. However, the RC frame structures still failed to achieve the ‘strong column, weak beam’ design target. Traditional timber frame structures with a light infill wall showed good aseismic performance.     

The seismotectonic and macroseismic features of the Wenchuan (Sichuan) earthquake (<Emphasis Type="Italic">M</Emphasis><Subscript><Emphasis Type="Italic">S</Emphasis></Subscript> = 8.0) of May 12, 2008

A disastrous earthquake with a magnitude M _S = 8.0 (M _W = 7.9), in China called “the 5.12 Wenchuan earthquake,” occurred on May 12, 2008, in Sichuan province on the border between the Sino-Tibetan Mountains and the Sichuan depression. The instrumental epicenter was registered in the southeastern part of Wenchuan county, and the hypocenter depth was 14 km. As the strongest and most destructive earthquake within mainland China, it caused numerous human losses and destruction of buildings and infrastructure. The seismic effect from the main shock and aftershocks was felt in many counties, towns, and villages, though Sichuan province suffered the most. The maximum intensity of the shocks was estimated at 11 degrees, according to the Chinese macroseismic scale. In the process of source opening, from the southern part of Wenchuan county to the vicinities of Quingchuan, a seismic fault system with a total length up to 240 km out-cropped on the earth’s surface, confined to the Longmenshan fault belt. The seismic fault system disturbed the original ground, resulting in the collapse or damage to various constructions, such as buildings, homes, bridges, roads, etc. Fault offsets had a dextral strike-slip and thrust kinematic combination. The earthquake generated several tens of thousands of landslides, rockfalls, and debris flows. Many dammed ponds appeared in the epicentral zone due to the activation of landslides. Thus, the geological effects turned out to be the most destructive factor in this case. At the same time, the seismic intensity of surface shaking was abnormally low even in direct proximity to the seismic fault system. Usually it was no more than 7–8 degrees. This macroseismic phenomenon may turn out to be rather typical for many major earthquakes.     

Damage of 1975 Haicheng <Emphasis Type="Italic">M</Emphasis><Subscript>S</Subscript>7.3 earthquake in the Korean Peninsula and its effect on Kyushu,Japan

The 1975 Haicheng M _S7.3 earthquake affected whole Korean Peninsula and even Kyushu, Japan. In this paper isoseismal map of this earthquake was drawn for these areas by sorting out and analyzing data systematically collected, furthermore, the characteristics of the earthquake damage were discussed. In the northern Korean Peninsula, the intensity is V in great majority of this area except local area with intensity VI, and the damage is basically in accordance with typical characteristics of corresponding intensity grade. In the southern Korean Peninsula, the intensity is IV in large part of the area, however, in some big cities such as Seoul etc., not only high buildings shook strongly, but also some people appeared perceptions such as feeling dizzy and so on, and electrical service was interrupted on one or two districts because of transformer tripping. These phenomena could be caused by the effect of long-period wave generated from a large earthquake on far-field.     

Soil H<Subscript>2</Subscript> and CO<Subscript>2</Subscript> Surveys at Several Active Faults in Japan

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.     

Distribution and characteristics of gravelly soil liquefaction in the Wenchuan <Emphasis Type="Italic">M</Emphasis><Subscript>s</Subscript> 8.0 earthquake

In this paper,a distribution map of gravelly soil liquefaction that was caused by the Wenchuan M_s 8.0 earthquake in China is proposed based on a detailed field investigation and an analysis of geological soil profiles. The geological background of the earthquake disaster region is summarized by compiling geological cross sections and borehole logs. Meanwhile,four typical liquefied sites were selected to conduct sample drillings,dynamic penetration tests (DPT),and shear wave velocity tests,to understand the features of liquefied gravelly soil. One hundred and eighteen (118) liquefied sites were investigated shortly after the earthquake. The field investigation showed:(1) sandboils and waterspouts occurred extensively,involving thousands of miles of farmland,120 villages,eight schools and five factories,which caused damage to some rural houses,schools,manufacturing facilities and wells,etc.; (2) the Chengdu plain is covered by a gravelly soil layer with a thickness of 0 m to 541 m according to the geological cross sections; (3) there were 80 gravelly soil liquefied sites in the Chengdu plain,shaped as five belt areas that varied from 20 km to 40 km in length,and about ten gravelly soil liquefied sites distributed within Mianyang area; and (4) the grain sizes of the sampled soil were relative larger than the ejected soil on the ground,thus the type of liquefied soil cannot be determined by the ejected soil. The gravelly soil liquefied sites are helpful in enriching the global database of gravelly soil liquefaction and developing a corresponding evaluation method in further research efforts.     

