scholarly journals Ground response of the Kathmandu Sedimentary Basin with reference to 30 August 2013 South-Tibet Earthquake

2014 ◽  
Vol 47 (1) ◽  
pp. 23-34 ◽  
Author(s):  
S. Rajaure ◽  
B. Koirala ◽  
R. Pandey ◽  
C. Timsina ◽  
M Jha ◽  
...  
Keyword(s):  
Site Response ◽  
Low Frequency ◽  
Frequency Range ◽  
Spectral Ratios ◽  
Ground Acceleration ◽  
Soil Layers ◽  
Nonlinear Site Response ◽  
Basin Effects ◽  
Acceleration Record ◽  
South Tibet

Ground acceleration of the 30 August 2013 (M4.9), South Tibet Earthquake has been recorded by five accelerometers deployed in the Kathmandu Valley. Analysis of the ground acceleration record reveals that that the EW component was dominant across the valley, and with the exception of one, all stations on sediments recorded PGA much higher than the station on rock. The site response functions, evaluated as the Fourier spectral ratios of the horizontal components on soil relative to the corresponding component on rock, are remarkably similar in the low frequency range (<0.8 Hz) and reveal strong amplification that likely corresponds to basin effects. By contrast, the high frequency site response shows strong variability across the soil sites, likely attributed to the underlying stratigraphy of the shallow soil layers of the valley. The most pronounced differences manifest in the frequency range >2Hz, which is consistent with the variability in PGA across the valley. Because of the small intensity of this event, the empirical site response recorded can be, approximately, considered linear. As such, this study establishes a reference for future studies on nonlinear site response, which is likely to be triggered during future stronger earthquakes.

Nonlinear Site Effects from the 30 November 2018 Anchorage, Alaska, Earthquake

2021 ◽  
Author(s):  
John D. Thornley ◽  
Utpal Dutta ◽  
John Douglas ◽  
Zhaohui (Joey) Yang
Keyword(s):  
Site Response ◽  
Strong Motion ◽  
North American Plate ◽  
Peak Ground Velocity ◽  
Reference Station ◽  
Earthquake Hazards ◽  
Ground Acceleration ◽  
Nonlinear Site Response ◽  
Generalized Inversion Technique ◽  
Versus Peak

ABSTRACT Anchorage, Alaska, is a natural laboratory for recording strong ground motions from a variety of earthquake sources. The city is situated in a tectonic region that includes the interface and intraslab earthquakes related to the subducting Pacific plate and crustal earthquakes from the upper North American plate. The generalized inversion technique was used with a local rock reference station to develop site response at &gt;20 strong-motion stations in Anchorage. A database of 94 events recorded at these sites from 2005 to 2019 was also compiled and processed to compare their site response with those in the 2018 Mw 7.1 event (main event). The database is divided into three datasets, including 75 events prior to the main event, the main event, and 19 aftershocks. The stations were subdivided into the site classes defined in the National Earthquake Hazards Reduction Program based on estimated average shear-wave velocity in of the upper 30 m (VS30), and site-response results from the datasets were compared. Nonlinear site response was observed at class D and DE sites (VS30 of 215–300 and 150–215  m/s, respectively) but not at class CD and C sites (VS30 of 300–440 and 440–640  m/s, respectively). The relationship of peak ground acceleration versus peak ground velocity divided by VS30 (shear-strain proxy) was shown to further support the observation that sites with lower VS30 experienced nonlinear site response.

A Ground-Motion Prediction Model for Shallow Crustal Earthquakes in Greece

2020 ◽  
Author(s):  
David M. Boore ◽  
Jonathan P. Stewart ◽  
Andreas A. Skarlatoudis ◽  
Emel Seyhan ◽  
Basil Margaris ◽  
...  
Keyword(s):  
Prediction Model ◽  
Ground Motion ◽  
Site Response ◽  
Epistemic Uncertainty ◽  
Peak Ground Velocity ◽  
Motion Prediction ◽  
Ground Motion Prediction ◽  
Ground Acceleration ◽  
Magnitude Scaling ◽  
Nonlinear Site Response

ABSTRACT Using a recently completed database of uniformly processed strong-motion data recorded in Greece, we derive a ground-motion prediction model (GMPM) for horizontal-component peak ground velocity, peak ground acceleration, and 5% damped pseudoacceleration response spectra, at 105 periods ranging from 0.01 to 10 s. The equations were developed by modifying a global GMPM, to account for more rapid attenuation and weaker magnitude scaling in the Greek ground motions than in the global GMPM. Our GMPM is calibrated using the Greek data for distances up to 300 km, magnitudes from 4.0 to 7.0, and time-averaged 30 m shear-wave velocities from 150 to 1200  m/s. The GMPM has important attributes for hazard applications including magnitude scaling that extends the range of applicability to M 8.0 and nonlinear site response. These features are possible because they are well constrained by data in the global GMPM from which our model is derived. An interesting feature of the Greek data, also observed previously in studies of mid-magnitude events (6.1–6.5) in Italy, is that they are substantially overpredicted by the global GMPM, which may be a repeatable regional feature, but may also be influenced by soil–structure interaction. This bias is an important source of epistemic uncertainty that should be considered in hazard analysis.

