Dynamic site characterization of Christchurch strong motion stations

2011 ◽  
Vol 44 (4) ◽  
pp. 195-204 ◽  
Author(s):  
Clinton M. Wood ◽  
Brady R. Cox ◽  
Liam M. Wotherspoon ◽  
Russell A. Green
Keyword(s):  
Dynamic Properties ◽  
Strong Motion ◽  
Small Strain ◽  
Site Classification ◽  
Source Surface ◽  
Natural Period ◽  
Site Class ◽  
Strong Motion Station ◽  
New Information ◽  
Over The Top

This paper details efforts to characterize the small-strain dynamic properties of 13 strong motion station (SMS) sites in the greater Christchurch, New Zealand area. These SMS recorded a unique set of ground motions (GM) from the 2010-2011 Canterbury earthquakes. Currently, little information about the subsurface layering and dynamic characteristics at these 13 SMS is available. Information provided by GeoNet consists only of generalised layering based on regional geological characteristics and nearby well logs, with no information on dynamic properties. Consequently, the seismic site classifications of these sites were largely based on assumptions. To better define the site classifications, we performed active- and passive-source surface wave testing to obtain shear wave velocity (Vs) profiles at each site. The Vs profiles were used to calculate the average Vs over the top 30 m of the subsurface and to estimate the natural period of vibration (Tn). Additionally, estimates of Tn were obtained by computing the horizontal-to-vertical spectral ratios from recorded GM at each SMS. Based on this new information, we have updated the site classifications at the 13 SMS sites tested; 10 of which ended up with a slightly different site classification than the original assumption (often one site class lower).

scholarly journals Investigation of Soil Characterization in Hatay Province in Turkey by Using Seismic Refraction, Multichannel Analysis of Surface Waves and Microtremor

2021 ◽  
Vol 24 (4) ◽  
pp. 473-484
Author(s):  
Cengiz Kurtuluş ◽  
Ibrahim Sertcelik ◽  
Fadime Sertçelik ◽  
Hamdullah Livaoğlu ◽  
Cüneyt Şaş
Keyword(s):  
Surface Waves ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Seismic Refraction ◽  
Strong Motion ◽  
Site Classification ◽  
Eurocode 8 ◽  
Site Class ◽  
Multichannel Analysis

In this study, shallow seismic surveys, including seismic refraction, Multichannel Analysis of Surface Waves (MASW), Refraction Microtremor (ReMi), and Microtremor measurements were conducted to estimate site characterization at 26 strong-motion stations of AFAD (Disaster and Emergency Management Presidency) in the province of Hatay, situated in one of the most seismically active regions in southern Turkey. The Horizontal to vertical spectral ratio (HVSR) technique was applied, using smoothed Fourier spectra derived from a long duration series to determine dominant frequency values at different amplification levels. Shear wave velocity up to 30 m of the ground was detected with MASW analysis. In the ReMi analysis, up to 80 m was reached with a corresponding average of 650 m/s shear wave velocity. The shear wave velocities estimated by the MASW method up to 30 m were compared with those found by the ReMi method, and they were observed to be very compatible. The province of Hatay was classified according to Vs30 based NEHRP Provisions, Eurocode-8, the Turkish Building Earthquake Regulation (TBDY-2018), and Rodriguez-Marek et al. (2001). The shear-wave velocity (Vs30), Horizontal to Vertical ratio’s (H/V) peak amplitude, dominant period, and site class of each site were determined. The H/V peak amplitudes range between 1.9 and 7.6, while the predominant periods vary from 0.23 sec to 2.94sec in the study area. These results are investigated to explain the consistency of site classification schemes.

Ground-motion model for subduction earthquakes in northern South America

2021 ◽  
pp. 875529302110275
Author(s):  
Carlos A Arteta ◽  
Cesar A Pajaro ◽  
Vicente Mercado ◽  
Julián Montejo ◽  
Mónica Arcila ◽  
...  
Keyword(s):  
South America ◽  
Ground Motion ◽  
Ground Motions ◽  
Strong Motion ◽  
Motion Prediction ◽  
Depth Range ◽  
Ground Motion Prediction ◽  
Natural Period ◽  
Nazca Plate ◽  
Northern South America

