SEM–EDS analysis of western Mediterranean obsidians: a new tool for Neolithic provenance studies

The contents of Na, Al, Si, K, Ca and Fe of 99 obsidians from the western Mediterranean islands of Lipari, Palmarola, Pantelleria and Sardinia were determined with the energy-dispersive spectrometer of a scanning electron microscope (SEM–EDS). The Na and in a lesser way other elements contents characterize any obsidian source-island. In Sardinia (80 samples), the four Monte Arci obsidian geochemical types can be discriminated from binary diagrams of element contents or by a discriminant analysis based on the six elements measured. It is concluded that SEM–EDS offers a new option for Neolithic obsidian provenance studies in this region. To cite this article: F.-X. Le Bourdonnec et al., C. R. Geoscience 338 (2006).     

Earthquakes in Switzerland and surrounding regions during 2012

This report of the Swiss Seismological Service summarizes the seismic activity in Switzerland and surrounding regions during 2012. During this period, 497 earthquakes and 88 quarry blasts were detected and located in the region under consideration. With a total of only 13 events with M_L ≥ 2.5, the seismic activity in the year 2012 was far below the average over the previous 37 years. Most noteworthy were the earthquake sequence of Filisur (GR) in January with two events of M_L 3.3 and 3.5, the M_L 4.2 and M_L 3.5 earthquakes at a depth of 32 km below Zug in February and the M_L 3.6 event near Vallorcine in October. The epicentral intensity of the M_L 4.2 event close to Zug was IV, with a maximum intensity of V reached in a few areas, probably due to site amplification effects.     

The characteristics of asymmetric pedestrian behavior: A preliminary study using passive smartphone location data

Understanding the movements of people is essential for the design and management of urban areas. This article presents a novel approach to understanding the asymmetry in route choice (i.e., the degree to which people choose different walking routes for their outbound and return journeys). The study utilizes a large volume of traces of individual routes, captured using a smartphone application. The routes are aggregated to a regular grid, and matrix statistics are developed to estimate the aggregate degree of route asymmetry for different types of route (shortest, longest, weekday, weekend, etc.). The results suggest that people change their route approximately 15% of the time. Although this varied little when observing trips made at the weekend or on a weekday, people taking journeys that deviated substantially from the shortest possible path were 6 percentage points less likely to change their routes than those taking journeys that were closest to the shortest path (14 and 20% asymmetry, respectively). The absolute length also impacted on the asymmetry of journeys, but not as substantially. This result is important because, for the first time, it reports a correlation between deviation from shortest route and aggregate pedestrian choice.     

Seismic hazard assessment of northern Pakistan

This article presents probabilistic seismic hazard analyses of northern Pakistan region carried out to produce macro-seismic hazard maps for the region that define new regional ground motion design parameters for 95-, 475-, 975- and 2475-year return period earthquakes as regional contour maps and horizontal uniform hazard at important cities. The Cornell–McGuire approach (Cornell in Bull Seismol Soc Am 58(05):1583–1606, 1968; McGuire in FORTRAN computer program for seismic risk analysis. US Geological Survey, Open file Report, 76-6768, 1976) is used to carry out the analyses at 0.1° rectangular grid. The seismotectonic model of the region used in analysis consists of shallow and deep area zones differentiated based on the focal depths of the earthquakes. Earthquake catalogue compiled and used in the analysis is a composite catalogue composed of 19,373 events. Ground motion prediction equations (GMPEs) used are calibrated using goodness-of-fitness measures and visual inspection with local strong motion data. Epistemic uncertainty in the GMPEs is taken into account through the logic tree approach. Comparison of ground motions due to deep earthquakes is made for the first time for the region. The comparison between ground motion due to shallow and deep earthquakes indicates that the seismic hazard would be underestimated if the deep earthquakes are excluded. Ground motion values obtained in this study considering all the earthquakes suggest ground motions are dominant towards the north east of the region. The proposed study indicates that the ground motion hazard values suggested by the current Building Code of Pakistan underestimate the seismic hazard. Final results of this study are in close agreement with the recent studies on the region.     

Water-table and discharge changes associated with the 2016–2017 seismic sequence in central Italy: hydrogeological data and a conceptual model for fractured carbonate aquifers

A seismic sequence in central Italy from August 2016 to January 2017 affected groundwater dynamics in fractured carbonate aquifers. Changes in spring discharge, water-table position, and streamflow were recorded for several months following nine Mw 5.0–6.5 seismic events. Data from 22 measurement sites, located within 100 km of the epicentral zones, were analyzed. The intensity of the induced changes were correlated with seismic magnitude and distance to epicenters. The additional post-seismic discharge from rivers and springs was found to be higher than 9 m³/s, totaling more than 0.1 km³ of groundwater release over 6 months. This huge and unexpected contribution increased streamflow in narrow mountainous valleys to previously unmeasured peak values. Analogously to the L’Aquila 2009 post-earthquake phenomenon, these hydrogeological changes might reflect an increase of bulk hydraulic conductivity at the aquifer scale, which would increase hydraulic heads in the discharge zones and lower them in some recharge areas. The observed changes may also be partly due to other mechanisms, such as shaking and/or squeezing effects related to intense subsidence in the core of the affected area, where effects had maximum extent, or breaching of hydraulic barriers.