Determination of Site Response in Anchorage, Alaska, on the Basis of Spectral Ratio Methods

2002 ◽  
Vol 18 (1) ◽  
pp. 85-104 ◽  
Author(s):  
A. Martirosyan ◽  
U. Dutta ◽  
N. Biswas ◽  
A. Papageorgiou ◽  
R. Combellick
Keyword(s):  
Shear Wave ◽  
Shear Wave Velocity ◽  
High Frequency ◽  
Site Response ◽  
Low Frequency ◽  
Spectral Ratio ◽  
Frequency Range ◽  
The West ◽  
Site Coefficients ◽  
Average Shear

This paper deals with the site response (SR) in the Anchorage basin in south-central Alaska. The investigation is based on the analysis of seismograms of 114 earthquakes recorded by 22 weak-motion stations and 46 earthquakes recorded by 19 strong-motion stations in the study area. We have computed SR for 41 sites, using standard spectral ratio and horizontal-to-vertical spectral ratio methods in the frequency range from 0.5 to 11 Hz. Based on these results, we have calculated band-average site response values in two frequency ranges: low frequency (from 0.5 to 2.5 Hz) and high frequency (from 3 to 7 Hz). There is a good correlation between SR values and surficial geology of the Anchorage area in the low-frequency range. SR values increase by a factor of three from the foothills of the Chugach Mountains in the east to the west towards the deeper part of the basin. The highest site response values (SR>2.5) in the same frequency range are observed in the west-central part of the city, which is underlain by cohesive facies of the Bootlegger Cove formation. The SR has a good correlation with the uppermost 30-m time-average shear-wave velocity with a correlation coefficient of 0.82. Moreover, the low-frequency SR values are close to the NEHRP site coefficients for 1 sec. However, high-frequency SR values lack correlation with 30-m average shear-wave velocity and short-period NEHRP site coefficients.

Nonlinear Seismic Soil-Pile-Structure Interaction Analysis of Fixed Offshore Platforms

2009 ◽  
Author(s):  
Ehssan Zargar ◽  
Ali Akbar Aghakouchak ◽  
Maziar Gholami
Keyword(s):  
Seismic Analysis ◽  
Interaction Analysis ◽  
Site Response ◽  
Geometrical Nonlinearity ◽  
Radiation Damping ◽  
Response Analysis ◽  
Offshore Platforms ◽  
Soil Layers ◽  
Structure Interaction ◽  
Nonlinear Site Response

A nonlinear seismic soil-pile-structure interaction (SSPSI) analysis of fixed offshore platforms constructed on pile foundations including both vertical and battered piles is presented. The analysis is carried out in time domain and the effects of soil nonlinearity, discontinuity at pile soil interfaces, energy dissipation through soil radiation damping, formation of soil layers on bed rock, structural material nonlinearity and geometrical nonlinearity are considered. A combination of FEM approach and BNWF approach is used in modeling pile (substructure), platform structure (superstructure) and soil media. Gapping in clay is modeled by a special connector configuration. To find out the ground motion of soil layers caused by earthquake excitations at bed rock, a nonlinear site response analysis is performed. The effects of soil-pile-structure interaction on nonlinear seismic analysis of offshore platforms are discussed. A comparison of SSPSI model and pile stub modeling is investigated and it is generally concluded that considering soil-pile-structure interaction causes higher deflections and lower stresses in the platform elements due to soil flexibility, nonlinearity and radiation damping and leads to a more feasible and realistic platform design. The sequence of generation of plastic zones in the structure and their distribution are also investigated. Results show that this nonlinear behavior is started at brace elements and then propagated to leg elements as earthquake last.

scholarly journals Seismic Hazard Maps for Seattle, Washington, Incorporating 3D Sedimentary Basin Effects, Nonlinear Site Response, and Rupture Directivity

2007 ◽  
Author(s):  
Arthur D. Frankel ◽  
William J. Stephenson ◽  
David L. Carver ◽  
Robert A. Williams ◽  
Jack K. Odum ◽  
...  
Keyword(s):  
Seismic Hazard ◽  
Sedimentary Basin ◽  
Site Response ◽  
Rupture Directivity ◽  
Hazard Maps ◽  
Seismic Hazard Maps ◽  
Nonlinear Site Response ◽  
Basin Effects

scholarly journals Prediction and evaluation of nonlinear site response with potentially liquefiable layers in the area of Nafplion (Peloponnesus, Greece) for a repeat of historical earthquakes