The moment magnitude <Emphasis Type="Italic">M</Emphasis><Subscript>w</Subscript> and the energy magnitude <Emphasis Type="Italic">M</Emphasis><Subscript>e</Subscript>: common roots and differences

Starting from the classical empirical magnitude-energy relationships, in this article, the derivation of the modern scales for moment magnitude M _w and energy magnitude M _e is outlined and critically discussed. The formulas for M _w and M _e calculation are presented in a way that reveals, besides the contributions of the physically defined measurement parameters seismic moment M ₀ and radiated seismic energy E _S, the role of the constants in the classical Gutenberg–Richter magnitude–energy relationship. Further, it is shown that M _w and M _e are linked via the parameter Θ = log(E _S/M ₀), and the formula for M _e can be written as M _e = M _w + (Θ + 4.7)/1.5. This relationship directly links M _e with M _w via their common scaling to classical magnitudes and, at the same time, highlights the reason why M _w and M _e can significantly differ. In fact, Θ is assumed to be constant when calculating M _w. However, variations over three to four orders of magnitude in stress drop Δσ (as well as related variations in rupture velocity V _R and seismic wave radiation efficiency η _R) are responsible for the large variability of actual Θ values of earthquakes. As a result, for the same earthquake, M _e may sometimes differ by more than one magnitude unit from M _w. Such a difference is highly relevant when assessing the actual damage potential associated with a given earthquake, because it expresses rather different static and dynamic source properties. While M _w is most appropriate for estimating the earthquake size (i.e., the product of rupture area times average displacement) and thus the potential tsunami hazard posed by strong and great earthquakes in marine environs, M _e is more suitable than M _w for assessing the potential hazard of damage due to strong ground shaking, i.e., the earthquake strength. Therefore, whenever possible, these two magnitudes should be both independently determined and jointly considered. Usually, only M _w is taken as a unified magnitude in many seismological applications (ShakeMap, seismic hazard studies, etc.) since procedures to calculate it are well developed and accepted to be stable with small uncertainty. For many reasons, procedures for E _S and M _e calculation are affected by a larger uncertainty and are currently not yet available for all global earthquakes. Thus, despite the physical importance of E _S in characterizing the seismic source, the use of M _e has been limited so far to the detriment of quicker and more complete rough estimates of both earthquake size and strength and their causal relationships. Further studies are needed to improve E _S estimations in order to allow M _e to be extensively used as an important complement to M _w in common seismological practice and its applications.     

<Emphasis Type="Italic">Q</Emphasis><Subscript>c</Subscript> and <Emphasis Type="Italic">Q</Emphasis><Subscript>S</Subscript> wave attenuation of South African earthquakes

Quality factor Q, which describes the attenuation of seismic waves with distance, was determined for South Africa using data recorded by the South African National Seismograph Network. Because of an objective paucity of seismicity in South Africa and modernisation of the seismograph network only in 2007, I carried out a coda wave decay analysis on only 13 tectonic earthquakes and 7 mine-related events for the magnitude range 3.6?≤?M _L ?≤?4.4. Up to five seismograph stations were utilised to determine Q _c for frequencies at 2, 4, 8 and 16 Hz resulting in 84 individual measurements. The constants Q ₀ and α were determined for the attenuation relation Q _c(f)?=?Q ₀ f ^α . The result was Q ₀?=?396?±?29 and α?=?0.72?±?0.04 for a lapse time of 1.9*(t _s???t ₀) (time from origin time t ₀ to the start of coda analysis window is 1.9 times the S-travel time, t _s) and a coda window length of 80 s. This lapse time and coda window length were found to fit the most individual frequencies for a signal-to-noise ratio of at least 3 and a minimum absolute correlation coefficient for the envelope of 0.5. For a positive correlation coefficient, the envelope amplitude increases with time and Q _c was not calculated. The derived Q _c was verified using the spectral ratio method on a smaller data set consisting of nine earthquakes and one mine-related event recorded by up to four seismograph stations. Since the spectral ratio method requires absolute amplitudes in its calculations, site response tests were performed to select four appropriate stations without soil amplification and/or signal distortion. The result obtained for Q _S was Q ₀?=?391?±?130 and α?=?0.60?±?0.16, which agrees well with the coda Q _c result.     

