Comparison of ground motions from the 2010 Mw 7.2 El Mayor–Cucapah earthquake with the next generation attenuation ground motion prediction equations

A total of 144 free-field ground motions with closest site-to-rupture distances (R_rup) less than 200 km recorded during the 2010 M_w 7.2 El Mayor–Cucapah earthquake are used to investigate predictive capabilities of the next generation attenuation (NGA) ground-motion prediction equations (GMPE). The NGA GMPEs underpredict observed spectral accelerations at sites with shear wave velocity in the upper 30 m of the site (V_s30) between 180 and 366 m/s with R_rup from about 10 to 50 km and overpredict at sites with R_rup from about 50 to 200 km. Intra-event residuals of the NGA GMPEs exhibit a noticeable negative trend for peak ground acceleration and 0.3, 1.0, and 2.0 s periods. Comparison of the inter-event residual between the 2010 M_w 7.2 El Mayor–Cucapah earthquake and the NGA dataset reveals that short-period inter-event residuals from the 2010 M_w 7.2 El Mayor–Cucapah earthquake is within the scatter of inter-event residuals from the NGA dataset but long-period inter-event residuals do not appear within of the scatter of inter-event residuals from the NGA dataset. Spectral accelerations predicted by the NGA GMPEs are generally unbiased against V_s30 and periods of less than 4.0 s. Observed spectral accelerations show a stronger V_s30 dependence for both short and long periods compared with the NGA GMPEs. The Boore and Atkinson (Earthq Spectra 24(1):99–138, 2008) and Chiou and Youngs (Earthq Spectra 24(1):173–215, 2008) GMPEs perform better in predicting observed short-period spectral accelerations at the sites with V_s30 between 180 and 250 m/s than the Abrahamson and Silva (Earthq Spectra 24(1):67–97, 2008) and Campbell and Bozorgnia (Earthq Spectra 24(1):139–171, 2008) GMPEs.     

Predicted ground motion after the L��Aquila 2009 earthquake (Italy, M w 6.3): input spectra for seismic microzoning

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.     

Ground motion prediction in Beirut: a multi-step procedure coupling empirical Green’s functions,ground motion prediction equations and instrumental transfer functions

The strike slip Yammouneh fault is the longest fault in Lebanon, crossing the territory from South to North. It was responsible for major historical earthquakes like the 1202 A.D. earthquake, estimated to M_s7.6. This paper presents a site-specific estimation of the ground motion caused by a potential M_w7.5 earthquake on the Yammouneh fault, similar to the 1202 event, for various sites within the Beirut area. The empirical Green’s function technique EGF is used to estimate the median and the standard deviations of the seismic ground motion at the reference station BHL, taking into account epistemic and aleatory uncertainties related to source parameters. These uncertainties were quantified through a sensitivity analysis of the position of the rupture nucleation X_nuc, the slip roughness parameter K, the corner frequency f_c and the magnitude M_c of the EGF. The rock ground motion is then transferred to various other sites within the Beirut area, using instrumental Fourier transfer functions. Site amplification factors are next deduced by computing the ratio between response spectra at sediment sites and at a reference rock station. Considering the limits of the EGF method in the near field of extended sources, the EGF approach is considered only up to a magnitude M_w of 6.5. Selected Ground Motion Predictive Equations are then used to simulate a M_w7.5 event at a reference station. By applying the amplification factors, the response spectra at the different sites of Beirut are also calculated and compared with the actual response spectra used in the Lebanese regulations.     

Development of attenuation relation for the near fault ground motion from the characteristic earthquake

A composite source model has been used to simulate a broadband strong ground motion with an associated fault rupture process. A scenario earthquake fault model has been used to generate 1 000 earthquake events with a magni-tude of Mw8.0. The simulated results show that, for the characteristic event with a strike-slip faulting, the character istics of near fault ground motion is strongly dependent on the rupture directivity. If the distance between the sites and fault was given, the ground motion in the forward direction (Site A) is much larger than that in the backward direction (Site C) and that close to the fault (Site B). The SH waves radiated from the fault, which corresponds to the fault-normal component plays a key role in the ground motion amplification. Corresponding to the sites A, B, and C, the statistical analysis shows that the ratio of their aPG is 2.15:1.5:1 and their standard deviations are about 0.12, 0.11, and 0.13, respectively. If these results are applied in the current probabilistic seismic hazard analysis (PSHA), then, for the lower annual frequency of exceedance of peak ground acceleration, the predicted aPG from the hazard curve could reduce by 30% or more compared with the current PSHA model used in the developing of seismic hazard map in the USA. Therefore, with a consideration of near fault ground motion caused by the rupture directivity, the regression model used in the development of the regional attenuation relation should be modified accordingly.     

