Are Synthetic Accelerograms Suitable for Local Seismic Response Analyses at Near-Field Sites?

2021 ◽  
Author(s):  
Francesca Mancini ◽  
Sebastiano D’Amico ◽  
Giovanna Vessia
Keyword(s):  
Seismic Response ◽  
Seismic Waves ◽  
Near Field ◽  
Central Italy ◽  
Propagation Path ◽  
Soil Behavior ◽  
Seismic Stations ◽  
Seismic Input ◽  
Local Seismic Response ◽  
Finite Fault

ABSTRACT Local seismic response (LSR) studies are considerably conditioned by the seismic input features due to the nonlinear soil behavior under dynamic loading and the subsurface site conditions (e.g., mechanical properties of soils and rocks and geological setting). The selection of the most suitable seismic input is a key point in LSR. Unfortunately, few recordings data are available at seismic stations in near-field areas. Then, synthetic accelerograms can be helpful in LSR analysis in urbanized near-field territories. Synthetic accelerograms are generated by simulation procedures that consider adequately supported hypotheses about the source mechanism at the seismotectonic region and the wave propagation path toward the surface. Hereafter, mainshocks recorded accelerograms at near-field seismic stations during the 2016–2017 Central Italy seismic sequence have been compared with synthetic accelerograms calculated by an extended finite-fault ground-motion simulation algorithm code. The outcomes show that synthetic seismograms can reproduce the high-frequency content of seismic waves at near-field areas. Then, in urbanized near-field areas, synthetic accelerograms can be fruitfully used in microzonation studies.

scholarly journals Physical stratigraphy and geotechnical properties controlling the local seismic response in explosive volcanic settings: the Stracciacappa maar (central Italy)

2020 ◽  
Vol 80 (1) ◽  
pp. 179-199
Author(s):  
M. Moscatelli ◽  
G. Vignaroli ◽  
A. Pagliaroli ◽  
R. Razzano ◽  
A. Avalle ◽  
...  
Keyword(s):  
Seismic Response ◽  
Ground Motion ◽  
Central Italy ◽  
Volcanic Event ◽  
Ground Motion Amplification ◽  
Local Seismic Response ◽  
Single Station ◽  
Seismic Scenarios ◽  
Physical Stratigraphy ◽  
Subsoil Model

AbstractNowadays, policies addressed to prevention and mitigation of seismic risk need a consolidated methodology finalised to the assessment of local seismic response in explosive volcanic settings. The quantitative reconstruction of the subsoil model provides a key instrument to understand how the geometry and the internal architecture of outcropping and buried geological units have influence on the propagation of seismic waves. On this regard, we present a multidisciplinary approach in the test area of the Stracciacappa maar (Sabatini Volcanic District, central Italy), with the aim to reconstruct its physical stratigraphy and to discuss how subsoil heterogeneities control the 1D and 2D local seismic response in such a volcanic setting. We first introduce a new multidisciplinary dataset, including geological (fieldwork and log from a 45-m-thick continuous coring borehole), geophysical (electrical resistivity tomographies, single station noise measurements, and 2D passive seismic arrays), and geotechnical (simple shear tests performed on undisturbed samples) approaches. Then, we reconstruct the subsoil model for the Stracciacappa maar in terms of vertical setting and distribution of its mechanical lithotypes, which we investigate for 1D and 2D finite element site response analyses through the application of two different seismic scenarios: a volcanic event and a tectonic event. The numerical modelling documents a significant ground motion amplification (in the 1–1.5 Hz range) revealed for both seismic scenarios, with a maximum within the centre of the maar. The ground motion amplification is related to both 1D and 2D phenomena including lithological heterogeneity within the upper part of the maar section and interaction of direct S-waves with Rayleigh waves generated at edges of the most superficial lithotypes. Finally, we use these insights to associate the expected distribution of ground motion amplification with the physical stratigraphy of an explosive volcanic setting, with insights for seismic microzonation studies and local seismic response assessment in populated environments.

scholarly journals The role of near-field interaction between seismic waves and slope on the triggering of a rockslide at Lorca (SE Spain)

2012 ◽  
Vol 12 (12) ◽  
pp. 3631-3643 ◽  
Author(s):  
P. Alfaro ◽  
J. Delgado ◽  
F. J. García-Tortosa ◽  
J. J. Giner ◽  
L. Lenti ◽  
...  
Keyword(s):  
Seismic Waves ◽  
Near Field ◽  
Specific Interaction ◽  
Se Spain ◽  
Local Seismic Response ◽  
Geological Conditions ◽  
Seismic Amplification ◽  
Slope Instabilities ◽  
Near Field Effect

Abstract. A ~1000 m3 rockslide occurred close to Lorca (SE Spain) during the main shock (Mw = 5.1) of the May 2011 seismic sequence. The location of the rockslide, within 10 km of the earthquake epicenter and along the southern slope of a valley in which similar geological conditions occur on both slopes of the valley, suggests a significant near-field effect due to local seismic response. This could be related to the specific interaction between the topography and the obliquely propagating seismic waves. A dynamic stress strain numerical model was constructed using the FLAC 7.0 finite difference code to back analyze the Lorca rockslide event and relate its occurrence to both the local seismic amplification and the interaction between seismic waves and local topography. The results indicate that only for seismic waves with incidence angles in the range 0°–50° are the occurred slope instabilities expected. These results do not significantly change when varying the values for either stiffness or strength parameters within the range of the experimental data.

