1989–1995 Earthquake sequences in the Galeras volcano region,SW Colombia,and possible volcano–earthquake interactions

The Galeras volcanic complex, located in the Nariño department, SW Colombia, includes the most historically active volcano in the country, Galeras, a 4276 m high stratovolcano located 9 km west of the city of San Juan de Pasto (400,000 inhabitants). The area is also affected by the continental faulting represented by the Buesaco, Aranda and Pasto faults belonging to one of the most seismically active structures in Colombia, the Romeral fault system. Several moderate to strong shallow earthquakes affected the city of San Juan de Pasto and its neighbouring region since the XVII century. The coexistence of an active volcanic complex and an active fault system complicates the study and interpretation of the different processes taking place in the region as well as the identification of any connection or interaction among them.The reactivation of the volcano in 1989 was characterized by three main magmatic events: (1) a series of Vulcanian eruptions during 4–9 May 1989, with semi-continuous ash emissions from a secondary crater; (2) the emplacement of an andesitic lava dome at the bottom of the main crater from September 1990 until December 1991; and (3) six Vulcanian eruptions from the main crater during 1992–1993, with destruction of most of the dome during the first one on 16 July 1992. During the same period, four earthquake sequences were located in a limited area N and NE of Galeras volcano on August–September 1989 (AUG1989), April–June 1993 (APR1993), November–December 1993 (NOV1993) and March–August 1995 (MAR1995). The last one included a Ml4.7 main shock on 4 March 1995 producing moderate to high damage in the epicentral region (MSK maximum intensity VIII), and in the city of San Juan de Pasto (VI–VII). The last damaging earthquake in the region was a MSK-intensity VIII–IX in 1947.A detailed analysis of the spatio-temporal characteristics of the four earthquake sequences allowed identifying their different origin and suggesting some interrelationship between the reactivated eruptive process and the contemporaneous seismic activity. The AUG1989 sequence presents a typical volcanic swarm-like pattern most probably related with the process of magma intrusion from depth at the beginning of the volcano's reactivation. The APR1993, the NOV1993 and the MAR1995 sequences show a clear tectonic origin with events occurring on rupture planes almost vertical that can be associated to the active faults in the area, The seismogenic process of these three sequences could have been activated or accelerated by the main eruptions during 1992–1993.These results suggest that constrains provided by improved relocations and the detailed analysis of the space–time characteristics of earthquake sequences in Galeras volcanic environment allow to establish the different generation mechanisms involved and to suggest feasible explanations on the possible interrelationships of the magmatic–volcanic processes and the seismicity observed.     

Speleothem preservation and diagenesis in South African hominin sites implications for paleoenvironments and geochronology

Plio‐Pleistocene speleothems from australopithecine‐bearing caves of South Africa have the potential to yield paleoenvironmental and geochronological information using isotope geochemistry. Prior to such studies it is important to assess the preservation of geochemical signals within the calcitic and aragonitic speleothems, given the tendency of aragonitic speleothems to recrystallize to calcite. This study documents the geochemical suitability of speleothems from the principal hominin‐bearing deposits of South Africa. We use petrography, together with stable isotope and trace element analysis, to identify the occurrence of primary aragonite, primary calcite, and secondary calcite. This study highlights the presence of diagenetic alteration at many of the sites, often observed as interbedded primary and secondary fabrics. Trace element and stable isotopic values distinguish primary calcite from secondary calcite and offer insights into geochemical aspects of the past cave environment. δ¹³C values of the primary and secondary calcites range from +6 to −9‰ and δ¹⁸O values range from −4 to −6‰. The data are thus typical of meteoric calcites with highly variable δ¹³C and relatively invariant δ¹⁸O. High carbon isotope values in these deposits are associated with the effects of recrystallization and rapid outgassing of CO₂ during precipitation. Mg/Ca and Sr/Ca ratios differ between primary and secondary calcite speleothems, aiding their identification. Carbon and oxygen isotope values in primary calcite reflect the proportion of C₃ and C₄ vegetation in the local environment and the oxygen isotope composition of rainfall. Primary calcite speleothems preserve the pristine geochemical signals vital for ongoing paleoenvironmental and geochronological research. © 2009 Wiley Periodicals, Inc.     

Comparison of risk from pyroclastic density current hazards to critical infrastructure in Mammoth Lakes,California, USA,from a new Inyo craters rhyolite dike eruption versus a dacitic dome eruption on Mammoth Mountain

Renewed volcanic activity near Mammoth Lakes, California, in the form of dome-collapse pyroclastic density currents (PDCs) from either a new eruption at Mammoth Mountain or the Inyo craters would pose a significant hazard to critical infrastructure there. This paper compares the risk from PDC impact hazards upon selected critical infrastructure from: (1) a 100 m tall dacite dome on Mammoth Mountain and (2) three 200 m tall rhyolite domes at the southern end of the Inyo craters. For each scenario, maximum estimated dynamic pressure and velocity from two PDC volumes (10⁶ and 10⁷ m³) are modeled with the EXPLORIS PDC software (Toyos et al. Nat Hazards 41(1):99–112, 2007). Risk to critical infrastructure from Mammoth Mountain PDCs would be much greater than the Inyo PDCs because of both location and the greater kinetic energy of the Mammoth PDC material, providing comparative insight to planners should a real eruption at one location or the other be forthcoming.     

