Record of recent river channel instability, Cheakamus Valley, British Columbia

Rivers flowing from glacier-clad Quaternary volcanoes in southwestern British Columbia have high sediment loads and anabranching and braided planforms. Their floodplains aggrade in response to recurrent large landslides on the volcanoes and to advance of glaciers during periods of climate cooling. In this paper, we document channel instability and aggradation during the last 200 years in lower Cheakamus River valley. Cheakamus River derives much of its flow and nearly all of its sediment from the Mount Garibaldi massif, which includes a number of volcanic centres dominated by Mount Garibaldi volcano. Stratigraphic analysis and radiocarbon and dendrochronological dating of recent floodplain sediments at North Vancouver Outdoor School in Cheakamus Valley show that Cheakamus River aggraded its floodplain about 1–2 m and buried a valley-floor forest in the early or mid 1800s. The aggradation was probably caused by a large (ca. 15–25×10⁶ m³) landslide from the flank of Mount Garibaldi, 15 km north of our study site, in 1855 or 1856. Examination of historical aerial photographs dating back to 1947 indicates that channel instability triggered by this event persisted until the river was dyked in the late 1950s. Our observations are consistent with data from many other mountain areas that suggest rivers with large, but highly variable sediment loads may rapidly aggrade their floodplains following a large spike in sediment supply. Channel instability may persist for decades to centuries after the triggering event.     

Geographic Information Technologies and the History of a Shoreline: The Case of Chapter 91 in New Bedford,Massachusetts*

This article discusses the use of geographic information technologies to assist researchers in the exploration of historical databases. The case study is a pilot project in which we used geographic information systems (GIS) and global positioning systems (GPS) to study the history of the Public Waterfront Act (the “Chapter 91” program), a policy designed to balance private property rights, public interest, and environmental protection in the Massachusetts tidelands. The issues discussed range from the role of GIS in society and its limitations as a representational tool to the ability of current GIS to deal with historical data and to manage temporal attributes.     

Late Triassic-Early Jurassic Paleokarst from the Ligurian Alps and its geological significance (Siderolitico Auct., Ligurian Briançonnais domain)

In the Ligurian Briançonnais domain, the thick Middle Triassic carbonateplatform units, formally known as the Costa Losera Fm. and S. Pietro dei Monti Dolomites, are followed by a significant unconformity separating them from the Rio di Nava neritic limestones of Bathonian age. According to the evolution of a passive continental margin, the end of subsidence and subsequent uplift led to the progressive erosion of the Triassic carbonate platform from outer to inner units, i.e., in the direction of the Ligurian Tethys. This erosion, possibly acting on a fault-controlled block system, created sedimentary sequences of differential composition, and the virtual absence of the entire Triassic complex and even the underlying Permian rocks. In the study area (and in many other locations belonging to the external Ormea unit), the so-called “briançonnais sedimentary gap” shows more than a nondepositional surface: the associated deposits (known as “Siderolitico” Auct.) include both red pelites between the above-mentioned units, and deep-penetrating karstic red breccia within the Ladinian carbonates. We performed detailed stratigraphic, microfacies and compositional analyses on the karsts and paleosoils associated with the unconformity in order to define their character, genesis and age. In addition, we discuss the regional context and importance of these deposits in a large-scale comparison with the classic Briançonnais domain and other locations of the Western Alpine Arch with the same unconformity. In light of these data, we propose an Upper Triassic to Early Jurassic age (until the Upper Bajocian?) for the karstic event in the Ligurian Alps.     

Insights about the formation of a complex impact structure formed in basalt from numerical modeling: The Vista Alegre structure,southern Brazil

We present the outcomes of simulations of the formation of the Vista Alegre impact structure, Paraná Basin, Brazil. The target comprised a thick sequence of volcanic rocks of predominantly basaltic composition of the Serra Geral Formation that had been deposited on top of sedimentary rocks (sandstones) of the Pirambóia/Botucatu formations. The cratering process was modeled using the iSALE shock physics code. Our best‐fit model suggests that (1) the crater was originally ~10 km in size; (2) it was formed in ~115 s by a stony projectile of 1000 m in diameter, for an assumed impact velocity of 12 km s^?1; (3) target rocks underwent a peak pressure of ~20 GPa, in agreement with previous petrographic investigations of shock deformation. Furthermore, the model points out that the sedimentary strata below the layer of volcanic rocks were raised by ~650 meters at the central part of the crater, which resulted in the current partial exposure of the sandstones at the surface. The outcomes of our modeling suggest that parameters like cohesion and strength of the target rocks, after shock compression, determined the final morphology of the crater, especially the absence of a topographically prominent central peak. Finally, the results of the numerical modeling are roughly in agreement with gravity data over the structure, in particular with respect to the presence of the uplifted sedimentary strata, which are responsible for a low gravity signature at the center of the structure.     

