Large Effects of Moho Reflections (SmS) on Peak Ground Motion in Northwestern Taiwan

Liu, Kun-Sung; Tsai, Yi-Hsuan

doi:10.1785/0120080258

Cited by 21 publications

(9 citation statements)

References 28 publications

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“…In particular, the attenuation along the Alps is higher than in the other two regions and they suggested that this effect could be caused by S-wave reflections from the Mohorovicic discontinuity (Moho). Similar amplification effects, generated by focusing and interference of SmS phases reflected by different portions of the Moho, have been already observed in other regions of the world (Burger et al 1987;Liu & Tsai 2009). In the area investigated in this work, the Moho depth changes from 25-30 km in Veneto to 40-45 km in northern Friuli (Tesauro et al 2008) Different attenuation properties with respect to the average high frequency attenuation estimated for the whole region were also observed in the Kobarid area.…”

Section: Regional Dependencesupporting

confidence: 75%

“…Similar amplification effects, generated by focusing and interference of SmS phases reflected by different portions of the Moho, have been already observed in other regions of the world (Burger et al . 1987; Liu & Tsai 2009). In the area investigated in this work, the Moho depth changes from 25–30 km in Veneto to 40–45 km in northern Friuli (Tesauro et al .…”

Section: Discussionmentioning

confidence: 99%

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High frequency attenuation of shear waves in the southeastern Alps and northern Dinarides

Gentili¹,

Franceschina²

2011

Geophysical Journal International

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S U M M A R YWe investigated the high frequency attenuation of S waves in the southeastern Alps and northern External Dinarides using waveforms from 331 earthquakes (3.0 < M w < 6.5). The spectral decay parameter, k, was computed using 1345 three component high quality records, collected by the Italian Strong Motion Network (RAN) and by the Short-Period Seismometric Network of northeastern Italy (NEI) in the period 1976-2007. Weak motion data from 11 stations of the NEI network and strong motion data collected by five accelerometers of the RAN were analysed. The k parameter was estimated in the 0-250 km distance range, in a frequency band extending from the corner frequency of the event up to 25 or 45 Hz, using the amplitude acceleration Fourier spectra of S waves. The observed record-to-record variability of k was modelled by applying a generalized inversion procedure, using both parametric and nonparametric approaches. Our results evidence that k is independent on earthquake size, while it shows both site and distance dependence. Stations of the NEI network present the same increase of k with epicentral distance, R E , and show values of the zero-distance k parameter, k 0 (S), between 0.017 and 0.053 s. For the whole region, the k increase with distance can be described through a linear model with slope dk/dR E = (1.4 ± 0.1) × 10 −4 s km -1 . Assuming an average S-wave velocity, β = 3.34 km s -1 between 5 and 15 km depth, we estimate an average frequency independent quality factor, Q I = 2140, for the corresponding crustal layer. The non-parametric approach evidences a weak positive concavity of the curve that describes the k increase with R E at about 90 km distance. This result can be approximated through a piecewise linear function with slopes of 1.0 × 10 −4 and 1.7 × 10 −4 s km -1 , in accordance with a three layers model where moving from the intermediate to the bottom layer both Q I and β decrease. Two regional dependences were found: data from earthquakes located westward to the NEI network evidence weaker attenuation properties, probably because of S-wave reflections from different parts of the Moho discontinuity under the eastern Po Plain, at about 25-30 km depth, while earthquakes located eastward (in western Slovenia), where the Moho deepens up to 45-50 km, evidence a higher attenuation. Moreover, the k estimates obtained with data from earthquakes located in the area of the 1998 (M w = 5.7) and 2004 (M w = 5.2) Kobarid events are 0.017 s higher than the values predicted for the whole region, probably because of the high level of fracturing that characterizes fault zones. The comparison between measured and theoretical values of k, computed at a few stations with available S-wave velocity profiles, reveals that the major contribution to the total k 0 (S) is due to the sedimentary column (from surface to 800 m depth). The hard rock section contribution is limited to 0.005 s, in accordance with a maximum contribution of 0.010 s predicted by the non-parametric inversion.

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Section: Regional Dependencesupporting

confidence: 75%

Section: Discussionmentioning

confidence: 99%

High frequency attenuation of shear waves in the southeastern Alps and northern Dinarides

Gentili¹,

Franceschina²

2011

Geophysical Journal International

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“…Somerville and Yoshimura 1990;Furumura 2001;Liu and Tsai 2009;Eberhart-Phillips et al 2010). In the azimuthal range from 0 • to 90 • in the northeastern Italy, ZOVE, SANR and ASOL, located at distances of about 75, 95 and 123 km respectively are characterized by the largest amplitude SmSM.…”

Section: Moho Reflections At Single Stationsmentioning

confidence: 94%

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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“…Somerville and Yoshimura (1990) present evidence of enhanced amplitudes of strong ground motion from the 1989 Loma Prieta earthquake recorded at San Francisco and Oakland. Liu and Tsai (2009) showed the significant effect of Moho reflection on peak ground motion in northwestern Taiwan. With the methodology implemented herein, it is possible to add another filter to represent the Moho reflection as G 6 (M, R, C 6 ) ( Figure 3D).…”

Section: Filter G 5 : Far-distance Attenuation Filtermentioning

confidence: 97%

Modular Filter-based Approach to Ground Motion Attenuation Modeling

Graizer

Kalkan

2011

Seismological Research Letters

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Large Effects of Moho Reflections (SmS) on Peak Ground Motion in Northwestern Taiwan

Cited by 21 publications

References 28 publications

High frequency attenuation of shear waves in the southeastern Alps and northern Dinarides

High frequency attenuation of shear waves in the southeastern Alps and northern Dinarides

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

Modular Filter-based Approach to Ground Motion Attenuation Modeling

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