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1.
In a companion article Akkar et al. (Bull Earthq Eng, doi:10.1007/s10518-013-9461-4, 2013a; Bull Earthq Eng, doi:10.1007/s10518-013-9508-6, 2013b) present a new ground-motion prediction equation (GMPE) for estimating 5 %-damped horizontal pseudo-acceleration spectral (PSA) ordinates for shallow active crustal regions in Europe and the Middle East. This study provides a supplementary viscous damping model to modify 5 %-damped horizontal spectral ordinates of Akkar et al. (Bull Earthq Eng, doi:10.1007/s10518-013-9461-4 2013a; Bull Earthq Eng, doi:10.1007/s10518-013-9508-6, 2013b) for damping ratios ranging from 1 to 50 %. The paper also presents another damping model for scaling 5 %-damped vertical spectral ordinates that can be estimated from the vertical-to-horizontal (V/H) spectral ratio GMPE that is also developed within the context of this study. For consistency in engineering applications, the horizontal and vertical damping models cover the same damping ratios as noted above. The article concludes by introducing period-dependent correlation coefficients to compute horizontal and vertical conditional mean spectra (Baker in J Struct Eng 137:322–331, 2011). The applicability range of the presented models is the same as of the horizontal GMPE proposed by Akkar et al. (Bull Earthq Eng, doi:10.1007/s10518-013-9461-4 2013a; Bull Earthq Eng, doi:10.1007/s10518-013-9508-6, 2013b): as for spectral periods $0.01 \hbox { s}\le \,\hbox {T}\le \,4\hbox { s}$ as well as PGA and PGV for V/H model; and in terms of seismological estimator parameters $4\le \hbox {M}_\mathrm{w} \le 8, \hbox { R} \le 200 \hbox { km}, 150\hbox { m/s}\le \hbox { V}_\mathrm{S30}\le $ 1,200 m/s, for reverse, normal and strike-slip faults. The source-to-site distance measures that can be used in the computations are epicentral $(\hbox {R}_\mathrm{epi})$ , hypocentral $(\hbox {R}_\mathrm{hyp})$ and Joyner–Boore $(\hbox {R}_\mathrm{JB})$ distances. The implementation of the proposed GMPEs will facilitate site-specific adjustments of the spectral amplitudes predicted from probabilistic seismic hazard assessment in Europe and the Middle East region. They can also help expressing the site-specific design ground motion in several formats. The consistency of the proposed models together with the Akkar et al. (Bull Earthq Eng, doi:10.1007/s10518-013-9461-4 2013a; Bull Earthq Eng, doi:10.1007/s10518-013-9508-6, 2013b) GMPE may be advantageous for future modifications in the ground-motion definition in Eurocode 8 (CEN in Eurocode 8, Design of structures for earthquake resistance—part 1: general rules, seismic actions and rules for buildings. European Standard NF EN 1998-1, Brussels, 2004).  相似文献   

2.
The seismic behaviour of caisson foundations supporting typical bridge piers is analysed with 3D finite elements, with due consideration to soil and interface nonlinearities. Single-degree-of freedom oscillators of varying mass and height, simulating heavily and lightly loaded bridge piers, founded on similar caissons are studied. Four different combinations of the static ( $\text{ FS }_\mathrm{V}$ FS V ) and seismic ( $\text{ FS }_\mathrm{E}$ FS E ) factors of safety are examined: (1) a lightly loaded ( $\text{ FS }_\mathrm{V}= 5$ FS V = 5 ) seismically under-designed ( $\text{ FS }_\mathrm{E} < 1$ FS E < 1 ) caisson, (2) a lightly loaded seismically over-designed ( $\text{ FS }_\mathrm{E} >1$ FS E > 1 ) caisson, (3) a heavily loaded ( $\text{ FS }_\mathrm{V} = 2.5$ FS V = 2.5 ) seismically under-designed ( $\text{ FS }_\mathrm{E} < 1$ FS E < 1 ) caisson and (4) a heavily loaded seismically over-designed caisson. The analysis is performed with use of seismic records appropriately modified so that the effective response periods (due to soil-structure-interaction effects) of the studied systems correspond to the same spectral acceleration, thus allowing their inelastic seismic performance to be compared on a fair basis. Key performance measures of the systems are then contrasted, such as: accelerations, displacements, rotations and settlements. It is shown that the performance of the lightly loaded seismically under-designed caisson is advantageous: not only does it reduce significantly the seismic load to the superstructure, but it also produces minimal residual displacements of the foundation. For heavily loaded foundations, however ( $\text{ FS }_{V} = 2.5$ FS V = 2.5 ), the performance of the two systems (over and under designed) is similar.  相似文献   

