Kinematics and significance of a poly-deformed crustal-scale shear zone in central to south-eastern Madagascar: the Itremo–Ikalamavony thrust

International Journal of Earth Sciences - Across the crystalline basement of Madagascar, late Archaean rocks of the Antananarivo Block are tectonically overlain by Proterozoic, predominantly...     

Stream Restoration Performance and Its Contribution to the Chesapeake Bay TMDL: Challenges Posed by Climate Change in Urban Areas

In large part driven by total maximum daily load (TMDL) mandates, the restoration community in the Chesapeake Bay region has been implementing novel best management practices (BMPs) and stream restoration designs in urban areas, such as regenerative stream/stormwater conveyance (RSC) structures and stream-wetland complexes (SWCs). However, the nutrient and sediment reduction efficiencies of these novel designs are virtually unknown, and the possibility of increasing riverine flow in the Chesapeake Bay watershed associated with climate change this century necessitates an evaluation of their performance to develop and utilize those that optimize reductions in nutrient and sediment fluxes. We compare pre- and post-construction loads (total nitrogen (TN), total phosphorus (TP), and total suspended solids (TSS)) from RSCs (i.e., upland BMPs) and a SWC (i.e., stream restoration) constructed at the outflow of a highly developed watershed in the Coastal Plain physiographic province of Maryland. The largest of the two RSCs performed best in relation to expected nutrient and sediment reductions because of superior water retention capability. By the length of river reach restored, the SWC attained from 79 to 88% of its N reduction TMDL goal, but only 19 to 23 and 2.7 to 3.1% for TP and TSS, respectively; by watershed area, % attainments of TMDL goals were much lower. Results indicate that SWCs have the potential to curtail N loading from developed catchments, but additional water quality benefits may be limited. Climate change projections indicate that there will be an increased frequency of larger-volume storms that will result in an increase in stormflow runoff from urban areas, and increased pollutant loads will likely curtail potential gains made by efforts to achieve TMDL goals. Given the large-scale implementation of BMPs currently underway to accommodate the Chesapeake Bay TMDL, the restoration community needs to adopt a concerted strategy of building climate resilience into many types of urban BMPs to help attain and maintain loads at TMDL levels in anticipation of a progressively wetter climate throughout this century.     

Satellite-Based Technologies in Use for Extreme Nocturnal Mountain Rescue Operations: a Synergetic Approach Applying Geophysical Principles

Mountain-rescue operations require rapid response whilst also ensuring the security of the rescue teams. Rescuing people in a big rock-face is even more difficult if night or fog prevent sight. The paper presents a technical solution to optimally support, under these aggravated conditions, the location of the casualties and the navigation of the rescue team(s) in a rock-face from a coordination station. In doing so, standard components like a smartphones with GPS functionality, a data communication on a client–server basis and VR visualisation software have been adapted to the specific requirements. Remote support of the navigation in steep rocky terrain requires a highly accurate wall model which permits the local experts of the coordination station to dependably estimate geometry and structure of the rock along the rescue route and to convey necessary directives to the retrieval team. Based on terrestrial laser-scans from different locations, such a model has been generated for the mighty Dachstein South Face (Austria) and texturised with digital photographs. Over a twelve-month period, a transdisciplinary team of the Dresden University of Technology (Informatics, Electrical Engineering, Cartography) developed and integrated the various technical modules of the mountain-rescue support-system (digital rock-face model, optimised GPS data transmission between mobile device, server and client, data filtering, and dynamic visualisation component). In summer 2011 the proper functioning of the prototype was demonstrated in a rescue exercise under foggy dusk conditions.     

Late Quaternary history of the Vakinankaratra volcanic field (central Madagascar): insights from luminescence dating of phreatomagmatic eruption deposits

The Quaternary Vakinankaratra volcanic field in the central Madagascar highlands consists of scoria cones, lava flows, tuff rings, and maars. These volcanic landforms are the result of processes triggered by intracontinental rifting and overlie Precambrian basement or Neogene volcanic rocks. Infrared-stimulated luminescence (IRSL) dating was applied to 13 samples taken from phreatomagmatic eruption deposits in the Antsirabe–Betafo region with the aim of constraining the chronology of the volcanic activity. Establishing such a chronology is important for evaluating volcanic hazards in this densely populated area. Stratigraphic correlations of eruption deposits and IRSL ages suggest at least five phreatomagmatic eruption events in Late Pleistocene times. In the Lake Andraikiba region, two such eruption layers can be clearly distinguished. The older one yields ages between 109?±?15 and 90?±?11 ka and is possibly related to an eruption at the Amboniloha volcanic complex to the north. The younger one gives ages between 58?±?4 and 47?±?7 ka and is clearly related to the phreatomagmatic eruption that formed Lake Andraikiba. IRSL ages of a similar eruption deposit directly overlying basement laterite in the vicinity of the Fizinana and Ampasamihaiky volcanic complexes yield coherent ages of 68?±?7 and 65?±?8 ka. These ages provide the upper age limit for the subsequently developed Iavoko, Antsifotra, and Fizinana scoria cones and their associated lava flows. Two phreatomagmatic deposits, identified near Lake Tritrivakely, yield the youngest IRSL ages in the region, with respective ages of 32?±?3 and 19?±?2 ka. The reported K-feldspar IRSL ages are the first recorded numerical ages of phreatomagmatic eruption deposits in Madagascar, and our results confirm the huge potential of this dating approach for reconstructing the volcanic activity of Late Pleistocene to Holocene volcanic provinces.     

