Hazard Assessment Studies Research Articles

Monitoring of temporal and spatial variations in fumarole helium and carbon dioxide characteristics at Po^|^aacute;s and Turrialba volcanoes, Costa Rica (2001-2009)

We report results of a 9-year monitoring program that took place from 2001 to 2009 of the helium and carbon isotope (3He/4He, δ13C) and relative abundances ratios (CO2/3He) of fumarole sites at Poás and Turrialba volcanoes, Costa Rica. Over the monitoring period, helium isotopes (3He/4He), δ13C(CO2) and CO2/3He values varied between 6.7-7.6 RA (where RA = 1.4 × 10-6), -5.5 to -1.3‰ (vs. PDB) and 8.2-59.5 (×109), respectively, at Poás Volcano. Corresponding values for Turrialba Volcano were 6.9-8.0 RA, -4.4 to -2.7‰ and 9.4-19.6 (×109), respectively. Notably, fumarole sites at both volcanoes underwent changes in temperature, intensity and areal extent during the 9-year period, and Poás Volcano experienced hydrophreatic eruptions and structural damage induced by a nearby earthquake. At both volcanoes, there were significant and sympathetic temporal changes involving all three geochemical parameters—notably in 2001 and 2006 at Poás and in 2001 and between 2005-2007 at Turrialba. We dismiss increased hydrothermal interaction, magma degassing and calcite precipitation as likely causes of the observed variations. Instead, by ascribing endmember compositions to the three principal contributors to the CO2 inventory—mantle wedge as well as limestone and organic (sedimentary) carbon (both slab and crust derived)—we show that changes in observed He-CO2 relationships mainly reflect enhanced crustal contributions of CO2 and increased inputs from magma degassing. Such changes in the relative roles of crust and magma as suppliers of CO2 are readily apparent in the He-CO2 temporal record. This work supports calls for long-term geochemical monitoring to be included within hazard assessment and mitigation studies at active volcanoes.

Development, testing, and applications of site‐specific tsunami inundation models for real‐time forecasting

The study describes the development, testing and applications of site‐specific tsunami inundation models (forecast models) for use in NOAA's tsunami forecast and warning system. The model development process includes sensitivity studies of tsunami wave characteristics in the nearshore and inundation, for a range of model grid setups, resolutions and parameters. To demonstrate the process, four forecast models in Hawaii, at Hilo, Kahului, Honolulu, and Nawiliwili are described. The models were validated with fourteen historical tsunamis and compared with numerical results from reference inundation models of higher resolution. The accuracy of the modeled maximum wave height is greater than 80% when the observation is greater than 0.5 m; when the observation is below 0.5 m the error is less than 0.3 m. The error of the modeled arrival time of the first peak is within 3% of the travel time. The developed forecast models were further applied to hazard assessment from simulated magnitude 7.5, 8.2, 8.7 and 9.3 tsunamis based on subduction zone earthquakes in the Pacific. The tsunami hazard assessment study indicates that use of a seismic magnitude alone for a tsunami source assessment is inadequate to achieve such accuracy for tsunami amplitude forecasts. The forecast models apply local bathymetric and topographic information, and utilize dynamic boundary conditions from the tsunami source function database, to provide site‐ and event‐specific coastal predictions. Only by combining a Deep‐ocean Assessment and Reporting of Tsunami‐constrained tsunami magnitude with site‐specific high‐resolution models can the forecasts completely cover the evolution of earthquake‐generated tsunami waves: generation, deep ocean propagation, and coastal inundation. Wavelet analysis of the tsunami waves suggests the coastal tsunami frequency responses at different sites are dominated by the local bathymetry, yet they can be partially related to the locations of the tsunami sources. The study also demonstrates the nonlinearity between offshore and nearshore maximum wave amplitudes.