3.
This paper describes a new method for the evaluation of the static eccentricity $e_{s}$ and the ratio $\Omega _{\uptheta } $ of uncoupled torsional to lateral frequencies in real multi-storey buildings. The above-mentioned parameters greatly affect the lateral-to-torsional coupling of the response of asymmetric systems and thus are of paramount importance in the assessment of the in-plan irregularity of buildings. The proposed method, which is a generalization of that suggested by Calderoni et al. (Earthq Spectra 18(2):219–231, 2002), allows the calculation of the static eccentricity $e_{s}$ and the ratio $\Omega _{\uptheta } $ from the structural response to arbitrary distributions of forces and torsional couples. The effectiveness of the method is validated on some regularly and non-regularly asymmetric buildings characterised by different in-plan irregularity. The analyses demonstrate that the results of the method are rigorous in the case of regularly asymmetric systems and only slightly depend upon the heightwise distribution of the forces in the case of non-regularly asymmetric systems. Finally, the values of the static eccentricity $e_{s}$ and the ratio $\Omega _{\uptheta } $ resulting from the proposed method are compared to those obtained by means of the procedure suggested by Makarios and Anastassiadis in (Struct Des Tall Spec Build 7(1):33–55, 1998a; Struct Des Tall Spec Build 7(1):57–71, 1998b) .  相似文献   

4.
We tested attenuation relations obtained for different regions of the world to verify their suitability to predict strong-motion data recorded by Medellín and Aburrá Valley Accelerographic Networks. We used as comparison criteria, the average of the difference between the observed and the predicted data as a function of epicenter distance and its standard deviation. We also used the approach developed by Sherbaum et al. (Bull Seism Soc Am 94:2164–2185, 2004) that provides a method to evaluate the overall goodness-of-fit of ground-motion prediction equations. The predictive models selected use a generic focal depth. We found that this parameter has an important influence in the ground-motion predictions and must be taken into account as an independent variable. We also found important to characterize the local soil amplification to improve the attenuation relations. We found empirical relations for peak horizontal acceleration PGA and velocity PGV based on the Kamiyama and Yanagisawa (Soils Found 26:16–32, 1986) approach. $$\begin{aligned} \log _{10} (PGA)=0.5886M_L -1.0902\log _{10}(R)-0.0035H+C_{st}\pm 0.\text{29} \end{aligned}$$ $$\begin{aligned} \log _{10} (PGV)=0.7255M_L -1.8812\log _{10}(R)-0.0016H+C_{st}\pm 0.36 \end{aligned}$$ where PGA is measured in cm/s $^{2}$ and PGV in cm/s, $M_{L}$ is local magnitude in the range 2.8–6.5, $R$ is epicentral distance up to 290 km, $H$ is focal depth in km and $C_{st}$ is a coefficient that accounts for the site response due to soil conditions of each recording station. The introduction of focal depth and local site conditions as independent variables, minimize the residuals and the dispersion of the predicted data. We conclude that $H$ and $C_{st}$ are sensitive parameters, having a strong influence on the strong-motion predictions. Using the same functional form, we also propose an empirical relation for the root mean square acceleration a $_\mathrm{rms}$ : $$\begin{aligned} \log _{10} \left( {a_{rms} } \right)=0.4797M_L -1.1665\log _{10} (R)-0.00201H+C_{st}\pm 0.40 \end{aligned}$$ where a $_\mathrm{rms}$ is measured in cm/s $^{2}$ , from the S-wave arrival and using a window length equal to the rupture duration. The other variables are the same as those for PGA and PGV. The site correction coefficients $C_{st}$ found for PGA, PGV and a $_\mathrm{rms}$ show a similar trend indicating a good correlation with the soil conditions of the recording sites.  相似文献   

