3D Nonlinear Ground‐Motion Simulation Using a Physics‐Based Method for the Kinburn Basin

Abstract We used a finite‐difference modeling method, developed by Olsen–Day–Cui, to simulate nonlinear‐viscoelastic basin effects in a spectral frequency range of 0.1–1 Hz in the Kinburn bedrock topographic basin, Ottawa, Canada, for large earthquakes. The geotechnical and geological features of the study area are unique: loose, postglacial sediments with very low shear‐wave velocities (<200 m/s) overlying very firm bedrock with high shear‐wave velocities (>2000 m/s). Comparing records and simulated velocity time series showed regular viscoelastic simulations could model the ground motions at the rock and soil sites in the Kinburn basin for the Ladysmith earthquake, a local earthquake occurred on 17 May 2013 with Mw 4.7 (MN 5.2). The Ladysmith earthquake was scaled to provide a strong level of shaking for investigating the nonlinear behavior of soil; therefore, a new nonlinear‐viscoelastic subroutine was introduced to the program. A modeled stress–strain relationship associated with ground‐motion modeling in the Kinburn basin using a scaled Ladysmith earthquake event of Mw 7.5 followed Masing’s rules. Using nonlinear‐viscoelastic ground‐motion simulations significantly reduced the amplitude of the horizontal component of the Fourier spectrum at low frequencies and the predicted peak ground acceleration and peak ground velocity values compared with regular linear viscoelastic simulations; hence, the lower soil amplification of seismic waves and the frequency and amplitude spectral content were altered by the nonlinear soil behavior. In addition, using a finite‐fault model to simulate an earthquake with Mw 7.5 was necessary to predict the higher levels of stresses and strains, which were generated in the basin. Using a finite‐fault source for the nonlinear‐viscoelastic simulation caused decreases in the horizontal components because of the shear modulus reduction and increase of damping.

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Variability of Ground Motion Amplitudes Recorded in Bucharest Area during Vrancea Intermediate-Depth Earthquakes

Shock and Vibration ◽

10.1155/2021/5189966 ◽

2021 ◽

Vol 2021 ◽

pp. 1-13

Author(s):

Florin Pavel

Keyword(s):

Shear Wave ◽

Ground Motion ◽

Site Amplification ◽

Peak Ground Velocity ◽

Eurocode 8 ◽

Intermediate Depth ◽

Wave Velocities ◽

Shear Wave Velocities ◽

Normal Probability ◽

Normal Probability Distribution

This study focuses on the assessment of the correlation and variability of ground motion amplitudes recorded in Bucharest area during Vrancea intermediate-depth earthquakes from a database of 119 pairs of horizontal components. Empirical models for the evaluation of the peak ground velocity and displacement from spectral accelerations are proposed in this study. The distribution of the shear wave velocities from 41 boreholes at specific depths appears to follow a normal probability distribution. The analysis performed in this study has also shown that the variability of peak ground velocities and displacements does not appear to be influenced by the earthquake magnitude. In addition, it was observed that the variability in terms of shear wave velocities at specific depths is smaller than the variability of the spectral amplitudes of the recorded ground motions. The empirical site-amplification factors from the Eurocode 8 draft fail to capture the long-period spectral amplifications observed in Bucharest area during large magnitude Vrancea intermediate-depth earthquakes.

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Smooth Crustal Velocity Models Cause a Depletion of High-Frequency Ground Motions on Soil in 2D Dynamic Rupture Simulations

Bulletin of the Seismological Society of America ◽

10.1785/0120200311 ◽

2021 ◽

Author(s):

Yihe Huang

Keyword(s):

Shear Wave ◽

High Frequency ◽

Ground Motions ◽

Velocity Model ◽

Dynamic Rupture ◽

Ground Acceleration ◽

Velocity Models ◽

Wave Velocities ◽

Shear Wave Velocities ◽

Crustal Velocity

ABSTRACT A depletion of high-frequency ground motions on soil sites has been observed in recent large earthquakes and is often attributed to a nonlinear soil response. Here, I show that the reduced amplitudes of high-frequency horizontal-to-vertical spectral ratios (HVSRs) on soil can also be caused by a smooth crustal velocity model with low shear-wave velocities underneath soil sites. I calculate near-fault ground motions using both 2D dynamic rupture simulations and point-source models for both rock and soil sites. The 1D velocity models used in the simulations are derived from empirical relationships between seismic wave velocities and depths in northern California. The simulations for soil sites feature lower shear-wave velocities and thus larger Poisson’s ratios at shallow depths than those for rock sites. The lower shear-wave velocities cause slower shallow rupture and smaller shallow slip, but both soil and rock simulations have similar rupture speeds and slip for the rest of the fault. However, the simulated near-fault ground motions on soil and rock sites have distinct features. Compared to ground motions on rock, horizontal ground acceleration on soil is only amplified at low frequencies, whereas vertical ground acceleration is deamplified for the whole frequency range. Thus, the HVSRs on soil exhibit a depletion of high-frequency energy. The comparison between smooth and layered velocity models demonstrates that the smoothness of the velocity model plays a critical role in the contrasting behaviors of HVSRs on soil and rock for different rupture styles and velocity profiles. The results reveal the significant role of shallow crustal velocity structure in the generation of high-frequency ground motions on soil sites.