Subduction ground motions in northern South America are about a factor of 2 smaller than the ground motions for similar events in other regions. Nevertheless, historical and recent large-interface and intermediate-depth slab earthquakes of moment magnitudes Mw = 7.8 (Ecuador, 2016) and 7.2 (Colombia, 2012) evidenced the vast potential damage that vulnerable populations close to earthquake epicenters could experience. This article proposes a new empirical ground-motion prediction model for subduction events in northern South America, a regionalization of the global AG2020 ground-motion prediction equations. An updated ground-motion database curated by the Colombian Geological Survey is employed. It comprises recordings from earthquakes associated with the subduction of the Nazca plate gathered by the National Strong Motion Network in Colombia and by the Institute of Geophysics at Escuela Politécnica Nacional in Ecuador. The regional terms of our model are estimated with 539 records from 60 subduction events in Colombia and Ecuador with epicenters in the range of −0.6° to 7.6°N and 75.5° to 79.6°W, with Mw≥4.5, hypocentral depth range of 4 ≤  Zhypo ≤ 210 km, for distances up to 350 km. The model includes forearc and backarc terms to account for larger attenuation at backarc sites for slab events and site categorization based on natural period. The proposed model corrects the median AG2020 global model to better account for the larger attenuation of local ground motions and includes a partially non-ergodic variance model.

scholarly journals Multi-Scale Study of The Small-Strain Damping Ratio of Fiber-Sand Composites

Polymers ◽  
2021 ◽  
Vol 13 (15) ◽  
pp. 2476
Author(s):  
Haiwen Li ◽  
Sathwik S. Kasyap ◽  
Kostas Senetakis
Keyword(s):  
Dynamic Properties ◽  
Wide Spectrum ◽  
Damping Ratio ◽  
Polypropylene Fiber ◽  
Small Strain ◽  
Treatment Method ◽  
Fiber Content ◽  
Polypropylene Fibers ◽  
Test Results ◽  
Fiber Reinforced

The use of polypropylene fibers as a geosynthetic in infrastructures is a promising ground treatment method with applications in the enhancement of the bearing capacity of foundations, slope rehabilitation, strengthening of backfills, as well as the improvement of the seismic behavior of geo-systems. Despite the large number of studies published in the literature investigating the properties of fiber-reinforced soils, less attention has been given in the evaluation of the dynamic properties of these composites, especially in examining damping characteristics and the influence of fiber inclusion and content. In the present study, the effect of polypropylene fiber inclusion on the small-strain damping ratio of sands with different gradations and various particle shapes was investigated through resonant column (macroscopic) experiments. The macroscopic test results suggested that the damping ratio of the mixtures tended to increase with increasing fiber content. Accordingly, a new expression was proposed which considers the influence of fiber content in the estimation of the small-strain damping of polypropylene fiber-sand mixtures and it can be complementary of damping modeling from small-to-medium strains based on previously developed expressions in the regime of medium strains. Additional insights were attempted to be obtained on the energy dissipation and contribution of fibers of these composite materials by performing grain-scale tests which further supported the macroscopic experimental test results. It was also attempted to interpret, based on the grain-scale tests results, the influence of fiber inclusion in a wide spectrum of properties for fiber-reinforced sands providing some general inferences on the contribution of polypropylene fibers on the constitutive behavior of granular materials.

Elastic displacements in the near-field of a propagating fault

1969 ◽  
Vol 59 (2) ◽  
pp. 865-908
Author(s):  
N. A. Haskell
Keyword(s):  
Fault Plane ◽  
Near Field ◽  
Strong Motion ◽  
Dislocation Motion ◽  
Displacement Discontinuity ◽  
Wave Form ◽  
Strong Motion Station ◽  
Ramp Function ◽  
Wave Forms ◽  
Parkfield Earthquake

abstract Displacement, particle velocity, and acceleration wave forms in the near field of a propagating fault have been computed by numerical integration of the Green's function integrals for an infinite medium. The displacement discontinuity (dislocation) on the fault plane is assumed to have the form of a unilaterally propagating finite ramp function in time. The calculated wave forms in the vicinity of the fault plane are quite similar to those observed at the strong motion station nearest the fault plane at the Parkfield earthquake. The comparison suggests that the propagating ramp time function is roughly representative of the main features of the dislocation motion on the fault plane, but that the actual motion has somewhat more high frequency complexity. Calculated amplitudes indicate that the average final dislocation on the fault at the Parkfield earthquake was more than an order of magnitude greater than the offsets observed on the visible surface trace. Computer generated wave form plots are presented for a variety of locations with respect to the fault plane and for two different assumptions on the relation between fault length and ramp function duration.

