Centroid-moment tensor solutions for 113 large earthquakes in 1977–1980

The Centroid-Moment Tensor technique is applied to 113 large earthquakes of the period 1977–1980, including all the shallow events with magnitude m_b, M_s or M_L 6.5. We use digital data recorded by the Global Digital Seismograph Network (GDSN) and International Deployment of Accelerometers (IDA) networks. Solutions are determined for three sequences of events close in time by inverting mantle wave data simultaneously for multiple sources.     

The Big Brother Experiment and seasonal predictability in the NCEP regional spectral model

The Big Brother Experiment methodology of Denis et al. (Clim Dyn 18:627-646, 2002) is applied to test the downscaling ability of a one-way nested regional climate model. This methodology consists of first obtaining a reference climate by performing a large domain, high resolution regional climate model simulation—the Big Brother. The small scales are then filtered out from the Big Brother’s output to produce a data set whose effective resolution is comparable to those of the data sets typically used to drive regional climate models. This filtered data set is then used to drive the same nested regional climate model, integrated over a smaller domain, but at the same high resolution as the Big Brother - the Little Brother. Any differences can only be attributed either to errors associated with the nesting strategy and downscaling technique, or to inherent unpredictability of the system, but not to model errors. This methodology was applied to the National Center for Environmental Prediction Regional Spectral Model over a tropical domain for a 1-month simulation period. The Little Brother reproduced most fields of the Big Brother quite well, with the important exception of the small-scale component of the precipitation field, which was poorly reproduced. Sensitivity experiments indicated that the poor agreement of the precipitation at these scales in a tropical domain was due primarily to the behavior of convective processes, and is specific to the Big Brother Experiment on the tropical domain. Much better agreement for the small-scale precipitation component was obtained in an extratropical winter case, suggesting that one factor explaining the tropical result is the importance of convective processes in controlling precipitation, versus the greater importance of large-scale dynamics in the winter extratropics. In the tropical case, results from two ensembles of five 3-month seasonal simulations forced by GCM output suggest a considerably greater predictability for the small-scale stationary component of tropical precipitation than did the Big Brother Experiment.     

Evidence for adiabatic decompression melting in the Southern Mariana Arc from high-Mg lavas and melt inclusions

Unusually magnesian (Mg# ∼76) basalts have been sampled from a small submarine volcano situated on the Mariana arc magmatic front. Total alkalis range from 1.7 to 1.94%, Al₂O₃ from 9.09 to 10.3% and CaO from 13.9 to 14.09%. These lavas can be classified based on mineralogy as picrite and ankaramite. Olivine-hosted melt inclusions (MIs) have median MgO contents of 17.17–17.86 wt%, 0.35–0.5% TiO₂, 42–50% SiO₂ and 1.66–3.43% total alkalis, which suggest that the parental magmas were primitive mantle melts. Trace element concentrations for both MIs and lavas are arc-like, although more depleted than most arc lavas. Chlorine (182–334 ppm) and H₂O contents (0.11–0.64 wt%) in the MIs are consistent with the estimated median oxygen fugacities (log ΔFMQ of + 1.53–1.66) which lie at the low end of the range estimates for arc basalts and picrites (ΔFMQ = + 1 to + 3). Isotopic compositions of Sr, Nd, Hf and Pb are similar to those of other Mariana arc lavas and indicate derivation from an Indian Ocean mantle domain. The averaged magmatic temperature estimate from several geothermometers was 1,367°C at 1–1.5 GPa. We propose that high-Mg magmagenesis in this region results from the adiabatic decompression melting of relatively anhydrous but metasomatized mantle wedge. This melting is attributed to enhanced upwelling related to unusual tectonics on the over-riding plate related to a tear or other discontinuity on the subducted slab.Electronic Supplementary Material Supplementary material is available for this article at and is accessible for authorized users.     

2-D seismic tomographic and ray tracing modelling of the crustal structure across the Sudetes Mountains basing on SUDETES 2003 experiment data

The seismic data obtained during SUDETES 2003 experiment are analysed, and detailed crustal structure for profiles S02, S03 and S06 is presented using three different 2-D techniques: (1) “smooth” tomography of refracted waves travel times, (2) ray tracing of reflected and refracted waves, and (3) joint velocity and depth of reflector tomographic inversion. In spite of different interpretation techniques used, the models of the crustal structure show common characteristic features. The low velocity (V_p < 4 km/s) sedimentary layer was documented in the northeastern part of the study area. The topmost basement has in general a velocity of 5.8–6.0 km/s, and velocities at ca. 20 km depth are 6.15–6.25 km/s. The strong reflecting boundaries were found at 20–23 and 25–28 km depth with a velocity contrast about 0.4 km/s, and the highest velocities in the lowermost crust are 6.8–7.2 km/s. In general, the crust of the Bohemian Massif is slightly thicker (33–35 km) than in the northern part of the area. Velocities beneath Moho are relatively low, of 7.95 km/s. On the basis of well recorded reflected waves, mantle reflectors were discovered in the depth interval ca. 40–70 km. Apart of new results for the geology and tectonics of the area, some conclusion could be made about different techniques used. In the 2-D case the “clasical” ray tracing method with using all correlated phases gives the most adequate model of the structure, because of full, manual control of the model creation. The “smooth” first arrival travel times tomography, although very fast, is not satisfactory enough to describe the complex structure. So, the best candidate in 3-D case seems to be travel time tomography for both refracted and reflected waves in multi-layers models.     

