Attenuation and Basin Amplification Revealed by the Dense Ground Motions of the 12 July 2020 Ms 5.1 Tangshan, China, Earthquake

2021 ◽  
Author(s):  
Hongwei Wang ◽  
Ruizhi Wen
Keyword(s):  
Surface Waves ◽  
Ground Motion ◽  
North China ◽  
Vertical Component ◽  
Strong Motion ◽  
Seismic Zone ◽  
Geometrical Spreading ◽  
Seismogenic Fault ◽  
Tangshan Earthquake ◽  
Moderate Earthquake

Abstract On 12 July 2020, an Ms 5.1 moderate earthquake occurred on the north segment of the Tangshan fault in North China, which was the seismogenic fault of the 1976 Ms 7.8 Tangshan earthquake and numerous small-to-moderate earthquakes in recent decades in the Tangshan seismic zone. The Ms 5.1 event was well-recorded by dense ground-motion observation stations, including the national strong-motion stations and seismic intensity stations. This many ground-motion recordings, obtained for such a moderate event in North China for the first time, provided a rare opportunity to investigate the attenuation and site effects on ground motion. The distance decay in the Tangshan seismic zone was first explored using the spectral amplitudes from the vertical component. The strong anelastic attenuation and weak geometrical spreading effects were clearly found. The hinged trilinear form may be more effective at describing the geometrical spreading. No geometrical spreading decay was visible at medium distances (60–100 km). Anomalous areas with extraordinary high amplitudes occurred in the spatial distribution of peak ground accelerations and peak ground velocities that we attribute to significant basin amplification effects, which was confirmed by the wideband and high amplifications on the standard spectral ratio and the later-arriving, long-period surface waves observed in waveforms in the Ninghe–Baodi area and south of Beijing. The basin-induced surface waves in the 2–5 s period were most prominent in the Ninghe–Baodi area. We further inferred that basin effects may be responsible for the high-intensity anomaly areas observed in the 1976 Ms 7.8 Tangshan earthquake.

Are Near-Fault Fling Effects Captured in the New NGA West2 Ground Motion Models?

2015 ◽  
Vol 31 (3) ◽  
pp. 1629-1645 ◽  
Author(s):  
Ronnie Kamai ◽  
Norman Abrahamson
Keyword(s):  
Ground Motion ◽  
Vertical Component ◽  
Strong Motion ◽  
Motion Processing ◽  
Large Set ◽  
Pass Filter ◽  
Motion Models ◽  
Finite Fault ◽  
Maximum Period ◽  
Ground Motion Models

We evaluate how much of the fling effect is removed from the NGA database and accompanying GMPEs due to standard strong motion processing. The analysis uses a large set of finite-fault simulations, processed with four different high-pass filter corners, representing the distribution within the PEER ground motion database. The effects of processing on the average horizontal component, the vertical component, and peak ground motion values are evaluated by taking the ratio between unprocessed and processed values. The results show that PGA, PGV, and other spectral values are not significantly affected by processing, partly thanks to the maximum period constraint used when developing the NGA GMPEs, but that the bias in peak ground displacement should not be ignored.

Basin Amplification Effects in the Puget Lowland, Washington, from Strong-Motion Recordings and 3D Simulations

2020 ◽  
Vol 110 (2) ◽  
pp. 534-555 ◽  
Author(s):  
Mika Thompson ◽  
Erin A. Wirth ◽  
Arthur D. Frankel ◽  
J. Renate Hartog ◽  
John E. Vidale
Keyword(s):  
Surface Waves ◽  
Ground Motion ◽  
Puget Sound ◽  
Strong Motion ◽  
Sedimentary Basins ◽  
Amplification Factors ◽  
Megathrust Earthquakes ◽  
Local Earthquakes ◽  
Basin Effects ◽  
Basin Edge

