scholarly journals Effects of fault finiteness on near-source ground motion

1981 ◽  
Vol 71 (4) ◽  
pp. 939-957
Author(s):  
Ralph J. Archuleta ◽  
Stephen H. Hartzell
Keyword(s):  
Ground Motion ◽  
Wave Speed ◽  
Sliding Friction ◽  
Ground Motions ◽  
Vertical Component ◽  
Displacement Function ◽  
Rupture Velocity ◽  
Maximum Acceleration ◽  
Shear Wave Speed ◽  
Spatially Varying

abstract Near-source ground motion at four azimuths but constant epicentral range is computed from a buried circular strike-slip fault in a half-space. Particle acceleration, velocity, and displacement at each station on the free surface is computed in the frequency band 0.0 to 5.0 Hz. The assumed dislocation is derived from the Kostrov (1964) displacement function for a continuously propagating stress relaxation. The azimuthal variations in the amplitudes and waveforms directly result from spatially varying slip on the fault, spatially varying radiation pattern over the fault, and the magnitude and direction of the rupture velocity. The near-source ground motions are dominated by the rupture in the direction of the receiver. Using a 100-bar effective stress (initial stress minus sliding friction) in a Poisson solid with β = 3.0 km/sec the shear wave speed, and shear modulus μ = 3.0 × 1011 dyne/cm2, the simulated earthquake has a moment Mo = 4.5 × 1025 dyne-cm. Using a rupture velocity of 0.9β, the peak acceleration is 1195 cm/sec2 and velocity 104 cm/sec for the receiver directly on strike. For a receiver 30° off strike, the maximum acceleration 236 cm/sec2 occurs on the vertical component.

A Source Physics Interpretation of Nonself-Similar Double-Corner-Frequency Source Spectral Model JA19_2S

2022 ◽  
Author(s):  
Chen Ji ◽  
Ralph J. Archuleta
Keyword(s):  
Stress Drop ◽  
Wave Speed ◽  
Dynamic Stress ◽  
Corner Frequency ◽  
Rupture Velocity ◽  
Scaling Relation ◽  
Shear Wave Speed ◽  
Dynamic Stress Drop ◽  
Static Stress Drop ◽  
Frequency Source

Abstract We investigate the relation between the kinematic double-corner-frequency source spectral model JA19_2S (Ji and Archuleta, 2020) and static fault geometry scaling relations proposed by Leonard (2010). We find that the nonself-similar low-corner-frequency scaling relation of JA19_2S model can be explained using the fault length scaling relation of Leonard’s model combined with an average rupture velocity ∼70% of shear-wave speed for earthquakes 5.3 < M< 6.9. Earthquakes consistent with both models have magnitude-independent average static stress drop and average dynamic stress drop around 3 MPa. Their scaled energy e˜ is not a constant. The decrease of e˜ with magnitude can be fully explained by the magnitude dependence of the fault aspect ratio. The high-frequency source radiation is generally controlled by seismic moment, static stress drop, and dynamic stress drop but is further modulated by the fault aspect ratio and the relative location of the hypocenter. Based on these two models, the commonly quoted average rupture velocity of 70%–80% of shear-wave speed implies predominantly unilateral rupture.

scholarly journals Application of the Incremental Modal Analysis for Bridges (IMPAb) Subjected to Near-Fault Ground Motions

2020 ◽  
Author(s):  
Alessandro Vittorio Bergami ◽  
Gabriele Fiorentino ◽  
Davide Lavorato ◽  
Bruno Briseghella ◽  
Camillo Nuti
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Pushover Analysis ◽  
Vertical Component ◽  
Vertical Motion ◽  
Strong Motion ◽  
Seismic Action ◽  
Near Fault ◽  
Benchmark Solutions

Near-fault ground motions can cause severe damage to civil structures, including bridges. Safety assessment of these structures for near fault ground motion is usually performed through Non-Linear Dynamic Analyses, while faster methods are often used. IMPAb (Incremental Modal Pushover Analysis for Bridges) permits to investigate the seismic response of a bridge by considering the effects of higher modes, which are often relevant for bridges. In this work, IMPAb is applied to a bridge case study considering near-fault pulse-like ground motion records. The records were analyzed and selected from the European Strong Motion Database and the pulse parameters were evaluated. In the paper results from standard pushover procedures and IMPAb are compared with nonlinear Response-History Analysis (NRHA), considering also the vertical component of the motion, as benchmark solutions and incremental dynamic analysis (IDA). Results from the case study demonstrate that the vertical seismic action has a minor influence on the structural response of the bridge. Therefore IMPAb, which can be applied considering vertical motion, remains very effective conserving the original formulation of the procedure, and can be considered a well performing procedure also for near-fault events.

scholarly journals Spatial Variability of Near-field Ground Motions from Pseudo-Dynamic Rupture Simulations

