58 research outputs found
A Computer-Aided Algorithm Combined with an Integrated Downhole Method to Improve Shear Wave Detection and Damping Ratio Assessment: Theory and Preliminary Results
No full textThis contribution introduces a computerized semi-automated procedure coupled with a dedicated algorithm to improve shear wave velocity assessment and the on-site elastic damping ratio estimation of ground materials. The standard equipment of the downhole method is integrated with a horizontal geophone (guardian) placed on the field surface. Mask tapering and band multi-filter functions improve first arrival, recognizing and isolating SH-wave trains to estimate damping ratio profiles. These are computed by treating signals using a frequency-time combined approach (frequency-time packets method). The signals are corrected to consider the different source pulse amplitude, the effects of the propagation path, and scattering. The damping ratio profile is statistically computed in terms of the local drift of trend on the amplitude ratio series that would otherwise have a normal distribution centered on zero. These profiles intercept the lithology changes in the test sites and meet the damping values stemming from previous field tests and the laboratory experimental tests available in the literature regarding materials such as the ones investigated here
SHAKER: A selector of consistent and energetically equalized natural ground motions using the Italian earthquake database
No full textInput motion set selection for nonlinear dynamic structural analysis is commonly based on spectral compatibility,
obtained through the uniform scaling of natural signals. Due to the aleatory nature of the expected time history,
alone spectral compatibility requirement appears very weak to guarantee scaled ground motions that suit local
seismic hazard. Magnitude-Distance interval pairs to control selection and scaling factor thresholds do not always
provide input motions with adequate energy levels. In order to tackle these critical issues, a novel computer aided selection method based on consistency analysis to provide conservative energy levels has been devel oped. The method equalizes the ground motions subject to the spectral compatibility process to the modified
Housner Intensity of the hazard spectra. A multi-parametric consistency analysis based on statistic confidence is
performed on the equalized (by uniform scaling) ground motion set by comparing it with the larger regional
natural dataset on the same Magnitude-Distance pairs. The consistency analysis involves multiple ground motion
parameters taken into relation with the focal mechanism too. Sensitivity tests show the capability of the method
to reach high spectral compatibility joined with high consistency degrees by multi-parametric calibration.
Compared with the traditional ones, this method also shows greater performance in composing ground motion
sets close to real occurrences with a more assorted spectral frequency distribution
Evaluation of minimum karst spring discharge using a simple rainfall-input model: The case study of Capodacqua di Spigno Spring (Central Italy)
No full textThe increasing occurrence of widespread drought phenomena is a global environmental emergency, especially for the effects of ongoing climate change on groundwater availability. Dry years and extreme temperatures are common drivers of current climate impacts all over the world, including, for example, the freshwater supply for drinking and agriculture purposes, ecosystems, forestry, health, etc. In this frame, to ensure temporal water availability in water-stressed areas, sustainable groundwater management is an increasing challenge. Most groundwater in the South-East Latium Region, Central Italy, as in the whole Apennine Mountains chain, is stored in karst aquifers. In this area important water resources are present, but even here in the last decades they are affected by groundwater depletion as a consequence of occurring drought events, the upward trend in the global average temperature and the increase in groundwater extraction. Due to the lack of flow rate data of springs in many areas of Italy, spring response modeling could be a useful tool for supporting proper water resource management. Several research studies proposed methods based on relationships between spring discharges and rainfall data. The goal of this paper is to propose a simple linear model, based on rainfall-discharge cross correlations, in order to be able to simulate the effects of variation in rainfall on water resource connected Capodacqua di Spigno Spring minimum discharge. The results obtained using the developed model has been compared to an existing method that uses the Standard Precipitation Index (SPI) for the estimation of the minimum annual spring discharge
Seismic site effects in the Red Zone of Amatrice hill detected via the mutual sustainment of experimental and computational approaches
No full textThis paper presents the results of numerical analyses of ground motion in the Red Zone sector of Amatrice hill, violently struck by the 2016–2017 Central Italy seismic sequence. The methodologies used in processing the data to define the numerical model are firstly described. The results obtained from the computational analyses are then presented and discussed by comparing them with experimental data set of weak motion recordings. Computational analyses were performed via both a 2D-numerical FEM model and a pseudo-three-dimensional hybrid model (SiSeRHMap) which develops multispectral maps taking into account topographic effects. Starting from available geological data and geophysical measurements, an original and specific subsoil GIS model was developed and utilised to perform the computational analyses. The preliminary map for fundamental periods computed from the subsoil model is in good agreement with the experimental data. A restricted set of weak ground motions acquired from an accelerometric station located in a reference site was used as input for the numerical analyses, while the signals of the corresponding events recorded at the top of the hill were used as targets in the reliability evaluation analysis of the outputs. In the area of Amatrice hill, which is characterized by a complex geological and topographical context, the reliability analysis shows a good performance of the hybrid model compared to the 2D-FEM model in the prediction of seismic response. Agreement generally was also good with regards to the experimental and computational results, both in relation to the amplitude and to the shape of the spectral amplification that change depending on the hill sector. Considering the predictive reliability of the models, a high amplification, due to topographic effects, was observed for the Red Zone by performing a back-simulation of the 24th August 2016 main shock. The analysis results highlight also that the maximum amplification factors, based on the definition of the Housner intensity, occur in the interval of periods 0–0.5 s covering the fundamental period range of the buildings in this area
