W Phase Inversion and Tsunami Inundation Modeling for Tsunami Early Warning: Case Study for the 2011 Tohoku Event

Centroid moment tensor solutions for the 2011 Tohoku earthquake are determined by W phase inversions using 5 and 10 min data recorded by the Full Range Seismograph Network of Japan (F-net). By a scaling relation of moment magnitude to rupture area and an assumption of rigidity of 4 × 10¹⁰ N m^?2, simple rectangular earthquake fault models are estimated from the solutions. Tsunami inundations in the Sendai Plain, Minamisanriku, Rikuzentakata, and Taro are simulated using the estimated fault models. Then the simulated tsunami inundation area and heights are compared with the observations. Even the simulated tsunami heights and inundations from the W phase solution that used only 5 min data are considerably similar to the observations. The results are improved when using 10 min of W phase data. These show that the W phase solutions are reliable to be used for tsunami inundation modeling. Furthermore, the technique that combines W phase inversion and tsunami inundation modeling can produce results that have sufficient accuracy for tsunami early warning purposes.     

Greenhouse effects of aircraft emissions as calculated by a radiative transfer model

With a radiative transfer model, assessments are made of the radiative forcing in northern mid-latitudes due to aircraft emissions up to 1990. Considered are the direct climate effects from the major combustion products carbon dioxide, nitrogen dioxide, water vapor and sulphur dioxide, as well as the indirect effect of ozone production from NO_x emissions. Our study indicates a local radiative forcing at the tropopause which should be negative in summer (-0.5 to 0.0 W/m²) and either negative or positive in winter (-0.3 to 0.2 W/m²). To these values the indirect effect of contrails has to be added, which for the North Atlantic Flight Corridor covers the range -0.2 to 0.3 W/m² in summer and 0.0 to 0.3 W/m² in winter. Apart from optically dense non-aged contrails during summer, negative forcings are due to solar screening by sulphate aerosols. The major positive contributions come from contrails, stratospheric water vapor in winter and ozone in summer. The direct effect of NO₂ is negligible and the contribution of CO₂ is relatively small.     

THREE-TERM TAYLOR SERIES FOR t2 - x2-CURVES OF P- AND S-WAVES OVER LAYERED TRANSVERSELY ISOTROPIC GROUND*

The arrival-time curve of a reflection from a horizontal interface, beneath a homogeneous isotropic layer, is a hyperbola in the x - t-domain. If the subsurface is one-dimensionally inhomogeneous (horizontally layered), or if some or all of the layers are transversely isotropic with vertical axis of symmetry, the statement is no longer strictly true, though the arrival-time curves are still hyperbola-like. In the case of transverse isotropy, however, classical interpretation of these curves fails. Interval velocities calculated from t² - x²-curves do not always approximate vertical velocities and therefore cannot be used to calculate depths of reflectors. To study the relationship between velocities calculated from t² - x²-curves and the true velocities of a transversely isotropic layer, we approximate t² - x²-curves over a vertically inhomogeneous transversely isotropic medium by a three-term Taylor series and calculate expressions for these terms as a function of the elastic parameters. It is shown that both inhomogeneity and transverse isotropy affect slope and curvature of t² - x²-curves. For P-waves the effect of transverse isotropy is that the t² - x²-curves are convex upwards; for SV-waves the curves are convex downwards. For SH-waves transverse isotropy has no effect on curvature.     

Steady flows driven by sources of random strength in heterogeneous aquifers with application to partially penetrating wells