2021 ◽  
Author(s):  
Jayalakshmi Sivasubramonian ◽  
Paul Martin Mai
Keyword(s):  
Ground Motion ◽  
Rise Time ◽  
Time Distribution ◽  
Velocity Structure ◽  
Ground Motions ◽  
Near Field ◽  
Source Parameters ◽  
Rupture Velocity ◽  
Earthquake Source Parameters ◽  
Ground Motion Variability

<p>We analyze the effect of earthquake source parameters on ground-motion variability based on near-field wavefield simulations for large earthquakes. We quantify residuals in simulated ground motion intensities with respect to observed records, the associated variabilities are then quantified with respect to source-to-site distance and azimuth. Additionally, we compute the variabilities due to complexities in rupture models by considering variations in hypocenter location and slip distribution that are implemented a new Pseudo-Dynamic (PD) source parameterization.</p><p>In this study, we consider two past events – the Mw 6.9 Iwate Miyagi Earthquake (2008), Japan, and the Mw 6.5 Imperial Valley Earthquake, California (1979). Assuming for each case a 1D velocity structure, we first generate ensembles of rupture models using the pseudo-dynamic approach of Guatteri et.al (2004), by assuming different hypocenter and asperities locations (Mai and Beroza, 2002, Mai et al., 2005; Thingbaijam and Mai, 2016). In order to efficiently include variations in high-frequency radiation, we adopt a PD parameterization for rupture velocity and rise time distribution in our rupture model generator. Overall, we generate a database of rupture models with 50 scenarios for each source parameterization. Synthetic near-field waveforms (0.1-2.5Hz) are computed out to Joyner-Boore distances Rjb ~ 150km using a discrete-wavenumber finite-element method (Olson et al., 1984). Our results show that ground-motion variability is most sensitive to hypocenter locations on the fault plane. We also find that locations of asperities do not alter waveforms significantly for a given hypocenter, rupture velocity and rise time distribution. We compare the scenario-event simulated ground motions with simulations that use the rupture models from the SRCMOD database (Mai and Thingbaijam, 2014), and find that the PD method is capable of reducing the ground motion variability at high frequencies. The PD models are calibrated by comparing the mean residuals with the residuals from SRCMOD models. We present the variability due to each source parameterization as a function of Joyner-Boore distance and azimuth at different natural period.</p>

scholarly journals Analysis of accelerograms—Parkfield earthquake

1967 ◽  
Vol 57 (6) ◽  
pp. 1193-1220 ◽  
Author(s):  
G. W. Housner ◽  
M. D. Trifunac
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Response Spectra ◽  
Horizontal Displacement ◽  
Ground Acceleration ◽  
Directional Characteristic ◽  
Maximum Acceleration ◽  
Small Magnitude ◽  
Near Fault ◽  
Parkfield Earthquake

Abstract Integrated velocities and displacements show that near the fault at Cholame the surface motion exhibited a transient horizontal displacement pulse of approximately ten inches amplitude and one and one-half seconds duration, normal to the fault. Although 50 per cent of g ground acceleration was recorded at the fault, the ground motion attenuated rapidly with distance and at ten miles from the fault the maximum acceleration was reduced to one-tenth of its near-fault value. The ground motion also changed its character with distance, losing its pulse-like directional characteristic and becoming isotropic. Computed response spectra are presented and the large spectrum ordinates for this shock of relatively small magnitude and moderate destructiveness indicate that in an engineering sense the Parkfield ground motion is in a different class from such large destructive ground motions as El Centro 1940, Tehachapi 1952, and Olympia 1949.

Analysis of Coupled Lateral-Torsional-Pounding Responses of One-Storey Asymmetric Adjacent Structures Subjected to Bi-Directional Ground Motions Part II: Spatially Varying Ground Motion Input

2005 ◽  
Vol 8 (5) ◽  
pp. 481-496 ◽  
Author(s):  
H. Hao ◽  
L. Gong
Keyword(s):  
Spatial Variation ◽  
Ground Motion ◽  
Response Spectrum ◽  
Ground Motions ◽  
Adjacent Structure ◽  
Design Response Spectrum ◽  
Adjacent Structures ◽  
Impact Element ◽  
Time Histories ◽  
Spatially Varying