5.
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6.
In this paper we describe a stable automatic method to estimate in real time the seismic moment, moment magnitude and corner frequency of events recorded by a network comprising broad-band and accelerometer sensors. The procedure produces reliable results even for small-magnitude events $\hbox {M}_{\mathrm{W}}\approx 3$ . The real-time data arise from both the Transfrontier network at the Alps-Dinarides junction and from the Italian National Accelerometric Network (RAN). The data is pre-processed and the S-wave train identified through the application of an automatic method, which estimates the arrival times based on the hypocenter location, recording site and regional velocity model. The transverse component of motion is used to minimize conversion effects. The source spectrum is obtained by correcting the signals for geometrical spreading and intrinsic attenuation. Source spectra for both velocity and displacement are computed and, following Andrews (1986), the seismic moment and the first estimate of the corner frequency, $f_{0}$ , derived. The procedure is validated using the recordings of some recent moderate earthquakes (Carnia 2002; Bovec 2004; Parma 2008; Aquila 2009; Macerata 2009; Emilia 2012) and the recordings of some minor events in the SE Alps area for which independent seismic moment and moment magnitude estimates are available. The results obtained with a dataset of 843 events recorded by the Transfrontier and RAN networks show that the procedure is reliable and robust for events with $\hbox {M}_{\mathrm{W}}\ge 3$ . The estimates of $f_{0}$ are less reliable. The results show a scatter, principally for small events with $\hbox {M}_{\mathrm{W}}\le 3$ , probably due to site effects and inaccurate locations.  相似文献   

7.
A systematic analysis was conducted of the different variability components that affect the prediction of $\text{ log }_{10}(PSA)$ (i.e., Pseudo-Spectral Acceleration) ordinates on (mostly) deep sedimentary soil sites using a sizable set of strong motion data recorded in the strong earthquake sequences of 2010 and 2012 in the Canterbury region of New Zealand. Following recent, well established approaches of residual analysis of ground motion predictions, as well as recent GMPEs based on a global dataset, it was found that the event-corrected single-station standard deviation (“sigma”) is strongly decreased, for all selected stations, with respect to the uncorrected sigma. Likewise, the event-corrected intraevent sigma estimated for the entire dataset is significantly reduced compared to the standard deviation associated to ground motion prediction models, i.e. the “ergodic” sigma, for all spectral periods. The event-corrected sigma values for the present dataset are surprisingly consistent with those recently derived using KiK-Net strong motion data from Japan and those by Boore and Atkinson (Earthq Spectra 34(1):99–138, 2008) GMPE, and remain fairly constant with respect to the spectral period at about $0.15\sim 0.2$ . An interpretation was provided of the physical meaning of the site correction term ( ${\delta }S2S)_{s}$ indicating a plausible correlation with prevailing geological conditions in the site area.  相似文献   

8.
The TKE dissipation rate in the northern South China Sea   总被引：1，自引：0，他引：1  
The microstructure measurements taken during the summer seasons of 2009 and 2010 in the northern South China Sea (between 18°N and 22.5°N, and from the Luzon Strait to the eastern shelf of China) were used to estimate the averaged dissipation rate in the upper pycnocline 〈ε p〉 of the deep basin and on the shelf. Linear correlation between 〈ε p〉 and the estimates of available potential energy of internal waves, which was found for this data set, indicates an impact of energetic internal waves on spatial structure and temporal variability of 〈ε p〉. On the shelf stations, the bottom boundary layer depth-integrated dissipation $ {\widehat{\varepsilon}}_{\mathrm{BBL}} $ reaches 17–19 mW/m2, dominating the dissipation in the water column below the surface layer. In the pycnocline, the integrated dissipation $ {\widehat{\varepsilon}}_{\mathrm{p}} $ was mostly ～10–30 % of $ {\widehat{\varepsilon}}_{\mathrm{BBL}} $ . A weak dependence of bin-averaged dissipation $ \overline{\varepsilon} $ on the Richardson number was noted, according to $ \overline{\varepsilon}={\varepsilon}_0+\frac{\varepsilon_{\mathrm{m}}}{{\left(1+ Ri/R{i}_{\mathrm{cr}}\right)}^{1/2}} $ , where ε 0 + ε m is the background value of $ \overline{\varepsilon} $ for weak stratification and Ri cr?=?0.25, pointing to the combined effects of shear instability of small-scale motions and the influence of larger-scale low frequency internal waves. The latter broadly agrees with the MacKinnon–Gregg scaling for internal-wave-induced turbulence dissipation.  相似文献   

