Empirical evidence of local seismic effects at sites with pronounced topography: a systematic approach

Burjánek, Jan; Edwards, Benjamin; Fäh, Donat

doi:10.1093/gji/ggu014

Cited by 90 publications

(61 citation statements)

References 35 publications

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“…The FSC proxy is thus useful in many regions where little or no information exists about the local geology and possible consequences of the ground shaking (i.e., landslides), providing a quantitative way to generate physical estimates (and reasonable variation ranges) for engineering purposes in mountainous regions. Yet, to investigate the amplification level, in detail, accounting on possible coupled effects due to both the local velocity structure and topography (Assimaki and Jeong, 2013;Burjánek et al, 2014;Massa et al, 2014), complementary on-field and numerical studies are convenient.…”

Section: Discussionmentioning

confidence: 99%

Frequency‐Scaled Curvature as a Proxy for Topographic Site‐Effect Amplification and Ground‐Motion Variability

Maufroy¹,

Cruz‐Atienza²,

Cotton³

et al. 2014

Bulletin of the Seismological Society of America

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We introduce a new methodology to predict the topographic site-effect amplification. Ground motions obtained from a large database of 3D earthquake simulations show that the curvature of the Earth's surface, defined as the second spatial derivative of the elevation map, is correlated with the topographic site amplification. The highest correlation between the frequency-dependent topographic amplification and the topographic curvature is reached when the curvature is smoothed over a characteristic length equal to the S wavelength divided by two (i.e., frequency-scaled curvature [FSC]). This implies the amplification is caused by topographic features for which horizontal dimensions are similar to half of the S wavelength. The largest ground-motion variabilities are found at sites located on slopes and on the largest summits, whereas intermediate variabilities occur over narrow ridges and a stable behavior in the bottom valleys. The FSC proxy allows the identification of topographic features with similar characteristic dimensions and probabilistic estimates of amplification values accounting on the variability of ground motions due to source-site interactions. Amplification estimates using the FSC proxy are robust and easily computed from digital elevation maps provided that reasonable values of S-wave velocities are available in the area of interest.

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Section: Discussionmentioning

confidence: 99%

Frequency‐Scaled Curvature as a Proxy for Topographic Site‐Effect Amplification and Ground‐Motion Variability

Maufroy¹,

Cruz‐Atienza²,

Cotton³

et al. 2014

Bulletin of the Seismological Society of America

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“…To explain these differences in amplification requires analysis of heterogeneous subsurface geology in combination with topography. This is beyond the scope of this paper, but the stations' subsurface geological structure is expected to have a larger effect than topographical characteristics (Burjánek et al, 2014).…”

Section: Site Amplificationmentioning

confidence: 94%

Testing seismic amplitude source location for fast debris-flow detection at Illgraben, Switzerland

Walter

Burtin

McArdell

et al. 2017

Nat. Hazards Earth Syst. Sci.

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Abstract. Heavy precipitation can mobilize tens to hundreds of thousands of cubic meters of sediment in steep Alpine torrents in a short time. The resulting debris flows (mixtures of water, sediment and boulders) move downstream with velocities of several meters per second and have a high destruction potential. Warning protocols for affected communities rely on raising awareness about the debris-flow threat, precipitation monitoring and rapid detection methods. The latter, in particular, is a challenge because debris-flow-prone torrents have their catchments in steep and inaccessible terrain, where instrumentation is difficult to install and maintain. Here we test amplitude source location (ASL) as a processing scheme for seismic network data for early warning purposes. We use debris-flow and noise seismograms from the Illgraben catchment, Switzerland, a torrent system which produces several debris-flow events per year. Automatic in situ detection is currently based on geophones mounted on concrete check dams and radar stage sensors suspended above the channel. The ASL approach has the advantage that it uses seismometers, which can be installed at more accessible locations where a stable connection to mobile phone networks is available for data communication. Our ASL processing uses time-averaged ground vibration amplitudes to estimate the location of the debris-flow front. Applied to continuous data streams, inversion of the seismic amplitude decay throughout the network is robust and efficient, requires no manual identification of seismic phase arrivals and eliminates the need for a local seismic velocity model. We apply the ASL technique to a small debris-flow event on 19 July 2011, which was captured with a temporary seismic monitoring network.The processing rapidly detects the debris-flow event half an hour before arrival at the outlet of the torrent and several minutes before detection by the in situ alarm system. An analysis of continuous seismic records furthermore indicates that detectability of Illgraben debris flows of this size is unaffected by changing environmental and anthropogenic seismic noise and that false detections can be greatly reduced with simple processing steps.

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“…The latter aspect has been specifically investigated by Marzorati et al (2011), who highlighted the primary influence of rock mass condition (orientation and opening of fractures and joints) on ground motion amplification along rocky ridges, where site effects are generally supposed to be related to ''canonical'' morphological/topographic issues. At these sites, observed amplification cannot be explained only in terms of geometry of the topography and it is mainly controlled by the subsurface shear wave velocity profile (Paolucci et al 1999;Glinsky and Bertrand 2011;Burjánek et al 2014). Massa et al (2014) classified topographic effects into ''typical'' and ''atypical'' effects.…”

Section: Introductionmentioning

confidence: 99%

Numerical and experimental evaluation of site effects at ridges characterized by complex geological setting

Pagliaroli

Avalle

Falcucci

et al. 2015

Bull Earthquake Eng

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The paper presents the results of site effects investigation at two villages, Castelvecchio Subequo and Castel di Ieri (Central Italy), located about 2 km from each other, on top of carbonate ridges characterized by complex geological/structural characteristics. Both villages suffered of an anomalous high damage degree determined by the Mw = 6.1, 2009 L'Aquila earthquake, highlighting the occurrence of significant ground motion amplification phenomena. Studying seismic response at rock sites characterized by complex geological setting is a challenging issue, as different factors can alter the expected ground motion. The difficulties arise from both the reconstruction of a suitable and thorough geological/geotechnical subsoil model and limitations of geophysical and numerical methods in such contexts. In order to overcome these difficulties, we here proposed an approach which integrates numerical modelling, based on the definition of a subsoil setting built from an accurate geological field analysis, with active and passive geophysical techniques. In particular, the calibration of numerical models based on transfer functions computed from Standard Spectral Ratio applied to noise recordings provided encouraging results.

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Empirical evidence of local seismic effects at sites with pronounced topography: a systematic approach

Cited by 90 publications

References 35 publications

Frequency‐Scaled Curvature as a Proxy for Topographic Site‐Effect Amplification and Ground‐Motion Variability

Frequency‐Scaled Curvature as a Proxy for Topographic Site‐Effect Amplification and Ground‐Motion Variability

Testing seismic amplitude source location for fast debris-flow detection at Illgraben, Switzerland

Numerical and experimental evaluation of site effects at ridges characterized by complex geological setting

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