An On Line Atmospheric Dispersion Model (OLADMO) for the World Wide Web

This paper presents an overview of earlier and current methods of modelling atmospheric dispersion, and proposes and evaluates a screening model for operation over the World Wide Web. The On Line Atmospheric Dispersion Model (OLADMO) is a quasi boundary layer parameterised Gaussian plume model with additional algorithms to account for plume rise, building wake effects and deposition processes. The Monin–Obukhov length boundary layer parameter is utilised to define six stability classes in order to determine atmospheric turbulence and stability, whilst new equations, derived from an intercomparison study of old and next generation dispersion models, are used to calculate the horizontal and vertical dispersion coefficients σ _y and σ _z . Using data from two field experiments in Copenhagen, Denmark and Lillestrøm, Norway, the model results from OLADMO are found to compare favourably with the results from several old and next generation dispersion models. As a consequence of the unique nature of the meteorological and location factors of the Lillestrøm experiment, all models struggled to represent the concentrations observed during the field study adequately. However, OLADMO was the best performing model in this case, with a mean normalised crosswind integrated concentration 13% closer to the mean observed concentration than its nearest competitor. Because the evaluation of the model was conducted with a limited dataset, several limitations and improvements to both the model and experimental procedure are suggested.     

Trace element characteristics of partial melts produced by melting of metabasalts at high pressures: Constraints on the formation condition of adakitic melts

Modern adakite, Archean tonalite-trondhjemite- granodiorite (TTG) and adakitic rocks derived from lower continental crust are high Na and Al felsic rocks and are characterized by strong heavy REE and Y de- pletion and high Sr/Y and La/Yb ratios, which sug…     

Northern Hemisphere circulation regimes: observed, simulated and predicted

Nonlinear principal component analysis provides evidence that the Northern Hemisphere extratropical atmosphere supports three distinct circulation regimes with an average residence time of about 7 days. The role of high- and low-frequency dynamics is studied and results indicate that they are both involved in the formation, maintenance and decay of the regimes. A global coupled climate model also supports three distinct circulation regimes with strikingly similar spatial structures, residence times and linked high- and low-frequency dynamics to those observed. The issue related to how long a data record is required to properly resolve the regime structures is addressed by exploiting the model output. Regime residence times and spatial structures are predicted to change over the next century given increasing concentrations of atmospheric greenhouse gases.     

Application of turning bands technique to simulate values of copper ore deposit parameters in Rudna mine (Lubin-Sieroszowice region in SW part of Poland)

ABSTRACT

The turning bands simulation is a valuable and highly useful tool in solving various geological-mining, environmental and geological-engineering problems when it is essential to determine the uncertainty of the estimates of simulated values Z_s (realizations) and assess the risk. This paper presents an investigative methodology and the results of calculations connected with the use of conditional turning bands simulation and bundled indicator kriging, making it possible to analyse the risk at different levels of uncertainty in the solution of optimization of the exploitation problems encountered in the mining of the polymetallic copper ore deposits in the Lubin-Sieroszowice region (Foresudetic monocline, the SW part of Poland). Examples of the evaluation of simulated values Z_s and probability P average values Z* of the deposit parameters within the block located in the Rudna Mine (the block R-3) area are provided.     

New insights into lake responses to rapid climate change: the Younger Dryas in Lake Gościąż, central Poland

The sediment profile from Lake Gościąż in central Poland comprises a continuous, seasonally resolved and exceptionally well-preserved archive of the Younger Dryas (YD) climate variation. This provides a unique opportunity for detailed investigation of lake system responses during periods of rapid climate cooling (YD onset) and warming (YD termination). The new varve record of Lake Gościąż presented here spans 1662 years from the late Allerød (AL) to the early Preboreal (PB). Microscopic varve counting provides an independent chronology with a YD duration of 1149+14/–22 years, which confirms previous results of 1140±40 years. We link stable oxygen isotopes and chironomid-based air temperature reconstructions with the response of various geochemical and varve microfacies proxies especially focusing on the onset and termination of the YD. Cooling at the YD onset lasted ~180 years, which is about a century longer than the terminal warming that was completed in ~70 years. During the AL/YD transition, environmental proxy data lagged the onset of cooling by ~90 years and revealed an increase of lake productivity and internal lake re-suspension as well as slightly higher detrital sediment input. In contrast, rapid warming and environmental changes during the YD/PB transition occurred simultaneously. However, initial changes such as declining diatom deposition and detrital input occurred already a few centuries before the rapid warming at the YD/PB transition. These environmental changes likely reflect a gradual increase in summer air temperatures already during the YD. Our data indicate complex and differing environmental responses to the major climate changes related to the YD, which involve different proxy sensitivities and threshold processes.