Moho Reflection Effects in the Po Plain (Northern Italy) Observed from Instrumental and Intensity Data

Bragato, Pier Luigi; Sugan, M.; Augliera, P.; Massa, Marco; Vuan, Alessandro; Saraò, Angela

doi:10.1785/0120100257

Cited by 39 publications

(25 citation statements)

References 30 publications

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“…Surface waves amplitudes can enhance at a disadvantage of SmSM amplitudes by using velocities or displacements instead of accelerations in the analysis (see Sugan and Vuan 2012). The existence of the SmSM domain can be detected predominantly in the azimuth range 0 • -90 • , in agreement with Bragato et al (2011) for northeastern Italy. Propagation of these kind of waves seems to be more efficient than elsewhere.…”

Section: Multiple Filter Technique Applied To the 201emilia Seismic Ssupporting

confidence: 85%

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On the ability of Moho reflections to affect the ground motion in northeastern Italy: a case study of the 2012 Emilia seismic sequence

Sugan

Vuan

2013

Bull Earthquake Eng

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It has been observed that post-critically reflected S-waves and multiples from the Moho discontinuity could play a relevant role on the ground motion due to medium to strong size earthquakes away from the source. Although some studies investigated the correlation between the Moho reflections amplitudes and the damage in the far field, little attention was given to the frequency content of these specific phases and their scaling with magnitude. The 2012 Emilia seismic sequence in northern Italy, recorded by velocimetric and accelerometric networks, is here exploited to investigate Moho reflections and multiples (SmSM). A single station method for group velocity-period estimation, based on the multiple filter technique, is applied to strong motion data to detect SmSM. Amplitude and frequency scaling with magnitude is defined for earthquakes from Mw = 3.9 to Mw = 5.9. Finally, the ability of SmSM to affect the ground motion for a maximum credible earthquake within the Po plain is investigated by extrapolating observed engineering parameters. Data analysis shows that high amplitude SmSM can be recognized within the Po plain, and at the boundaries between the Po plain and the Alpine chain, at epicentral distances larger than 80 km, in the period range from 0.25 to 3 s and in the group velocity window from about 2.6 to 3.2 km/s. 5 % damped pseudo-spectral accelerations at different periods (0.3, 1.0 and 2.0 s), and Housner intensities, are obtained from data characterized by large amplitude SmSM. A scaling relationship for both pseudo-spectral accelerations and Housner intensities is found for the earthquakes of the 2012 Emilia seismic sequence. I MCS from VII to VIII is estimated, as a result of SmSM amplitude enhancement, at about 100 km for a maximum credible earthquake (Mw = 6.7) in the Po plain, showing that moderate to high damage cloud be caused by these specific phases.

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Section: Multiple Filter Technique Applied To the 201emilia Seismic Ssupporting

confidence: 85%

“…seismic sequence is of particular interest to understand if amplitude enhancement at specific distances due to SmSM can be observed also for earthquakes located within the Po plain and at shallower depth than those previously investigated in Bragato et al (2011).…”

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confidence: 98%

On the ability of Moho reflections to affect the ground motion in northeastern Italy: a case study of the 2012 Emilia seismic sequence

Sugan

Vuan

2013

Bull Earthquake Eng

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“…We can observe that the PGA recorded by stations located to the north of the Po Plain is 3-5 times larger than the PGA recorded to the south. This phenomenon has been already observed by Douglas et al (2004) in central Italy and southern Iceland and by Bragato et al (2011) in northern Italy and is explained as the enhancement of ground motion due to S-wave reflection at the Moho discontinuity (SmS phase).…”

Section: High-and Low-frequency Ground-motion Featuressupporting

confidence: 62%

“…In particular, Bragato et al (2011) investigated the ground-motion characteristics using two datasets: the first composed of waveforms of the 2008 M L 5.2 Parma and small-magnitude earthquakes of the 1976 Friuli seismic sequence and the second composed of macroseismic intensity points in northern Italy, converted in PGA, using the Faenza and Michelini (2010) recognized the enhancement of PGA around 50 km due to the Moho reflection from both datasets (their figs. 8 and 11).…”

Section: High-and Low-frequency Ground-motion Featuresmentioning

confidence: 99%

“…Bragato et al (2011) observed that PGA is systematically enhanced at distances between 70 and 200 km, due to the effect of the reflection of S waves at the Moho discontinuity (SmS phase). Luzi et al (2013) found that, in the Po Plain, the trapping and conversion of the body waves in the thick sedimentary cover causes the generation of surface waves, which dominate the seismic signals at periods longer than 2 s for the horizontal and vertical components.…”

Section: Introductionmentioning

confidence: 98%

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Ground‐Motion Prediction Equations for Region‐Specific Probabilistic Seismic‐Hazard Analysis

Lanzano¹,

D’Amico²,

Felicetta³

et al. 2016

Bulletin of the Seismological Society of America

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The goal of this article is to investigate the possibility of reducing the uncertainty of the ground motion predicted for a specific target area (Po Plain and northeastern Italy), by calibrating a set of ad hoc ground-motion prediction equations (GMPEs). The derived GMPEs account for peculiarities that are not generally considered by standard predictive models, such as (1) an attenuation rate dependent on distance ranges and geological domains; (2) enhancement of short-period spectral ordinates, due to the reflection of S waves at the Moho discontinuity; and (3) generation of surface waves inside an alluvial basin.The analyzed strong-motion dataset was compiled by selecting events in the 4.0-6.4 magnitude range, records with distances shorter than 200 km, and focal depths shallower than 30 km; the major contribution comes from the recent 2012 Emilia sequence (first mainshock, 20 May 2012 M w 6

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Source inversion of the 1570 Ferrara earthquake and definitive diversion of the Po River (Italy)

Sirovich

Pettenati

2015

JGR Solid Earth

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An 11‐parameter, kinematic‐function (KF) model was used to retrieve the approximate geometrical and kinematic characteristics of the fault source of the 1570 Mw 5.8 Ferrara earthquake in the Po Plain, including the double‐couple orientation (strike angle 127 ± 16°, dip 28 ± 7°, and rake 77 ± 16°). These results are compatible with either the outermost thrust fronts of the northern Apennines, which are buried beneath the Po Plain's alluvial deposits, or the blind crustal‐scale thrust. The 1570 event developed to the ENE of the two main shocks on 20 May 2012 (M 6.1) and 29 May 2012 (M 5.9). The three earthquakes had similar kinematics and are found 20–30 km from each other en echelon in the buried chain. Geomorphological and historical evidence exist which suggest the following: (i) the long‐lasting uplift of the buried Apenninic front shifted the central part of the course of the Po River approximately 20 km northward in historical times and (ii) the 1570 earthquake marked the definitive diversion of the final part of the Po River away from Ferrara and the closure of the Po delta 40 km south of its present position.

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Moho Reflection Effects in the Po Plain (Northern Italy) Observed from Instrumental and Intensity Data

Cited by 39 publications

References 30 publications

On the ability of Moho reflections to affect the ground motion in northeastern Italy: a case study of the 2012 Emilia seismic sequence

On the ability of Moho reflections to affect the ground motion in northeastern Italy: a case study of the 2012 Emilia seismic sequence

Ground‐Motion Prediction Equations for Region‐Specific Probabilistic Seismic‐Hazard Analysis

Source inversion of the 1570 Ferrara earthquake and definitive diversion of the Po River (Italy)

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