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121.
Statistical analyses on a catalogue of instrumental data for earthquakes in northeastern Italy since 1900 are presented. The different types of magnitude, which are the main parameters under study, have been evaluated so as to be as homogeneous as possible. Comparisons of the different magnitude values show linear dependence, at least in the medium magnitude range represented by the available data set. Correlations between the magnitude most significant for this region and chosen macroseismic data indicate a methodology for assessing the macroseismic magnitude of historical earthquakes which seems to be stable. 相似文献
122.
Remote sensed data for automatic detection of land-use changes due to human activity in support to landslide studies 总被引:1,自引:1,他引:1
Slope instability studies appear to recognize a number of potential superficial slide-producing agents, which may be directly
detected and monitored with Earth Observation (EO) data. The main objective of this work is to use conventional EO data and
automatic techniques for providing land-use change maps useful in landslide prevention. The idea is to use the detection of
changes in areas already involved in landslide events as a precursory sign of variations in the equilibrium status of the
slope, independently from other natural triggering events, such as rain and seismic events. Attention is focused on man-induced
surface changes, such as deforestation, urban expansion and construction of artificial structures.
A historical set of 20 multi-temporal Landsat TM images, covering the period 1987–2000, was analyzed using a supervised change
detection technique on a test site affected by slope instability phenomena located in the Abruzzo region in Southern Italy.
A change image is obtained by comparing year-specific thematic map pairs. It contains useful information not only on the place
where a transition occurred, but also on the specific classes involved in the transitions between two different years. The
full set of change images is used to extract class-conditional transition probabilities, to evaluate variations in specific
class distribution and the total number of changed pixels in time. Four classes and their transitions were considered in the
analysis: (1) arboreous land, (2) agricultural land, (3) barren land, and (4) artificial structures.
The quantitative analysis of the class-joint transition probability values of some specific class-transitions that may worsen
slope stability showed that in an area prone to landslides the probability of landslide re-activation or first activation
is higher where changes have occurred. Although based on a limited number of known events, such a result encourages extensive
experimentation of the proposed technique on better documented landslide test sites. 相似文献
123.
The characteristics of the strong ground motion accelerograms from the 1999 Kocaeli earthquake are investigated in detail
in this study. The emphasis is on the comparison of the response spectra for the fault normal (FN) and fault parallel (FP)
components of the ground motions. The results show that the near-fault records with directivity effects characterize themselves
with increased base shear demands rather than increased displacement demands for both the FN and FP components and a narrower
velocity sensitive region for the FN component. This study also shows that the effectiveness of base isolation may vary from
site to site and for a given site, from component to component. The site effects in the Marmara region during the 1999 Kocaeli
earthquake are examined. Site amplifications are predicted by the classical spectral ratio (CSR) and the receiver function
(RF) methods. The CSR method gives higher estimates for the site amplifications compared to the RF method and is in better
conformity with the observed damage during the Kocaeli earthquake. The districts of Istanbul that are especially susceptible
to site amplification hazard are determined. It is apparent from the results that the site amplification hazard risk is the
highest for Avcilar and Bakirkoy districts. This study also shows that for sites which have the risk of soil amplification
for long-period structures, liquefaction may not be beneficial as a natural base isolator, and may result in shifting the
eigenperiod of the low- and mid-rise structures to the critical periods with high site amplifications. This may be especially
the case for Avcilar and Bakirkoy districts. In Fatih, Bakirkoy, and Cekmece districts, the predominant period of the ground
motion is calculated to be very close to the eigenperiods of the typical residential buildings. Therefore, these three districts
are expected to experience heavier damages in future earthquakes due to resonance effects. 相似文献
124.
Effect of dust storm on ocean color and snow parameters 总被引:1,自引:0,他引:1
Vinay K. Kayetha Senthil Kumar J. Anup K. Prasad Guido Cervone Ramesh P. Singh 《Journal of the Indian Society of Remote Sensing》2007,35(1):1-9
The present study clearly shows the influence of dust storms on chlorophyll bloom in the offshore region of the Arabian Sea,
with a time lag of few days, during the pre-monsoon season. Various satellite derived parameters over the Arabian Sea, Himalayan
and Tibet snow covered regions show large changes due to the influence of dust storms. The MODIS snow albedo gives unreliable
values under the influence of dust storms due to increase in the aerosol loading over these regions and snow albedo product
must be used in combination with snow pixel counts during the dust storm season. A detailed study is required for the quantitative
evaluation of dust storms on the chlorophyll blooms in the Arabian Sea region and on the snow parameters in the Himalayan
region. 相似文献
125.