High-resolution dating of Co-rich crusts: A comparative study using the methods of orbital pacing and <Superscript>230</Superscript>Th<Subscript>ex</Subscript>/<Superscript>232</Superscript>Th dating

Due to their slow growth rates, seamount Co-rich crusts are very difficult to date with high resolution and precision. This paper is to test the use of orbital pacing on the growth profile of crusts to determine high-resolution age and growth rate. Crust CB14 from the central Pacific Ocean was selected for this study. We first examined the growth pattern in detail under a reflected-light microscope and ascertained that the growth environment was stable for the sub-layer 1 (0–3 mm). We then used electron microprobe line-scanning to obtain elemental profiles. The pattern of the power spectrum analysis of the Al-profile revealed that there are significant cycles of 113.9, 87.8, 51.5, 42.2 and 25.8 μm. These cycles correspond to the Milankovitch cycles of 53.1, 41, 24, 19.7 and 12 ka, respectively, and yield the growth rate of about 2.14 mm/Ma and an age of about 1.40 Ma for the boundary between the sub-layer 1 and sub-layer 2. We also used a drilling machine with a numerically controlled drive to obtain high-resolution samples at 0.1mm intervals, and used the ²³⁰Th_ex/²³²Th method to date the samples. For the uppermost 1.3 mm, the growth rate was about 2.15 mm/Ma, and the age for the layer at the depth of 3 mm was about 1.40 Ma, which coincides perfectly with the results obtained from orbital pacing. Thus, it is considered that orbital pacing is a new and effective method to determine the growth rate of the seamount Co-rich crust. This method is applicable for establishing a high-resolution age frame for the crusts of the world’s oceans. Supported by China Ocean Mineral Resources R & P Association (Grant No. DY105-01-01-08) and National Natural Science Foundation of China (Grant Nos. 40106005, 40476050)     

The August 27, 2008, <Emphasis Type="Italic">M</Emphasis><Subscript>W</Subscript> = 6.3, Kultuk earthquake effects in the Nearepicenter zone: Macroseismic survey results

In this work, the macroseismic effects of the Kultuk earthquake (M _W = 6.3), which took place on August 27, 2008 in the southwestern closure of the Baikal Lake, are under consideration. The intensity of shocks in inhabited localities located in the epicentral zone reached 7–8 points on the MSK-64 scale. The earthquake was named after the local settlement of Kultuk, which was the mostly damaged area by the earthquake. The considered seismic event caused significant material damage (about 250 million rubles according to preliminary estimates). In inhabited localities of Southern Pribaikalie thousands of cases of damaged ovens and chimneys were registered. Some buildings were highly damaged and, accordingly, they are unfit for further use. The earthquake was the cause of numerous rockslides, rockfalls, and landslides on steep natural and artificial slopes. A macroseismic survey allowed us to establish the asymmetrical distribution of the intensity of shocks relative to the epicenter.     

Rupture behavior and deformation localization of the Kunlunshan earthquake (<Emphasis Type="Italic">M</Emphasis><Subscript><Emphasis Type="Italic">w</Emphasis></Subscript>7.8) and their tectonic implications