A systematic analysis of the <Emphasis Type="Italic">XMM-Newton</Emphasis> background: II. Properties of the in-Field-Of-View excess component

We present an accurate characterization of the particle background behaviour on XMM-Newton based on the entire EPIC archive. This corresponds to the largest EPIC data set ever examined. Our results have been obtained thanks to the collaboration between the FP7 European program EXTraS and the ESA R&D ATHENA activity AREMBES. We used as a diagnostic an improved version of the diagnostic which compares the data collected in unexposed region of the detector with the region of the field of view in the EPIC-MOS. We will show that the in Field-of-View excess background is made up of two different components, one associated to flares produced by soft protons and the other one to a low-intensity background. Its origin needs to be further investigated.     

A systematic analysis of the XMM-Newton background: I. Dataset and extraction procedures

XMM-Newton is the direct precursor of the future ESA ATHENA mission. A study of its particle-induced background provides therefore significant insight for the ATHENA mission design. We make use of ～12 years of data, products from the third XMM-Newton catalog as well as FP7 EXTraS project to avoid celestial sources contamination and to disentangle the different components of the XMM-Newton particle-induced background. Within the ESA R&D AREMBES collaboration, we built new analysis pipelines to study the different components of this background: this covers time behavior as well as spectral and spatial characteristics.     

Source Parameters of Old Earthquakes: Semi-Automatic Digitization of Analog Records and Seismic Moment Assessment

Recovering seismic information contained in old analog records could increase our knowledge of seismic source characteristics and the seismicity of a region. This is particularly important in zones with low to moderate seismicity.To extract the available information, it is necessary to digitize the seismic records. This is not an easy task especially owing to the generally poor quality of the original records, with illegible or missing parts. However some exceptions were found in the records of a few seismological stations in Germany, Sweden and France.This paper presents an example of the recovering of source parameters and can be divided in two parts: the first one presents a simple semi-automatic technique for digitization of old analog seismic records, developed using commercial software on a PC; the second part describes the methodology of assessing the seismic moment, using empirical and theoretical relations, as well as the seismic source dimensions.The earthquake selected to illustrate this procedure is the 23 April 1909 Benavente (Portugal) earthquake. This earthquake occurred in the Lower Tagus Valley region and caused great destruction in the meizoseismal area. It is the biggest earthquake that occurred during this century in the central part of the country and its magnitude has been estimated between 6.6 and 7.6.The digitization procedure allowed the recovery of seismic information contained in old analog records, in particular, the seismic moment estimation. The results obtained indicated that 7.6 was a very high value for the magnitude of the 23 April 1909 earthquake, suggesting that the magnitude reported in the Portuguese catalogue is overestimated. The estimated moment magnitude is 6.0.     

Probabilistic analysis of risk and mitigation of deepwater well blowouts and oil spills

The development of robust risk assessment procedures for offshore oil and gas operations is a major element for the assessment of the potential feedback between planned activities and the environment. We illustrate a methodological and computational framework conducive to (1) a quantitative risk analysis of deepwater well barrier failures and subsequent hydrocarbon release to the environment and (2) the analysis of the value of the deployment of conventional and/or innovative mitigation measures. Our methodological framework is grounded on historical records and combines the use of Dynamic Event Trees and Decision Trees from which we estimate probability of occurrence and impact of post-blowout events. Each sequence of response actions, which are undertaken immediately after the event or in the subsequent days, is considered within the context of appropriately structured event paths. This approach is conducive to an estimate of the expected value of key decisions and underlying technologies, with an emphasis on their potential to reduce the oil spill volume, which can critically impact the environment. Our study yields an original comparative analysis of diverse intervention strategies, and forms a basis to guiding future efforts towards the development and deployment of technologies and operating procedures yielding maximum benefit in terms of safety of operations and environmental protection.