Average steady source flow in heterogeneous porous formations is modelled by regarding the hydraulic conductivity K(x) as a stationary random space function (RSF). As a consequence, the flow variables become RSFs as well, and we are interested into calculating their moments. This problem has been intensively studied in the case of a Neumann type boundary condition at the source. However, there are many applications (such as well-type flows) for which the required boundary condition is that of Dirichlet. In order to fulfill such a requirement the strength of the source must be proportional to K(x), and therefore the source itself results a RSF. To solve flows driven by sources whose strength is spatially variable, we have used a perturbation procedure similar to that developed by Indelman and Abramovich (Water Resour Res 30:3385–3393, 1994) to analyze flows generated by sources of deterministic strength. Due to the linearity of the mathematical problem, we have focused on the explicit derivation of the mean head distribution G _d (x) generated by a unit pulse. Such a distribution represents the fundamental solution to the average flow equations, and it is termed as mean Green function. The function G _d (x) is derived here at the second order of approximation in the variance σ² of the fluctuation (where K _A is the mean value of K(x)), for arbitrary correlation function ρ(x), and any dimensionality d of the flow domain. We represent G _d (x) as product between the homogeneous Green function G _d ⁽⁰⁾(x) valid in a domain with constant K _A , and a distortion term Ψ _d (x) = 1 + σ²ψ _d (x) which modifies G _d ⁽⁰⁾(x) to account for the medium heterogeneity. In the case of isotropic formations ψ _d (x) is expressed via one quadrature. This quadrature can be analytically calculated after adopting specific (e.g.. exponential and Gaussian) shape for ρ(x). These general results are subsequently used to investigate flow toward a partially-penetrating well in a semi-infinite domain. Indeed, we construct a σ²-order approximation to the mean as well as variance of the head by replacing the well with a singular segment. It is shown how the well-length combined with the medium heterogeneity affects the head distribution. We have introduced the concept of equivalent conductivity K ^eq(r,z). The main result is the relationship where the characteristic function ψ^(w)(r,z) adjusts the homogeneous conductivity K _A to account for the impact of the heterogeneity. In this way, a procedure can be developed to identify the aquifer hydraulic properties by means of field-scale head measurements. Finally, in the case of a fully penetrating well we have expressed the equivalent conductivity in analytical form, and we have shown that (being the effective conductivity for mean uniform flow), in agreement with the numerical simulations of Firmani et al. (Water Resour Res 42:W03422, 2006).     

Heat discharge from summit crater of Mihara volcano, Ooshima, Japan

Using an infrared radiation thermometer, measurements by remote sensing were carried out for surface temperatures of the bottom-floor and wall of the central pit and its surrounding crater bottom of Mihara volcano, Ooshima, Japan. Isotherms for the wall of the central pit are compared with the thermal and other surface manifestations. Heat discharge from the summit crater of Mihara volcano is estimated on the basis of various meteorological and other techniques, and for convenience of computation it is divided into the following three categories; latent and sensible heat transferred by ascending volcanic gas; heat emitted from the bottom-floor and wall of the central pit; and heat transported conductively and convectively from the underground heat source through the western, southern and eastern parts of the crater bottom. The computed heat discharge is estimated to be 1.4 x 10⁷ cal s⁻¹, which is about one order of magnitude less than that of the minor eruption on 28 February 1974. The methodology developed here for estimation of the heat discharge from a volcano can also be applied to other volcanoes.     

Recent developments in photochemistry of atmospheric ozone

Summary A review is given of the increasingly rapid development of the photochemistry of odd oxygen particles which has taken place since the validity of the classical (oxygen only) theory was for the first time questioned by Hampson and Hunt less than 10 years ago. The relative importance of different reactions is discussed as a function of altitude and also the alterations of the H-system, introduced by NO_x, are investigated. It is shown that the fact that not only the observed ozone but also the HNO₃ distribution should be explained considerably limits the acceptable values of poorly known rate constants. The influence of stratospheric pollution on ozone concentration is also discussed under the assumption of photochemical equilibrium.List of symbols Õ Odd oxygen particles - active hydrogen particles - O^* excited (¹ D)-O-atom - NO_x nitrogen oxides (odd nitrogen) - n ₁ concentration of atomic oxygen [particles cm^–3] - n ₁ ^* concentration of excited [¹ D]-oxygen-atoms - n ₂ concentration of molecular oxygen - n _m concentration of air molecules - s =n _m /n ₂ - ñ n ₁+n ^*+n ₃, concentration of odd oxygen particles - x concentration of atomic hydrogen - y concentration of OH-radicals - z concentration of HO₂-radicals - [NO] concentration of nitric oxide - [NO₂] concentration of nitrogen dioxide - [NO₃] concentration of nitrogen trioxide - [NO_x] concentration of total odd nitrogen - [HNO₃] concentration of nitric acid - k _i reaction rates - f _i dissociation rates - a ₃ fraction off ₃ yielding excited O-atoms - [nomix] NO _x /air mixing ratio - relaxation time Part of the research reported in this article was done at the National Center for Atmospheric Research, Boulder, Colo. (sponsored by the National Science Foundation). The opportunity of using NCAR's computing facilities is especially acknowledged. This study has also been supported by the Swiss National Foundation.     