Soil–structure interaction analysis of cable-stayed bridges for spatially varying ground motion components

In this study, it is intended to determine the effects of soil–structure interaction (SSI) and spatially varying ground motion on the dynamic characteristics of cable-stayed bridges. For this purpose, ground motion time histories are simulated for spatially varying ground motions, depending on its components of incoherence, wave-passage and site-response effects. The substructure method, which partitions the total soil–structure system into the structural system and the soil system, is used to treat the soil–structure interaction problem. To emphasize the relative importance of the spatial variability effects of earthquake ground motion, bridge responses are determined for the fixed base bridge model, which neglects the soil–structure interaction (no SSI) and for the bridge model including the soil–structure interaction (SSI). This parametric study concerning the relative importance of the soil–structure interaction and spatially varying ground motion shows that these effects should be considered in the dynamic analyses of cable-stayed bridges.     

A Mw 6.3 earthquake scenario in the city of Nice (southeast France): ground motion simulations

The southern Alps–Ligurian basin junction is one of the most seismically active zone of the western Europe. A constant microseismicity and moderate size events (3.5 < M < 5) are regularly recorded. The last reported historical event took place in February 1887 and reached an estimated magnitude between 6 and 6.5, causing human losses and extensive damages (intensity X, Medvedev–Sponheuer–Karnik). Such an event, occurring nowadays, could have critical consequences given the high density of population living on the French and Italian Riviera. We study the case of an offshore Mw 6.3 earthquake located at the place where two moderate size events (Mw 4.5) occurred recently and where a morphotectonic feature has been detected by a bathymetric survey. We used a stochastic empirical Green’s functions (EGFs) summation method to produce a population of realistic accelerograms on rock and soil sites in the city of Nice. The ground motion simulations are calibrated on a rock site with a set of ground motion prediction equations (GMPEs) in order to estimate a reasonable stress-drop ratio between the February 25th, 2001, Mw 4.5, event taken as an EGF and the target earthquake. Our results show that the combination of the GMPEs and EGF techniques is an interesting tool for site-specific strong ground motion estimation.     

On the rocking–sliding instability of rigid blocks under ground excitation: Some new findings

Rocking (overturning) instability analyses of rigid blocks based on the assumption that the friction between the block and the ground is sufficiently large to exclude the effect of sliding, are reconsidered by including the effect in question. Both modes of overturning instability – without impact and after one impact – are thoroughly discussed in connection with small sliding, whose value depends on the values of kinetic (dry) friction coefficient and the external frequency excitation. Using an energy approach the analytical derivation of the nonlinear differential equations of motion of free-standing rigid blocks under one-sine ground pulse including the effect of sliding, are comprehensively established. The serious difficulties in solving this problem on one hand the change of the kinetic friction coefficient during the motion and on the other hand the reliable evaluation of the actual friction effect when rocking is included, are effectively confronted. This is achieved through a reliable approximation of an equivalent (reduced) coefficient assuming that the major part of friction takes place from the initiation of motion and terminates shortly after the onset of rocking. In cases of slender blocks closed form solutions for overturning due to simultaneous rocking–sliding without or after one impact, are conveniently derived. Among other findings, it was explored that the single block in question for small values of the external frequency (long periods of excitation) the sliding effect is beneficial (stabilizing the block), while for large values of external frequency this effect is detrimental (destabilizing the block).     

23 November 1980 Irpinia–Basilicata earthquake (Southern Italy): towards a full knowledge of the seismic effects

This paper overviews the procedures and tools used for a systematic study of the macroseismic consequences caused by a strong earthquake that struck Southern Italy. The event referred to the 23 November 1980 (Io = X MCS, Ms = 6.9) which affected the Campania and Basilicata regions. Two aspects are addressed here: to broaden the knowledge of the macroseismic field and delineate damage maps of the sites affected on an urban scale. The target area of this study is the Basilicata region about which the current macroseismic information is poor. This research study, based only on unpublished documentary sources, supplies about 50 new assessments and about 30 new re-assessments of the macroseismic site intensity (MCS scale) as outputs. Moreover, about 80 thematic maps showing the damage pattern of the sites affected are also supplied. It is the first time that a large earthquake has been the subject of such extensive studies from a macroseismic point of view, with special attention to the analysis of damage effects at town scale.     

