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1.
Elisa Zambonelli Rita de Nardis Luisa Filippi Mario Nicoletti Mauro Dolce 《Bulletin of Earthquake Engineering》2011,9(1):39-65
On April 6, 2009, the town of L’Aquila in the Abruzzo region (central Italy) was struck by a seismic event at 01:32 (UTC),
of magnitude MW = 6.3. The mainshock was followed by a long period of intense seismic activity and within seven days after the mainshock
there were seven events of magnitude MW ≥ 5 that occurred from April 6 to April 13. This long seismic sequence was characterized by a complex rupture mechanism that
involved two major normal faults of the central Apennines: the Paganica and the Gorzano faults. The strong-motions of the
mainshock were recorded by 64 stations of the Italian Strong-motion Network (RAN) operated by the National Civil Protection
Department (DPC). Six stations of a local strong-motion array were working in NW L’Aquila suburb area. One of them, located
at about 6 km from the Paganica fault surface tip-line, set up in trigger mode, recorded continuously for more than 20 min
the mainshock and the aftershocks. Besides the mainshock, the RAN stations recorded in total 78 foreshocks and aftershocks
of ML ≥ 3.5, during the period from January to December 2009. The corresponding waveforms provide the most extensive digital strong
ground motion data set ever recorded in Italy. Moreover, the 48 three-component observations of events of magnitude MW ≥ 5, recorded at a distance less than 15 km from each of the major involved faults, provide a significant increasing of near-field
records available for the Italian territory. Six days after the mainshock, the strong-motion dataset, referred to preliminary
locations of the events with ML ≥ 4.0, was made available on the DPC web site () and at the same time it was delivered to the ITACA database (). This dataset has been used by many authors in scientific papers and by engineers, geophysicists and geologists for professional
technical works. In this paper, the present-day available strong-motion signals from the L’Aquila sequence and the performance
of the Italian strong-motion network in terms of the number and quality of recorded data, the geometry and data transmission
system are described. In addition the role of the temporary network that represents an extension of the permanent Italian
strong-motion network, supporting the emergency response by civil protection authorities and improving the network coverage
has been evaluated. 相似文献
2.
Peak and integral seismic parameters of L��Aquila 2009 ground motions: observed versus code provision values 总被引:1,自引:1,他引:0
A. Masi L. Chiauzzi F. Braga M. Mucciarelli M. Vona R. Ditommaso 《Bulletin of Earthquake Engineering》2011,9(1):139-156
The M
w 6.3 L’Aquila earthquake of April 6, 2009 hit a wide area of the Abruzzo region (Central Italy). The epicentre of the main
shock was very close to the urban centre of L’Aquila, the regional capital, with an epicentral distance less than 10 km. It
was the strongest earthquake ever recorded in Italy which has provided ground motion recordings from accelerometric stations
located in close proximity to the epicentre. Because of this, several remarkable results can be achieved by analysing the
strong motion recorded signals in terms of peak (PGA, PGV and PGD) and integral (Housner Intensity, I
H) seismic parameters. Additionally, an alternative time-domain representation of recorded signals has been used to furnish
a rapid comparison of traces recorded at different stations and along different directions. Some comparisons between the response
spectra derived from the recordings and the elastic demand spectra provided in the new seismic Italian code have also been
performed. PGA recorded values are very high and generally higher than code values for seismic actions with return period
T
R = 475 years. In some cases, this also happens for seismic actions with T
R up to 2,475 years. With regard to I
H, recorded values are generally higher for T
R = 475 years, whilst they are remarkably lower for T
R = 2,475 years. Accurate analyses have been carried out in the article to better understand the above differences and their
significance and implications. 相似文献
3.
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
4.
R. Puglia R. Ditommaso F. Pacor M. Mucciarelli L. Luzi M. Bianca 《Bulletin of Earthquake Engineering》2011,9(3):869-892
Previous works based mainly on strong-motion recordings of large Japanese earthquakes showed that site amplification and soil
fundamental frequency could vary over long and short time scales. These phenomena were attributed to non-linear soil behaviour:
the starting fundamental frequency and amplification were both instantaneously decreasing and then recovering for a time varying
from few seconds to several months. The recent April 6, 2009 earthquake (M
W 6.3), occurred in the L’Aquila district (central Italy), gave us the possibility to test hypotheses on time variation of
amplification function and soil fundamental frequency, thanks to the recordings provided by a pre-existing strong-motion array
and by a large number of temporary stations. We investigated the intra- and inter-event soil frequency variations through
different spectral analyses, including time-frequency spectral ratios and S-Transform (Stockwell et al. in IEEE Trans Signal
Process 44:998–1001, 1996). Finally, analyses on noise recordings were performed, in order to study the soil behaviour in linear conditions. The results
provided puzzling evidences. Concerning the long time scale, little variation was observed at the permanent stations of the
Aterno Valley array. As for the short time-scale variation, the evidence was often contrasting, with some station showing
a time-varying behavior, while others did not change their frequency with respect to the one evaluated from noise measurements.