9.
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10.
Fragility curves for risk-targeted seismic design maps   总被引：1，自引：0，他引：1  
Seismic design using maps based on “risk-targeting” would lead to an annual probability of attaining or exceeding a certain damage state that is uniform over an entire territory. These maps are based on convolving seismic hazard curves from a standard probabilistic analysis with the derivative of fragility curves expressing the chance for a code-designed structure to attain or exceed a certain damage state given a level of input motion, e.g. peak ground acceleration (PGA). There are few published fragility curves for structures respecting the Eurocodes (ECs, principally EC8 for seismic design) that can be used for the development of risk-targeted design maps for Europe. In this article a set of fragility curves for a regular three-storey reinforced-concrete building designed using EC2 and EC8 for medium ductility and increasing levels of design acceleration \((\hbox {a}_\mathrm{g})\) is developed. These curves show that structures designed using EC8 against PGAs up to about 1 m/s \(^{2}\) have similar fragilities to those that respect only EC2 (although this conclusion may not hold for irregular buildings, other geometries or materials). From these curves, the probability of yielding for a structure subjected to a PGA equal to \(\hbox {a}_\mathrm{g}\) varies between 0.14 ( \(\hbox {a}_\mathrm{g}=0.7\) m/s \(^{2})\) and 0.85 ( \(\hbox {a}_\mathrm{g}=3\) m/s \(^{2})\) whereas the probability of collapse for a structure subjected to a PGA equal to \(\hbox {a}_\mathrm{g}\) varies between 1.7 \(\times 10^{-7}\) ( \(\hbox {a}_\mathrm{g}=0.7\) m/s \(^{2})\) and 1.0 \(\times 10^{-5}\) ( \(\hbox {a}_\mathrm{g}=3\) m/s \(^{2})\) .  相似文献   

11.
In the last two decades, south-central Europe and the Eastern Alps have been widely explored by many seismic refraction experiments (e.g., CELEBRATION 2000, ALP 2002, SUDETES 2003). Although quite detailed images are available along linear profiles, a comprehensive, three-dimensional crustal model of the region is still missing. This limitation makes this region a weak spot in continental-wide comprehensive representations of crustal structure. To improve on this situation, we select and collect 37 published active-source seismic lines in this region. After geo-referencing each line, we sample them along vertical profiles—every 50?km or less along the line—and derive P-wave velocities in a stack of homogeneous layers (separated by discontinuities: depth of crystalline basement, top of lower crust, and Moho). We finally merge the information using geostatistical methods, and infer S-wave velocity and density using empirical scaling relations. We present here the resulting crustal model for a region encompassing the Eastern Alps, Dinarides, Pannonian basin, Western Carpathians and Bohemian Massif, covering the region within $45^{\circ}\text{--}51^{\circ}\hbox{N}$ and $11^{\circ} \text{--} 22^{\circ}\hbox{E}$ with a resolution of $0.2^{\circ} \times 0.2^{\circ}.$ We are also able to extend and update the map of Moho depth in a wider region within $35^{\circ}\text{--}51^{\circ}\hbox{N}$ and $12^{\circ}\text{--}45^{\circ}\hbox{E},$ gathering Moho values from the collected seismic lines, other published dataset and using the European plate reference EPcrust as a background. All the digitized profiles and the resulting model are available online.  相似文献   

12.
A damaging seismic sequence hit a wide area mainly located in the Emilia-Romagna region (Northern Italy) during 2012 with several events of local magnitude \(\hbox {M}_\mathrm{l} \ge 5\) , among which the \(\hbox {M}_\mathrm{l}\) 5.9 May 20 and the \(\hbox {M}_\mathrm{l}\) 5.8 May 29 were the main events. Thanks to the presence of a permanent accelerometric station very close to the epicentre and to the temporary installations performed in the aftermath of the first shock, a large number of strong motion recordings are available, on the basis of which, we compared the recorded signals with the values provided by the current Italian seismic regulations, and we observed several differences with respect to horizontal components when the simplified approach for site conditions (based on Vs30 classes) is used. On the contrary, when using the more accurate approach based on the local seismic response, we generally obtain a much better agreement, at least in the frequency range corresponding to a quarter wavelength comparable with the depth of the available subsoil data. Some unresolved questions still remain, such as the low frequency behaviour ( \(<\) 1 Hz) that could be due either to complex propagation at depth larger than the one presently investigated or to near source effects, and the behaviour of vertical spectra whose recorded/code difference is too large to be explained with the information currently available.  相似文献   