This is the second paper presenting numerical results of a parametric study of seismic induced lateral-torsional-pounding responses of an asymmetric and a symmetric one-storey adjacent structure. The accompany paper (Part I) (Gong and Hao 2004) assumed ground motion input at all structural supports as uniform. Torsional responses are generated because of inherent structural eccentricity and eccentric pounding. In reality, seismic ground motion at different structural supports inevitably varies owing to wave propagation. Spatially varying ground motion will induce torsional responses of structures, and generate out-of-phase responses between adjacent structures. Thus it might have a significant effect on coupled lateral-torsional-pounding responses. This paper studies the ground motion spatial variation effect. For comparison purpose, same adjacent structure models and impact element used in Part I of this study are adopted here again. 20 sets of spatially varying ground motion time histories are stochastically simulated. All the time histories are compatible with the Newmark-Hall design response spectrum with 5% damping and normalized to 0.5g. The spatial variation of any two simulated time histories is compatible with an empirical coherency loss function. Coupled lateral-torsional-pounding responses of the two structures to the simulated ground motions are calculated. Discussions on the ground motion spatial variation effects are made.

scholarly journals Seismic Response of Power Transmission Tower-Line System Subjected to Spatially Varying Ground Motions

2010 ◽  
Vol 2010 ◽  
pp. 1-20 ◽  
Author(s):  
Li Tian ◽  
Hongnan Li ◽  
Guohuan Liu
Keyword(s):  
Ground Motion ◽  
Power Transmission ◽  
Ground Motions ◽  
Time History ◽  
System Response ◽  
Transmission Tower ◽  
Line System ◽  
Wave Travel ◽  
Spatially Varying Ground Motions ◽  
Spatially Varying

The behavior of power transmission tower-line system subjected to spatially varying base excitations is studied in this paper. The transmission towers are modeled by beam elements while the transmission lines are modeled by cable elements that account for the nonlinear geometry of the cables. The real multistation data from SMART-1 are used to analyze the system response subjected to spatially varying ground motions. The seismic input waves for vertical and horizontal ground motions are also generated based on the Code for Design of Seismic of Electrical Installations. Both the incoherency of seismic waves and wave travel effects are accounted for. The nonlinear time history analytical method is used in the analysis. The effects of boundary conditions, ground motion spatial variations, the incident angle of the seismic wave, coherency loss, and wave travel on the system are investigated. The results show that the uniform ground motion at all supports of system does not provide the most critical case for the response calculations.

scholarly journals How significant is vertical ground motion from low magnitude earthquakes?

2020 ◽  
Author(s):  
Janneke van Ginkel ◽  
Elmer Ruigrok ◽  
Rien Herber
Keyword(s):  
The Netherlands ◽  
Ground Motion ◽  
Hazard Assessment ◽  
Site Response ◽  
Ground Motions ◽  
Vertical Component ◽  
Vertical Motion ◽  
Vertical Ground Motion ◽  
Vertical Ground ◽  
Low Magnitude

<p>Up to now, almost all of the ground motion modeling and hazard assessment for seismicity in the Netherlands focuses on horizontal motion. As a rule of thumb, the strength of vertical ground motions is taken as 2/3 of that of horizontal ground motions. In reality of course, amplifications and V/H ratios are site-dependent and thus vary regionally.  Recent studies have indeed shown that vertical ground motion is not always simply 2/3 of the horizontal motion. However, these studies are performed in areas with high magnitude (Mw>5.0) earthquakes and the question is whether vertical motion is relevant to be included in seismic hazard assessment for low magnitude earthquakes (to date, max Mw=3.6 in Groningen).</p><p>In the Netherlands, the top part of the soils is practically always unconsolidated, so the elastic waves generated by deeper (~3000m) seated earthquakes will be subject to transformation when arriving in these layers. Recordings over a range of depth levels in the Groningen borehole network show the largest amplification to occur in the upper 50 meters of the sedimentary cover. We not only observe a strong amplification from shear waves on the horizontal components, but also from longitudinal waves on the vertical component. A better understanding of vertical motion of low magnitude earthquakes aims to support the design of re-enforcement measures for buildings in areas affected by low magnitude seismicity. Furthermore, interference between the longitudinal -and shear waves might contribute to damage on structures.</p><p>This study presents observations of longitudinal wave amplification in the frequency band 1-10 Hz, corresponding to resonance periods of Dutch buildings. From 19 seismic events, with a minimum of magnitude two, we retrieved transfer functions (TFs) from the vertical component, showing a strong site response at certain locations. In addition, we calculate event V/H ratios and VH factors from the surface seismometer. These results are compared with the TFs and show a similar pattern in terms of site response. Furthermore, the sites with highest vertical amplification correspond to very low (800-900 m/s) P-wave velocities. Our study shows that vertical amplification is very site dependent. However, the question whether the vertical motion is significant enough to form a real hazard can only be answered through cooperation between seismologist and structural engineer.</p>

Seismic Fragility Analysis of Reinforced Concrete Bridges with Chloride Induced Corrosion Subjected to Spatially Varying Ground Motions