Even when a time-varying fundamental frequency was observed, it was difficult to attribute it to a classical, softening non-linear
behaviour. Even for the strongest recorded shocks, with peak ground acceleration reaching 0.7 g, variations in frequency and
amplitude seems not relevant from building design standpoint. The only exception seems to be the site named AQV, where the
analyses evidence a fundamental frequency of the soil shifting from 3 Hz to about 1.5 Hz during the mainshock. 相似文献
5.
《地震研究进展(英文)》2023,3(1):100184
The 2022 MS 6.8 Luding earthquake is the strongest earthquake in Sichuan Province, Western China, since the 2017 MS 7.0 Jiuzhaigou earthquake. It occurred on the Moxi fault in the southeastern segment of the Xianshuihe fault, a tectonically active and mountainous region with severe secondary earthquake disasters. To better understand the seismogenic mechanism and provide scientific support for future hazard mitigation, we summarize the preliminary results of the Luding earthquake, including seismotectonic background, seismicity and mainshock source characteristics and aftershock properties, and direct and secondary damage associated with the mainshock. The peak ground displacements in the NS and EW directions observed by the nearest GNSS station SCCM are ~35 mm and ~55 mm, respectively, resulting in the maximum coseismic dislocation of 20 mm along the NWW direction, which is consistent with the sinistral slip on the Xianshuihe fault. Back-projection of teleseismic P waves suggest that the mainshock rupture propagated toward south-southeast. The seismic intensity of the mainshock estimated from the back-projection results indicates a Mercalli scale of VIII or above near the ruptured area, consistent with the results from instrumental measurements and field surveys. Numerous aftershocks were reported, with the largest being MS 4.5. Aftershock locations (up to September 18, 2022) exhibit 3 clusters spanning an area of 100 km long and 30 km wide. The magnitude and rate of aftershocks decreased as expected, and the depths became shallower with time. The mainshock and two aftershocks show left-lateral strike-slip focal mechanisms. For the aftershock sequence, the b-value from the Gutenberg-Richter frequency-magnitude relationship, h-value, and p-value for Omori’s law for aftershock decay are 0.81, 1.4, and 1.21, respectively, indicating that this is a typical mainshock-aftershock sequence. The low b-value implies high background stress in the hypocenter region. Analysis from remote sensing satellite images and UAV data shows that the distribution of earthquake-triggered landslides was consistent with the aftershock area. Numerous small-size landslides with limited volumes were revealed, which damaged or buried the roads and severely hindered the rescue process. 相似文献
6.
G. Ameri A. Oth M. Pilz D. Bindi S. Parolai L. Luzi M. Mucciarelli G. Cultrera 《Bulletin of Earthquake Engineering》2011,9(3):717-739
We exploit S-wave spectral amplitudes from 112 aftershocks (3.0 ≤ ML ≤ 5.3) of the L’Aquila 2009 seismic sequence recorded at 23 temporary stations in the epicentral area to estimate the source
parameters of these events, the seismic attenuation characteristics and the site amplification effects at the recording sites.
The spectral attenuation curves exhibit a very fast decay in the first few kilometers that could be attributed to the large
attenuation of waves traveling trough the highly heterogeneous and fractured crust in the fault zone of the L’Aquila mainshock.
The S-waves total attenuation in the first 30 km can be parameterized by a quality factor QS(f) = 23f
0.58 obtained by fixing the geometrical spreading to 1/R. The source spectra can be satisfactorily modeled using the omega-square
model that provides stress drops between 0.3 and 60 MPa with a mean value of 3.3±2.8 MPa. The site responses show a large
variability over the study area and significant amplification peaks are visible in the frequency range from 1 to more than
10 Hz. Finally, the vertical component of the motion is amplified at a number of sites where, as a consequence, the horizontal-to-vertical
spectral ratios (HVSR) method fails in detecting the amplitude levels and in few cases the resonance frequencies. 相似文献
7.