ABSTRACT Sedimentary basins in the Puget Sound region, Washington State, increase ground-motion intensity and duration of shaking during local earthquakes. We analyze Pacific Northwest Seismic Network and U.S. Geological Survey strong-motion recordings of five local earthquakes (M 3.9–6.8), including the 2001 Nisqually earthquake, to characterize sedimentary basin effects within the Seattle and Tacoma basins. We observe basin-edge generated surface waves at sites within the Seattle basin for most ray paths that cross the Seattle fault zone. We also note previously undocumented basin-edge surface waves in the Tacoma basin during one of the local earthquakes. To place quantitative constraints on basin amplification, we determine amplification factors by computing the spectral ratios of inside-basin sites to outside-basin sites at 1, 2, 3, and 5 s periods. Ground shaking is amplified in the Seattle basin for all the earthquakes analyzed and for a subset of events in the Tacoma basin. We find that the largest amplification factors in the Seattle basin are produced by a shallow earthquake located to the southwest of the basin. Our observation suggests that future shallow crustal and megathrust earthquakes rupturing west of the Puget Lowland will produce greater amplification within the Seattle basin than has been seen for intraslab events. We also perform ground-motion simulations using a finite-difference method to validate a 3D Cascadia velocity model (CVM) by comparing properties of observed and synthetic waveforms up to a frequency of 1 Hz. Basin-edge effects are well reproduced in the Seattle basin, but are less well resolved in the Tacoma basin. Continued study of basin effects in the Tacoma basin would improve the CVM.

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.

Surface-wave dispersion analysis in Mexico City

1995 ◽  
Vol 85 (4) ◽  
pp. 1116-1126
Author(s):  
Francisco J. Chávez-García ◽  
Jaime Ramos-Martínez ◽  
Evangelina Romero-Jiménez
Keyword(s):  
Surface Wave ◽  
Surface Waves ◽  
Ground Motion ◽  
Mexico City ◽  
Rayleigh Waves ◽  
Strong Motion ◽  
Clay Layer ◽  
Period Range ◽  
Wave Trains ◽  
Refraction Data

Abstract In this article, we present an observational investigation of ground motion at Mexico City focused on surface waves. Our purpose is 2-fold; first, to understand incident ground motion during the great Michoacán earthquake of 19 September 1985, and second, to characterize surface waves propagating in the lake-bed zone. To this end we analyze the strong-motion records obtained at Mexico City for the large (MS = 8.1) earthquake of 19 September 1985. It is shown that, in the low-frequency range, we observe the Rayleigh fundamental mode in both the vertical and the radial components, and the Love fundamental mode in the transverse component at all the strong-motion stations. The vertical component also shows the first higher mode of Rayleigh waves. We use a very broadband record obtained at station CU for the smaller (MS = 6.7) earthquake of 14 May 1993 to verify that the dispersion computed from the model of Campillo et al. (1989) represents well the average surface-wave propagation between the coast and Mexico City in the 7- to 10-sec period range. We use this result to assign absolute times to the strong-motion records of the Michoacán event. This allowed us to identify additional wave trains that propagate laterally in directions other than great circle in the 3- to 5-sec period range. These wave trains are identified as Love waves. In a second analysis, we study a set of refraction data obtained during a small-scale (250 m) experiment on the virgin clay of the lake-bed zone. Phase-velocity dispersion curves for several modes of Rayleigh waves are identified in the refraction data and inverted to obtain an S-wave velocity profile. This profile is used as the uppermost layering in a 2D model of Mexico City valley. The results of numerical simulation show that surface waves generated by lateral finiteness of the clay layer suffer large dispersion and attenuation. We conclude that surface waves generated by the lateral heterogeneity of the upper-most stratigraphy very significantly affect ground motion near the edge of the valley, but their importance is negligible for distances larger than 1.5 km from the edge. Thus, locally generated surface waves propagating through the clay layer cannot explain late arrivals observed for the 1985 event. We suggest that the long duration of strong motion is due to the interaction between lateral propagation of waves guided by deep layers (1 to 4 km) and the surficial clay layer. This interaction is possible by the coincidence of the dominant frequency of the uppermost layers and the frequency of the deeply guided waves.