Earthquake surface rupture is the result of transformation from crustal elastic strain accumulation to permanent tectonic deformation. The surface rupture zone produced by the 2001 Kunlunshan earthquake (M _w 7.8) on the Kusaihu segment of the Kunlun fault extends over 426 km. It consists of three relatively independent surface rupture sections: the western strike-slip section, the middle transtensional section and the eastern strike-slip section. Hence this implies that the Kunlunshan earthquake is composed of three earthquake rupturing events, i.e. the M _w =6.8, M _w =6.2 and M _w ⩽=7.8 events, respectively. The M _w =7.8 earthquake, along the eastern section, is the main shock of the Kunlunshan earthquake, further decomposed into four rupturing subevents. Field measurements indicate that the width of a single surface break on different sections ranges from several meters to 15 m, with a maximum value of less than 30 m. The width of the surface rupture zone that consists of en echelon breaks depends on its geometric structures, especially the stepover width of the secondary surface rupture zones in en echelon, displaying a basic feature of deformation localization. Consistency between the Quaternary geologic slip rate, the GPS-monitored strain rate and the localization of the surface ruptures of the 2001 Kunlunshan earthquake may indicate that the tectonic deformation between the Bayan Har block and Qilian-Qaidam block in the northern Tibetan Plateau is characterized by strike-slip faulting along the limited width of the Kunlun fault, while the blocks themselves on both sides of the Kunlun fault are characterized by block motion. The localization of earthquake surface rupture zone is of great significance to determine the width of the fault-surface-rupture hazard zone, along which direct destruction will be caused by co-seismic surface rupturing along a strike-slip fault, that should be considered before the major engineering project, residental buildings and life line construction. Supported by the National Natural Science Foundation of China (Grant No. 40474037) and the National Basic Research Program of China (Grant No. 2004CB418401)     

Improved method to determine the molar volume and compositions of the NaCl-H<Subscript>2</Subscript>O-CO<Subscript>2</Subscript> system inclusion

On the basis of Parry’s method (1986), an improved method was established to determine the molar volume (Vm) and compositions (X) of the NaCl-H2O-CO2 (NHC) system inclusion. To use this method, the determination of Vm-X only requires three microthermometric data of a NHC inclusion: partial homog-enization temperature (Th ,CO2), salinity (S) and total homogenization temperature (Th). Theoretically, four associated equations are needed containing four unknown parameters: X CO2, XNaCl, Vm and F (volume fraction of CO2 phase in total inclusion when occurring partial homogenization). When they are released, the Vm-X are determined. The former three equations, only correlated with Th ,CO2, S and F, have simplified expressions:XCO2=f1(Th,CO2,S,F),XNaCl=f2(Th,CO2,S,F),Vm=f3(Th,CO2,S,F). The last one is the thermodynamic relationship of X CO2, XNaCl, Vm and Th:f4(XCO2,XNaCl,Vm,Th)=0.Since the above four associated equations are complicated, it is necessary to adopt iterative technique to release them. The technique can be described by:(i) Freely input a F value (0≤F≤1),with Th ,CO2 and S, into the former three equations. As a result,X CO 2,XNaCl and the molar volume value recorded as Vm1 are derived. (ii) Input the X CO2 and XNaCl gotten in the step above into the last equation, and another molar volume value recorded as Vm2 is determined. (iii) If Vm1 is unequal to Vm2, the calculation will be restarted from “(i)”. The iteration is completed until Vm1 is equal to Vm2, which means that the four associated equations are released. Compared to Parry’s (1986) solution method, the improved method is more convenient to use, as well as more accurate to determine X CO 2. It is available for a NHC inlusion whose partial homogenization temperature is higher than clatherate melting temperature and there are no solid salt crystals in the inclusion at parital homogenization.     

Rapid report of seismic damage to buildings in the 2022 M 6.8 Luding earthquake,China

The report summarizes the observed damage to a variety of buildings near the epicenter of the M6.8 Luding earthquake in Sichuan Province, China. They include base-isolated buildings, multi-story reinforced concrete (RC) frame buildings, and masonry buildings. The near-field region is known to be tectonically highly active, and the local intensity level is the highest, that is, 0.4g peak ground acceleration (PGA) for the design basis earthquake, in the Chinese zonation of seismic ground motion parameters. The extent of damage ranged from the weak-story collapse that claimed lives to the extensive nonstructural damage that suspended occupancy. The report highlights the first observation of the destruction of rubber bearings and viscous dampers in the isolation layer of Chinese seismically isolated buildings. It also features the rare observation of the brittle shear failure of RC columns in moment-resisting frames in a region of such a high seismic design requirement. Possible reasons that may have attributed to the reported damage are suggested by providing facts observed in the field. However, careful forensic analyses are needed before any conclusive judgment can be made.     