     

Aquatic macrophyte diversity assessment: Validation of a new sampling method for circular-shaped lakes

We propose and validate a new sampling method to assess the presence, abundance and distribution of macrophytes in circular-shaped lakes according to the requirements of the Water Framework Directive (WFD2000/60/EC). The results of the macrophyte survey, and in particular of macrophyte diversity, obtained using this method are also discussed.The sampling is based on randomly selected transects homogeneously distributed around the perimeter of the lake. The number of transects is proportional to the lake's size. The method was validated on six Italian volcanic lakes using computational resampling procedures on a total of 126 transects.Using resampling procedures, we show that the proposed approach identifies more than 75% of the overall species richness through a moderate sampling effort. According to our results, Charophytes dominate aquatic vegetation in Italian volcanic lakes. Species diversity is highest at shallow depths, whereas the most abundant species, such as Chara polyacantha, are located at an intermediate depth between the shoreline and the maximum growing depth.     

Seismic input at the archaeological site of Kancheepuram in Southern India

A probabilistic seismic hazard assessment at Kancheepuram in Southern India was carried out with the scope of defining the seismic input for the vulnerability assessment of historical and monumental structures at the site, in terms of horizontal Uniform Hazard Spectra and a suite of spectrum-compatible natural accelerograms to perform time-history analysis. The standard Cornell?CMcGuire and a zone-free approach have been used for hazard computations after the compilation of a composite earthquake catalogue for Kancheepuram. Epistemic uncertainty in the seismic hazard was addressed within a logic-tree framework. Deaggregation of the seismic hazard for the peak ground acceleration shows low seismicity at Kancheepuram controlled by weak-to-moderate earthquakes with sources located at short distances from the archaeological site. Suites of natural accelerograms recorded on rock have been selected by imposing a custom-defined compatibility criterion with the probabilistic spectra. The site of Kancheepuram is characterized by a seismicity controlled by weak-to-moderate earthquakes with sources at short distances from the site, the PGA expected for 475- and 2,475-year return period are, respectively, 0.075 and 0.132?g. The Indian code-defined spectra (DBE and MCE) tend to underestimate spectral ordinates at low periods. On the other hand, the PGA are comparable and the spectral ordinates for longer periods from the probabilistic study are significantly lower.     

The origin of Lake Cheko and the 1908 Tunguska Event recorded by forest trees

Several lines of evidence indicate that Cheko, a small lake close to the epicentre of the 1908 Tunguska Event (TE), fills a crater left behind by a fragment of the Tunguska Cosmic Body that impacted the ground downrange of the main explosion. It is thought that over 80 million trees were flattened or burnt as a consequence of the TE. However, a small number of trees in the devastated area survived the explosion and recorded in their growth‐ring patterns the environmental changes that followed this event. Some of those trees were found around Lake Cheko, ~10 km NW of the inferred TE epicentre. We analysed new data from the floor of Lake Cheko, including seismic‐reflection profiles, side‐scan sonar and video images, as well as dendrochronological evidence in tree samples collected along the shores, to test the hypothesis of a 1908 formation of the lake.     

Measurement of field-saturated hydraulic conductivity on fractured rock outcrops near Altamura (Southern Italy) with an adjustable large ring infiltrometer

Up to now, field studies set up to measure field-saturated hydraulic conductivity to evaluate contamination risks, have employed small cylinders that may not be representative of the scale of measurements in heterogeneous media. In this study, a large adjustable ring infiltrometer was designed to be installed on-site directly on rock to measure its field-saturated hydraulic conductivity. The proposed device is inexpensive and simple to implement, yet also very versatile, due to its large adjustable diameter that can be fixed on-site. It thus allows an improved representation of the natural system’s heterogeneity, while also taking into consideration irregularities in the soil/rock surface. The new apparatus was tested on an outcrop of karstic fractured limestone overlying the deep Murge aquifer in the South of Italy, which has recently been affected by untreated sludge disposal, derived from municipal and industrial wastewater treatment plants. The quasi-steady vertical flow into the unsaturated fractures was investigated by measuring water levels during infiltrometer tests. Simultaneously, subsurface electrical resistivity measurements were used to visualize the infiltration of water in the subsoil, due to unsaturated water flow in the fractures. The proposed experimental apparatus works well on rock outcrops, and allows the repetition of infiltration tests at many locations in order to reduce model uncertainties in heterogeneous media.     

Mapping and monitoring net primary productivity with AVHRR NDVI time-series: statistical equivalence of cumulative vegetation indices

In the last two decades, numerous investigators have proposed cumulative vegetation indices (i.e., functions which encode the cumulative effect of NDVI maximum value composite time-series into a single variable) for net primary productivity (NPP) mapping and monitoring on a regional to continental basis. In this paper, we investigate the relationships among three of the most commonly used cumulative vegetation indices, expanding on the definition of equivalence of remotely sensed vegetation indices for decision making. We consider two cumulative vegetation indices as equivalent, if the value of one index is statistically predictable from the value of the other index. Using an annual time-series of broad-scale AVHRR NDVI monthly maximum value composites of the island of Corsica (France), we show that the pairwise linear association among the analysed cumulative vegetation indices shows coefficients of determination (R²) higher than 0.99. That is, knowing the value of one index is statistically equivalent to knowing the value of the other indices for application purposes.