IzmirNet: A strong-motion Network in Metropolitan Izmir, Western Anatolia, Turkey

A 16-station strong-motion seismic monitoring network covering metropolitan Izmir and the surrounding region was established in July 2008. The seismic network was installed as a cooperative effort involving the Earthquake Research and Implementation Center (ERIC-DAUM) of Dokuz Eylul University (DEU, Izmir), the Earthquake Research Department (ERD) of the General Directorate of Disaster Affairs (GDDA, Ankara), the Izmir Metropolitan Municipality, and the Ministry of Public Works and Settlement. The project was funded by the Scientific and Technological Research Council of Turkey (TUBITAK) to collect strong-motion data for earthquake hazard assessment studies and to develop a real-time monitoring system in Turkey (Inan et al. 2007) to address public safety issues. The network is critically important to addressing earthquake hazard issues in western Turkey, an area known to have historically damaging earthquakes. Izmir is the third largest city in Turkey in terms of population, industrial density, economic capacity, and contribution to the national economy, and the economic and human consequences of a damaging earthquake in the Izmir area would be significant. A primary goal of this project is to acquire strong ground-motion data in order to understand propagation and site response characteristics of the Quaternary and Neogene sediments that underlie the Izmir metropolitan area and are thought to produce large site amplification and seismic hazard (Aydinoglu 2000; Masure et al. 2000). These data will complement laboratory data to characterize the properties of the soft soils underlying the Izmir metropolitan residential area so that engineers and architects can design appropriate earthquake-resistant structures for the region. This project is also a first step toward developing a “Rapid Response and Damage Prediction System” for metropolitan Izmir where near real-time strong ground-motion records can be used to compute ground-shaking maps showing the areas most strongly affected by earthquakes. The tectonic framework of western Anatolia is dominated …

Development of dike fragility curves for piping and micro-instability breach mechanisms

Abstract. The paper analyses the prevailing breach mechanisms of fluvial dikes. Piping in the dike foundation and slope failure as a consequence of seepage flow through a dike core (micro-instability) were identified as two of the dominant breach mechanisms for historically-grown dikes along with overtopping and slope macro-instability. For the former two mechanisms the physically-based and empirical process descriptions were reviewed and led to the formulation of the reliability functions. Evaluation of these functions in the Monte Carlo framework for the time dependent load led to the development of fragility functions. These functions indicate the probability of failure of a dike section upon loading and can be computed for each spatially discretised dike section. The probability of breaching is conditioned by the uncertainty in geometrical and geotechnical dike parameters. This uncertainty is explicitly taken into account during computation of the fragility functions in a Monte Carlo simulation. Sensitivity analysis was carried out in order to identify the sensitive geotechnical parameters influencing the distribution of failure probability. The identification of sensitive parameters indicates the priorities in geotechnical measurement campaigns aimed at the assessment of dike stability. The newly developed fragility functions can be applied in flood hazard and risk assessment studies for modelling of dike failures in a probabilistic framework.

Uncertainties in Strong Ground-Motion Prediction with Finite-Fault Synthetic Seismograms: An Application to the 1984 M 5.7 Gubbio, Central Italy, Earthquake

Abstract This study investigates the engineering applicability of two conceptually different finite-fault simulation techniques. We focus our attention on two important aspects: first to quantify the capability of the methods to reproduce the observed ground-motion parameters (peaks and integral quantities); second to quantify the dependence of the strong-motion parameters on the variability in the large-scale kinematic definition of the source (i.e., position of the nucleation point, value of the rupture velocity, and distribution of the final slip on the fault). We applied an approximated simulation technique, the deterministic-stochastic method and a broadband technique, the hybrid-integral-composite method, to model the 1984 M w 5.7 Gubbio, central Italy, earthquake, at five accelerometric stations. We first optimize the position of the nucleation point and the value of the rupture velocity for three different final slip distributions on the fault by minimizing an error function in terms of acceleration response spectra in the frequency band from 1 to 9 Hz. We found that the best model is given by a rupture propagating at about 2.65 km/sec from a hypocenter located approximately at the center of the fault. In the second part of the article we calculate more than 2400 scenarios varying the kinematic source parameters. At the five sites we compute the residuals distributions for the various strong-motion parameters and show that their standard deviations depend on the source parameterization adopted by the two techniques. Furthermore, we show that Arias Intensity (AI) and significant duration are characterized by the largest and smallest standard deviation, respectively. Housner Intensity is better modeled and less affected by uncertainties in the source kinematic parameters than AI. The fact that the uncertainties in the kinematic model affects the variability of different ground-motion parameters in different ways has to be taken into account when performing hazard assessment and earthquake engineering studies for future events.