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ESTIMATION OF STATIC COULOMB STRESS CHANGE AND STRONG MOTION SIMULATION FOR JIUZHAIGOU 7.0 EARTHQUAKE BASE ON SENTINEL-1 INSAR DATA INVERSION

ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences ◽

10.5194/isprs-archives-xlii-3-1533-2018 ◽

2018 ◽

Vol XLII-3 ◽

pp. 1533-1537

Author(s):

W. H. Shen ◽

Y. Luo ◽

Q. S. Jiao

Keyword(s):

Ground Motion ◽

Static Stress ◽

Peak Ground Velocity ◽

Coseismic Deformation ◽

Coulomb Stress ◽

Slip Model ◽

Ground Acceleration ◽

Low Level ◽

Finite Fault ◽

Stress Changes

On August 8, 2017, an earthquake of M&thinsp;7.0 occurred at Jiuzhaigou. Based on the Sentinel-1 satellite InSAR data, we obtained coseismic deformation field and inverted the source slip model. Results show that this event is dominated by strike slip, and the total released seismic moment is 8.06&thinsp;&times;&thinsp;1018&thinsp;Nm, equivalent to an earthquake of <i>M<sub>w</sub></i>&thinsp;~&thinsp;6.57. We calculated static stress changes along strike and dip direction, and the static stress analysis show that the average stress drop are at low level, which may be responsible for the low level of ground motion during Jiuzhaigou earthquake. The coseismic Coulomb stress changes are calculated base on the inverted slip model, which revealed that 82.59&thinsp;% of aftershocks are located in the Coulomb stress increasing area, 78.42&thinsp;% of total aftershocks may be triggered by the mainshock aftershock, indicating that the mainshock has a significant triggering effect on the subsequent aftershocks. Based on stochastic finite fault model, we simulated regional peak ground acceleration (PGA), peak ground velocity (PGV) and the intensity, and results could capture basic features associated with the ground motion patterns. Moreover, the simulated results reflect the obvious rupture directivity effect.

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Implications of the Mw9.0 Tohoku-Oki Earthquake for Ground Motion Scaling with Source, Path, and Site Parameters

Earthquake Spectra ◽

10.1193/1.4000115 ◽

2013 ◽

Vol 29 (1_suppl) ◽

pp. 1-21 ◽

Cited By ~ 17

Author(s):

Jonathan P. Stewart ◽

Saburoh Midorikawa ◽

Robert W. Graves ◽

Khatareh Khodaverdi ◽

Tadahiro Kishida ◽

...

Keyword(s):

Ground Motion ◽

Ground Motions ◽

Site Amplification ◽

Low Frequencies ◽

High Frequencies ◽

Wave Velocities ◽

Shear Wave Velocities ◽

Active Tectonic ◽

Motion Scaling ◽

Ground Motion Scaling

The Mw9.0 Tohoku-oki Japan earthquake produced approximately 2,000 ground motion recordings. We consider 1,238 three-component accelerograms corrected with component-specific low-cut filters. The recordings have rupture distances between 44 km and 1,000 km, time-averaged shear wave velocities of VS30 = 90 m/s to 1,900 m/s, and usable response spectral periods of 0.01 sec to >10 sec. The data support the notion that the increase of ground motions with magnitude saturates at large magnitudes. High-frequency ground motions demonstrate faster attenuation with distance in backarc than in forearc regions, which is only captured by one of the four considered ground motion prediction equations for subduction earthquakes. Recordings within 100 km of the fault are used to estimate event terms, which are generally positive (indicating model underprediction) at short periods and zero or negative (overprediction) at long periods. We find site amplification to scale minimally with VS30 at high frequencies, in contrast with other active tectonic regions, but to scale strongly with VS30 at low frequencies.