Calculation of ground motion in a three-dimensional model of the 1966 Parkfield earthquake

1976 ◽  
Vol 66 (2) ◽  
pp. 405-423
Author(s):  
N. A. Levy ◽  
A. K. Mal
Keyword(s):  
Surface Waves ◽  
Ground Motion ◽  
Near Field ◽  
Three Dimensional ◽  
Vertical Component ◽  
Elastic Half Space ◽  
The Body ◽  
Body Waves ◽  
Three Dimensional Model ◽  
Ground Displacements

abstract Near-field ground displacements are calculated from an earthquake source in a homogeneous, elastic half-space. An analytical formulation of the problem is presented that requires no physical approximations except at the source. A model of the source is constructed by retaining the essential kinematic character of the faulting process. A computer program is developed to calculate ground motion from an assumed model of the 1966 Parkfield, California earthquake. Favorable agreement is obtained between the theoretically computed ground displacements and those derived from the recorded accelerations. The relative contributions of the body waves and surface waves to the displacement field are examined. The results indicate that a significant portion of near-field motion may consist of surface waves, especially in the vertical component of the ground motion.

scholarly journals Application of the Incremental Modal Pushover Analysis to Bridges Subjected to Near-Fault Ground Motions

2020 ◽  
Vol 10 (19) ◽  
pp. 6738
Author(s):  
Alessandro Vittorio Bergami ◽  
Gabriele Fiorentino ◽  
Davide Lavorato ◽  
Bruno Briseghella ◽  
Camillo Nuti
Keyword(s):  
Ground Motion ◽  
Pushover Analysis ◽  
Vertical Component ◽  
Structural Response ◽  
Strong Motion ◽  
Seismic Action ◽  
Modal Pushover Analysis ◽  
Near Fault ◽  
Modal Pushover

Near-fault events can cause severe damage to civil structures, including bridges. Many studies have demonstrated that the seismic assessment is not straightforward. Usually, dealing with near-fault ground motion, the structural analysis is performed using Nonlinear Response-History Analysis (NRHA) but in the last years, many authors have tested existing pushover-based procedures originally developed and validated using far-field events. Between those procedures, the Incremental Modal Pushover Analysis (IMPAβ) is a pushover-based procedure specifically developed for bridges that, in this work, was applied to a case study considering near-fault pulse-like ground motion records. The records were analyzed and selected from the European Strong Motion Database. In the paper the results obtained with IMPAβ together with other standard pushover procedures, are compared with NRHA and incremental dynamic analyses; the vertical component of the motion has been also considered. Results obtained with the bridge case study demonstrate that the vertical seismic action has a minor influence on the structural response and that IMPAβ is confirmed as a very effective pushover-based method that can be applied also for near-fault events.

Some Aspects of the Seismic Scaling and the Strong Ground Motion of the Eastern Missouri Earthquake of January 12, 1984

1987 ◽  
Vol 58 (2) ◽  
pp. 53-58 ◽  
Author(s):  
Otto W. Nuttli ◽  
David S. Bowling ◽  
J. E. Lawson ◽  
Randall Wheeler
Keyword(s):  
Ground Motion ◽  
Strong Ground Motion ◽  
Epicentral Distance ◽  
Vertical Component ◽  
Strong Motion ◽  
Radial Component ◽  
Transverse Component ◽  
Corner Frequency ◽  
Scaling Relation ◽  
Strong Ground

Abstract Strong-motion records from a velocity meter were recorded at an epicentral distance of 4.5 km from the January 12, 1984 eastern Missouri earthquake of mb = 3.0. Peak values of ground velocity, associated with only one or two wave cycles, are: transverse component, 0.18 cm/sec; radial component, 0.16 cm/sec; vertical component, 0.12 cm/sec. The levels of the sustained motion, which extends from the onset of S to about 0.4 sec later, are: transverse component, 0.064 cm/sec; radial component, 0.061 cm/sec; vertical component, 0.061 cm/sec. The data are consistent with a spectral scaling relation assuming either a 3.5 or 4.0 slope of the logarithm of the seismic moment versus the logarithm of the corner frequency, but cannot be used to choose between the two relations.