Generating ground motion by two new techniques of adding harmonic wave in the time domain and approximating to response spectrum as a whole

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Stress Drops of the 1997–1998 Colfiorito,Central Italy Earthquakes: Hints for a Common Behaviour of Normal Faults in the Apennines

Stress drop estimates of moderate-magnitude earthquakes in the Umbria–Marche region, in the northern Apennines, exhibit a large scatter. For the two M _w 5.7 and 6.0 main shocks of 26 September 1997 near Colfiorito, several papers resulted in stress drop estimates of 20 MPa, but values as low as 2–3 MPa were proposed as well. Also for the largest aftershocks (M _w > 4), estimates spread from < 1 MPa up to values ten times larger. We have critically revisited methods and data used in the literature. We have specifically faced the trade-off between source and propagation effects, as we believe that it is responsible for a part of the large scatter. To keep this trade-off under control, we have applied a methodology that combines the best fit of both source spectra after Empirical Green’s Function (EGF) deconvolution and observed ground motion spectra, finding that the results of the two different data sets converge independently at the same solution. We have used ground motions observed in the Colfiorito basin, where an accelerograph and a co-located seismological broad-band station recorded three clusters of earthquakes in a broad magnitude interval (1.7 ≤ M _w ≤ 6.0). We have found that the mainshock–aftershock sequences result in stress drops of 2–5 MPa at M _w ≥ 5.6, with an average tendency to decrease at smaller magnitudes where stress drop variability increases. These findings confirm the source scaling recently assessed through Empirical Green’s Function deconvolution for another well-monitored seismic sequence of normal-faulting earthquakes, which struck the city of L’Aquila in the central Apennines in April 2009. The similar scaling law of the two areas suggests common mechanisms of stress release for the shallow normal faults in the Apennines. The propensity of smaller earthquakes to increase in variability, with a tendency toward smaller stress drops, may reflect an effect of fault strength heterogeneities for smaller size ruptures.     

Performance of the Italian strong motion network during the 2009, L��Aquila seismic sequence (central Italy)

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 M_W = 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 M_W ≥ 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 M_L ≥ 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 M_W ≥ 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 M_L ≥ 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.     

New predictors and a new prediction model for the typhoon frequency over western North Pacific

In this paper, the impacts of the atmospheric circulation during boreal winter-spring on the western North Pacific (WNP) typhoon frequency (WNPTF) are studied. Several new factors in winter-spring in- fluencing the typhoon frequency were identified, including the sea ice cover in the North Pacific and the North Pacific oscillation. Based on these results, the multi-linear regression was applied to establishing a new forecast model for the typhoon frequency by using the datasets of 1965―1999. The forecast model shows a high correlation coefficient (0.79) between the model simulated and the actual typhoon frequencies in the period of 1965―1999. The forecast model also exhibits reasonable hindcasts for the typhoon frequencies for the years 2000―2006. Therefore, this work demonstrates that the new pre- dictors are significant for the prediction of the interannual variability of the WNPTF, which could be potentially used in the operational seasonal forecast of the typhoon frequency in the WNP to get a more physically based operational prediction model and higher forecast skill.     

Amplification of in-plane seismic ground motion by group cavities in layered half-space (Ⅰ)

Amplification of in-plane seismic ground motion by underground group cavities in layered half-space is studied both in frequency domain and time domain by using indirect boundary element method (IBEM), and the effect of cavity interval and spectrum of incident waves on the amplification are studied by numerical examples. It is shown that there may be large interaction between cavities, and group cavities with certain intervals may have significant amplification to seismic ground motion. The amplification of PGA (peak ground acceleration) and its PRS (peak response spectrum) can be increased up to 45.2% and 84.4%, for an example site in Tianjin, under the excitation of Taft wave and El Centro wave; and group cavities may also affect the spectra of the seismic ground motion. It is suggested that the effect of underground group cavities on design seismic ground motion should be considered.     

Long-period ground motion characteristic of the 1999 Jiji (Chi-Chi),Taiwan,main-shock and aftershocks

Introduction The study of attenuation relations for long-period ground motion is to meet the requirement of economy development. During the earthquakes such as the June 16, 1964 Niigata, Japan, M=7.5 earthquake, the March 24, 1977 Romania M=7.3 earthquake, the March 29, 1970 Gediz, Turkey, M=7.1 earthquake, the May 26, 1983 M=7.7 earthquake in the middle Japanese Sea, the September 19, 1985 Mexico M=8.1 earthquake, the September 16, 1994 M=7.3 earthquake in Tai- wan Strait, and the No…     

How useful is the Waldmeier effect for prediction of a sunspot cycle?