Interrelations between socio-economic development and environmental quality: a simulation integrating system dynamics models with GIS

System dynamics （SD） theory has long been deployed in modeling complex non-linear interrelationships but, so far it has not been common to do the kind of modeling in support of bringing environmental sustainability policies to practice. This is largely because the challenge of including spatial data has not yet been well met. Potential for adoption of SD and GIS methods in combination is exemplified with the results of a decision-support exercise designed for simulation and prediction of the dynamic inter-relationships between socio-economic development and environmental quality for the “Wen, Pi, Du” county in Sichuan province, southwestern China.     

A combined spectrophotometric and morphometric study of the lunar mare dome fields near Cauchy, Arago, Hortensius, and Milichius

In this study we examine the spectral and morphometric properties of the four important lunar mare dome fields near Cauchy, Arago, Hortensius, and Milichius. We utilize Clementine UV-vis multispectral data to examine the soil composition of the mare domes while employing telescopic CCD imagery to compute digital elevation maps in order to determine their morphometric properties, especially flank slope, height, and edifice volume. After reviewing previous attempts to determine topographic data for lunar domes, we propose an image-based 3D reconstruction approach which is based on a combination of photoclinometry and shape from shading. Accordingly, we devise a classification scheme for lunar mare domes which is based on a principal component analysis of the determined spectral and morphometric features. For the effusive mare domes of the examined fields we establish four classes, two of which are further divided into two subclasses, respectively, where each class represents distinct combinations of spectral and morphometric dome properties. As a general trend, shallow and steep domes formed out of low-TiO₂ basalts are observed in the Hortensius and Milichius dome fields, while the domes near Cauchy and Arago that consist of high-TiO₂ basalts are all very shallow. The intrusive domes of our data set cover a wide continuous range of spectral and morphometric quantities, generally characterized by larger diameters and shallower flank slopes than effusive domes. A comparison to effusive and intrusive mare domes in other lunar regions, highland domes, and lunar cones has shown that the examined four mare dome fields display such a richness in spectral properties and 3D dome shape that the established representation remains valid in a more global context. Furthermore, we estimate the physical parameters of dome formation for the examined domes based on a rheologic model. Each class of effusive domes defined in terms of spectral and morphometric properties is characterized by its specific range of values for lava viscosity, effusion rate, and duration of the effusion process. For our data set we report lava viscosities between about 10² and , effusion rates between 25 and , and durations of the effusion process between three weeks and 18 years. Lava viscosity decreases with increasing R₄₁₅/R₇₅₀ spectral ratio and thus TiO₂ content; however, the correlation is not strong, implying an important influence of further parameters like effusion temperature on lava viscosity.     

Embedding isochronous cells overland flow module into MODFLOW

This study integrates a simple overland flow module (isochronous cells model) with the river module of MODFLOW such that temporal and spatial interactions between stream flow and groundwater can be simulated using net rainfall data of a watershed. The isochronous cells model is an efficient travel time runoff approach based on geographic information system (GIS) that considers both spatial and temporal variations of net rainfall through hill slope of the watershed. This overland module is easily coupled with MODFLOW river routing module. Specifically, the stream flow from the isochronous cells model is directly assigned to both sides of river cells of the MODFLOW model. Such an integration of MODFLOW and isochronous cells model is especially useful in watersheds where river flow data are limited. The feasibility of this integrated model was demonstrated using a case study in the middle and downstream regions of the Yitong River watershed, China. Copyright © 2012 John Wiley & Sons, Ltd.     

Relationship between wind power production and North Atlantic atmospheric circulation over the northeastern Iberian Peninsula

The wind power generated during winter months 1999–2003 at several wind farms in the northeastern Iberian Peninsula is investigated through the application of a statistical downscaling. This allows for an improved understanding of the wind power variability and its relationship to the large scale atmospheric circulation. It is found that 97 % of the variability of this non-climatic variable is connected to changes in the atmospheric circulation. The methodological uncertainty associated with multiple configurations of the statistical downscaling method replicates well the observed variability of the wind power, an indication of the robustness of the methodology to changes in the model set up. In addition, the use of the statistical model is extended out of the observational period providing an estimation of the long-term variability of wind power throughout the twentieth century. The extended wind power reconstruction shows large inter-annual and multidecadal variability. Alternative approaches to calibrate the empirical downscaling model using actual wind power observations have also been investigated. They involve the estimation of wind power changes from downscaled wind values and make use of several transfer functions based on the linearity between wind and wind energy. The performance of the latter approaches is similar to the direct downscaling of wind power and may allow wind power production estimations even in the absence of historical wind turbine records. These results can be of great interest for deriving medium/long term impact-oriented energy assessments, especially when wind power observations are missing as well as in the context of climate change scenarios.     

Physically based evaluation of climate models over the Iberian Peninsula

A novel approach is proposed for evaluating regional climate models based on the comparison of empirical relationships among model outcome variables. The approach is actually a quantitative adaptation of the method for evaluating global climate models proposed by Betts (Bull Am Meteorol Soc 85:1673–1688, 2004). Three selected relationships among different magnitudes involved in water and energy land surface budgets are firstly established using daily re-analysis data. The selected relationships are obtained for an area encompassing two river basins in the southern Iberian Peninsula corresponding to 2 months, representative of dry and wet seasons. The same corresponding relations are also computed for each of the thirteen regional simulations of the ENSEMBLES project over the same area. The usage of a metric based on the Hellinger coefficient allows a quantitative estimation of how well models are performing in simulating the relations among surface magnitudes. Finally, a series of six rankings of the thirteen regional climate models participating in the ENSEMBLES project is obtained based on their ability to simulate such surface processes.