Soil-Structure Interaction in Buildings from Earthquake Records

1990 ◽  
Vol 6 (4) ◽  
pp. 641-655 ◽  
Author(s):  
Gregory L. Fenves ◽  
Giorgio Serino
Keyword(s):  
Soil Structure ◽  
Dynamic Properties ◽  
Strong Motion ◽  
Longitudinal Direction ◽  
Soil Structure Interaction ◽  
Base Shear ◽  
Foundation Soil ◽  
Soil System ◽  
Structure Interaction ◽  
Building Foundation

An evaluation of the response of a fourteen story reinforced concrete building to the 1 October 1987 Whittier earthquake and 4 October 1987 aftershock shows significant effects of soil-structure interaction. A mathematical model of the building-foundation-soil system provides response quantities not directly available from the records. The model is calibrated using the dynamic properties of the building as determined from the processed strong motion records. Soil-structure interaction reduces the base shear force in the longitudinal direction of the building compared with the typical assumption in which interaction is neglected. The reduction in base shear for this building and earthquake is approximately represented by proposed building code provisions for soil-structure interaction.

A Method to Directly Estimate S-Wave Site Amplification Factor from Horizontal-to-Vertical Spectral Ratio of Earthquakes (eHVSRs)

2020 ◽  
Vol 110 (6) ◽  
pp. 2892-2911
Author(s):  
Eri Ito ◽  
Kenichi Nakano ◽  
Fumiaki Nagashima ◽  
Hiroshi Kawase
Keyword(s):  
Amplification Factor ◽  
Strong Motion ◽  
Spectral Ratio ◽  
Site Amplification ◽  
Body Waves ◽  
Correction Function ◽  
Site Classification ◽  
Frequency Range ◽  
S Wave ◽  
Site Amplification Factor

ABSTRACT The main purpose of the site classification or velocity determination at a target site is to obtain or estimate the horizontal site amplification factor (HSAF) at that site during future earthquakes because HSAF would have significant effects on the strong-motion characteristics. We have been investigating various kinds of methods to delineate the S-wave velocity structures and the subsequent HSAF, as precisely as possible. After the advent of the diffuse field concept, we have derived a simple formula based on the equipartitioned energy density observed in the layered half-space for incident body waves. In this study, based on the diffuse field concept, together with the generalized spectral inversion technique (GIT), we propose a method to directly estimate the HSAF of the S-wave portion from the horizontal-to-vertical spectral ratio of earthquakes (eHVSRs). Because the vertical amplification is included in the denominator of eHVSR, it cannot be viewed as HSAF without correction. We used GIT to determine both the HSAF and the vertical site amplification factor (VSAF) simultaneously from strong-motion data observed by the networks in Japan and then deduced the log-averaged vertical amplification correction function (VACF) from VSAFs at a total of 1678 sites in which 10 or more earthquakes have been observed. The VACF without a category has a constant amplitude of about 2 in the frequency range from 1 to 15 Hz. By multiplying eHVSR by VACF, we obtained the simulated HSAF. We verified the effectiveness of this correction method using data from observation sites not used in the aforementioned averaging in the frequency range from 0.12 to 15 Hz.

scholarly journals Influence of ground motion duration on ductility demands of reinforced concrete structures

2019 ◽  
Vol 11 (4) ◽  
pp. 503-517 ◽  
Author(s):  
Eric De Jesus Vega ◽  
Luis A. Montejo
Keyword(s):  
Reinforced Concrete ◽  
Short Duration ◽  
Numerical Models ◽  
Dynamic Properties ◽  
Response Spectrum ◽  
Concrete Structures ◽  
Strong Motion ◽  
Reinforced Concrete Structures ◽  
Inelastic Demand ◽  
Long Duration

Abstract This article investigates the level of influence that strong motion duration may have on the inelastic demand of reinforced concrete structures. Sets of short-duration spectrally equivalent records are generated using as target the response spectrum of an actual long-duration record. The sets of short-duration records are applied to carefully calibrated numerical models of the structures along with the target long-duration records. The input motions are applied in an incremental dynamic analysis fashion, so that the duration effect at different levels of inelastic demand can be investigated. It was found that long-duration records tend to impose larger inelastic demands. However, such influence is difficult to quantify, as it was found to depend on the dynamic properties of the structure, the strength, and stiffness degrading characteristics, the approach used to generate the numerical model and the seismic scenario (target spectrum). While for some scenarios, the dominance of the long record was evident; in other scenarios, the set of short records clearly imposed larger demands than the long record. The detrimental effect of large strong motion durations was mainly observed in relatively rigid structures and poorly detailed flexible structures. The modeling approach was found to play an important role in the perceived effect of duration, with the lumped plasticity multilinear hysteretic models suggesting that the demands from the long records can be up to twice the inferred from distributed plasticity fiber models.

Site classification of Indian strong motion network using response spectra ratios

2017 ◽  
Vol 22 (2) ◽  
pp. 419-438 ◽  
Author(s):  
Sumer Chopra ◽  
Vikas Kumar ◽  
Pallabee Choudhury ◽  
R. B. S. Yadav
Keyword(s):  
Strong Motion ◽  
Response Spectra ◽  
Site Classification ◽  
Strong Motion Network
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