Robust H∞ control for aseismic structures with uncertainties in model parameters

This paper presents a robust H∞ output feedback control approach for structural systems with uncertainties in model parameters by using available acceleration measurements and proposes conditions for the existence of such a robust output feedback controller. The uncertainties of structural stiffness, damping and mass parameters are assumed to be norm-bounded. The proposed control approach is formulated within the framework of linear matrix inequalities, for which existing convex optimization techniques, such as the LMI toolbox in MATLAB, can be used effectively and conveniently. To illustrate the effectiveness of the proposed robust H∞ strategy, a six-story building was subjected both to the 1940 El Centro earthquake record and to a suddenly applied Kanai-Tajimi filtered white noise random excitation. The results show that the proposed robust H∞ controller provides satisfactory results with or without variation of the structural stiffness, damping and mass parameters.     

Slope topography-induced spatial variation correlation with observed building damages in Corso during the May 21, 2003, <Emphasis Type="Italic">M</Emphasis><Subscript><Emphasis Type="Italic">w</Emphasis></Subscript> 6.8, Boumerdes earthquake (Algeria)

During the May 21, 2003 M _w 6.8 Boumerdes earthquake, in the “Cité des 102 Logements” built on a hilltop, in Corso, heavy damages were observed: near the crest, a four-story RC building collapsed while others experienced severe structural damage and far from the crest, slight damage was observed. In the present paper, we perform a 2D slope topography seismic analysis and investigate its effects on the response at the plateau as well as the correlation with the observed damage distribution. A site-specific seismic scenario is used involving seismological, geological, and geotechnical data. 2D finite element numerical seismic study of the idealized Corso site subjected to vertical SV wave propagation is carried out by the universal code FLUSH. The results highlighted the main factors that explain the causes of block collapse, located 8-26 m far from the crest. These are as follows: (i) a significant spatial variation of ground response along the plateau due to the topographic effect, (ii) this spatial variation presents high loss of coherence, (iii) the seismic ground responses (PGA and response spectra) reach their maxima, and (iv) the fundamental frequency of the collapsed blocks coincides with the frequency content of the topographic component. For distances far from the crest where slight damages were observed, the topographic contribution is found negligible. On the basis of these results, it is important to take into account the topographic effect and the induced spatial variability in the seismic design of structures sited near the crest of slope.     

On the Ultra Long Propagation of Felt Ground Motion Due to the <Emphasis Type="Italic">M</Emphasis><Subscript><Emphasis Type="Italic">w</Emphasis></Subscript> 8.3 Deep-Focus Sea-of-Okhotsk Earthquake of May 24, 2013

This study uses macroseismic data and wave equations to solve the problem of ultra long propagation of felt ground motion (over 9000 km from the epicenter) due to the Sea-of-Okhotsk earthquake. We show that the principal mechanism of this phenomenon could be excitation of a previously unknown standing radial wave as a mode of the Earth’s free oscillations, ₀S₀, due to the superposition of an incident and a reflected spherical P wave in the epicentral area of the Sea-of-Okhotsk earthquake. The standing wave generates slowly attenuating P waves that travel over the earth’s surface that act as carrying waves; when superposed on these, direct body waves acquire the ability to travel over great distances. We show previously unknown parameters of the radial mode ₀S₀ for the initial phase of earth deformation due to the large deep-focus earthquake. We used data on the Sea-of-Okhotsk and Bolivian earthquakes to show that large deep-focus earthquakes can excite free oscillations of the Earth that are not only recorded by instrumental means, but are also felt by people, with the amplification of the macroseismic effect being directly related to the phenomenon of resonance for multistory buildings.     