13.
A new methodology is developed to estimate an aquatic community toxicity threshold concentration based on the limited toxicity data that are available for thiosalts. To analyze the indirect effect of thiosalts on decreasing pH, an exposure model is developed that estimates the residual concentration of thiosalts and pH in the water body. The results from this model are incorporated in thiosalts risk assessment and a case study is used to illustrate the applicability of the proposed model. In this study, the exposure model predicts that, trithionate and tetrathionate degraded to $ {{\text{SO}}_{4}}^{2 - } $ ions, $ {{\text{HSO}}_{3}}^{ - } $ ions, $ {{\text{SO}}_{3}}^{2 - } $ ions and elemental sulfur. The concentration of thiosulfate, trithionate and tetrathionate, initially at 25, 40 and 6 mg/L, respectively are expected to decrease. Over the duration of 77 h, thiosulfate degrades completely, while the estimated residual trithionate and tetrathionate concentrations are 13 and 5.77 mg/L, respectively. pH of the undiluted effluent is estimated to decrease from 9.2 to 5.6 within an hour of the effluent discharge and decreases further to 4 over a period of next 3 days. A framework and methodology developed in this paper can be utilized to estimate the potential direct and indirect risk of thiosalts exposure to ecological entities.  相似文献   

14.
A simple biogeochemical model coupled to an offline ocean tracer transport model driven by reanalysis ocean data is used to simulate the seasonal and interannual CO $_2$ flux variability in the northern Indian Ocean. The maximum of seasonal and interannual CO $_2$ emission variances in the northern Indian Ocean are located in the coastal Arabian Sea (AS) and Southern Peninsular India (SP) with a basin-wide seasonal amplitude and standard deviation of 0.044 $\pm $ 0.04 Pg C year $^{-1}$ . The area integrated CO $_2$ emissions from these two regions in the model are significantly correlated (above a 95 % level) with the observations of Takahashi et al. (Deep-Sea Res-II, 56:554–577, 2009). The interannual anomalies of CO $_2$ emission from the AS and SP are found as 40 and 30 % of their respective seasonal amplitudes. Both the Arabian Sea (AS) and Southern Peninsular India (SP) interannual CO $_2$ emission anomalies show a 3–4-year variability. The correlations of AS and SP CO $_2$ emission anomalies with the Indian Ocean Dipole/Zonal Mode (IODZM) and Southern Oscillation (SO) indices from 1980 to 1999 are 0.35, 0.21 and 0.32, 0.01 respectively. A 5-year window moving correlation analysis shows that the relationship of AS and SP CO $_2$ emission to the SO and IODZM are complementary to each other. During the years when the correlation of air–sea CO $_2$ emission with the IODZM is stronger, the corresponding correlation with the SO is weaker or opposite. The total change in pCO $_2$ is broken down into changes induced by the individual components such as dissolved inorganic carbon (DIC), sea surface temperature (SST), alkalinity, and salinity and found that (1) the effect of SST in the AS CO $_2$ emission increases (decreases) when the correlation of CO $_2$ emission with the IODZM is positive (negative), and (2) the SP CO $_2$ emission is strongly controlled by the circulation-driven DIC changes; however, this relation is found to be weaker when the SO correlates negatively with the SP CO $_2$ emission.  相似文献   