Regional Be production rate calibration for the past 12 ka deduced from the radiocarbon-dated Grøtlandsura and Russenes rock avalanches at 69° N, Norway

Two rock avalanches in Troms County – the Grøtlandsura and Russenes – were selected as CRONUS-EU natural cosmogenic ¹⁰Be production-rate calibration sites because they (a) preserve large boulders that have been continuously exposed to cosmic irradiation since their emplacement; (b) contain boulders with abundant quartz phenocrysts and veins with low concentrations of naturally-occurring ⁹Be (typically < 1.5 ppb); and (c) have reliable minimum radiocarbon ages of 11,424 ± 108 cal yr BP and 10,942 ± 77 cal yr BP (1σ), respectively. Quartz samples (n = 6) from these two sites contained between 4.28 × 10⁴ and 5.06 × 10⁴ at ¹⁰Be/g using the 1.387 Myr ¹⁰Be half-life. Determination of these concentrations accounts for topographic and self-shielding, and effects on nuclide production due to isostatic rebound are shown to be negligible. Persistent, constant snow and moss cover cannot be proven, but if taken into consideration they may have reduced ¹⁰Be concentrations by 10%. Using the ¹⁰Be half-life of 1.387 Myr and the Stone scaling scheme, and accounting for snow- and moss-cover, we calculate an error-weighted mean total ¹⁰Be production rate of 4.12 ± 0.19 at/g/yr (1σ). A corresponding error-weighted mean spallogenic ¹⁰Be production rate is 3.96 ± 0.16 at/g/yr (1σ), respectively. These are in agreement within uncertainty with other ¹⁰Be production rates in the literature, but are significantly, statistically lower than the global average ¹⁰Be production rate. This research indicates, like other recent studies, that the production of cosmogenic ¹⁰Be in quartz is lower than previously established by other production-rate calibration projects. Similarly, our findings indicate that regional cosmogenic production rates should be used for determining exposure ages of landforms in order to increase the accuracy of those ages. As such, using the total ¹⁰Be production rate from our study, we determine an error-weighted mean surface-exposure age of a third rock avalanche in Troms County (the Hølen avalanche) to be 7.5 ± 0.3 kyr (1σ). This age suggests that the rock avalanche occurred shortly after the 8.2 kyr cooling event, just as the radiocarbon ages of the Grøtlandsura and Russenes avalanches confirm field evidence that those rock-slope failures occurred shortly after deglaciation.     

THE INDUCTIVE RESPONSE OF A HORIZONTAL CONDUCTING CYLINDER BURIED IN A UNIFORM EARTH FOR A UNIFORM INDUCING FIELD*

The inductive response of a conducting horizontal cylinder embedded in a uniform earth is studied using numerical results obtained for an analytical solution for the problem of a conducting cylinder buried in a homogeneous earth for the case of a uniform inducing field. A check of the validity of the numerical results is made by a comparison with analogue model measurements for a number of cases. Numerical results for a range of cylinder radii (a = 1–10 km), depths of burial (d= 0–4 km), conductivity contrasts (σ₂= 10^?2-10 Sm^?1), and source frequencies (f= 10^?1-10^?4 Hz) of interest in the interpretation of magnetotelluric field measurements are presented. The results indicate that for a uniform inducing field the conductivity and depth of burial of a horizontal cylindrical inhomogeneity are best determined through a measurement of the amplitudes H_y, H_z and E_x and the phases φ_y and Ψ_x.     