SPI and recession curves analysis for karst spring management. A case study in central Italy
No full textWater crises have become more and more frequent in recent years. In fact, the ongoing climate changes have led very often to periods of drought, which, together with the increasing of groundwater exploitation, leads to a depletion of thess resources, which are fundamental for human life. Most of the most important springs, in the world, are located in karst areas. Specifically, for a large part of the Mediterranean region, karst springs play an essential role in water supply systems. The quantitative analysis of karst aquifers is therefore of primary importance, in order to undertake a sustainable management of groundwater resources. Monitoring the karst spring discharge during the entire hydrological year is recommended. When measurements are not possible, spring discharge estimation, should be done. In this study, authors monitored the Capodacqua di Spigno Spring from January 2018 to September 2020. They have measured the surplus discharges in the river near the spring, using a current-meter. It was thus possible to reconstruct the flow rate delivered by the spring for the entire monitoring period. The most important value to be considered, in groundwater management, is the minimum discharge that the spring supplies during the year. In this paper, an existing forecasting method, that uses the Standard Precipitation Index (SPI), for the estimation of the minimum annual spring discharge, in the Capodacqua di Spigno Spring, was applied. The forecasting method using the SPI does not give any indication on the timing of the minimum flow rate. Using the recession curves, it was possible to estimate when the expected minimum will occur. The estimated minimum flow rates were compared with the measurements carried out and with the real flow rates supplied by the spring. In conclusion, it has been demonstrated how important is to associate discharge estimation methods with its monitoring. The comparative analysis in fact leads to a better knowledge of the spring drought phenomenon
Seismic hazard prediction using multispectral amplification maps in a complex topographic area: A case study of Qiaozhuang town, Sichuan Province, Southwest China
No full textEarthquakes can cause widely distributed slope failures and damage in mountainous areas. The accurate prediction of ground motions in mountainous areas is essential for managing the seismic risk of urban cities near mountains but is restricted primarily by complex seismic site amplification effects in areas of uneven terrain. This study selected Qiaozhuang town located in the Qingchuan—Pingwu fault zone, Southwest China, as a case study. A simulator for mapped seismic responses using a hybrid model (SiSeRHMap) was applied to compute the multispectral seismic topographic amplification maps at the three slope units surrounding Qiaozhuang town (Weigan hill, Mt. Dong, and Mt. Shizi). Post-earthquake damage survey maps, 1D seismic site response spectral ratios, and H/V spectral ratios of earthquake data were used to validate the computed seismic site amplification factors and resonance frequencies. The results suggest that strong topographic amplification effects usually occur at distinct slope locations, such as hilltops, convex slope positions, upslope, and narrow ridges. The computed topographic amplification factors in the study area reached up to 2.4 at upslope or hilltops, and the resonance frequencies were between 3 and 10 Hz. Topographic effects can be as important as stratigraphic effects when assessing seismic amplification effects in the study area. We conclude that both topographic and stratigraphic effects should be considered in the comprehensive seismic hazard assessment of the study area or other similar mountain towns
Procedure innovative per l’analisi della risposta sismica delle costruzioni monumentali realizzate a blocchi rigidi il caso del tempio di Nettuno a Paestum.
No full textMagnesium as Environmental Tracer for Karst Spring Baseflow/Overflow Assessment—A Case Study of the Pertuso Karst Spring (Latium Region, Italy)
No full textFollowing a previous research carried out on the same site, this paper presents the update of the Mg2+ based method for the estimation of Pertuso Spring discharge, located in Central Italy. New collected data confirmed the validity of the proposed model and the conservative behaviour of Mg2+ for groundwater related to the Pertuso Spring aquifer. Further analysis allowed to obtain a local linear relationship between magnesium concentration and total spring discharge (including exploitation rate), regardless of the mixing model proposed with the Aniene River. As regards two samples which fall out of the linear relationship and could have been detected as “outliers”, more in-depth data processing and sensitivity analyses revealed that the lowering in magnesium, at equal discharges, is determined by the appearance of the quick-flow component, less mineralized and related to storm events. Results showed that under specific conditions, related to the absence or presence of previous intense rainfall events, Mg2+ could be effectively a useful tracer for separating spring conduit flow (overflow) from diffuse flow (baseflow) within the karst aquif
Frequency-dependent topographic seismic amplification by a "gray box model" using GIS morphometric data
No full textTopographic seismic amplification can have a relevant effect in hilly and mountain areas and it assumes a relevant role in urban planning and seismic slope instability. On the other hand, recent studies on this topic strongly suggest the necessity to assess or predict topographic effect as a frequency depending variable and in an adequate way, in contrast with the simplistic models that use an inadequate uniform spectral scaling factor.
Following this suggestion and taking into account the results of the aforesaid studies, a computerized model was developed based on common topographic attributes such as DTM, slope angle and curvature, taking into consideration the uniform rigidity of the relief. The model is defined as grey box model due to the fact that it is constructed on the awaited physical behaviour along the relief and initially trained on topographic amplified data of uniform regular relief, data product by 2D numerical analysis The validation of model was performed on two well-known areas. The results show a high prediction capacity of the model and how it can be driven for the optimization of performance in different real areas
Multi-temporal mapping of the Caforchio earth flow, southern Italy
No full textWe used aerial photos and field observations to produce multi-temporal maps of the Caforchio earth flow from 1954 to 2013. The maps show the distribution of back-tilted surfaces, flank ridges, normal, thrust, and strike-slip faults and, springs, creeks, and ponds. The maps provide a basis for interpreting how geometric and hydrologic constraints influence earth-flow evolutio
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