Seyyedeh Halimeh Hashemi Azizi Payman Rezaee Mahdi Jafarzadeh Guido Meinhold Seyyed Reza Moussavi Harami Mehdi Masoodi 《Chemie der Erde / Geochemistry》2018,78(3):340-355
In Central Iran, the mixed siliciclastic?carbonate Nakhlak Group of Triassic age is commonly seen to have a Cimmerian affinity, although it shows considerable resemblances with the Triassic Aghdarband Group in far northeastern Iran, east of Kopeh-Dagh area, with Eurasian affinity. The Nakhlak Group is composed of the Alam (Late Olenekian?Anisian), Baqoroq (Late Anisian??Early Ladinian), and Ashin (Ladinian??Early Carnian) formations consisting mainly of volcanoclastic sandstone and shale and fossiliferous limestone. The Baqoroq Formation contains also metamorphic detritus. Sandstone petrofacies reflect the detrital evolution from active volcanism to growing orogen and again active volcanism. Textural and modal analyses of volcanic lithic fragments from the Alam Formation reflect the eruption style and magma composition of a felsic to intermediate syn-sedimentary arc activity. The detrital modes of the Baqoroq Formation sediments suggest a recycled orogenic source followed by arc activity in a remnant fore-arc basin. The sandstone samples from the Ashin Formation demonstrate a continuity of felsic to intermediate arc activity. Major and trace element concentrations of the Nakhlak Group clastic samples support sediment supply from first-cycle material and felsic magmatic arc input. The enrichment in LREE, the negative Eu anomalies, and the flat HREE patterns indicate origination from the old upper continental crust and young arc material. The chemical index of alteration (CIA ~51–70 for sandstone and 64–76 for shale samples) indicates medium degrees of chemical weathering at the source. Petrographical and geochemical evidence together with facies analysis constructed the following depositional conditions for the Nakhlak Group sediments: In the Olenekian, a fore-arc shallow to deep marine depositional basin developed that later was filled by recycled and arc-related detritus and changed into a continental basin in the Anisian. Ladinian extension let to a deepening of the basin. With respect to the similarities between the Nakhlak and Aghdarband (NE Iran) groups and unusual present-day position of the Nakhlak Group with no stratigraphic connection to the surrounding area, the development of first a fore-arc basin and later change into a back-arc depositional basin in close relation with the Aghdarband basin at the southern Eurasian active margin in the Triassic are here proposed. Understanding the basin development recorded in the Nakhlak Group provides constraints on the closure history of Palaeotethys and of the tectonic evolution of early Mesozoic basins at the southern Eurasian margin before the Cimmerian Orogeny. 相似文献
126.
When using the analysis of vibration measurements as a tool for health monitoring of bridges, the problem arises of separating abnormal changes from normal changes in the dynamic behaviour. Normal changes are caused by varying environmental conditions such as humidity, wind and most important, temperature. The temperature may have an impact on the boundary conditions and the material properties. Abnormal changes on the other hand are caused by a loss of stiffness somewhere along the bridge. It is clear that the normal changes should not raise an alarm in the monitoring system (i.e. a false positive), whereas the abnormal changes may be critical for the structure's safety. In the frame of the European SIMCES‐project, the Z24‐Bridge in Switzerland was monitored during almost one year before it was artificially damaged. Black‐box models are determined from the healthy‐bridge data. These models describe the variations of eigenfrequencies as a function of temperature. New data are compared with the models. If an eigenfrequency exceeds certain confidence intervals of the model, there is probably another cause than the temperature that drives the eigenfrequency variations, for instance damage. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献
127.
128.