Seismic Response of Gravity Dam under Oblique Incidence of Seismic Waves

2013 ◽  
Vol 838-841 ◽  
pp. 1585-1590
Author(s):  
Li Chen ◽  
Liao Jun Zhang
Keyword(s):  
Seismic Response ◽  
Oblique Incidence ◽  
Seismic Waves ◽  
Near Field ◽  
P Wave ◽  
Gravity Dam ◽  
Response Analysis ◽  
Uniform Motion ◽  
Obvious Effect ◽  
Obliquely Incident

The selection of proper seismic input is essential for seismic response analysis of the gravity dam structures. For the near-field earthquakes, the direction of seismic waves is not always considered as vertical. The non-uniform motion produced by oblique incidence can cause significant influence to the structure. In this study, the obliquely incident method is applied in the finite element model of a typical section of a gravity dam located in southwestern China. The seismic response under obliquely incident of plane P wave and plane SV with different incident angles and tilt directions are discussed. The results show that the oblique incidence has an obvious effect on the seismic response of the gravity dam, and the inconsistence produced by oblique incidence cannot be neglected.

scholarly journals Rapid estimation of tsunami earthquake magnitudes at local distance

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Akio Katsumata ◽  
Masayuki Tanaka ◽  
Takahito Nishimiya
Keyword(s):  
Magnitude Estimation ◽  
Seismic Wave ◽  
Seismic Waves ◽  
Wave Amplitude ◽  
Amplitude Distribution ◽  
Distribution Method ◽  
Finite Fault ◽  
Tsunami Earthquakes ◽  
Tsunami Earthquake ◽  
The Moment

AbstractA tsunami earthquake is an earthquake event that generates abnormally high tsunami waves considering the amplitude of the seismic waves. These abnormally high waves relative to the seismic wave amplitude are related to the longer rupture duration of such earthquakes compared with typical events. Rapid magnitude estimation is essential for the timely issuance of effective tsunami warnings for tsunami earthquakes. For local events, event magnitude estimated from the observed displacement amplitudes of the seismic waves, which can be obtained before estimation of the seismic moment, is often used for the first tsunami warning. However, because the observed displacement amplitude is approximately proportional to the moment rate, conventional magnitudes of tsunami earthquakes estimated based on the seismic wave amplitude tend to underestimate the event size. To overcome this problem, we investigated several methods of magnitude estimation, including magnitudes based on long-period displacement, integrated displacement, and multiband amplitude distribution. We tested the methods using synthetic waveforms calculated from finite fault models of tsunami earthquakes. We found that methods based on observed amplitudes could not estimate magnitude properly, but the method based on the multiband amplitude distribution gave values close to the moment magnitude for many tsunami earthquakes. In this method, peak amplitudes of bandpass filtered waveforms are compared with those of synthetic records for an assumed source duration and fault mechanism. We applied the multiband amplitude distribution method to the records of events that occurred around the Japanese Islands and to those of tsunami earthquakes, and confirmed that this method could be used to estimate event magnitudes close to the moment magnitudes.

Seismic waves from a horizontal stress discontinuity in a layered solid

1982 ◽  
Vol 72 (5) ◽  
pp. 1483-1498
Author(s):  
F. Abramovici ◽  
E. R. Kanasewich ◽  
P. G. Kelamis
Keyword(s):  
Half Space ◽  
Seismic Waves ◽  
Horizontal Stress ◽  
Radial Component ◽  
Elastic Half Space ◽  
Homogeneous Layer ◽  
Approximate Methods ◽  
Crustal Layer ◽  
Finite Fault ◽  
Stress Discontinuity

abstract The displacement components for a horizontal stress discontinuity along a buried finite fault in an elastic homogeneous layer on top of an elastic half-space are given analytically in terms of generalized rays. For a particular case of a concentrated horizontal force pointing in an arbitrary direction, detailed time-dependent expressions are given. For a simple model of a “crustal” layer over a “mantle” half-space, the numerical seismograms in the near- and intermediate-field show some interesting features. These include a prominent group of compressional waves whose radial component is substantial at distances four times the crustal thickness. All the dominant shear arrivals (s, SS, and sSS) are important and show large variations of amplitude as the source depth and receiver distance are varied. Some of the prominent individual generalized rays are shown, and it is found that they can be grouped naturally into families based on the number of interactions with the boundaries. The subdivision into individual generalized rays is useful for analysis and for checks on the numerical stability of the synthetic seismograms. Since the solution is analytic and the numerical evaluation is complete up to any desired time, the results are useful in comparing other approximate methods for the computation of seismograms.

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