A neural network method for analysis of hyperspectral imagery with application to the Cassas landslide (Susa Valley, NW-Italy)

Geomorphological analysis is an essential element of many landslide monitoring and hazard assessment studies. Remote sensing techniques have long been an effective tool for such analyses. This paper presents results regarding a geomorphological investigation performed exploiting information derived from high resolution hyper-spectral airborne sensor MIVIS ( Multi-spectral Infrared and Visible Imaging Spectrometer) images. The authors propose a workflow based on neural network algorithms used both for image geometric correction and classification. The case study area is the Middle Susa Valley (Italian Western-Alps). It includes the Cassas landslide, a well-known complex landslide affecting slopes on the southern side of the valley, near the town of Salbertrand. At this location several “lifelines” (railway, main roads, hydroelectric tunnels, etc.) are concentrated, and they suffer from a constant threat of landslide activity. Traditional geomorphological characterization of the landslide slope was improved by comparing field campaigns with further information extracted from remote-sensed datasets. Presented results include the identification and characterization of major elements of the present-day active unstable slope (debris-covered areas, fractured/disjointed rock walls, landslide accumulation borders), as well as of individual structural features and landforms (major faults and fractures, trenches, elongated depressions, counterslope scarps), related to long-term deep-seated gravitational slope deformation.

Quantifying uncertainty in mean earthquake interevent times for a finite sample

Seismic activity is routinely quantified using means in event rate or interevent time. Standard estimates of the error on such mean values implicitly assume that the events used to calculate the mean are independent. However, earthquakes can be triggered by other events and are thus not necessarily independent. As a result, the errors on mean earthquake interevent times do not exhibit Gaussian convergence with increasing sample size according to the central limit theorem. In this paper we investigate how the errors decay with sample size in real earthquake catalogues and how the nature of this convergence varies with the spatial extent of the region under investigation. We demonstrate that the errors in mean interevent times, as a function of sample size, are well estimated by defining an effective sample size, using the autocorrelation function to estimate the number of pieces of independent data that exist in samples of different length. This allows us to accurately project error estimates from finite natural earthquake catalogues into the future and promotes a definition of stability wherein the autocorrelation function is not varying in time. The technique is easy to apply, and we suggest that it is routinely applied to define errors on mean interevent times as part of seismic hazard assessment studies. This is particularly important for studies that utilize small catalogue subsets (fewer than ∼1000 events) in time‐dependent or high spatial resolution (e.g., for catastrophe modeling) hazard assessment.

زلزالية شبه جزيرة سيناء - مصر

The Sinai Peninsula has a triangular shape between the African and Arabian Plates and is bounded from the western and eastern borders by the Gulf of Suez and Gulf of Aqaba–Dead Sea rift systems, respectively. It is affected by strong and destructive earthquakes (e.g., March 31, 1969 and November 22, 1995) and moderate earthquakes (mb > 5) throughout its history. After the installation of the Egyptian National Seismic Network (ENSN), a great number of earthquakes has been recorded within and around Sinai. Consequently, the seismogenic source zones and seismotectonic behavior can be clearly identified. Available data, including both historical and instrumental (1900–1997), have been collected from national and international data centers. While the data from 1998 till December 2007 are gathered from ENSN bulletins. The seismogenic source zones that might affect Sinai Peninsula are defined more precisely in this work depending on the distribution of earthquakes, seismicity rate (a value), b value, and fault plane solution of the major earthquakes. In addition, the type of faults prevailed and characterized these zones. It is concluded that the Gulf of Aqaba zone–Dead Sea transform zone, Gulf of Suez rift zone, Cairo–Suez District zone, and Eastern Mediterranean dislocation zone represent the major effective zones for Sinai. Furthermore, there are two local seismic zones passing through Sinai contributing to the earthquake activities of Sinai, these are the Negev shear zone and Central Sinai fault (Themed fault) zone. The source parameters, a and b values, and the maximum expected moment magnitude have been determined for each of these zones. These results will contribute to a great extent in the seismic hazard assessment and risk mitigation studies for Sinai Peninsula to protect the developmental projects.