15.
Towards fully data driven ground-motion prediction models for Europe   总被引：2，自引：2，他引：0  
We have used the Artificial Neural Network method (ANN) for the derivation of physically sound, easy-to-handle, predictive ground-motion models from a subset of the Reference database for Seismic ground-motion prediction in Europe (RESORCE). Only shallow earthquakes (depth smaller than 25 km) and recordings corresponding to stations with measured $V_{s30}$ properties have been selected. Five input parameters were selected: the moment magnitude $M_{W}$ , the Joyner–Boore distance $R_{JB}$ , the focal mechanism, the hypocentral depth, and the site proxy $V_{S30}$ . A feed-forward ANN type is used, with one 5-neuron hidden layer, and an output layer grouping all the considered ground motion parameters, i.e., peak ground acceleration (PGA), peak ground velocity (PGV) and 5 %-damped pseudo-spectral acceleration (PSA) at 62 periods from 0.01 to 4 s. A procedure similar to the random-effects approach was developed to provide between and within event standard deviations. The total standard deviation ( $\sigma $ ) varies between 0.298 and 0.378 (log $_{10}$ unit) depending on the period, with between-event and within-event variabilities in the range 0.149–0.190 and 0.258–0.327, respectively. Those values prove comparable to those of conventional GMPEs. Despite the absence of any a priori assumption on the functional dependence, our results exhibit a number of physically sound features: magnitude scaling of the distance dependency, near-fault saturation distance increasing with magnitude, amplification on soft soils and even indications for nonlinear effects in softer soils.  相似文献   

16.
We applied the maximum likelihood method produced by Kijko and Sellevoll (Bull Seismol Soc Am 79:645–654, 1989; Bull Seismol Soc Am 82:120–134, 1992) to study the spatial distributions of seismicity and earthquake hazard parameters for the different regions in western Anatolia (WA). Since the historical earthquake data are very important for examining regional earthquake hazard parameters, a procedure that allows the use of either historical or instrumental data, or even a combination of the two has been applied in this study. By using this method, we estimated the earthquake hazard parameters, which include the maximum regional magnitude $ \hat{M}_{\max } , $ the activity rate of seismic events and the well-known $ \hat{b} $ value, which is the slope of the frequency-magnitude Gutenberg-Richter relationship. The whole examined area is divided into 15 different seismic regions based on their tectonic and seismotectonic regimes. The probabilities, return periods of earthquakes with a magnitude M?≥?m and the relative earthquake hazard level (defined as the index K) are also evaluated for each seismic region. Each of the computed earthquake hazard parameters is mapped on the different seismic regions to represent regional variation of these parameters. Furthermore, the investigated regions are classified into different seismic hazard level groups considering the K index. According to these maps and the classification of seismic hazard, the most seismically active regions in WA are 1, 8, 10 and 12 related to the Alia?a Fault and the Büyük Menderes Graben, Aegean Arc and Aegean Islands.  相似文献   

17.
This work proposes design energy spectra in terms of an equivalent velocity, intended for regions with design peak acceleration 0.3 g or higher. These spectra were derived through linear and nonlinear dynamic analyses on a number of selected Turkish strong ground motion records. In the long and mid period ranges the analyses are linear, given the relative insensitivity of the spectra to structural parameters other than the fundamental period; conversely, in the short period range, the spectra are more sensitive to the structural parameters and, hence, nonlinear analyses are required. The selected records are classified in eight groups with respect to soil type (stiff or soft soil), the severity of the earthquake in terms of surface magnitude $M _\mathrm{s} (M_\mathrm{s} \le $ 5.5 and $M _\mathrm{s} >$ 5.5) and the relevance of the near-source effects (impulsive or vibratory). For each of these groups, median and characteristic spectra are proposed; such levels would respectively correspond to 50 and 95 % percentiles. These spectra have an initial linear growing branch in the short period range, a horizontal branch in the mid period range and a descending branch in the long period range. Empirical criteria for estimating the hysteretic energy from the input energy are suggested. The proposed design spectra are compared with those obtained from other studies.  相似文献   

18.
Despite the seismic vulnerability of gas systems and the significance of the direct and indirect consequences that loss functionality might have on large communities, the analysis of the earthquake performance and of post-earthquake management for this kind of distribution networks appears under-represented in the international literature, with respect to other lifeline systems. To contribute on this matter, the study presented comprises an investigation of the impact of L’Aquila 2009 earthquake ( $\text{ M }_\mathrm{w}$ 6.3) on the performance of the local medium- and low-pressure gas distribution networks. The assessment of the physical impact of the earthquake to the buried components of network, namely pipes, valves, and demand nodes, was carried out when processing post-earthquake repair activity reports. Repair data, along with geometrical and constructive features, were collected in a geographic information system linked to the digitized maps of the network, and compared with the interpolated map of recorded transient ground motion, measured in terms of peak ground velocity (i.e., a $Shakemap^\mathrm{TM}$ ). The impact of permanent ground deformation was also investigated and found to be limited in the study area. The resulting observed repair rates (number of repairs per km), presented for different pipeline materials, were compared with repair ratio fragility functions available in literature, showing relatively agreement especially to those for steel pipes, likely also because of the uncertainties in the estimations. Finally, the management of the L’Aquila gas system in the emergency phase and the resilience (functionality recover versus time) of the system was discussed.  相似文献   