Attenuation and excitation of three-component ground motion in southern California

1999 ◽  
Vol 89 (4) ◽  
pp. 888-902 ◽  
Author(s):  
M. Raoof ◽  
R. B. Herrmann ◽  
L. Malagnini
Keyword(s):  
Ground Motion ◽  
Southern California ◽  
Vertical Component ◽  
Stochastic Simulations ◽  
Geometrical Spreading ◽  
Data Set ◽  
Frequency Dependent ◽  
Ground Motion Attenuation ◽  
Spreading Function ◽  
Velocity Spectra

Abstract Ground motion attenuation with distance and the variation of excitation with magnitude are parameterized using three-component, 0.25 to 5.0-Hz earthquake ground motions recorded in the distance range of 15-500 km for southern California to define a consistent model that describes both peak ground motion and Fourier spectra observations. The data set consists of 820 three-component TERRAscope recordings from 140 earthquakes, recorded at 17 stations, with moment magnitudes between 3.1 and 6.7. Regression analysis uses a simple model to relate the logarithm of measured ground motion to excitation, site, and propagation effects. The peak motions are Fourier velocity spectra and peak velocities in selected narrow bandpass-filtered frequency ranges. Regression results for Fourier amplitude spectra and peak velocities are used to define a piecewise continuous geometrical spreading function, frequency dependent Q(f), and a distance dependent duration that can be used with random vibration theory (RVT) or stochastic simulations to predict other characteristics of the ground motion. The duration results indicate that both the variation of the duration data with distance and its scattering decrease with increasing frequency. The ratio of horizontal to vertical component site terms is about √2 for all frequencies. However, this ratio is near unity for rock sites and is larger for soil sites. Simple modeling indicates that the Fourier velocity spectra are best fit by bilinear geometrical spreading of r−1 for r < 40 km and r−1/2 for r > 40 km. The frequency-dependent quality factor is Q(f) = 180f0.45 for each of the three components and also for the combined three-component data sets. The T5%-75% duration window provides good agreement between observed and RVT predicted peak values.

Theoretical Synthesis and Analysis of Strong Motion Spectra of Earthquakes

1974 ◽  
Vol 11 (2) ◽  
pp. 278-297 ◽  
Author(s):  
H. S. Hasegawa
Keyword(s):  
Surface Waves ◽  
Ground Motion ◽  
Nuclear Reactor ◽  
Attenuation Factor ◽  
Strong Motion ◽  
Response Spectra ◽  
Acceleration Response ◽  
Response Level ◽  
Motion Signal ◽  
Predicted Values

A comparison of theoretical Fourier amplitude spectra of strong ground motion (FS) with the corresponding spectra of real earthquake accelerograms is useful in elucidating the physical processes that contribute significantly to the ground motion signal. At low freqencies the contribution from surface waves tends to predominate. At intermediate frequencies the joint contributions from the direct shear wave and from complex crustal reverberations are important. At high frequencies the attenuation factor and/or source mechanism effects tend to dominate, depending on type of material and distance traversed.For a specified ground motion spectra and a particular acceleration response level, there are many theoretically predicted smoothed response spectra for velocity and displacement, depending on the particular combination of earthquake magnitude and source-to-receiver distance selected. In contrast the Newmark–Hall method (for nuclear reactor facilities) predicts a single value for the velocity and displacement response level when the acceleration response level is specified; the Newmark–Hall response values for velocity and displacement are somewhat greater than the corresponding maximum theoretically predicted values. Much of this difference is likely due to the fact that, in the theoretical spectra used for comparison purposes, contributions from complex crustal reverberations and from surface waves were not included.

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