Comparison of Probabilistic Seismic Hazard Estimates in Italy

Abstract Macroseismic intensity has recently attracted attention as a tool for validating probabilistic seismic hazard assessment (PSHA) studies or as an alternative method for PSHA in countries where the historical catalog is much longer than the instrumental one. In Italy, the new seismic hazard map was recently produced using the Cornell–McGuire approach in terms of the peak ground acceleration characterized by a 10% exceedance probability for an exposure time of 50 yr ( A max ). We compare this map with an alternative one, produced using a different approach based on a nonparametric and zonation-free statistical analysis of local seismic histories. In this case, results are expressed in terms of the maximum intensity corresponding to an exceedance probability of not less than 10% for an exposure time of 50 yr ( I ref ). In order to compare the two maps, we selected 1401 control sites, where local seismic history includes at least 10 intensity values relative to felt effects documented during past earthquakes. The values of A max and I ref at these sites have been ranked in the respective domains. The spatial distribution of rank differences of A max and I ref values shows a strong correlation with the seismogenic zoning used in the calculation of PSHA following the Cornell–McGuire approach. This suggests that the adopted zoning could be incomplete (some further “hidden” sources may exist) and too rough to capture actual seismogenic sources. Because more detailed zoning is prevented by the amount of data available, the results obtained suggest the preference of zonation-free approaches for seismic hazard assessment in Italy. Furthermore, among the possible zonation-free approaches, those that offer better exploitation of local information about the effects of past earthquakes would be preferred.

Uncertainties in the estimation of M max

In the present paper, the parameters affecting the uncertainties on the estimation of Mmax have been investigated by exploring different methodologies being used in the analysis of seismicity catalogue and estimation of seismicity parameters. A critical issue to be addressed before any scientific analysis is to assess the quality, consistency, and homogeneity of the data. The empirical relationships between different magnitude scales have been used for conversions for homogenization of seismicity catalogues to be used for further seismic hazard assessment studies. An endeavour has been made to quantify the uncertainties due to magnitude conversions and the seismic hazard parameters are then estimated using different methods to consider the epistemic uncertainty in the process. The study area chosen is around Delhi. The b value and the magnitude of completeness for the four seismogenic sources considered around Delhi varied more than 40% using the three catalogues compiled based on different magnitude conversion relationships. The effect of the uncertainties has been then shown on the estimation of Mmax and the probabilities of occurrence of different magnitudes. It has been emphasized to consider the uncertainties and their quantification to carry out seismic hazard assessment and in turn the seismic microzonation.

Trampoline Effect in Extreme Ground Motion

In earthquake hazard assessment studies, the focus is usually on horizontal ground motion. However, records from the 14 June 2008 Iwate-Miyagi earthquake in Japan, a crustal event with a moment magnitude of 6.9, revealed an unprecedented vertical surface acceleration of nearly four times gravity, more than twice its horizontal counterpart. The vertical acceleration was distinctly asymmetric; the waveform envelope was about 1.6 times as large in the upward direction as in the downward direction, which is not explained by existing models of the soil response. We present a simple model of a mass bouncing on a trampoline to account for this asymmetry and the large vertical amplitude. The finding of a hitherto-unknown mode of strong ground motion may prompt major progress in near-source shaking assessments.