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Estimation of ground motion in Xalapa, Veracruz, Mexico during the 1920 (M~6.4) crustal earthquake, and some significant intraslab earthquakes of the last century

Geofísica Internacional ◽

10.22201/igeof.00167169p.2018.57.2.2039 ◽

2018 ◽

Vol 57 (2) ◽

Author(s):

Francisco Córdoba-Montiel Córdoba-Montiel ◽

Srhi Krishna Singh ◽

Arturo Iglesias ◽

Xyoli Pérez-Campos ◽

K. Sieron

Keyword(s):

Ground Motion ◽

Stress Drop ◽

Seismic Waves ◽

Volcanic Belt ◽

Spectral Ratio ◽

Site Effect ◽

Peak Ground Velocity ◽

Ground Acceleration ◽

Scenario Earthquakes ◽

The City

Ground motions in Xalapa, Veracruz, Mexico, during the earthquake of January 4, 1920 (M~6.4), and three significant intraslab earthquakes (Mw7.0) of the last century were estimated. These events are reasonable scenario earthquakes for Xalapa. Towards this goal, portable broadband seismographs at nine sites in the city and an additional one at a reference hard site outside the city were deployed. Peak ground acceleration (Amax) and peak ground velocity (Amax) in Xalapa were estimated based on Brune w -2 source model and the site effect, obtained from earthquake recordings by using the standard spectral ratio (SSR) technique, and the application of a stochastic method. During the 1920 Xalapa earthquake the estimated Amax values corresponding to a stress drop, Ds, of 50 bar are between 100 and 250 cm/s2, except at two sites where the site effect is very large and Amax values reach 300 and 600 cm/s2. Estimated Vmax values are between 10 and 20 cm/s, except at the site with the largest site effect where it is ~ 40 cm/s. Ds of 30 and 100 bar produce about half and twice of these peak values, respectively. The main uncertainty in the present estimations is due the Ds value, because although a range of 30 to 100 bar for crustal earthquakes in the Trans-Mexican Volcanic Belt (in which Xalapa is located) seems reasonable, it is not constrained by the data. The mean stress drop for intraslab events, ~ 300 bar, is better constrained from previous studies. A median Amax of ~ 30 cm/s2 and a median Vmax of 4 cm/s in Xalapa during the 1973 (Orizaba) and 1999 (Tehuacán) earthquakes was estimated; the corresponding values during the 1980 (Huajuapan) earthquake are ~ 10 cm/s2 and 2 cm/s. The uncertainty in the estimation is probably within a factor of 2 to 3.The ground motion prediction equations developed from data in the forearc region with less attenuation (than the backarc region) and recorded at hard sites appear to work reasonably well for Xalapa sites, which lie in the back arc. This observation suggests that the seismic waves from intraslab earthquakes, traveling through the mantle wedge before arriving Xalapa, suffer relatively large attenuation. However, these waves get amplified due to local site effects. It seems that in Xalapa these two effects, roughly, balance each other.

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Determine Shear wave velocities and Elasto-Dynamic properties for Nassiriya Refinery project in Thi qar Governorate- Nassiriya District- South of Iraq

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/790/1/012005 ◽

2021 ◽

Vol 790 (1) ◽

pp. 012005

Author(s):

Ahmed Jalal Fakher ◽

Ahmed Salman Hassan

Keyword(s):

Shear Wave ◽

Dynamic Properties ◽

Wave Velocities ◽

Shear Wave Velocities ◽

South Of Iraq

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Seismic Hazard Assessment for the Tianshui Urban Area, Gansu Province, China

International Journal of Geophysics ◽

10.1155/2012/461863 ◽

2012 ◽

Vol 2012 ◽

pp. 1-10 ◽

Cited By ~ 3

Author(s):

Zhenming Wang ◽

David T. Butler ◽

Edward W. Woolery ◽

Lanmin Wang

Keyword(s):

Seismic Hazard ◽

Ground Motion ◽

Seismic Design ◽

Hazard Analysis ◽

Seismic Hazard Assessment ◽

Gansu Province ◽

Mitigation Measures ◽

Peak Ground Velocity ◽

Ground Acceleration ◽

Acceleration Time Histories

A scenario seismic hazard analysis was performed for the city of Tianshui. The scenario hazard analysis utilized the best available geologic and seismological information as well as composite source model (i.e., ground motion simulation) to derive ground motion hazards in terms of acceleration time histories, peak values (e.g., peak ground acceleration and peak ground velocity), and response spectra. This study confirms that Tianshui is facing significant seismic hazard, and certain mitigation measures, such as better seismic design for buildings and other structures, should be developed and implemented. This study shows that PGA of 0.3 g (equivalent to Chinese intensity VIII) should be considered for seismic design of general building and PGA of 0.4 g (equivalent to Chinese intensity IX) for seismic design of critical facility in Tianshui.

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