Waldmeier effect [Waldmeier M., 1955. Ergebnisse und Probleme der Sonnenforschung. Second Ed., Leipzig, p. 154] states that the rise-time of a cycle depends upon a single parameter, namely the sunspot number Rz(max) at the maximum. Strong cycles have a steeper rise, while moderate cycles rise more slowly. In this paper, using the past data for sunspot cycles 1–23, these aspects are re-examined. It was noticed that the inverse relationship between Rz(max) and rise-time is discernable only when average patterns obtained by superposition of several cycles (separately for strong and weak cycles) are compared. In individual cycles, considerable deviations from the average patterns can occur (several tens of units of Rz and several months of rise-time). For a study of the relationship of Rz(max) with features in the early part of a cycle, the features chosen were Ro (i.e., Rz(min)) and Rz values Ra, Rb, and Rc, 12, 24 and 36 months, respectively, later than Ro (only 12-monthly running means were used). Ro had a moderate correlation (<0.6) with Rz(max), but Ra, Rb, Rc had better correlations. For hindsight predictions for cycles 18–23, the predictions for cycle 19 was grossly erroneous (observed value almost double of the predicted value). For other cycles, the errors were within 25%. For cycle 24, the Rz monthly values up to March 2008 give 12-month running means centered in June, July, August, September 2007 as 7.6, 6.5, 5.8, 6.1. Thus, though we cannot be absolutely sure yet that Rz(min) for cycle 24 has occurred, a tentative, provisional prediction using Rz(min) (i.e., Ro) as 5.8 is Rz(max)=113±19, i.e., in the range 94–132. This is an upper limit, as Ro value may reduce further in coming months, but most probably not very much. For Ro=5.0, the prediction would be Rz(max)= 109±17, while in the extreme hypothetical case of Ro=0.0, the prediction would be Rz(max)=79±14.     

Dissolution/crystallization kinetics recorded in the 2002–2003 lavas of Stromboli (Italy)

On 28 December 2002, new vents opened on the flanks of Stromboli, just below the summit craters, interrupting the persistent activity of the volcano with a 7-month-long effusive eruption. We here report on the plagioclase size distribution (PlgSD) in lava samples collected following the chronology of the 2002–2003 eruption. Data reveal a linear PlgSD similar to that found in samples of normal Stromboli activity, indicating that the switch from Strombolian explosive to effusive activity is not associated with changes in texture. Nevertheless, the crystal size distribution slopes and intercepts exhibit slight sinusoidal temporal variations that are here ascribed to a magma supply mechanism able to induce “resonance” in the crystal size distribution, with an amplitude that depends on the supply rate.     

Rare-earth element (REE) behaviour in the alteration facies of the active magmatic–hydrothermal system of Vulcano (Aeolian Islands,Italy)

This work reports a study on the rare-earth element (REE) behaviour in the high-sulfidation-type superficial alteration and in the phyllic and propylitic alteration in the subsurface of the island of Vulcano. The results of this study demonstrate notable differences in the REE behaviour in the different alteration facies. In silicic alteration, all REE are equally strongly depleted; in advanced argillic alteration, LREE are quite immobile whereas HREE are strongly depleted; in intermediate argillic, phyllic and propylitic alteration, REE patterns are almost unchanged compared with their fresh rock equivalents. These features indicate that the behaviour of REE in hydrothermal alteration facies at La Fossa is mainly controlled by pH, availability of complexing ions in the fluid (mainly SO₄²⁻ and, in the silicic facies, F⁻) and the presence of secondary minerals able to host REE in their structures. The origin of the acid fluids is related to the hypogenic introduction of prevalently magmatic acid gases produced by the degassing of the shallow magmatic system of La Fossa volcano. In the active high-temperature fumarolic field of La Fossa, REE behaviour illustrates the transition from a dry vapor system, corresponding to the high-temperature fumaroles, to a wet condensing system in the surrounding area. The results of this research, carried out on an active high-sulfidation system, provide a useful tool for the study of high-sulfidation epithermal ore deposits and particularly help to understand the alteration processes during the main stage of hypogene wall rock alteration.     

The use of bioestimation—a new method for the control of water self-purification

Examples are given of the application of bioestimation??a conceptually new hydrobiological method used to control the process of water quality formation. This paper is the continuation of the paper ??Bioestimation: A New Method for the Control of Water Self-Purification Process and Its Comparison with Bioindication??. The experience in the use of bioestimation in water bodies with different use type, size, salinity, flowage, and geographic position confirmed its universal character, information value, promptness, and the possibility to limit the volume of sample to be sent to 10?C20 cm³, thus simplifying the field works. Each significant factor, which affects the self-purification process, is identified independently, since the bioestimators reflecting it are biotically independent; their number varies depending only on changes in the environmental factors that are external with respect to the community of environmental factors. Bioestimation shows prognostic properties, since it makes it possible to prevent water quality deterioration and to restore the normal course of water self-purification at the stage of its quality formation. The use of bioestimation will extend the positive anthropogenic impact on water bodies.