B. Pace D. Albarello P. Boncio M. Dolce P. Galli P. Messina L. Peruzza F. Sabetta T. San�� F. Visini 《Bulletin of Earthquake Engineering》2011,9(1):199-230
After the April 6th 2009 L’Aquila earthquake (M
w
6.3), where 306 people died and a further 60,000 were displaced, seismic microzoning investigations have been carried out
for towns affected by a macroseismic intensity equal to or greater than 7 MCS. Based upon seismotectonic data, historical
seismicity and strong motion records, we defined input spectra to be used in the numerical simulations of seismic microzoning
in four key municipalities, including the town of L’Aquila. We adopted two main approaches: uniform hazard response spectra
are obtained by a probabilistic seismic hazard assessment introducing some time-dependency for individual faults on the study
area; a deterministic design spectrum is computed from magnitude/distance pairs extracted by a stationary probabilistic analysis
of historical intensities. The uniform hazard spectrum of the present Italian building code represents the third, less restrictive,
response spectrum to be used for the numerical simulations in seismic microzoning. Strong motions recordings of the main shock
of the L’Aquila sequence enlighten the critical role played by both the local response and distances metric for sites located
above a seismogenic fault; however, these time-histories are compatible with the uncertainties of a deterministic utilization
of ground motion predictive equations. As recordings at very near field are rare, they cannot be neglected while defining
the seismic input. Disaggregation on the non-Possonian seismotectonic analysis and on the stationary site-intensity estimates
reach very similar results in magnitude-distance pairs identification; we interpret this convergence as a validation of the
geology-based model by historical observations. 相似文献
8.
Ionospheric precursor of a destructive earthquake that occurred on April 6, 2009 at L’Aquila (Italy)
On the basis of the 15-min data from a series of ground-based vertical ionospheric sounding stations, a study of variations
of the foF2 critical frequency before the strong earthquake (M = 6.3) that occurred on April 6, 2009 at L’Aquila (Italy) was carried out. The earthquake epicenter was located 85 km north-eastward
from Rome. Approximately 20 h prior to the earthquake, a well-pronounced statistically significant effect of foF2 increase relative to the average background for magnetically quiet days was observed for almost 1.5 h at the Rome ionospheric
station. In this case, at control stations distanced from the earthquake epicenter, no statistically significant deviations
of foF2 from the background values were detected during the same observations period. This fact provides grounds for consideration
of the foF2 increase observed at Rome station as a possible ionospheric precursor of this earthquake. 相似文献
9.
Paola Monaco Filippo Santucci de Magistris Salvatore Grasso Silvano Marchetti Michele Maugeri Gianfranco Totani 《Bulletin of Earthquake Engineering》2011,9(1):231-261
This paper describes a case-history of liquefaction occurred near the village of Vittorito after the April 6, 2009 L’Aquila
earthquake (moment magnitude Mw = 6.3), approximately 45 km far from the epicentre. In the document, first, an estimation of the seismic motion in the area
has been made. Thereafter, the performed geotechnical investigation is described, followed by the application of some fast
assessment criteria for the occurrence of liquefaction, recently proposed by the new Italian Building Code. A careful assessment
of all the parameters involved in conventional Seed and Idriss (1971) liquefaction analyses is considered. The cyclic resistance ratio CRR is evaluated by cone penetration tests CPT and by in
situ seismic dilatometer tests SMDT; in the latter case CRR is evaluated by different empirical correlations with shear wave
velocity Vs and horizontal stress index KD. Analytical data confirmed the observed occurrence of the liquefaction in Vittorito, even if the acceleration field in the
area, produced by the L’Aquila earthquake, was very low. 相似文献
10.
Petko Nenovski Maria Chamati Umberto Villante Marcello De Lauretis Patrizia Francia 《Acta Geophysica》2013,61(2):311-337
We apply detrended fluctuation analysis (DFA) on fluxgate and search-coil data in ULF range (scales 10–90 s or 0.1–0.011 Hz) for the months January–April 2009 available from the South European GeoMagnetic Array stations: Castello Tesino (CST), Ranchio (RNC), and L’Aquila (AQU) in Italy; Nagycenk (NCK) in Hungary; and Panagyuriste (PAG) in Bulgaria. DFA is a data processing method that allows for the detection of scaling behaviors in observational time series even in the presence of non-stationarities. The H and Z magnetic field components at night hours (00-03 UT, 01–04 LT) and their variations at the stations CST, AQU, NCK, and PAG have been examined and their scaling characteristics are analyzed depending on geomagnetic and local conditions. As expected, the scaling exponents are found to increase when the K p index increases, indicating a good correlation with geomagnetic activity. The scaling exponent reveals also local changes (at L’Aquila), which include an increase for the Z (vertical) component, followed by a considerable decrease for the X (horizontal) component in the midst of February 2009. Attempts are made to explain this unique feature with artificial and/or natural sources including the enhanced earthquake activity in the months January–April 2009 at the L’Aquila district. 相似文献