19.
On Sunday, October 23rd, 2011, the Van province, in the Eastern Turkey, was stricken by a magnitude $\text{ M}_{\mathrm{w}} \!=\! 7.1$ earthquake. The maximum horizontal peak ground acceleration, i.e. 0.182 g, was measured from the seismic station in Muradiye, at about 40 km from the epicenter. Several $\text{ M}_\mathrm{w} > 5.7$ strong motion aftershocks were recorded in November 2011. The exceptionally rich sequence of ground motions was due to the dense seismotectonic activity of the Eastern Turkey, where many active historical faults exist and newly generated can also be found because of the ongoing continental collision between the Arabian and the Eurasian Plates. The 2011 Van earthquake sequence caused 644 casualties, 1966 injuries with 252 rescues; the total economic losses are estimated at around 1 billion US dollars. The present paper deals with the seismological and structural damage assessment of two major seismic events and aftershock sequences in Van region; special emphasis is on the findings of the site investigations performed in the aftermath of the major seismic event. The performed investigation has shown that there is substantial field evidence demonstrating that the losses generated to the local social communities were caused by typical structural and non-structural deficiencies that have been surveyed in the past in several moderate-to-major earthquakes worldwide, especially in poor countries. Comprehensive numerical simulations were also carried out to assess the characteristics of the strong motion records and their effects on existing representative building type of structures in the earthquake-affected region. It was found that the local building stock is highly vulnerable and requires urgent major structural interventions for seismic strengthening. A cost-efficient retrofitting scheme is however not straightforward. It should be a trade-off between two competing aspects: the use of innovative materials and technologies on one hand, and the low-quality of the workmanships and lack of adequate quality control during construction phase, which are available in the Van province, on the other hand.  相似文献   

20.
Seismic coda wave attenuation ( $ Q_{\text{c}}^{ - 1} $ ) characteristics in the Garhwal region, northwestern Himalaya is studied using 113 short-period, vertical component seismic observations from local events with hypocentral distance less than 250?km and magnitude range between 1.0 to 4.0. They are located mainly in the vicinity of the Main Boundary Thrust (MBT) and the Main Central Thrust (MCT), which are well-defined tectonic discontinuities in the Himalayas. Coda wave attenuation ( $ Q_{\text{c}}^{ - 1} $ ) is estimated using the single isotropic scattering method at central frequencies 1.5, 3, 5, 7, 9, 12, 16, 20, 24 and 28?Hz using several starting lapse times and coda window lengths for the analysis. Results show that the ( $ Q_{\text{c}}^{ - 1} $ ) values are frequency dependent in the considered frequency range, and they fit the frequency power law ( $ Q_{\text{c}}^{ - 1} \left( f \right) = Q_{0}^{ - 1} f^{ - n} $ ). The Q 0 (Q c at 1?Hz) estimates vary from about 50 for a 10?s lapse time and 10?s window length, to about 350 for a 60?s lapse time and 60?s window length combination. The exponent of the frequency dependence law, n ranges from 1.2 to 0.7; however, it is greater than 0.8, in general, which correlates well with the values obtained in other seismically and tectonically active and highly heterogeneous regions. The attenuation in the Garhwal region is found to be lower than the Q c ?1 values obtained for other seismically active regions of the world; however, it is comparable to other regions of India. The spatial variation of coda attenuation indicates that the level of heterogeneity decreases with increasing depth. The variation of coda attenuation has been estimated for different lapse time and window length combinations to observe the effect with depth and it indicates that the upper lithosphere is more active seismically as compared to the lower lithosphere and the heterogeneity decreases with increasing depth.  相似文献   

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