2016 ◽  
Vol 16 (05) ◽  
pp. 1550010 ◽  
Author(s):  
Chao Li ◽  
Hong Hao ◽  
Hongnan Li ◽  
Kaiming Bi
Keyword(s):  
Ground Motion ◽  
Fragility Curves ◽  
Ground Motions ◽  
Spatial Variations ◽  
Concrete Bridges ◽  
Seismic Fragility ◽  
Reinforced Concrete Bridges ◽  
Chloride Induced Corrosion ◽  
Spatially Varying Ground Motions ◽  
Spatially Varying

This paper studies the time-dependent seismic fragility of reinforced concrete bridges with chloride induced corrosion under spatially varying ground motions. The time-varying characteristic of the chloride corrosion current density and the uncertainties related to the structural, material and corrosion parameters are both considered in the probabilistic finite element modeling of the example RC bridge at different time steps during its life-cycle. Spatially varying ground motions at different bridge supports are stochastically simulated and used as inputs in the fragility analysis. Seismic fragility curves of the corroded RC bridge at different time steps are generated using the probabilistic seismic demand analysis (PSDA) method. Numerical results indicate that both chloride induced corrosion and ground motion spatial variations have a significant effect on the bridge structural seismic fragility. As compared to the intact bridge, the mean peak ground accelerations (PGAs) of the fragility curves of the RC bridge decrease by approximately 40% after 90 years since the initiation of corrosion. Moreover, the effect of ground motion spatial variations changes along with the process of chloride induced corrosion owing to the structural stiffness degradation. Neglecting seismic ground motion spatial variations may not lead to an accurate estimation of the lifetime seismic fragility of RC bridges with chloride induced corrosion.

Behavior of near-source peak horizontal and vertical ground motions over SMART-1 Array, Taiwan

1991 ◽  
Vol 81 (3) ◽  
pp. 715-732
Author(s):  
M. Niazi ◽  
Y. Bozorgnia
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Near Field ◽  
Source Region ◽  
Vertical Component ◽  
Ground Acceleration ◽  
Hypocentral Distance ◽  
Magnitude Scaling ◽  
Vertical Ground ◽  
Lower Magnitude

Abstract Over 700 accelerograms recorded from 12 earthquakes in northeast Taiwan have been analyzed for investigating the behavior of vertical and horizontal peak and spectral ground motion in the near-source region. Peak horizontal and vertical ground acceleration (PGA), velocity (PGV), and displacement (PGD) in the range of engineering interest have been subjected to a two-step nonlinear regression procedure in terms of magnitude and hypocentral distance. In comparison with a number of other studies of global PGA observations, our predictions show lower far-field attenuation, lower near-source amplitudes, higher magnitude saturation for the vertical component, lower magnitude saturation for the horizontal component, and higher magnitude scaling. The 2 / 3 ratio of vertical to horizontal ground motion, commonly used in engineering applications, may be unconservative in the very near-field for high-frequency ground motion. It falls below 1 / 2 at distances greater than 50 km. The same ratio for PGV and PGD tends to increase with distance, the latter at a faster rate. For SMART-1 data the major source of uncertainty appears to be inter-event rather than intra-event randomness. The predominance of the inter-event uncertainty in ground motions near the source is expected to be a characteristic of all dense arrays.

Vector-Valued Probabilistic Seismic Hazard Assessment for the Effects of Vertical Ground Motions on the Seismic Response of Highway Bridges

2010 ◽  
Vol 26 (4) ◽  
pp. 999-1016 ◽  
Author(s):  
Zeynep Gülerce ◽  
Norman A. Abrahamson
Keyword(s):  
Seismic Hazard ◽  
Seismic Response ◽  
Ground Motion ◽  
Ground Motions ◽  
Vertical Component ◽  
Highway Bridges ◽  
Probabilistic Seismic Hazard ◽  
Vertical Ground Motion ◽  
Vertical Ground Motions ◽  
Vertical Ground

The vertical ground motion component is disregarded in the design of ordinary highway bridges in California, except for the bridges located in high seismic zones (sites with design horizontal peak ground acceleration greater than 0.6 g). The influence of vertical ground motion on the seismic response of single-bent, two-span highway bridges designed according to Caltrans Seismic Design Code (SDC-2006) is evaluated. A probabilistic seismic hazard framework is used to address the probability of exceeding the elastic capacity for various structural parameters when the vertical component is included. Negative mid-span moment demand is found to be the structural parameter that is most sensitive to vertical accelerations.A series of hazard curves for negative mid-span moment are developed for a suite of sites in Northern California. The annual probability of exceeding the elastic capacity of the negative mid-span moment is as large as 0.01 for the sites close to active faults when the vertical component is included. Simplified approaches based on the distance to major faults or the median design peak acceleration show that there is a large chance (0.4 to 0.65) of exceeding the elastic limit if the current 0.6 g threshold is used for the consideration of vertical ground motions for ordinary highway bridges. The results of this study provide the technical basis for consideration of a revision of the 0.6 g threshold.

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