2010 ◽  
Vol 10 (11) ◽  
pp. 2281-2304 ◽  
Author(s):  
V. K. Karastathis ◽  
G. A. Papadopoulos ◽  
T. Novikova ◽  
Z. Roumelioti ◽  
P. Karmis ◽  
...  
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Site Response ◽  
Soft Soil ◽  
Soil Layer ◽  
Ground Acceleration ◽  
Nonlinear Site Response ◽  
Strong Ground Motion Simulation ◽  
Scenario Earthquakes ◽  
Strong Ground

Abstract. We examine the possible non-linear behaviour of potentially liquefiable layers at selected sites located within the expansion area of the town of Nafplion, East Peloponnese, Greece. Input motion is computed for three scenario earthquakes, selected on the basis of historical seismicity data, using a stochastic strong ground motion simulation technique, which takes into account the finite dimensions of the earthquake sources. Site-specific ground acceleration synthetics and soil profiles are then used to evaluate the liquefaction potential at the sites of interest. The activation scenario of the Iria fault, which is the closest one to Nafplion (M=6.4), is found to be the most hazardous in terms of liquefaction initiation. In this scenario almost all the examined sites exhibit liquefaction features at depths of 6–12 m. For scenario earthquakes at two more distant seismic sources (Epidaurus fault – M6.3; Xylokastro fault – M6.7) strong ground motion amplification phenomena by the shallow soft soil layer are expected to be observed.

Non Linear Response of Fixed Offshore Platforms to Seismic Excitation Including Soil-Pile-Structure Interaction

2008 ◽  
Author(s):  
Ehssan Zargar ◽  
Ali Akbar Aghakouchak ◽  
Amin Aghakouchak
Keyword(s):  
Seismic Analysis ◽  
Site Response ◽  
Damping Ratio ◽  
Geometrical Nonlinearity ◽  
Radiation Damping ◽  
Response Analysis ◽  
Offshore Platforms ◽  
Soil Layers ◽  
Structure Interaction ◽  
Nonlinear Site Response

A nonlinear seismic soil-pile-structure interaction (SSPSI) analysis of fixed offshore platforms constructed on pile foundations including both vertical and battered piles is presented. The analysis is carried out in time domain and the effects of soil nonlinearity, discontinuity at pile soil interfaces, energy dissipation through soil radiation damping, formation of soil layers on bed rock, structural material nonlinearity and geometrical nonlinearity are considered. A combination of FEM approach and BNWF approach is used in modeling pile (substructure), platform structure (superstructure) and soil media. Gapping in clay is modeled by a special connector configuration. To find out the ground motion of soil layers caused by earthquake excitations at bed rock, a nonlinear site response analysis is performed. The effects of soil-pile-structure interaction on nonlinear seismic analysis of offshore platforms are discussed. It is generally concluded that considering soil-pile-structure interaction causes higher deflections and lower stresses in the platform elements due to soil flexibility, nonlinearity and radiation damping and leads to a more feasible and realistic platform design. The sequence of generation of plastic zones in the structure and their distribution are also investigated. Sensitivity of results to soil layers configuration and soil material damping ratio are discussed.

Comparison of Equivalent Linear and Nonlinear Site Response Analysis Results and Model to Estimate Maximum Shear Strain

2016 ◽  
Vol 32 (3) ◽  
pp. 1867-1887 ◽  
Author(s):  
Brian Carlton ◽  
Kohji Tokimatsu
Keyword(s):  
Shear Strain ◽  
Site Response ◽  
Response Spectrum ◽  
Peak Ground Velocity ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Ground Acceleration ◽  
Maximum Shear Strain ◽  
Nonlinear Site Response ◽  
Equivalent Linear

We compared the results of equivalent linear (ELA) and nonlinear site response analyses (NLA) and found that the differences between the values of the peak ground acceleration ( PGA), peak ground velocity ( PGV), Arias intensity ( I a), significant duration ( D5–75), and response spectrum for periods between 0.025 s and 2 s predicted by each method are non-negligible for maximum shear strain values predicted by ELA ( γ max, ELA) greater than 0.04% to 1.0%. As γ max, ELA increases, ELA in general predict smaller shear strain and D5–75 values, and larger PGA, PGV, I a, mean period, and response spectral values for periods less than 0.1 s and periods near the natural site period than NLA. To help researchers and practitioners decide when to use ELA and/or NLA, we developed a model to estimate γ max, ELA before conducting a site response analysis.

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