Ra in the Japan Sea and the residence time of the Japan Sea water

The surface water of the Japan Sea contained²²⁶Ra of70 ± 4dpm m⁻³ which was nearly equal to that of the surface water in the North Pacific. The concentration of²²⁶Ra in the Japan Sea deep water below 500 m was151 ± 8dpm m⁻³, showing a vertically and regionally small variation. This concentration of²²⁶Ra in the deep water is unexpectedly high, because the Japan Sea deep water has a higher Δ¹⁴ C value by about 50‰ than the Atlantic deep water containing the same²²⁶Ra. One of the causes to be considered is larger contribution of²²⁶Ra from biogenic particles dissolving in the Japan Sea deep water, but the Japan Sea is not so fertile in comparison to the Bering Sea. The other more plausible cause is the internal ventilation of the Japan Sea water, which means that the residence time of the Japan Sea Proper water is considerably long although the water is vertically mixed fairly well especially in winter. The ventilation may supply some amounts of radiocarbon and oxygen but does not change the inventory of²²⁶Ra. The residence times of the Japan Sea deep water and of water within the Japan Sea are calculated by solving simultaneous equations for²²⁶Ra and¹⁴C with a three-box model to be 300–400 years and 700–1000 years, respectively.     

A thin film approach for producing mineral diffusion couples

Few diffusion coefficient values have been measured for silicate minerals at pertinent geologic conditions because of experimental restrictions. Until recently, analysis of diffusion couples was conducted principally with electron microprobes which have rather poor spatial resolution (micrometer scale). Ion microprobe analyses, however, eliminate many of the previous experimental restrictions; in depth profile mode they have excellent spatial resolution (tens of angstroms) and diffusion couples can be analyzed normal to the interface. Diffusion couples analyzed by ion microprobe must be well-defined and uniform; previous methods using solution precipitates to form the diffusion couples were heterogeneous and had limited success. A new approach, the thermal evaporation of²⁵MgO under high vacuum onto a crystalline substrate (oxide, silicate), produces a 1000 Å thick²⁵MgO _x (x<1) thin film. This method yields an excellent diffusion couple for low-temperature diffusion experiments. Diffusion anneal experiments using this approach for garnet provide a Mg self-diffusion coefficient ofD=0.60±0.09×10^–21 m²/s at 1000°C (logFO₂=–11.3,P=1 atm,X _Almandine=0.24).     

Helium-isotope systematics at Nevado del Ruiz volcano, Colombia: implications for the volcanic hydrothermal system

We have collected 14 water and gas samples from 9 thermal springs and gas vents near Nevado del Ruiz volcano, Colombia. The ³He/⁴He and ⁴He/²⁰Ne ratios vary significantly from 0.98 R_atm (where R_atm is the atmospheric ³He/⁴He ratio of 1.4 × 10⁻⁶) to 6.30 R_atm, and from 0.37 to 7.0, respectively. The ³He/⁴He ratio (corrected for air contamination) decreases with increasing distance from the central crater of the volcano to the sampling site. The trend is very similar to that observed at Ontake volcano, Japan. A hydrodynamic porous-media dispersion model can explain the ³He/⁴He trend. The temporal variations in the ³He/⁴He ratio at four sites provide useful information on the apparent velocity of the magmatic fluid flow brought on by a volcanic eruption. The estimated value of several tens m day⁻¹ agrees well with the inferred velocity of flow in Oshima volcano, Japan and is comparable to the largest rate of groundwater movement in a deep sedimentary basin.     

Gopher bioturbation: field evidence for non‐linear hillslope diffusion

It has generally been assumed that diffusive sediment transport on soil‐mantled hillslopes is linearly dependent on hillslope gradient. Fieldwork was done near Santa Barbara, California, to develop a sediment transport equation for bioturbation by the pocket gopher (Thomomys bottae) and to determine whether it supports linear diffusion. The route taken by the sediment is divided into two parts, a subsurface path followed by a surface path. The first is the transport of soil through the burrow to the burrow opening. The second is the discharge of sediment from the burrow opening onto the hillslope surface. The total volumetric sediment flux, as a function of hillslope gradient, is found to be: q_s (cm³ cm⁻¹ a⁻¹) = 176(dz/dx)³ − 189(dz/dx)² + 68(dz/dx) + 34(dz/dx)^0·4. This result does not support the use of linear diffusion for hillslopes where gopher bioturbation is the dominant mode of sediment transport. A one‐dimensional hillslope evolution program was used to evolve hillslope profiles according to non‐linear and linear diffusion and to compare them to a typical hillslope. The non‐linear case more closely resembles the actual profile with a convex cap at the divide leading into a straight midslope section. Copyright © 2000 John Wiley & Sons, Ltd.     