Seismic Hazard of Hong Kong

This paper reviews the probabilistic seismic hazard assessment studies undertaken in recent years to estimate the potential seismic ground motion levels on bedrock in Hong Kong. A detailed catalogue of historical and recent seismicity within the South China region has been compiled. A suite of published empirical and stochastic attenuation relationships have been used with alternative source models and source parameters in a logic tree hazard analysis. Uniform hazard bedrock ground-motion spectra having various probabilities of being exceeded in 50 years have been calculated. The results have been de-aggregated to investigate what earthquake magnitude and distance combinations have contributed most to the hazard levels for the different probabilities and structural periods. The obtained uniform hazard spectra have been compared to the study using an alternative assessment approach developed by the University of Hong Kong. Recent recorded earthquake ground motions in Hong Kong are also presented with the uniform hazard spectra.

ナノ粒子の有害性評価

Methods and end-points used in assessing the hazards of fibrous materials, whose hazards have been assessed, are often employed in studies on the hazards of nanoparticles. Since a possible route of exposure to nanoparticles in work environments is inhalation, data from animal inhalation and intratracheal instillation studies are thought to provide useful insights for assessing the hazards of such particles. Persistent inflammation and fibrosis in the chronic phase and their related factors are particularly important indicators of lung injury. On the other hand, there are some differences in the results of hazard assessment studies due mainly to a lack of detailed physiochemical characterizations of the nanoparticles evaluated. Dispersion properties in the chambers just before exposure in inhalation studies and those in the suspension to be injected in intratracheal instillation studies need to be determined. The number of hazard assessment studies in which characterization of nanoparticles is conducted, while small at present, is increasing and this could consequently yield reliable hazard assessment and risk assessment.

Subsurface electrical imaging of anisotropic formations affected by a slow active reverse fault, Provence, France

In seismic hazard assessment studies, near-surface geophysical prospecting is increasingly used to help in identifying active faults and to constrain seismic deformation parameters (fault offset, recurrence…). In the current study, electrical tomography was used (1) to locate the Trévaresse slow reverse fault (Provence, SE France), the source of the most important seismic event recorded in the 20th century in France and (2) to test electrical tomography's ability to detect faults and tectonic deformation in a complex geological environment. Our study is supported by a detailed geologic and geomorphic field study. In the investigated area, where the geology is made of a succession of folded marl and limestone layers, electrical images are strongly influenced by electrical macro-anisotropy which plays a critical role in this survey, depending on the investigation scale. When resolution (i.e. the smallest target that can be resolved) is larger than the layer thickness (at depth and/or for large electrode spacing), inversion is unable to retrieve the real structure. To successfully interpret these electrical images, in terms of tectonically induced dip variations, we constrain field data interpretation by comparing measured and inverted electrical data with synthetic modelling results and geological data. The synthetic models were hypothetical coarse geological structures determined on the basis of geological/geomorphologic information (e.g. outcropping layers). For shallow depths, when the resolution is smaller or equal to the anisotropy scale, an electrical tomogram yields straightforward interpretation of the subsurface structure. Coupled with numerical modelling, electrical results successfully helped in positioning a trench for fault characterization.

Understanding environmental geophysical anomalies - an interdisciplinary case study from the West Rand

