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Ground motion scaling in the Marmara region, Turkey 总被引:1,自引:0,他引:1
A. Akinci L. Malagnini R. B. Herrmann R. Gok M. B. Sørensen 《Geophysical Journal International》2006,166(2):635-651
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Valentina?MontaldoEmail author Ezio?Faccioli Gaetano?Zonno Aybige?Akinci Luca?Malagnini 《Journal of Seismology》2005,9(3):295-316
In the framework of the 2004 reference seismic hazard map of Italy the amplitude of the strong-motion (expressed in terms
of Peak Horizontal Acceleration with 10% probability of non-exceedence in 50 years, referred to average hard ground conditions)
was computed using different predictive relationships. Equations derived in Italy and in Europe from strong-motion data, as
well as a set of weak and strong-motion based empirical predictive relationships were employed in a logic tree procedure,
in order to capture the epistemic uncertainty affecting ground-motion attenuation. This article describes the adjustments
and conversions required to eliminate the incompatibilities amongst the relations. Particularly significant are distance conversions
and style-of-faulting adjustments, as well as the problems related to the use of regional relations, such as the selection
of a reference depth, the quantification of random variability and the strong-motion prediction. Moreover, a regional attenuation
relationship specific for volcanic areas was also employed, allowing a more realistic evaluation of seismic hazard, as confirmed
by the attenuation of macroseismic intensities. 相似文献
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Uncertainties in probability of occurrence of strong earthquakes for fault sources in the Central Apennines,Italy 总被引:1,自引:1,他引:0
Aybige Akinci David Perkins Anna Maria Lombardi Roberto Basili 《Journal of Seismology》2010,14(1):95-117
Using the characteristic earthquake model, we calculate the probability of occurrence of earthquakes M
w > 5.5 for individual fault sources in the Central Apennines for the 30-year period (2007–2037). We show the effect of time-dependent
and time-independent occurrence (Brownian passage time (BPT) and Poisson) models together with uncertain slip rates and uncertain
maximum magnitudes and, hence, uncertain recurrence times. In order to reduce the large prior geological slip rate uncertainty
distribution for most faults, we obtain a posterior slip rate uncertainty distribution using a likelihood function obtained
from regional historical seismicity. We assess the uncertainty of maximum magnitude by assuming that the uncertainty in fault
width and length are described by a normal distribution with standard deviation equal to ±20% of the mean values. We then
estimate the uncertainties of the 30-year probability of occurrence of a characteristic event using a Monte Carlo procedure.
Uncertainty on each parameter is represented by the 16th and the 84th percentiles of simulated values. These percentiles bound
the range that has a 68% probability of including the real value of the parameter. We do these both for the Poisson case and
for the BPT case by varying the aperiodicity parameter (α value) using the values 0.3, 0.5, and 0.7. The Bayesian posterior slip rate uncertainties typically differ by a factor of
about 2 from the 16th to the 84th percentile. Occurrence probabilities for the next 30 years at the 84th percentile typically
range from 1% to 2% for faults where the Poisson model dominates and from 2% to 21% where one of the BPT models dominates.
The uncertainty in occurrence probability under the time-dependent hypothesis is very large, when measured by the ratio of
the 84th to the 16th percentile, frequently being as much as two orders of magnitude. On the other hand, when measured by
standard deviation, these standard deviations range from 2% to 6% for those faults whose elapsed time since previous event
is large, but always 2% or less for faults with relatively recent previous occurrence, because the probability of occurrence
is always small. 相似文献
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Aybige Akinci Luca Malagnini Fabio Sabetta 《Soil Dynamics and Earthquake Engineering》2010,30(5):320-335
An Mw 6.25 earthquake occurred on April 6, 2009 at 03:33 a.m. local time, in the Abruzzo region (Central Italy), close to the city of L’Aquila. The earthquake ruptured a North-West (NW)–South-East (SE) oriented normal fault dipping toward the South-West (SW), with the city of L’Aquila lying a few kilometers away on the hanging wall.The main shock has been recorded by fifty-eight accelerometric stations: the highest number of digital recordings ever obtained in Italy for a single earthquake, one of the best-recorded earthquakes with a normal fault mechanism. Very high values of peak ground acceleration (0.3–0.65 g) were observed close to the center of L’Aquila (6 stations at zero JB distance from the fault). The earthquake caused severe loss of lives (299 victims and 1500 injured) and damage (about 18000 unusable buildings) in the epicentral area.In this study we analyze the ground motion characteristics of both the main shock in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and pseudo-acceleration response spectra (5% of damping ratio). In particular, we compare the pseudo-acceleration response spectra for horizontal directions with the EC8 design spectrum and the new Italian building code (NTC08). In order to understand the characteristics of the ground motions induced by L’Aquila earthquake, we also study the source-related effects and site response of the strong motion stations that recorded the seismic sequence. A novel method is used for the analysis of inter-station and site-specific H/V spectral ratios for the main event and for 12 aftershocks. 相似文献
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A. Ansal A. Akinci G. Cultrera M. Erdik V. Pessina G. Tönük G. Ameri 《Soil Dynamics and Earthquake Engineering》2009
The rapid urban development in Istanbul has lead to an increase in the exposure levels of the urban vulnerability. Due to the steadily increasing population, with improper land-use planning, inappropriate construction techniques and inadequate infrastructure systems, associated with an existing high hazard level, Istanbul is one of the most risky cities in the Mediterranean region. Estimations of casualties and losses, expected for given earthquake scenarios, are necessary to develop sustainable rehabilitation programs and for improving preparedness. Deterministic hazard scenarios and time-dependent probabilistic hazard assessment were used as input to a GIS-based loss estimation model, to evaluate the earthquake risk for Istanbul. 相似文献
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—?We have used micro-earthquake recordings (M= 1.8–4.1) of local events in the distance range of 5–60?km in order to quantify the attenuation and site effects in the vicinity of the Bursa city, Marmara region, Turkey. The data set consists of 120 three-component recorded accelograms from 69 earthquakes, recorded at six stations. Each station is deployed on different geologic units, such as massive limestone, slope deposit and Quaternary young sediments, in the framework of the Marmara Poly-Project.¶In this study a nonparametric inversion method was applied to acceleration records from the Bursa region to estimate source, site and path effects using a two-step inversion. At the first step, we determined attenuation functions by analyzing the distance dependence of the spectral amplitudes and retrieved values of Q s (f) = 46.59f 0.67. At the second step, the corrected S-waves spectral records for the attenuation function, including the geometrical spreading effect, were inverted to separate source and site response for 21 different frequencies selected between 0.5 and ~25?Hz. The near-surface attenuation, κ value, was also estimated by using the model proposed by Anderson and Hough (1984) at each site. We observed that κ0 is smaller for stations located on rock site (I?dιr, SIGD, κ0~0.004) compared to the one that is located on Neogene sediment (Çukurca, SCKR, κ0~0.018).¶Site amplifications from inversion showed that the station located within the Bursa basin, Çukurca (SCKR), is the most important site with about 4.0 amplification value at 1.8?Hz. Demirta? (SDEM) amplifies the spectral amplitudes about 3.0 times at 2.0?Hz, SHMK about 3.5 times between 2.5 and 3.5?Hz and SHMT nearly reaching 3.5 times between 1.5 and 4.0?Hz. However, stations located on the Uluda? Mountain Massif (SKAY and SIGD), which correspond to a deep limestone geological unit, have the smallest amplification, that values between 0.6 and 1.4. 相似文献