The response of a horizontal conducting cylinder embedded in a uniform earth for uniform and line current sources

The response of a horizontal conducting cylinder embedded in a uniform conducting earth is studied using mathematical models of uniform and line current source excitation for the period range 10 to 10⁴ s. The line current source is located at heights ranging from 100–750 km above the surface of the earth. From the calculated results, it is shown that for periods greater than 10³ s the ratioE _x /H _y at the surface of the earth for localized fields, such as the auroral and equatorial electrojet normally situated at heights of about 100 km, is considerably different from that for a uniform source. The results presented also show that the magneto-telluric method of geophysical prospecting for ore bodies in regions of the electrojet may not be very practicable for periods exceeding 10³ s.     

Instantaneous global ozone balance including observed nitrogen dioxide

The catalytic destruction of stratospheric ozone by the oxides of nitrogen is believed to be an important part of the global ozone balance. The lack of sufficient measurements of NO _x concentrations has impeded efforts to quantify this process. Recent measurements of stratospheric nitrogen dioxide from ground-based stations as well as aircraft and balloons have provided a first approximation to a global distribution of NO₂ vertical columns at sunset. These observed vertical columns have been translated into time-dependent vertical NO₂ profiles by means of a one-dimensional atmospheric photochemical model. Using recent observations of air temperature and ozone along with this information, the independent instantaneous (one second) rates of ozone production from oxygen photolysis P(O₃), of ozone destruction from pure oxygen species (Chapman reactions) L(O _x ), and of ozone destruction by nitrogen oxides L(NO _x ) were estimated over the three-dimensional atmosphere. These quantities are displayed as zonal average contour maps, summed over various latitude zones, summed over various altitude bands, and integrated globally between 15 and 45 km. Although the global summation between 15 and 45 km by no means tells the complete story, these numbers are of some interest, and the relative values are: P(O₃), 100; L(O _x ), 15; L(NO _x ), 45±15. It is to be emphasized that this relative NO _x contribution to the integrated ozone balance is not a measure of the sensitivity of ozone to possible perturbations of stratospheric NO _x ; recent model results must be examined for current estimates of this sensitivity.     

大型浅水湖泊与大气之间的动量和水热交换系数——以太湖为例

湖泊水面与大气之间垂直方向的动量、水汽和热量通量与风速、湿度和温度梯度之间存在比例关系,因此在湖泊水-气相互作用研究中,这比例系数(交换系数)是关键因子.在以往的研究中,交换系数通常直接采用水面梯度观测法或海洋大气近地层的参数化方案进行计算.本文采用涡度相关系统和小气候系统仪器在太湖平台上直接观测的通量和气象要素,对上述交换系数(最小均方差原则)进行优化,结果为:动量交换系数C_D10N=1.52×10^-3、水汽交换系数C_E10N=0.82×10^-3、热量交换系数CH10N=1.02×10^-3,与其他内陆湖泊涡度相关观测数据的推导结果一致.本文的研究结果表明:与海洋参数化方案相比,在相同的风速条件下,湖面的空气动力学粗糙度比海洋高,这可能是由于受到水深的影响;如果采用海洋参数化方案,会导致湖泊年蒸发量的估算值偏大40%.太湖的动量、水汽和热量交换系数可以视为常数,可以不考虑稳定度和风速的影响.这是因为本文中83%的数据为近中性条件.敏感性分析表明:如果考虑稳定度的影响,LE模拟值的平均误差降低了0.5 W/m²,H的平均误差降低了0.4 W/m²,u*的计算值没有变化;如果考虑风速的影响,u*模拟值的平均误差降低了0.004 m/s,LE的平均误差升高了1.3 W/m²,H的模拟结果几乎不受影响.这一结果能为湖气相互作用研究提供参考.     