Riccardo R. Milanesi Paolo Morandi Guido Magenes 《Bulletin of Earthquake Engineering》2018,16(9):4053-4080
Unreinforced masonry infills are widely used in many parts of the world and it is common practice for seismic design to use simplified methods that usually do not take into account the interaction between the infill and the structure. Starting from the 1950s, many researchers have investigated the lateral response of masonry infills focusing on several different topics. The scientific interest on masonry infills is continuously raising due to the unsatisfactory seismic response of the infilled frame structures observed during post-event inspections and to the difficulty to contrive a widely scientifically and practical recognized solution. Although some modern codes consider the presence of infills with some specifications to prevent damage in the masonry panels and global and local effects on the structure, an effective evaluation of these detrimental effects has not been achieved yet. Within this paper, a FEM simulation of in-plane pseudo-static cyclic tests on a RC frame specimen infilled with unreinforced Autoclaved Aerated Concrete (AAC) masonry infill has been performed in order to study accurately the influence and the interaction of the infill with the RC structure. The experimental results performed by Calvi and Bolognini (J Earthq Eng 5:153–185, 1999), and Penna and Calvi (Campagna sperimentale su telai in c.a. con tamponamenti in Gasbeton (AAC) con diverse soluzioni di rinforzo” (in Italian), 2006) on one-bay one-storey full scale specimens are taken as reference. Non-linear static analyses using a “meso-modelling” approach have been carried out. The masonry used in the model has been calibrated according to tests of mechanical characterization and to in-plane cyclic tests on load-bearing AAC masonry conducted by Costa et al. (J Earthq Eng 15:1–31, 2011). The analyses performed have allowed to investigate the local effects on the frame and, in particular, the changes in the moment and shear demands on the RC elements due to the presence of the AAC infill in comparison with the ones in the bare structure, and to estimate the thrust and the contact length activated by the infill on the frame. 相似文献
129.
Probable maximum flood (PMF) event estimation has challenged the scientific community for many years. Although the concept of the PMF is often applied, there is no consensus on the methods that should be applied to estimate it. In PMF estimation, the spatio-temporal representation of the probable maximum precipitation (PMP) as well as the choice of modelling approach is often not theoretically founded. Moreover, it is not clear how these choices influence PMF estimation itself. In this study, combinations of three different spatio-temporal PMP representations and three different modelling approaches are applied to determine the PMF of a mesoscale basin keeping the antecedent catchment conditions and the total precipitation amount constant. The nine resulting PMF estimations are used to evaluate each combination of methods. The results show that basic methods allow for a rough estimation of the PMF. In cases where a physically plausible and reliable estimation is required, sophisticated PMP and PMF estimation approaches are recommended.
EDITOR D. Koutsoyiannis; ASSOCIATE EDITOR A. Viglione 相似文献
130.
Jayde N. Hirniak Eugene I. Smith Racheal Johnsen Minghua Ren Jamie Hodgkins Caley Orr Fabio Negrino Julien Riel-Salvatore Shelby Fitch Christopher E. Miller Andrea Zerboni Guido S. Mariani Jacob A. Harris Claudine Gravel-Miguel David Strait Marco Peresani Stefano Benazzi Curtis W. Marean 《第四纪科学杂志》2020,35(1-2):199-212
Chemical characterization of cryptotephra is critical for temporally linking archaeological sites. Here, we describe cryptotephra investigations of two Middle–Upper Paleolithic sites from north-west Italy, Arma Veirana and Riparo Bombrini. Cryptotephra are present as small (<100 µm) rhyolitic glass shards at both sites, with geochemical signatures rare for volcanoes in the Mediterranean region. Two chemically distinct shard populations are present at Arma Veirana (P1 and P2). P1 is a high silica rhyolite (>75 wt.%) with low FeO (<1 wt.%) and a K2O/Na2O > 1 and P2 is also a high silica rhyolite (>75 wt.%) but with higher FeO (2.33–2.65 wt.%). Shards at Riparo Bombrini (P3) are of the same composition as P1 shards at Arma Veirana, providing a distinct link between deposits at both sites. Geochemical characteristics suggest three possible sources for P1 and P3: eruptions from Lipari Island (56–37.7 ka) in Italy, the Acigöl volcanic field (200–20 ka) in Turkey and the Miocene Kirka-Phrigian caldera (18 Ma) in Turkey. Eruptions from Lipari Island are the most likely source for P1,3 cryptotephra. This study highlights how cryptotephra can benefit archaeology, by providing a direct link between Arma Veirana and Riparo Bombrini as well as other deposits throughout the Mediterranean. 相似文献