Experimental study on N<Subscript>2</Subscript>O and CH<Subscript>4</Subscript> fluxes from the dark coniferous forest zone soil of the Gongga Mountain,China

The static closed chamber technique is used in the study on the CH₄ and N₂O fluxes from the soils of primeval Abies fabri forest, the succession Abies fabri forest and the clear-cut areas of mid-aged Abies fabri forest in the Gongga Mountain from May 1998 to September 1999. The results indicate the following: (i) The forest soil serves as the source of atmospheric N₂O at the three measurement sites, while the fluxes of CH₄ are all negative, and soil is the sink of atmospheric CH₄. The comparative relations of N₂O emissions between the three sites are expressed as primeval Abies fabri forest < clear-cut areas < succession Abies fabri forest, and those of CH₄ consumption fluxes are primeval Abies fabri forest < succession Abies fabri forest < clear-cut areas, (ii) Significant seasonal variations of N₂O emission at various sites were observed, and two emission peaks of N₂O occurr during summer (July—August) and spring (February—March), whereas N₂O emission is relatively low in winter and spring (mid March—April). Seasonal variations of CH₄ consumption at each measurement site fluctuate drastically with unclear regularities. Generally, CH₄ consumption fluxes of succession Abies fabri forest and clear-cut areas are higher from mid May to late July but lower in the rest of sampling time, while the CH₄ flux keeps a relatively high value even up to September in primeval Abies fabri forest. In contrast to primeval Abies fabri forest, the CH₄ absorbabilities of succession Abies fabri forest and clear-cut areas of mid-aged Abies fabri forest are weaker. Particularly, the absorbability of the clear-cut areas is even weaker as compared with the other two sites, for the deforestation reduces the soil absorbability of atmospheric CH₄. (iii) Evident diurnal variation regularity exists in the N₂O emissions of primeval Abies fabri forest, and there is a statistic positive correlation between the fluxes of N₂O and air temperature (R=0.95, n=11, α· 0.01), and also the soil temperature of 5-cm layer (R=0.81, n=11, α> 0.01), whereas the CH₄ diurnal variation regularities are unclear and have no significant correlation with the soil temperature of 5-cm layer and air temperature.     

Experimental study on supercritical phenomena of WO<Subscript>3</Subscript> solubility in NaCl-H<Subscript>2</Subscript>O system

The solubility measurements of WO₃ in NaCl-H₂O system with 4.0% by weight salt were carried out to study the supercritical phenomena of solubility. These experiments were carried out using rapid-quench pressure vessels, with quantitative Na₂WO₄-2H₂O, HCl, NaCl and H₂O in Pt capsule to determine the solubility of WO₃ from supersaturated solution. The pressure was kept at 34 MPa, which was near the critical pressure 31.4 MPa and the temperatures varied from 250°C to 550°C. The experimental results indicate that the solubility of WO₃ has the features of supercritical phenomenon in critical region and is sensitive to the change of system temperature and solvent density. The temperature and pressure in this experiment are close to those of ore-forming fluids in many tungsten deposits, so the features of supercritical geofluids can be helpful to investigating the ore-forming mechanism of tungsten deposit.     

The instability of the <Emphasis Type="Italic">M</Emphasis><Subscript>W</Subscript> and <Emphasis Type="Italic">M</Emphasis><Subscript>L</Subscript> comparison for earthquakes in Greece for the period 1969 to 2007

We use 576 earthquakes of magnitude, M _w, 3.3 to 6.8 that occurred within the region 33° N–42.5° N, 19° E–30° E in the time period 1969 to 2007 to investigate the stability of the relation between moment magnitude, M _w, and local magnitude, M _L, for earthquakes in Greece and the surrounding regions. We compare M _w to M _L as reported in the monthly bulletins of the National Observatory of Athens (NOA) and to M _L as reported in the bulletins of the Seismological Station of the Aristotle University of Thessaloniki. All earthquakes have been analyzed through regional or teleseismic waveform inversion, to obtain M _w, and have measured maximum trace amplitudes on the Wood–Anderson seismograph in Athens, which has been in operation since 1964. We show that the Athens Wood–Anderson seismograph performance has changed through time, affecting the computed by NOA M _L by at least 0.1 magnitude units. Specifically, since the beginning of 1996, its east–west component has been recording systematically much larger amplitudes compared to the north–south component. From the comparison between M _w and M _L reported by Thessaloniki, we also show that the performance of the sensors has changed several times through time, affecting the calculated M _L’s. We propose scaling relations to convert the M _L values reported from the two centers to M _w. The procedures followed here can be applied to other regions as well to examine the stability of magnitude calculations through time.