Performance of masonry buildings during the Emilia 2012 earthquake

The earthquake sequence started on May \(20\) th 2012 in Emilia (Italy) affected a region where masonry constructions represent a large part of the existing building stock and the construction of new modern masonry buildings is a common practice. The paper is focused on the performance of common architectural configurations, typical for residential or business use. The large majority of old masonry buildings is made of fired clay bricks. The seismic performance of these buildings is particularly interesting since major past earthquakes in Italy affected areas with mainly stone masonry structures. Apart from examples showing systematic or peculiar structural deficiencies governing the vulnerability of several buildings, the overall seismic performance of these structures to repeated shaking, with PGA as large as 0.25–0.3 g was rather good, despite the major part of them were only conceived for carrying vertical loads. In fact, seismic design is mandatory in the area only since 2003. Modern low-rise masonry buildings erected after this date and incorporating seismic design and proper detailing resulted in most cases practically undamaged. The examples reported in the paper allow an evaluation of the superior performance of seismically designed modern masonry buildings in comparison to older ones.     

Multidisciplinary inferences on a newly recognized active east‐dipping extensional system in Central Italy

We use a multidisciplinary approach to gather preliminary evidence for a Quaternary east‐dipping extensional detachment in Central Italy. This structure crops out in the Sabini‐Eastern Simbruini (SES) and would be hidden at mid‐crustal depths beneath the L'Aquila 2009 (M_w6.3) epicentral area. The SES geometry is reconstructed through geological mapping, structural analysis and seismic line interpretation. The geometry of the mid‐crustal segment, referred to as the Ocre Segment (OS), is interpreted through seismological analyses of the largest aftershock (M_w5.4) of the L'Aquila 2009 sequence. The kinematic compatibility between the SES and the OS under a common SW–NE tensional field is tested through stress inversion of both geological and seismological data. The reliability of OS activation is tested through slip tendency analysis. Like other Italian cases, the SES and the OS are preliminarily interpreted as expressions at different depths of the same unknown east‐dipping extensional detachment, characterized by a ramp–flat–ramp geometry.     

On the SAR derived alert in the detection of oil spills according to the analysis of the EGEMP

Satellite services that deliver information about possible oil spills at sea currently use different labels of “confidence” to describe the detections based on radar image processing. A common approach is to use a classification differentiating between low, medium and high levels of confidence. There is an ongoing discussion on the suitability of the existing classification systems of possible oil spills detected by radar satellite images with regard to the relevant significance and correspondence to user requirements. This paper contains a basic analysis of user requirements, current technical possibilities of satellite services as well as proposals for a redesign of the classification system as an evolution towards a more structured alert system. This research work offers a first review of implemented methodologies for the categorisation of detected oil spills, together with the proposal of explorative ideas evaluated by the European Group of Experts on satellite Monitoring of sea-based oil Pollution (EGEMP).     

Modeling ground deformations of Panarea volcano hydrothermal/geothermal system (Aeolian Islands, Italy) from GPS data

Panarea volcano (Aeolian Islands, Italy) was considered extinct until November 3, 2002, when a submarine gas eruption began in the area of the islets of Lisca Bianca, Bottaro, Lisca Nera, Dattilo, and Panarelli, about 2.5 km east of Panarea Island. The gas eruption decreased to a state of low degassing by July 2003. Before 2002, the activity of Panarea volcano was characterized by mild degassing of hydrothermal fluid. The compositions of the 2002 gases and their isotopic signatures suggested that the emissions originated from a hydrothermal/geothermal reservoir fed by magmatic fluids. We investigate crustal deformation of Panarea volcano using the global positioning system (GPS) velocity field obtained by the combination of continuous and episodic site observations of the Panarea GPS network in the time span 1995–2007. We present a combined model of Okada sources, which explains the GPS results acquired in the area from December 2002. The kinematics of Panarea volcano show two distinct active crustal domains characterized by different styles of horizontal deformation, supported also by volcanological and structural evidence. Subsidence on order of several millimeters/year is affecting the entire Panarea volcano, and a shortening of 10⁻⁶ year⁻¹ has been estimated in the Islets area. Our model reveals that the degassing intensity and distribution are strongly influenced by geophysical-geochemical changes within the hydrothermal/geothermal system. These variations may be triggered by changes in the regional stress field as suggested by the geophysical and volcanological events which occurred in 2002 in the Southern Tyrrhenian area.     

A note on maar eruption energetics: current models and their application

Hydromagmatic eruptions convert thermal into mechanical energy via the expansion of ground- and/or surface-water. Several models address the energetics of these eruptions based on different physical-volcanological approaches. Here we test different models with two case studies in the Colli Albani Volcanic District (central Italy): the monogenetic Prata Porci and the polygenetic Albano maars. Test results are mutually consistent, and show cumulative mechanical energy releases on the order of 10¹⁵–10¹⁷ J for single maars. The fraction of thermal energy turned into mechanical ranges from 0.45 (as calculated from the theoretical maximum mechanical energy), through 0.1 (calculated from country rock fragmentation, crater formation and ballistic ejection), to 0.03 (derived from magma fragmentation by thermohydraulic explosions). It appears that the energy released during the most intense hydromagmatic events may account for a dominant fraction of the total mechanical energy released during the whole maar eruptive histories. Finally, we consider the role of magmatic explosive activity intervening during maar eruptions in causing departures from predictions of the models evaluated.