The impact of changing subcanopy radiation on snowmelt in a disturbed coniferous forest

Understanding the role of forests on snowmelt processes enables better estimates of snow storages at a catchment scale and contributes to a higher accuracy of spring flood forecasting. A coniferous forest modifies the snowpack energy balance by reducing the total amount of solar shortwave radiation (SWR) and enhancing the role of longwave radiation (LWR) emitted by trees. This study focuses on changes in SWR and LWR at three sites with different canopy structure (Bohemian Forest, Czechia), including one site affected by the bark beetle (Ips typographus). Measurements of incoming and outgoing SWR and LWR were performed at all sites equipped with CNR4 Net Radiometers for three cold seasons. In addition to SWR and LWR, sensible and latent heat, and ground heat and energy supplied by liquid precipitation were calculated. The results showed that net SWR at the healthy forest site represented only 7% of the amount at the open site due to the shading effect of trees. In contrast, net LWR represented a positive component of the snowpack energy balance at the healthy forest site and thus contributed the most to snowmelt. However, the modelled snowmelt rates were significantly lower in the forest than in the open area since the higher LWR in the forest did not compensated for the lower SWR. The progressive decay of disturbed forest caused the decrease in mean net LWR from −3.1 W/m² to −12.9 W/m² and the increase in mean net SWR from 31.6 W/m² to 96.2 W/m² during the study period. These changes caused an increase in modelled snowmelt rates by 50% in the disturbed forest, compared to the healthy forest site, during the study period. Our findings have important implications for runoff from areas affected by land cover changes due to either human activity or climate change.     

Fermat's Variational Principle for Anisotropic Inhomogeneous Media

Fermat's variational principle states that the signal propagates from point S to R along a curve which renders Fermat's functional (l) stationary. Fermat's functional (l) depends on curves l which connect points S and R, and represents the travel times from S to R along l. In seismology, it is mostly expressed by the integral (l) = (x ^k,x ^k ')du, taken along curve l, where (x ^k,x ^k ') is the relevant Lagrangian, x ^k are coordinates, u is a parameter used to specify the position of points along l, and x ^k ' = dx ^k÷du. If Lagrangian (x ^k,x ^k ') is a homogeneous function of the first degree in x ^k ', Fermat's principle is valid for arbitrary monotonic parameter u. We than speak of the first-degree Lagrangian ⁽¹⁾(x ^k,x ^k '). It is shown that the conventional Legendre transform cannot be applied to the first-degree Lagrangian ⁽¹⁾(x ^k,x ^k ') to derive the relevant Hamiltonian ⁽¹⁾(x ^k,p _k), and Hamiltonian ray equations. The reason is that the Hessian determinant of the transform vanishes identically for first-degree Lagrangians ⁽¹⁾(x ^k,x ^k '). The Lagrangians must be modified so that the Hessian determinant is different from zero. A modification to overcome this difficulty is proposed in this article, and is based on second-degree Lagrangians ⁽²⁾. Parameter u along the curves is taken to correspond to travel time , and the second-degree Lagrangian ⁽²⁾(x ^k, ^k ) is then introduced by the relation ⁽²⁾(x ^k, ^k ) = [⁽¹⁾(x ^k, ^k )]², with ^k = dx ^k÷d. The second-degree Lagrangian ⁽²⁾(x ^k, ^k ) yields the same Euler/Lagrange equations for rays as the first-degree Lagrangian ⁽¹⁾(x ^k, ^k ). The relevant Hessian determinant, however, does not vanish identically. Consequently, the Legendre transform can then be used to compute Hamiltonian ⁽²⁾(x ^k,p _k) from Lagrangian ⁽²⁾(x ^k, ^k ), and vice versa, and the Hamiltonian canonical equations can be derived from the Euler-Lagrange equations. Both ⁽²⁾(x ^k, ^k ) and ⁽²⁾(x ^k,p _k) can be expressed in terms of the wave propagation metric tensor g _ij(x ^k, ^k ), which depends not only on position x ^k, but also on the direction of vector ^k . It is defined in a Finsler space, in which the distance is measured by the travel time. It is shown that the standard form of the Hamiltonian, derived from the elastodynamic equation and representing the eikonal equation, which has been broadly used in the seismic ray method, corresponds to the second-degree Lagrangian ⁽²⁾(x ^k, ^k ), not to the first-degree Lagrangian ⁽¹⁾(x ^k, ^k ). It is also shown that relations ⁽²⁾(x ^k, ^k ) = ; and ⁽²⁾(x ^k,p _k) = are valid at any point of the ray and that they represent the group velocity surface and the slowness surface, respectively. All procedures and derived equations are valid for general anisotropic inhomogeneous media, and for general curvilinear coordinates x ⁱ. To make certain procedures and equations more transparent and objective, the simpler cases of isotropic and ellipsoidally anisotropic media are briefly discussed as special cases.