Research Article| December 01, 2006 Understanding environmental geophysical anomalies – an interdisciplinary case study from the West Rand Henk Coetzee; Henk Coetzee Environmental Geoscience Unit, Council for Geoscience, Private Bag X112, Pretoria, 0001, South Africa, e-mail: henkc@geoscience.org.za, pwade@geoscience.org.za Search for other works by this author on: GSW Google Scholar Peter Wade; Peter Wade Environmental Geoscience Unit, Council for Geoscience, Private Bag X112, Pretoria, 0001, South Africa, e-mail: henkc@geoscience.org.za, pwade@geoscience.org.za Search for other works by this author on: GSW Google Scholar Frank Winde Frank Winde North West University, School of Environmental Sciences and Development, Private Bag X6001, Potchefstroom 2520, South Africa, e-mail: frank.winde@nwu.ac.za Search for other works by this author on: GSW Google Scholar Author and Article Information Henk Coetzee Environmental Geoscience Unit, Council for Geoscience, Private Bag X112, Pretoria, 0001, South Africa, e-mail: henkc@geoscience.org.za, pwade@geoscience.org.za Peter Wade Environmental Geoscience Unit, Council for Geoscience, Private Bag X112, Pretoria, 0001, South Africa, e-mail: henkc@geoscience.org.za, pwade@geoscience.org.za Frank Winde North West University, School of Environmental Sciences and Development, Private Bag X6001, Potchefstroom 2520, South Africa, e-mail: frank.winde@nwu.ac.za Publisher: Geological Society of South Africa First Online: 09 Mar 2017 Online ISSN: 1996-8590 Print ISSN: 1012-0750 © 2006 Geological Society of South Africa South African Journal of Geology (2006) 109 (4): 495–502. https://doi.org/10.2113/gssajg.109.4.495 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Henk Coetzee, Peter Wade, Frank Winde; Understanding environmental geophysical anomalies – an interdisciplinary case study from the West Rand. South African Journal of Geology 2006;; 109 (4): 495–502. doi: https://doi.org/10.2113/gssajg.109.4.495 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySouth African Journal of Geology Search Advanced Search Abstract Environmental geophysics is often limited to surveying and “anomaly-picking” or performed as an add-on to other environmental investigation techniques. There is usually little scope for detailed quantitative interpretation or meaningful combination with other environmental investigation results. In this study, we have combined ground and airborne radiometric data with related geochemical, geographic, hydrologic and radiation protection results from the Wonderfonteinspruit catchment of the West Rand. An improved understanding of the environmental contamination processes in the vicinity of gold/uranium mining and processing operations has been obtained. Information of this type can form the basis for hazard and risk assessment studies. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Comparative estimations of 137Cs distribution in a boreal forest in northern Sweden using a traditional sampling approach and a portable NaI detector

Field-portable detectors have been frequently used in routine monitoring and hazard assessment studies. However, there have been few thorough attempts to evaluate their potential as an alternative to the traditional procedure of collecting samples and analysing them in the laboratory. Thus, in this study the two approaches were compared in terms of their utility for monitoring 137Cs activity in the Nyänget catchment in northern Sweden. The objectives were: (i) to determine the 137Cs activity in soils associated with three types of vegetation, (ii) to map the geographical distribution of 137Cs using the portable NaI detector connected to a GPS system (GDM-40), (iii) to identify 137Cs anomalies in the catchment, and (iv) to compare the measurements obtained with the NaI detector and traditional sampling followed by laboratory analysis. Our results demonstrate that the GDM-40 has very good potential for making 137Cs inventories and for detecting 137Cs anomalies within large areas. The GDM-40 measurements identified differences between different hydrological areas that were not determined with the soil sampling method. The GDM-40 method is much faster than a traditional soil sampling method. However, soil sampling cannot be totally excluded because it is needed to calibrate the GDM-40. The agreement between the 137Cs activity values obtained by the two approaches was 20% which is good in the field where so many factors vary.

Estimating aerosol hazards from an anthrax letter

Events following the anthrax letter incidences in 2001 changed many previously held assumptions regarding biological aerosol hazards. As there were significant fatalities resulting from the sorting of a single anthrax letter, it suggests there is a need to reevaluate how best to measure biological aerosols and to use the information to make accurate predictions. This paper describes the biological aerosol created from manipulating envelopes containing Bacillus subtilis globigii spores (a simulant for anthrax). In addition, the measurements on dispersion of spores from an envelope processed by a mail sorter provide important dynamic aerosol characteristics, information previously unavailable for health risk assessment. The findings produced a number of significant aerosol dosage estimates related to spore contaminated letters. Graphic presentations show significant hazard in handling anthrax-laced letters. Aerosol particle dynamics are described and specific lethal dosage values are listed for a range of activities; these will be useful in assisting the modeling community to create more realistic predictions in hazard assessment studies.

The combined effects of water and fluorine on the viscosity of silicic magmas

The Newtonian viscosity of water-plus-fluorine-bearing silicate melt of haplogranitic composition (HPG8) has been determined. Viscosities of HPG8 melt with addition of 3.11 and 4.25 wt.% of F and up to 3 wt.% H 2O have been obtained using a micropenetration technique in the interval 10 9.74 to 10 11.84 Pa · s and temperatures varying from 370 to 700°C, at ambient pressure. Determination of the temperature dependence of viscosity from this and previous studies permits the parameterization of the viscosity of melts containing water and fluorine, having similar composition, within a 0.3 log units standard error. The viscosity of water-bearing, F-rich haplogranitic samples is represented by a modified Vogel-Fulcher-Tammann (VFT) equation which provides a non-Arrhenian description of the temperature dependence of the viscosity. The results of this study indicate that, taken individually or together, both H 2O and F − have a strong and similar effect on the viscosity of SiO 2-rich compositions. This similarity between F 2O −1 and H 2O greatly simplifies the task of predicting viscosity for volatile-rich, highly silicic magmas. The low viscosities of hydrous fluorine-bearing granitic melts favour efficient crystallization-fractionaction paths for these liquids, controlling degassing paths and consequently the eruptive behaviour. Numerical simulations of eruptive events normally do not take into account the contribution of fluorine; this may introduce a significant error in the description of the fluid-dynamic properties of magma and, therefore, in the accurate prediction of eruptive scenarios, as well as in hazard assessment studies. Fluorine, unlike water, remains dissolved in the melt at high concentrations and low confining pressures. The incorporation of fluorine data and the modelling of fluorine-bearing viscosity data are therefore of fundamental importance for simulations of magma dynamics and prediction of eruptive scenarios.

Animal models for the study of childhood leukemia: considerations for model identification and optimization to identify potential risk factors.

Leukemias are the most common pediatric malignancies diagnosed in western industrialized societies. In spite of the substantial incidence of childhood leukemia in the United States and other countries, neither epidemiology studies conducted in human populations nor hazard identification studies conducted using traditional animal models have identified environmental or other factors that are directly linked to increased risk of disease. Molecular biology data and mathematical modeling of incidence patterns suggest that pediatric leukemogenesis may occur through a multistage or "multihit" mechanism that involves both in utero and postnatal events. The authors propose that pediatric leukemias can be modeled experimentally using a "multihit" paradigm analogous to the "initiation-promotion" and "complete carcinogenesis" models developed for tumor induction in mouse skin and rat liver. In this model for childhood leukemia, an initial genetic alteration occurs during in utero or early postnatal development, but clinical disease develops only upon additional genetic or nongenetic events that occur during the postnatal period. Application of this multistage or "multihit" model to hazard assessment studies conducted in transgenic or knockout mice carrying relevant molecular lesions may provide a sensitive approach to the identification of environmental agents that are important risk factors for childhood leukemia.

Seismic ground motion estimates for the M6.1 earthquake of July 26, 1963 at Skopje, Republic of Macedonia

The identification and characterization of active faults as earthquake sources are essential parts of seismic hazard assessment studies. In the area struck by the 1963 Skopje (M = 6.1) earthquake, we define an input fault model according to the proposed source mechanism, the magnitude, and the aftershocks distribution. We test different position for the nucleation point along the fault and we calculate maximum horizontal velocities for a maximum frequency content of 1 Hz. We compare the velocity field with the reported macroseismic intensity one in order to select the fault model that fits the observations best. Our results are in agreement with a seismic source modelled as a 15 × 8 km rectangular plane with magnitude equal to 5.9.